Comparison of long-term oncologic outcomes of central lumpectomy and conventional breast-conserving surgery for invasive breast cancer: propensity score matching analysis

PURPOSE

Central lumpectomy (CL) is a breast-conserving surgical (BCS) technique that involves excision of the nipple-areolar complex with breast tumor in centrally located breast cancers. We aimed to investigate the long-term clinical outcomes of CL in comparison with conventional BCS (cBCS).

METHODS

Patient records who underwent BCS with clear resection margins for invasive breast cancer between 2004 and 2018 were retrospectively reviewed. Of the total 6,533 patients, 106 (1.6%) underwent CL. Median follow-up duration was 73.4 months. 1:3 propensity score matching (PSM) and inverse probability of treatment weighting (IPTW) were used to minimize selection bias.

RESULTS

The CL group showed a significantly higher ipsilateral breast tumor recurrence (IBTR) rate than the cBCS group (10-year IBTR rate: 5.8% vs. 3.1%, p = 0.004), even after adjusting for other variables (hazard ratio (HR), 2.65; 95% confidence interval (CI), 1.07-6.60, p = 0.048). However, there were no significant differences observed in regional recurrence, distant metastasis, or overall survival rates between the two groups. Both PSM and IPTW analyses showed significantly higher IBTR in the CL group (PSM HR, 3.27; 95% CI, 0.94-11.36; p = 0.048 and IPTW HR, 4.66; 95%CI, 1.85-11.77; p < 0.001). Lastly, when analyzing 2,213 patients whose tumors were located within 3 cm of the nipple, the CL group showed a significantly higher IBTR than the cBCS group before and after PSM.

CONCLUSION

CL was associated with a higher rate of IBTR compared to cBCS, while other survival outcomes were comparable. For centrally located tumors, CL may be considered for patients preferring breast preservation. However, higher risk for IBTR should be informed and careful surveillance may be necessary during the early post-operative follow-up periods.

Outcomes in Nonmetastatic Hormone Receptor-Positive HER2-Negative Pure Mucinous Breast Cancer: A Multicenter Cohort Study

BACKGROUND

Although considered a favorable subtype, pure mucinous breast cancer (PMBC) can recur, and evidence for adjuvant therapy is limited. We aimed to compare outcomes of nonmetastatic PMBC with invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) to address these uncertainties.

METHODS

Individual patient-level data from 6 centers on stage I-III hormone receptor-positive and HER2-negative PMBC, IDC, and ILC were used to analyze recurrence-free interval (RFI), recurrence-free survival (RFS), and overall survival (OS), and to identify prognostic factors for PMBC.

RESULTS

Data from 20,684 IDC cases, 1,475 ILC cases, and 943 PMBC cases were used. Median follow-up was 6.6 years. Five-year RFI, RFS, and OS for PMBC were 96.1%, 94.9%, and 98.1%, respectively. On multivariable Cox regression, PMBC demonstrated superior RFI (hazard ratio [HR], 0.59; 95% CI, 0.43-0.80), RFS (HR, 0.70; 95% CI, 0.56-0.89), and OS (HR, 0.71; 95% CI, 0.53-0.96) compared with IDC. ILC showed comparable outcomes to IDC. Fewer than half (48.7%) of recurrences in PMBC were distant, which was a lower rate than for IDC (67.3%) and ILC (80.6%). In contrast to RFI, RFS events were driven more by non-breast cancer deaths in older patients. Significant prognostic factors for RFI among PMBC included positive lymph node(s) (HR, 2.42; 95% CI, 1.08-5.40), radiotherapy (HR, 0.44; 95% CI, 0.23-0.85), and endocrine therapy (HR, 0.25; 95% CI, 0.09-0.70). No differential chemotherapy associations with outcomes were detected across PMBC subgroups by nodal stage, tumor size, and age. A separate SEER database analysis also did not find any association of improved survival with adjuvant chemotherapy in these subgroups.

CONCLUSIONS

Compared with IDC, PMBC demonstrated superior RFI, RFS, and OS. Lymph node negativity, adjuvant radiotherapy, and endocrine therapy were associated with superior RFI. Adjuvant chemotherapy was not associated with better outcomes.

Oncological Safety of Skipping Axillary Lymph Node Dissection in Patients with Clinical N0, Sentinel Node-Positive Breast Cancer Undergoing Total Mastectomy

OBJECTIVE

This study aimed to determine whether sentinel lymph node biopsy (SLNB) alone could afford oncological outcomes comparable with axillary lymph node dissection (ALND) in patients with early breast cancer without palpable lymphadenopathy who underwent total mastectomy (TM) and were SLN-positive.

METHODS

This study analyzed clinical data of 6747 patients with breast cancer who underwent TM between 2014 and 2018 in two tertiary hospitals in Korea. Overall, 643 clinical stage T1-3 N0 patients who did not receive neoadjuvant therapy and had one to two metastatic SLNs at the time of surgery were included. Propensity score matching was performed between the SLNB alone and ALND groups, adjusting for clinical T stage and number of metastatic SLNs. In total, 237 patients were allocated to each group.

RESULTS

Mean number of metastatic SLNs was 1.2 for the SLNB group and 1.6 for the ALND group. With a median follow-up of 65.0 months, 5 year disease-free survival was 90.8% for the SLNB group and 93.9% for the ALND group (hazard ratio [HR] 1.35, 95% confidence interval [CI] 0.70-2.58; p = 0.36). 5 year ipsilateral locoregional recurrence-free survival (LRRFS) was not significantly different between the two groups (95.1% and 98.3% for the SLNB and ALND groups, respectively) [HR 1.86, 95% CI 0.69-5.04; p = 0.21]. In the SLNB group, patients who received radiation therapy (RT) showed superior 5 year LRRFS than patients who did not receive RT (100% vs. 92.9%; p = 0.02).

CONCLUSION

Collectively, our findings suggest that SLNB could afford comparable outcomes to ALND in patients with early breast cancer and one to two metastatic SLNs who underwent TM. Importantly, RT could decrease locoregional recurrence in patients who underwent SLNB alone.

Protocol for the development of a core outcome set and reporting guidelines for locoregional treatment in neoadjuvant systemic breast cancer treatment trials: the PRECEDENT project

INTRODUCTION

Neoadjuvant systemic anticancer therapy (neoSACT) is increasingly used in the treatment of early breast cancer. Response to therapy is prognostic and allows locoregional and adjuvant systemic treatments to be tailored to minimise morbidity and optimise oncological outcomes and quality of life. Accurate information about locoregional treatments following neoSACT is vital to allow the translation of downstaging benefits into practice and facilitate meaningful interpretation of oncological outcomes, particularly locoregional recurrence. Reporting of locoregional treatments in neoSACT studies, however, is currently poor. The development of a core outcome set (COS) and reporting guidelines is one strategy by which this may be improved.

METHODS AND ANALYSIS

A COS for reporting locoregional treatment (surgery and radiotherapy) in neoSACT trials will be developed in accordance with Core Outcome Measures in Effectiveness Trials (COMET) and Core Outcome Set-Standards for Development guidelines. Reporting guidance will be developed concurrently.The project will have three phases: (1) generation of a long list of relevant outcome domains and reporting items from a systematic review of published neoSACT studies and interviews with key stakeholders. Identified items and domains will be categorised and formatted into Delphi consensus questionnaire items. (2) At least two rounds of an international online Delphi survey in which at least 250 key stakeholders (surgeons/oncologists/radiologists/pathologists/trialists/methodologists) will score the importance of reporting each outcome. (3) A consensus meeting with key stakeholders to discuss and agree the final COS and reporting guidance.

ETHICS AND DISSEMINATION

Ethical approval for the consensus process will be obtained from the Queen's University Belfast Faculty Ethics Committee. The COS/reporting guidelines will be presented at international meetings and published in peer-reviewed journals. Dissemination materials will be produced in collaboration with our steering group and patient advocates so the results can be shared widely.

REGISTRATION

The study has been prospectively registered on the COMET website (https://www.comet-initiative.org/Studies/Details/2854).

Disruption of G-quadruplex dynamicity by BRCA2 abrogation instigates phase separation and break-induced replication at telomeres

Dynamic interaction between BRCA2 and telomeric G-quadruplexes (G4) is crucial for maintaining telomere replication homeostasis. Cells lacking BRCA2 display telomeric damage with a subset of these cells bypassing senescence to initiate break-induced replication (BIR) for telomere synthesis. Here we show that the abnormal stabilization of telomeric G4 following BRCA2 depletion leads to telomeric repeat-containing RNA (TERRA)-R-loop accumulation, triggering liquid-liquid phase separation (LLPS) and the assembly of Alternative Lengthening of Telomeres (ALT)-associated promyelocytic leukemia (PML) bodies (APBs). Disruption of R-loops abolishes LLPS and impairs telomere synthesis. Artificial engineering of telomeric LLPS restores telomere synthesis, underscoring the critical role of LLPS in ALT. TERRA-R-loops also recruit Polycomb Repressive Complex 2 (PRC2), leading to tri-methylation of Lys27 on histone H3 (H3K27me3) at telomeres. Half of paraffin-embedded tissue sections from human breast cancers exhibit APBs and telomere length heterogeneity, suggesting that BRCA2 mutations can predispose individuals to ALT-type tumorigenesis. Overall, BRCA2 abrogation disrupts the dynamicity of telomeric G4, producing TERRA-R-loops, finally leading to the assembly of telomeric liquid condensates crucial for ALT. We propose that modulating the dynamicity of telomeric G4 and targeting TERRA-R-loops in telomeric LLPS maintenance may represent effective therapeutic strategies for treating ALT-like cancers with APBs, including those with BRCA2 disruptions.

Selective Avoidance of Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy in Human Epidermal Growth Factor 2-Positive/Triple-Negative Breast Cancer Patients With Excellent Response

PURPOSE

The Avoid Axillary Sentinel Lymph Node Biopsy After Neoadjuvant Chemotherapy (ASLAN) trial aims to demonstrate the oncologic safety of omitting axillary surgery in patients with excellent response after neoadjuvant chemotherapy (NACT) for early human epidermal growth factor 2 (HER2)-positive (+)/triple-negative breast cancer (TNBC) who have undergone breast-conserving surgery (BCS) and adjuvant radiotherapy. The ASLAN trial will provide crucial information that could change the procedure in highly selected patients undergoing axillary surgery after NACT.

METHODS

ASLAN is a prospective, multicenter, and single-arm surgical trial. The recruitment will be conducted among five tertiary care hospitals in the Republic of Korea. The total number of patients to be recruited will be 178, and we plan to complete patient enrollment by December 2023. The enrollment is considered among patients with HER2+ breast cancer (BC) or TNBC at clinical stage T1-3N0-1M0 who are expected to achieve breast pathological complete response (BpCR) based on a combination of radiologic imaging and physical examination after NACT. BCS was performed on eligible patients. After BCS, patients who showed BpCR were enrolled with the omission of sentinel lymph node biopsy (SLNB). The primary study endpoint upon completion of this trial is 5-year recurrence-free survival, and the secondary endpoints include the 5-year ipsilateral breast tumor recurrence interval, 5-year ipsilateral axillary recurrence interval, 5-year distant metastasis-free survival, 5-year BC-specific survival, 5-year overall survival, 5-year contralateral BC-free survival, re-operation rate according to breast biopsy after NACT, adverse events within 5 years, and quality of life.

DISCUSSION

Several clinical trials are currently underway to determine whether SLNB can be omitted after NACT in patients with HER2+ BC or TNBC that are expected to achieve pathologic complete response. The ASLAN trial is expected to provide valuable clues regarding the feasibility of omitting axillary surgery in highly selected patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04993625. Registered on August 6, 2021. Clinical Research Information Service Identifier: KCT0006371. Registered on July 22, 2021.

Dynamic insights into infection risk over time in two-stage implant-based breast reconstruction: a retrospective cohort study

BACKGROUND

Infections following postmastectomy implant-based breast reconstruction (IBR) can compromise surgical outcomes and lead to significant morbidity. This study aimed to discern the timing of infections in two-stage IBR and associated risk factors.

METHOD

A review of electronic health records was conducted on 1,096 breasts in 1,058 patients undergoing two-stage IBR at ** National University Hospital (2015-2020). Infections following the first-stage tissue expander (TE) insertion and second-stage TE exchange were analyzed separately, considering associated risk factors.

RESULTS

Over a median follow-up of 53.5 months, infections occurred in 2.9% (32/1096) after the first stage and 4.1% (44/1070) after the second stage. Infections following the first-stage procedure exhibited a bimodal distribution across time, while those after the second-stage procedure showed a unimodal pattern. When analyzing risk factors for infection after the first-stage procedure, axillary lymph node dissection (ALND) was associated with early (≤7 weeks) infection, while both ALND and obesity were independent predictors of late (>7 weeks) infection. For infections following the second-stage procedure, obesity, postmastectomy radiotherapy, a history of expander infection, ALND, and the use of textured implants were identified as independent risk factors. Postmastectomy radiotherapy was related to non-salvaged outcomes after infection following both stages.

CONCLUSION

Infections following first and second-stage IBR exhibit distinct timelines reflecting different pathophysiology. Understanding these timelines and associated risk factors will inform patient selection for IBR and aid in tailored postoperative surveillance planning. These findings contribute to refining patient suitability for IBR and optimizing personalized postoperative care strategies.

ANXA2 (annexin A2) is crucial to ATG7-mediated autophagy, leading to tumor aggressiveness in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) is associated with a poor prognosis and metastatic growth. TNBC cells frequently undergo macroautophagy/autophagy, contributing to tumor progression and chemotherapeutic resistance. ANXA2 (annexin A2), a potential therapeutic target for TNBC, has been reported to stimulate autophagy. In this study, we investigated the role of ANXA2 in autophagic processes in TNBC cells. TNBC patients exhibited high levels of ANXA2, which correlated with poor outcomes. ANXA2 increased LC3B-II levels following bafilomycin A1 treatment and enhanced autophagic flux in TNBC cells. Notably, ANXA2 upregulated the phosphorylation of HSF1 (heat shock transcription factor 1), resulting in the transcriptional activation of ATG7 (autophagy related 7). The mechanistic target of rapamycin kinase complex 2 (MTORC2) played an important role in ANXA2-mediated ATG7 transcription by HSF1. MTORC2 did not affect the mRNA level of ANXA2, but it was involved in the protein stability of ANXA2. HSPA (heat shock protein family A (Hsp70)) was a potential interacting protein with ANXA2, which may protect ANXA2 from lysosomal proteolysis. ANXA2 knockdown significantly increased sensitivity to doxorubicin, the first-line chemotherapeutic regimen for TNBC treatment, suggesting that the inhibition of autophagy by ANXA2 knockdown may overcome doxorubicin resistance. In a TNBC xenograft mouse model, we demonstrated that ANXA2 knockdown combined with doxorubicin administration significantly inhibited tumor growth compared to doxorubicin treatment alone, offering a promising avenue to enhance the effectiveness of chemotherapy. In summary, our study elucidated the molecular mechanism by which ANXA2 modulates autophagy, suggesting a potential therapeutic approach for TNBC treatment.Abbreviation: ATG: autophagy related; ChIP: chromatin-immunoprecipitation; HBSS: Hanks' balanced salt solution; HSF1: heat shock transcription factor 1; MTOR: mechanistic target of rapamycin kinase; TNBC: triple-negative breast cancer; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3.

B-Cell-Mediated Immunity Predicts Survival of Patients With Estrogen Receptor-Positive Breast Cancer

PURPOSE

The estrogen receptor-positive (ER+) breast cancer (BC), which constitutes the majority of BC cases, exhibits highly heterogeneous clinical behavior. To aid precision treatments, we aimed to find molecular subtypes of ER+ BC representing the tumor microenvironment and prognosis.

METHODS

We analyzed RNA-seq data of 113 patients with BC and classified them according to the PAM50 intrinsic subtypes using gene expression profiles. Among them, we further focused on 44 patients with luminal-type (ER+) BC for subclassification. The Cancer Genome Atlas (TCGA) data of patients with BC were used as a validation data set to verify the new classification. We estimated the immune cell composition using CIBERSORT and further analyzed its association with clinical or molecular parameters.

RESULTS

Principal component analysis clearly divided the patients into two subgroups separately from the luminal A and B classification. The top differentially expressed genes between the subgroups were distinctly characterized by immunoglobulin and B-cell-related genes. We could also cluster a separate cohort of patients with luminal-type BC from TCGA into two subgroups on the basis of the expression of a B-cell-specific gene set, and patients who were predicted to have high B-cell immune activity had better prognoses than other patients.

CONCLUSION

Our transcriptomic approach emphasize a molecular phenotype of B-cell immunity in ER+ BC that may help to predict disease prognosis. Although further researches are required, B-cell immunity for patients with ER+ BC may be helpful for identifying patients who are good responders to chemotherapy or immunotherapy.

Omission of Breast Surgery in Exceptional Responders

Breast cancer management has transformed significantly over the last decades, primarily through the integration of neoadjuvant systemic therapy (NST) and the evolving understanding of tumor biology, enabling more tailored treatment strategies. The aim of this review is to critically present the historical context and contemporary evidence surrounding the potential of omission of surgery post-NST, focusing on exceptional responders who have achieved a pathologic complete response (pCR). Identifying these exceptional responders before surgery remains a challenge, however standardized image-guided biopsy may allow optimized patient selection. The safety and feasibility of omitting breast and axillary surgeries in these exceptional responders are explored in ongoing clinical trials and the reported preliminary results appear promising. Moreover, understanding patient and physician perspectives regarding the potential elimination of surgery post-NST is integral. While some patients express a preference to omit or minimize surgery, the majority of healthcare providers are intrigued by the prospect of avoiding surgical interventions and endorse further research in this field.

Omission of Breast Surgery in Predicted Pathologic Complete Response after Neoadjuvant Systemic Therapy: A Multicenter, Single-Arm, Non-inferiority Trial

PURPOSE

Advances in chemotherapeutic and targeted agents have increased pathologic complete response (pCR) rates after neoadjuvant systemic therapy (NST). Vacuum-assisted biopsy (VAB) has been suggested to accurately evaluate pCR. This study aims to confirm the non-inferiority of the 5-year disease-free survival of patients who omitted breast surgery when predicted to have a pCR based on breast magnetic resonance imaging (MRI) and VAB after NST, compared with patients with a pCR who had undergone breast surgery in previous studies.

METHODS

The Omission of breast surgery for PredicTed pCR patients wIth MRI and vacuum-assisted bIopsy in breaST cancer after neoadjuvant systemic therapy (OPTIMIST) trial is a prospective, multicenter, single-arm, non-inferiority study enrolling in 17 tertiary care hospitals in the Republic of Korea. Eligible patients must have a clip marker placed in the tumor and meet the MRI criteria suggesting complete clinical response (post-NST MRI size ≤ 1 cm and lesion-to-background signal enhancement ratio ≤ 1.6) after NST. Patients will undergo VAB, and breast surgery will be omitted for those with no residual tumor. Axillary surgery can also be omitted if the patient was clinically node-negative before and after NST and met the stringent criteria of MRI size ≤ 0.5 cm. Survival and efficacy outcomes are evaluated over five years.

DISCUSSION

This study seeks to establish evidence for the safe omission of breast surgery in exceptional responders to NST while minimizing patient burden. The trial will address concerns about potential undertreatment due to false-negative results and recurrence as well as improved patient-reported quality of life issues from the omission of surgery. Successful completion of this trial may reshape clinical practice for certain breast cancer subtypes and lead to a safe and less invasive approach for selected patients.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05505357. Registered on August 17, 2022. Clinical Research Information Service Identifier: KCT0007638. Registered on July 25, 2022.

Increased risk of contralateral breast cancer for BRCA1/2 wild-type, high-risk Korean breast cancer patients: a retrospective cohort study

BACKGROUND

This study aimed to investigate the contralateral breast cancer (CBC) recurrence rate in Korean breast cancer patients according to their BRCA1/2 germline mutation status, focusing particularly on the CBC recurrence risk in BRCA1/2 negative (BRCAx) patients.

METHODS

We conducted a retrospective study on 13,107 primary breast cancer patients. The patients were divided into high-risk and low-risk groups for hereditary breast cancer based on the Korean National Health Insurance Service's eligibility criteria for BRCA1/2 germline mutation testing. The high-risk group was further categorized into the BRCA mutation group, the BRCAx group, and the not tested group. We evaluated the overall survival and cumulative risk of developing CBC in these patients.

RESULTS

Among 4494 high-risk patients, 973 (21.7%) underwent genetic testing for BRCA1/2 germline mutation, revealing mutations in 158 patients (16.2%). We observed significant overall survival differences across all four groups, with the high-risk, not-tested group demonstrating notably worse overall survival (p < 0.001). However, when adjusted for other prognostic factors, there was no significant differences in hazard ratio of death between the four groups. The cumulative risk of CBC also varied among the groups. Patients with BRCA1/2 mutations showed a 7.3-fold increased risk of CBC compared to the low-risk group (95% CI 4.11-13.0, p < 0.001). Interestingly, BRCAx patients also demonstrated a significantly higher risk of CBC (HR 2.77, 95% CI 1.76-4.35, p < 0.001). The prognostic importance of the BRCAx for CBC recurrence persisted after adjusting for the age and subtype, but became insignificant when the family history of breast cancer was adjusted.

CONCLUSION

Breast cancer patients who are at high risk of hereditary breast cancer but with wild-type BRCA 1/2 genes (BRCAx) have increased risk of developing contralateral breast cancer when compared to the low-risk patients. More careful surveillance and follow-up can be offered to these patients especially when they have family history of breast cancer.

A Survey of Practice Patterns for Clinical Nodal Staging Prior to Neoadjuvant Chemotherapy in Breast Cancer

BACKGROUND

The importance of clinical staging in breast cancer has increased owing to the wide use of neoadjuvant systemic therapy (NST). This study aimed to investigate the current practice patterns regarding clinical nodal staging in breast cancer in real-world settings.

MATERIALS AND METHODS

A web-based survey was administered to board-certified oncologists in Korea, including breast surgical, medical, and radiation oncologists, from January to April 2022. The survey included 19 general questions and 4 case-based questions.

RESULTS

In total, 122 oncologists (45 radiation, 44 surgical, and 33 medical oncologists) completed the survey. Among them, 108 (88%) responded that clinical staging before NST was primarily performed by breast surgeons. All the respondents referred to imaging studies during nodal staging. Overall, 64 (52.5%) responders determined the stage strictly based on the radiology reports, whereas 58 (47.5%) made their own decision while noting radiology reports. Of those who made their own decisions, 88% referred to the number or size of the suspicious node. Of the 75 respondents involved in prescribing regimens for neoadjuvant chemotherapy, 58 (77.3%) responded that the reimbursement regulations in the selection of NST regimens affected nodal staging in clinical practice. In the case-based questions, high variability was observed among the clinicians in the same cases.

CONCLUSIONS

Diverse assessments by specialists owing to the lack of a clear, harmonized staging system for the clinical nodal staging of breast cancer can lead to diverse practice patterns. Thus, practical, harmonized, and objective methods for clinical nodal staging and for the outcomes of post-NST response are warranted for appropriate treatment decisions and accurate outcome evaluation.

The percentage of unnecessary mastectomy due to false size prediction using preoperative ultrasonography and MRI in breast cancer patients who underwent neoadjuvant chemotherapy: a prospective cohort study

BACKGROUND

Imaging-estimated tumour extent after neoadjuvant chemotherapy tends to be discordant with the pathological extent. The authors aimed to prospectively determine the proportion of decisions regarding total mastectomy for potential breast-conserving surgery candidates owing to false size prediction with imaging in neoadjuvant chemotherapy and non-neoadjuvant chemotherapy patients.

MATERIALS AND METHODS

The authors prospectively enroled clinical stage II or III breast cancer patients who are scheduled for total mastectomy between 2018 and 2021. This study was conducted at Seoul National University Hospital at South Korea. Before surgery, each surgeon recorded the hypothetical maximum tumour size at which the surgeon would have been able to attempt breast-conserving surgery if the patient had actually less than the size of the tumour at that location in the breast. After surgery, the hypothetical maximum tumour size was compared with the final pathologic total extent of the tumour, including invasive and in situ cancers.

RESULTS

Among the 360 enroled patients, 130 underwent neoadjuvant chemotherapy, and 230 did not undergo neoadjuvant chemotherapy. Of the total of each group, 47.7% in the neoadjuvant chemotherapy group and 21.3% in the non-neoadjuvant chemotherapy group had a smaller pathologic tumour extent than the pre-recorded hypothetical maximum tumour size (P<0.001). Further analyses were conducted for the neoadjuvant chemotherapy group. The proportions of total mastectomy with false size prediction were higher in HER2-positive (63.3%) and triple-negative (57.6%) patients compared with ER-positive/HER2-negative (25.0%) patients (P<0.001). Both magnetic resonance imaging-pathology and ultrasonography-pathology size discrepancies were significantly associated with false decisions for total mastectomy (both P<0.001). Without magnetic resonance imaging, the false decision may be reduced by 21.5%.

CONCLUSION

A total of 47.7% of patients who received total mastectomy after neoadjuvant chemotherapy were breast-conserving surgery eligible, which was significantly higher than that of non-neoadjuvant chemotherapy patients. Magnetic resonance imaging contributed the most to false size predictions.

Residual Risk of Ipsilateral Tumor Recurrence in Patients Who Achieved Clear Lumpectomy Margins After Repeated Resection

PURPOSE

Patients with breast cancer with positive lumpectomy margins have a two-fold increased risk of ipsilateral breast tumor recurrence (IBTR). This can be the result of either technically incomplete resection or the biological characteristics of the tumor that lead to a positive margin. We hypothesized that if achieving negative margins by re-excision nullifies the IBTR risk, then the increased risk is mainly attributed to the technical incompleteness of the initial surgeries. Thus, we investigated IBTR rates in patients with breast cancer who achieved clear margins after re-excision.

METHODS

We retrospectively reviewed patients who underwent breast lumpectomy for invasive breast cancer between 2004 and 2018 at a single institution, and investigated IBTR events.

RESULTS

Among 5,598 patients, 793 achieved clear margins after re-excision of their initial positive margins. During the median follow-up period of 76.4 months, 121 (2.2%) patients experienced IBTR. Patients who underwent re-excision to achieve negative margin experienced significantly higher IBTR rates compared to those achieving clear margin at first lumpectomy (10-year IBTR rate: 5.3% vs. 2.6% [25 vs. 84 events]; unadjusted p = 0.031, hazard ratio, 1.61, 95% confidence interval [CI], 1.04-2.48; adjusted p = 0.030, hazard ratio, 1.69, 95% CI, 1.05-2.72). This difference was more evident in patients aged < 50 years and those with delayed IBTR. Additionally, no statistically significant differences were observed in the spatial distribution of IBTR locations.

CONCLUSION

Patients who underwent re-excision for initial positive margins had an increased risk of IBTR, even after achieving a final negative margin, compared to patients with negative margins initially. This increased risk of IBTR is mostly observed in young patients and delayed cases.

Life-Threatening Hematoma in an Elderly Breast Cancer Patient Undergoing Chemotherapy

The use of neoadjuvant chemotherapy in older patients is increasing. However, chemotherapy should be administered considering the medical comorbidities of the patients and the toxicity of chemotherapeutic agents. Here, we present a case of abdominal wall hematoma with spontaneous inferior epigastric artery injury caused by coughing in a 70-year-old woman who was treated with neoadjuvant chemotherapy. Abdominal computed tomography demonstrated an abdominal wall hematoma with active bleeding. However, angiography with selective embolization of the right inferior epigastric artery and the right internal mammary artery was performed successfully. Scheduled chemotherapy was discontinued over concerns of rebleeding and breast-conserving surgery was performed. When deciding on chemotherapy for older patients, attention should be paid to the various complications.

Impact of media compositions and culture systems on the immunophenotypes of patient-derived breast cancer cells

BACKGROUND

Heterogeneous tumor cells are thought to be a significant factor in the failure of endocrine therapy in estrogen receptor-positive (ER+) cancers. Culturing patient-derived breast cancer cells (PDBCCs) provides an invaluable tool in pre-clinical and translational research for the heterogeneity of cancer cells. This study aimed to investigate the effects of different media components and culture methods on the BCSC-associated immunophenotypes and gene expression in ER + PDBCCs.

METHODS

Ten patients with ER + breast cancer were employed in this study, six of whom had neoadjuvant chemotherapy and four of whom did not. PDBCCs were isolated by enzymatic methods using collagen I and hyaluronidase. PDBCCs were grown as monolayers in mediums with different compositions and as multicellular spheroid in a suspended condition. Collagen I-coated plate and ultralow attachment plate coated with polymer-X were used for monolayer and spheroid culture. Flow cytometry, immunofluorescent staining, RT-PCR, and RNA-sequencing were employed to examine the immunophenotype and genetic profile of PDBCCs.

RESULTS

More than 95% of PDBCCs sustain EpCAM high/+/fibroblast marker- phenotypes in monolayer conditions by subculturing 3-4 times. A83-01 removal induced senescent cells with high β-galactosidase activity. PDBCCs grown as monolayers were characterized by the majority of cells having an EpCAM+/CD49f + phenotype. Compared to full media in monolayer culture, EGF removal increased EpCAM+/CD49f - phenotype (13.8-fold, p = 0.028), whereas R-spondin removal reduced it (0.8-fold, p = 0.02). A83-01 removal increased EpCAM+/CD24 + phenotype (1.82-fold, p = 0.023) and decreased EpCAM low/-/CD44+/CD24- phenotype (0.45-fold, p = 0.026). Compared to monolayer, spheroid resulted in a significant increase in the population with EpCAM-/CD49+ (14.6-fold, p = 0.006) and EpCAM low/-/CD44+/CD24- phenotypes (4.16-fold, p = 0.022) and ALDH high activity (9.66-fold, p = 0.037). ALDH1A and EMT-related genes were upregulated. In RNA-sequencing analysis between spheroids and monolayers, a total of 561 differentially expressed genes (2-fold change, p < 0.05) were enriched in 27 KEGG pathways including signaling pathways regulating pluripotency of stem cells. In a recurrence-free survival analysis based on the Kaplan-Meier Plotter database of the up-and down-regulated genes identified in spheroids, 15 up-, and 14 down-regulated genes were associated with poor prognosis of breast cancer patients.

CONCLUSION

The media composition and spheroid culture method change in the BCSCs and EMT markers of PDBCCs, implying the importance of defining the media composition and culture method for studying PDBCCs in vitro.

Development of a Breast Cancer Risk Prediction Model Incorporating Polygenic Risk Scores and Nongenetic Risk Factors for Korean Women

BACKGROUND

To develop a breast cancer prediction model for Korean women using published polygenic risk scores (PRS) combined with nongenetic risk factors (NGRF).

METHODS

Thirteen PRS models generated from single or multiple combinations of the Asian and European PRSs were evaluated among 20,434 Korean women. The AUC and increase in OR per SD were compared for each PRS. The PRSs with the highest predictive power were combined with NGRFs; then, an integrated prediction model was established using the Individualized Coherent Absolute Risk Estimation (iCARE) tool. The absolute breast cancer risk was stratified for 18,142 women with available follow-up data.

RESULTS

PRS38_ASN+PRS190_EB, a combination of Asian and European PRSs, had the highest AUC (0.621) among PRSs, with an OR per SD increase of 1.45 (95% confidence interval: 1.31-1.61). Compared with the average risk group (35%-65%), women in the top 5% had a 2.5-fold higher risk of breast cancer. Incorporating NGRFs yielded a modest increase in the AUC of women ages >50 years. For PRS38_ASN+PRS190_EB+NGRF, the average absolute risk was 5.06%. The lifetime absolute risk at age 80 years for women in the top 5% was 9.93%, whereas that of women in the lowest 5% was 2.22%. Women at higher risks were more sensitive to NGRF incorporation.

CONCLUSIONS

Combined Asian and European PRSs were predictive of breast cancer in Korean women. Our findings support the use of these models for personalized screening and prevention of breast cancer.

IMPACT

Our study provides insights into genetic susceptibility and NGRFs for predicting breast cancer in Korean women.

Barcoded multiple displacement amplification for high coverage sequencing in spatial genomics

Determining mutational landscapes in a spatial context is essential for understanding genetically heterogeneous cell microniches. Current approaches, such as Multiple Displacement Amplification (MDA), offer high genome coverage but limited multiplexing, which hinders large-scale spatial genomic studies. Here, we introduce barcoded MDA (bMDA), a technique that achieves high-coverage genomic analysis of low-input DNA while enhancing the multiplexing capabilities. By incorporating cell barcodes during MDA, bMDA streamlines library preparation in one pot, thereby overcoming a key bottleneck in spatial genomics. We apply bMDA to the integrative spatial analysis of triple-negative breast cancer tissues by examining copy number alterations, single nucleotide variations, structural variations, and kataegis signatures for each spatial microniche. This enables the assessment of subclonal evolutionary relationships within a spatial context. Therefore, bMDA has emerged as a scalable technology with the potential to advance the field of spatial genomics significantly.

Comparison of Quality of Life and Cosmetic Outcome of Latissimus Dorsi Mini-Flap With Breast Conservation Surgery Without Reconstruction

PURPOSE

Latissimus dorsi mini-flap (LDMF) reconstruction after breast-conserving surgery (BCS) is a useful volume replacement technique when a large tumor is located in the upper or outer portion of the breast. However, few studies have reported the impact of LDMF on patients' quality of life (QoL) and cosmesis compared with conventional BCS.

METHODS

We identified patients who underwent BCS with or without LDMF between 2010 and 2020 at a single center. At least 1 year after surgery, we prospectively administered the BREAST-Q to assess QoL and obtained the patients' breast photographs. The cosmetic outcome was assessed using four panels composed of physicians and the BCCT.core software.

RESULTS

A total of 120 patients were enrolled, of whom 62 and 58 underwent LDMF or BCS only, respectively. The LDMF group had significantly larger tumors, shorter nipple-to-tumor distances in preoperative examinations, and larger resected breast volumes than did the BCS-only group (p < 0.001). The questionnaires revealed that QoL was poorer in the LDMF group, particularly in terms of the physical well-being score (40.9 vs. 20.1, p < 0.001). Notably, the level of patients' cosmetic satisfaction with their breasts was comparable, and the cosmetic evaluation was assessed by panels and the BCCT.core software showed no differences between the groups.

CONCLUSION

Our results showed that cosmetic outcomes of performing LDMF are comparable to those of BCS alone while having the advantage of resecting larger volumes of breast tissue. Therefore, for those who strongly wish to preserve the cosmesis of their breasts, LDMF can be considered a favorable surgical option after the patient is oriented toward the potential for physical dysfunction after surgery.

Locoregional Recurrence Patterns in Patients With Different Molecular Subtypes of Breast Cancer

IMPORTANCE

While numerous studies have consistently reported that the molecular subtypes of breast cancer (BC) are associated with different patterns of distant metastasis, few studies have investigated the association of tumor subtypes with locoregional recurrence.

OBJECTIVE

To investigate the patterns of ipsilateral breast tumor recurrence (IBTR), regional recurrence (RR), and contralateral BC (CBC) according to tumor subtypes.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used the clinical records of patients who underwent BC surgery at a single institution in South Korea between January 2000 and December 2018. Data were analyzed from May 1, 2019, to February 20, 2023.

EXPOSURES

Ipsilateral breast tumor recurrence, RR, and CBC events.

MAIN OUTCOMES AND MEASURES

The primary outcome was differences in annual incidence patterns of IBTR, RR, and CBC according to tumor subtypes. Hormone receptor (HR) status was assessed by immunohistochemical staining assay, and ERBB2 status was evaluated according to American Society of Clinical Oncology and College of American Pathologists guidelines.

RESULTS

A total of 16 462 female patients were included in the analysis (median age at time of operation, 49.0 years [IQR, 43.0-57.0 years]). The 10-year IBTR-, RR-, and CBC-free survival rates were 95.9%, 96.1%, and 96.5%, respectively. On univariate analysis, HR-/ERBB2+ tumors had the worst IBTR-free survival (vs HR+/ERBB2- subtype: adjusted hazard ratio, 2.95; 95% CI, 2.15-4.06), while the HR-/ERBB2- subtype had the worst RR- and CBC-free survival among all subtypes (vs HR+/ERBB2- subtype, RR: adjusted hazard ratio, 2.95; 95% CI, 2.37-3.67; CBC: adjusted hazard ratio, 2.12; 95% CI, 1.64-2.75). Subtype remained significantly associated with recurrence events in Cox proportional hazards regression analysis. Regarding the annual recurrence pattern, the IBTR patterns of HR-/ERBB2+ and HR-/ERBB2- subtypes showed double peaks, while HR+/ERBB2- tumors showed a steadily increasing pattern without distinguishable peaks. Additionally, the HR+/ERBB2- subtype seemed to have a steady RR pattern, but other subtypes showed the highest RR incidence at 1 year following surgery, which then gradually decreased. The annual recurrence incidence of CBC gradually increased among all subtypes, and patients with the HR-/ERBB2- subtype had a higher incidence than patients with other subtypes over 10 years. Younger patients (age ≤40 years) had greater differences in IBTR, RR, and CBC patterns between subtypes than did older patients.

CONCLUSIONS AND RELEVANCE

In this study, locoregional recurrence occurred with different patterns according to BC subtypes, with younger patients having greater differences in patterns among subtypes than older patients. The findings suggest that tailoring surveillance should be recommended regarding differences in locoregional recurrence patterns according to tumor subtypes, particularly for younger patients.

The Lucerne Toolbox 2 to optimise axillary management for early breast cancer: a multidisciplinary expert consensus

Clinical axillary lymph node management in early breast cancer has evolved from being merely an aspect of surgical management and now includes the entire multidisciplinary team. The second edition of the "Lucerne Toolbox", a multidisciplinary consortium of European cancer societies and patient representatives, addresses the challenges of clinical axillary lymph node management, from diagnosis to local therapy of the axilla. Five working packages were developed, following the patients' journey and addressing specific clinical scenarios. Panellists voted on 72 statements, reaching consensus (agreement of 75% or more) in 52.8%, majority (51%-74% agreement) in 43.1%, and no decision in 4.2%. Based on the votes, targeted imaging and standardized pathology of lymph nodes should be a prerequisite to planning local and systemic therapy, axillary lymph node dissection can be replaced by sentinel lymph node biopsy ( ± targeted approaches) in a majority of scenarios; and positive patient outcomes should be driven by both low recurrence risks and low rates of lymphoedema.

Prediction of Tumor Progression During Neoadjuvant Chemotherapy and Survival Outcome in Patients With Triple-Negative Breast Cancer

OBJECTIVE

To investigate the association of clinical, pathologic, and magnetic resonance imaging (MRI) variables with progressive disease (PD) during neoadjuvant chemotherapy (NAC) and distant metastasis-free survival (DMFS) in patients with triple-negative breast cancer (TNBC).

MATERIALS AND METHODS

This single-center retrospective study included 252 women with TNBC who underwent NAC between 2010 and 2019. Clinical, pathologic, and treatment data were collected. Two radiologists analyzed the pre-NAC MRI. After random allocation to the development and validation sets in a 2:1 ratio, we developed models to predict PD and DMFS using logistic regression and Cox proportional hazard regression, respectively, and validated them.

RESULTS

Among the 252 patients (age, 48.3 ± 10.7 years; 168 in the development set; 84 in the validation set), PD was occurred in 17 patients and 9 patients in the development and validation sets, respectively. In the clinical-pathologic-MRI model, the metaplastic histology (odds ratio [OR], 8.0; P = 0.032), Ki-67 index (OR, 1.02; P = 0.044), and subcutaneous edema (OR, 30.6; P = 0.004) were independently associated with PD in the development set. The clinical-pathologic-MRI model showed a higher area under the receiver-operating characteristic curve (AUC) than the clinical-pathologic model (AUC: 0.69 vs. 0.54; P = 0.017) for predicting PD in the validation set. Distant metastases occurred in 49 patients and 18 patients in the development and validation sets, respectively. Residual disease in both the breast and lymph nodes (hazard ratio [HR], 6.0; P = 0.005) and the presence of lymphovascular invasion (HR, 3.3; P < 0.001) were independently associated with DMFS. The model consisting of these pathologic variables showed a Harrell's C-index of 0.86 in the validation set.

CONCLUSION

The clinical-pathologic-MRI model, which considered subcutaneous edema observed using MRI, performed better than the clinical-pathologic model for predicting PD. However, MRI did not independently contribute to the prediction of DMFS.

Never in mitosis gene A-related kinase-8 promotes proliferation, migration, invasion, and stemness of breast cancer cells via β-catenin signalling activation

Never in mitosis gene A (NIMA)-related kinase-8 (NEK8) is involved in cell cycle progression, cytoskeleton development, and DNA damage repair. However, its role in breast cancer has not yet been explored. To investigate this, NEK8 was knocked down in MDA-MB-231, BT549, and HCC38 breast cancer cell lines. We observed a decrease in cell proliferation and colony formation owing to regulation of the G1/S and G2/M transitions. Furthermore, the expression of several cell cycle regulatory proteins was altered, including that of cyclin D1, cyclin B1, CDK4, CDK2, and surviving. NEK8 knockdown impaired cell migration and invasion as well as reduced the expression of epithelial-mesenchymal transition markers. Regarding stem-cell characteristics, NEK8 knockdown decreased the tumour sphere formation, aldehyde dehydrogenase activity, and stem-cell marker expression, including that of CD44, Sox2, Oct4a, and Nanog. Further analysis revealed that NEK8 interacts with β-catenin. Also, NEK8 knockdown promoted β-catenin degradation. NEK8-silenced MDA-MB-231 cells inhibited xenograft tumour growth, metastasis, and tumour initiation in vivo. Using the Oncomine and TNMplot public databases, we found a significant correlation between NEK8 overexpression and poor clinical outcomes in breast cancer patients. Thus, NEK8 may be a crucial regulator of breast cancer progression and a potential therapeutic target.

Triple-negative breast cancer-derived extracellular vesicles promote a hepatic pre-metastatic niche via a cascade of microenvironment remodeling

Triple negative breast cancer (TNBC) patients often develop metastases in visceral organs including the liver but the detailed molecular mechanisms of TNBC liver metastasis is not clearly understood. In this study, we tried to dissect the process of pre-metastatic niche formation in liver by using patient-derived xenograft (PDX) models of TNBC with different metastatic propensity. RNA sequencing of TNBC PDX models that successfully metastasized to liver showed up-regulation of Cx3cr1 gene in the liver microenvironment. In syngeneic breast cancer models, the Cx3cr1 up-regulation in liver preceded the development of cancer cell metastasis and was the results of recruitment of CX3CR1-expressing macrophages. The recruitment was induced by the CX3CL1 production from the liver endothelial cells and this CX3CL1-CX3CR1 signaling in the pre-metastatic niche resulted in up-regulation of MMP9 that promoted macrophage migration and cancer cell invasion. Additionally, our data suggest that the extra-cellular vesicles derived from the breast cancer cells induced the TNF-alpha expression in liver which leads to the CX3CL1 up-regulation. Lastly, the plasma CX3CL1 levels in 155 breast cancer patients were significantly associated with development of liver metastasis. Implications: Our data provides previously unknown cascades regarding the molecular education of pre-metastatic niche in liver for TNBC.

Abstract 6654: Association PD-L1 overexpression with immune checkpoint inhibitor effect in triple-negative breast cancer

Background: Recently, studies on the antitumor effects of PD-L1 inhibitors have gained importance in difficult to treat solid tumors. In particular, the expression of PD-L1 could be an important factor in evaluating the possibility of immunotherapy in triple-negative breast cancer where targeted therapy is not possible and the prognosis is poor. Accordingly, this study investigated the effect of PD-L1 overexpression on the immune checkpoint inhibitor effect in triple-negative breast cancer.

Method: The relationship between T stage and N stage according to PD-L1 mRNA expression was analyzed in the TCGA and METABRIC datasets of breast cancer. To evaluate the role of PD-L1, PD-L1-overexpressing breast cancer cell lines for in vitro and in vivo experiments were established.

Result: Using TCGA and METABRIC datasets, we found that PD-L1 showed the highest expression in breast cancer of the basal subtype, but the correlation between T stage and N stage according to PD-L1 expression was not statistically significant. To determine the functional importance of PD-L1 in breast cancer, we established 4T1-PD-L1-overexpressing breast cancer cell lines. We observed that the overexpression of PD-L1 promoted cell proliferation, migration, and invasion. In the orthotopic tumor mouse model, PD-L1 showed no significant difference in tumor growth compared to the control group, but anti-PD-L1 treatment showed a significant antitumor effect.

Conclusion: We confirmed that overexpression of PD-L1 in an orthotopic breast cancer model did not induce increased tumor growth. Above all, it was confirmed that a high PD-L1 level enhances the antitumor effect of immune checkpoint inhibitors. Our findings show that the expression level of PD-L1 in breast cancer has a significant effect on the immune checkpoint inhibitor effect. We need to further investigate the role of PD-L1 in breast cancer.

Citation Format: A Young Park, Ju Hee Kim, Sangen Lee, Hong Kyu Kim, Han-Byoel Lee, Wonshick Han. Association PD-L1 overexpression with immune checkpoint inhibitor effect in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6654.

Abstract P3-04-11: Longitudinal Changes of Contralateral Breast Mammographic Artificial Intelligence Algorithms Score in Ductal Carcinoma In Situ patient with Tamoxifen

Background Mammographic Artificial intelligence (AI) algorithms (Lunit insight MMG) draws attention as a diagnostic support tool for breast cancer detection. Lunit insight MMG provides a location suspected of breast cancer with a heatmap and a score reflecting the probability of the presence of suspicious areas. We investigated whether the Lunit insight MMG score is relevant for predicting the response to adjuvant tamoxifen. Methods Patients diagnosed with DCIS and underwent treatment at Seoul National University Hospital in 2010 were retrospectively enrolled. Clinical characteristics, tamoxifen use, survival data, and mammography images were extracted from the electronic medical records, and Lunit insight MMG scores were calculated retrospectively. We classified two groups according to tamoxifen treatment and compared the score change of contralateral breast from baseline to 5 years after surgery for DCIS. Change categories of Lunit insight MMG score included maintaining high risk, maintaining low risk, increasing from low risk to high risk, and decreasing from high risk to low risk. Results Of 100 patients, 50 (50%) had undergone tamoxifen treatment (group 1) and 50 (50%) had not (group 2). The median age of the patients was 48.4 years for group 1 and 51.5 years for group 2 (p=0.172). The median follow-up duration was 8.7 years for the whole cohort. Using Lunit insight MMG score, more patients in group 1 decreased in contralateral breast cancer (CBC) risk compared with group 2 (6.0% vs. 2.0%; P=.008). No patients in group 1 had an increase in CBC risk while 9 patients increased in group 2 (0% vs. 18.0%; P =.008). There was no ipsilateral breast cancer recurrence for the whole cohort, and two patients experienced contralateral invasive breast cancer in group 2. In two patients with CBC, the Lunit insight MMG score increased five years after surgery, one year and three years before the CBC diagnosis. Conclusions Longitudinal Changes of Mammographic AI algorithms Score may be a predictive surrogate marker for response to tamoxifen therapy in hormone receptor-positive DCIS.

Citation Format: Changjin Lim, Eun Kyung Park, Hong-Kyu Kim, Eunhye Kang, Ji-Jung Jung, Hyunsu Yeoh, Jang-il Kim, Jung Whan Chun, Han-Byoel Lee, Hyeong-Gon Moon, Wonshik Han. Longitudinal Changes of Contralateral Breast Mammographic Artificial Intelligence Algorithms Score in Ductal Carcinoma In Situ patient with Tamoxifen [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-04-11.

Abstract P2-14-15: Comparison of recurrence-free survival according to axillary surgery extent for clinical N0, sentinel node(s) positive, primary breast cancer patients who underwent total mastectomy

Purpose We investigated the recurrence-free survival difference between limited axillary node surgery and axillary node dissection (ALND) in clinical N0 primary breast cancer patients with one to three sentinel node metastasis who underwent total mastectomy. Method We retrospectively analyzed clinical data of 579 primary breast cancer patients who underwent total mastectomy between 2014 and 2018 from Seoul National University Hospital and Asan Medical Center. All included patients had clinical T1-2, N0 disease at the time of diagnosis based on physical exam, radiologic evaluation, and pathologic assessment if needed. The patients had one to three metastatic sentinel node(s) at the time of surgery. The patients received sentinel lymph node biopsy (SLNB) with result of one to three metastatic node(s) and either proceeded to ALND or not. We performed propensity score matching between the SLNB and ALND group with baseline clinical factors including clinical T stage and number of metastatic sentinel node(s). Finally, 208 patients were matched 1:1 for each group respectively for further analysis. Also, we stratified the eligible patients based on radiation therapy for subgroup analysis. We examined disease-free survival, regional recurrence-free survival, distant metastasis-free survival and compared the results between the groups. Result The median follow-up period was 64.7 months. Among matched cohorts, mean number of metastatic nodes on final pathology result was 1.2 for SLNB group and 1.7 for ALND group. Also, mean number of total removed nodes was 8.3 for SLNB group and 17.4 for ALND group. The disease-free survival [DFS] at 7 years was 89.7% for SLNB group and 91.1% for ALND group with no statistically significant difference. (hazard ratio [HR] 1.43, 95% confidence interval [CI] 0.70 to 2.92, p=0.32) Among patients who were treated with radiation, the DFS was 94.1% in the SLNB group and 94.4% in the ALND group. (HR, 0.82, 95% CI 0.17 to 4.0, p=0.81) For the subgroup without radiation, the DFS was 87.7% in the SLNB group and 89.4% in the ALND group. (HR, 1.68, 95% CI 0.75 to 3.75, p=0.19) We observed no statistically significant differences in the regional recurrence-free survival at 7 years (95.8% in the SLNB vs. 95% in the ALND, HR 0.62, 95% CI 0.53-4.95, p=0.39), and in the distant metastasis-free survival at 7 years (95.8% in the SLNB vs. 95% in the ALND, HR 1.28, 95% CI 0.59 to 2.73, p=0.52) Conclusion Our results suggest that limited axillary surgery with sentinel node biopsy may be as effective as axillary node dissection in terms of recurrence-free survival, for clinically node negative, primary breast cancer patients with limited metastatic sentinel node(s) who are candidates for total mastectomy. Key words: Breast cancer, Total mastectomy, Axillary lymph node dissection, Sentinel lymph node biopsy.

Citation Format: Jung Whan Chun, Hong-Kyu Kim, Han-Byoel Lee, Hyeong-Gon Moon, Jong Won Lee, Wonshik Han. Comparison of recurrence-free survival according to axillary surgery extent for clinical N0, sentinel node(s) positive, primary breast cancer patients who underwent total mastectomy. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-14-15.

Abstract P2-20-05: Personalized tumor vaccine can suppress tumor growth and metastasis in the syngeneic mouse breast cancer model

Objective Immunotherapy using the tumor-specific antigens (TSAs) is a promising strategy in breast cancer. Studies have suggested that the in vivo exposures to certain tumors can induce adaptive anti-tumor immunity in syngeneic tumor models. In this study, we show the efficacy of the tumor lysate vaccine and peptide-based vaccine against tumor neoantigen in suppressing tumor growth and metastasis in 4T1 syngeneic tumor models. Method We used BALB/c mice and its syngeneic tumor cell lines to evaluate the anti-tumor effect induced by the transient exposure to the tumor cells. For tumor vaccines, we synthesized the tumor lysate vaccine by the freeze-thaw method or synthetic peptide against the selected tumor neoantigens identified by exome sequencing. We systemic and local immune remodeling was investigated by using immunohistochemistry, flow cytometry, and single cell RNA sequencing. Results We observed a significant reduction of tumor growth and metastasis in 4T1 syngeneic tumors when the mice were previously exposed to the same cells (pre-exposure group). This anti-tumor effect induced by the exposures to the tumor was cell line-specific. The 4T1 tumor lysate vaccines administered prior to the tumor cell injection also showed significant inhibitory effect on tumor growth and metastasis. T lymphocytes, isolated from the tumor tissues of the 4T1 pre-exposure mice and lysate vaccine-treated mice, showed higher levels of TNF-ɑ and IFN-ɣ when compared to the control those from the control tumors. The lysate vaccine treatment resulted in a substantial remodeling of tumor microenvironment including reduction of myeloid-derived suppressor cells and M2 tumor-associated macrophages. On the other hand, the numbers of M1 tumor-associated macrophages and effector memory CD8+ T cells were increased by the lysate vaccine. While the peptide vaccine showed no inhibitory effect on the primary tumor growth, it also suppressed spontaneous lung metastasis. Finally, we administered lysate tumor vaccine after the tumor establishment to determine the therapeutic effect. The lysate vaccine significantly suppressed the tumor growth and lung metastasis of the syngeneic 4T1 tumors. Conclusion Tumor lysate vaccine can suppress the tumor growth and metastasis in the 4T1 syngeneic mouse models by inducing substantial remodeling of tumor immune microenvironment. Additionally, tumor lysate vaccine can elicit similar anti-tumor immune response when administered after the establishment of the primary tumor suggesting a potential therapeutic value.

Citation Format: Hyeong-Gon Moon, Hye Youn Son, Woo Hang Heo, Mingji Quan, SONGBIN LI, Haritonova Valentina, Hamin Jeong, Wonshik Han, Han-Byoel Lee, YUJEONG HER, Ju Hee Kim. Personalized tumor vaccine can suppress tumor growth and metastasis in the syngeneic mouse breast cancer model [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-05.

Abstract P2-26-10: Statins exhibit an anti-tumor effect by attenuating PD-L1 in breast cancer cells and macrophages and reducing breast tumor progression in xenograft mouse model

Background: Statins were suggested for repurposed drugs, having multifaceted effects which include anti-tumor activities by modulating the immune response. Here, we aimed to demonstrate the effect of statins on programmed death-ligand 1 (PD-L1) expression in triple-negative breast cancer (TNBC) cells. Methods: Thirteen human TNBC cell lines, mouse macrophage cell line (RAW 264.7), cholesterol and 27-hydroxycholesterol, and clinically approved lovastatin and simvastatin were used. Flow cytometry, Annexin V/propidium iodide assay, western blot, qRT-PCR, transwell migration assay, and immunohistochemistry were employed. A co-culture of macrophages with various breast cancer cells was performed. An orthotopic breast tumor mouse model and metastasis model by injection of GFP-tagged MDA-MB-231 cells into mammary gland fat pad and the tail vein injection were produced. In tumor model mice, lovastatin(10mg/kg) was daily injected intraperitoneally. In vivo fluorescent imaging was used to identify primary tumor development and lung metastasis. Results: Among thirteen TNBC cell lines, MDA-MB-231, HCC38, and HCC70 highly expressed endogenous/constitutive PD-L1. Statins reduced PD-L1 expression and exerted anti-proliferative and apoptotic effects in MDA-MB-231, HCC38, HCC70, and Raw264.7 in a dose- and time-dependent manner (p&lt; 0.05). Meanwhile, statins increased the expression of PD-L1 in Hs578T and MDA-MB-468. STAT3 phosphorylation was inhibited in MDA-MB-231 and HCC70, but not in Hs578T, while AKT phosphorylation was reduced in MDA-MB-231, HCC70, Hs578T, and MDA-MB-468 when statins were treated. The migration of MDA-MB-231 and Raw264.7 in statin-treated conditioned media was decreased (p&lt; 0.05). Cholesterol and 27-hydroxy cholesterol did not restore PD-L1 expression in statin-treated MDA-MB-231. Statins suppressed the expression of M2 markers (PD-L1, CD206, YM-1, Fizz1, arginase-1) in RAW26437 stimulated by a conditioned medium of MDA-MB-231. Lovastatin suppressed the primary tumor growth and metastasis in xenograft tumor mice. Conclusions: Our findings show that statins have an anti-tumor effect, which kills breast cancer cells and triggers macrophage reprogramming by reducing PD-L1 expression, impairing the AKT, ERK, and STAT3 signal pathways, and decreasing M2 markers. Further study is needed to investigate an in-depth molecular mechanism study by which statins regulate PD-L1 expression in TNBC and to confirm the safe and effective use of statins as adjuvant therapy in TNBC.

Citation Format: Sangeun Lee, Hoe Suk Kim, So-Hyun Yoon, Seungyeon Ryu, Moonjou Baek, A Young Park, Han-Byoel Lee, Wonshik Han. Statins exhibit an anti-tumor effect by attenuating PD-L1 in breast cancer cells and macrophages and reducing breast tumor progression in xenograft mouse model [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-26-10.

Abstract P5-01-04: Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression?

Background: Contralateral axillary lymph node metastasis (CAM) in breast cancer is currently classified as a stage IV disease but its prognosis is still controversial. Purpose: To determine outcomes in overall survival (OS) and disease-free survival (DFS) in patients with and without locoregional tumor recurrence who present with contralateral axillary lymph node metastasis (CAM). Methods: Patients with pathologically confirmed invasive breast cancer with metachronous CAM who received treatment between 1988 and 2017 were retrospectively reviewed. Patients with other distant metastases at the time of CAM diagnosis were excluded. The outcome of CAM in cases of IBTR and regional recurrence (RR) were compared to CAM not accompanied by locoregional tumor recurrence. Results: Thirty-eight patients with metachronous CAM were included in the study. Metachronous CAM occurred 55 months (interquartile range, 17-77 months) after surgical treatment of the primary tumor and median follow-up was 95 months (interquartile range, 49-117 months) from the initial operation date and 40 months (interquartile range, 15-54 months) from the diagnosis of CAM. At the time of initial CAM diagnosis, 11 patients had IBTR, 12 patients had RR, and 15 patients had no locoregional recurrence. The estimated 5-year OS was 49.1% and 5-year DFS was 45.3%. Although statistically insignificant due to small sample size, when stratified by loco regional recurrence, the prognosis of CAM patients with IBTR appeared to be better than those without locoregional recurrence (5-year OS: 88.9% vs. 41.4%, HR 5.88, p = 0.09) whereas the prognosis of CAM patients with RR was worse than those without locoregional recurrence (5-year OS: 35.4% vs. 41.4%, HR 0.44, p = 0.20). Axillary lymph node dissection (ALND) improved median OS (83 vs. 36 months, p = 0.069) in all patients. When stratified, improvement in median OS was 13 vs 27 months (p = 0.094) in patients with RR, and 36 vs. 65 months (p = 0.061) in patients without locoregional recurrence. For patients accompanied by IBTR, ALND was performed in 8 out of 11 and only one patient died during the follow-up period. Conclusion: Our study indicates that the patients with CAM have superior survival outcome when compared to other stage IV patients, especially when CAM was accompanied by other loco regional recurrences. These data suggest that the CAM patients may benefit from active loco regional treatment.

Citation Format: Ji-Jung Jung, Hyeong-Gon Moon, Wonshik Han, Han-Byoel Lee, Hong-Kyu Kim, Jung Whan Chun, Eunhye Kang, Changjin Lim, Jang-il Kim, Hyunsu Yeoh. Contralateral Axillary Lymph Node Metastasis after Ipsilateral Breast Tumor Recurrence: Is it distant metastasis or locoregional progression? [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-01-04.

Abstract P3-05-36: Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study

Background: Mucinous carcinoma is the third most common histological subtype of breast cancer after ductal and lobular carcinomas, accounting for approximately 3% of invasive breast cancers. Although considered a favourable subtype with de-escalation of treatment recommended in the National Comprehensive Cancer Network guidelines, recurrence can occur and supporting data is limited. We thus examined prognostic factors of pure mucinous breast cancer (PMBC) in an international multicentre cohort study. Methods: Patients diagnosed between January 2000 to December 2015 with hormone receptor-positive HER2-negative stage I to III PMBC, invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) at 6 centers in Singapore, Taiwan, Korea and Japan were evaluated. Cox proportional hazards regression analyses were used to compare relapse-free survival (RFS), distant relapse-free survival (DRFS) and overall survival (OS) by histological subtypes, and to identify prognostic factors for PMBC. Results: Of 23,105 women eligible for analysis, 20,684 had IDC, 1,475 had ILC and 946 had PMBC. The median follow-up was 6.6 years; 5-year RFS, DRFS and OS for PMBC were 94.6%, 96.5% and 98.1% respectively. On multivariable cox regression analyses, PMBC demonstrated superior RFS (hazard ratio [HR] = 0.70, 95% CI: 0.56 - 0.88), DRFS (HR = 0.69, 95% CI: 0.53 - 0.89) and OS (HR = 0.70, 95% CI: 0.52 - 0.93) compared to IDC, while ILC had comparable survival outcomes as IDC. When restricted to only PMBC, significant independent prognostic factors for RFS included ethnicity (vs Chinese, “Others” [non-Chinese/Japanese/Korean, mainly Malay and Indian]: HR = 2.62, 95% CI 1.23 – 5.57), older age (vs &lt; 40 years, &gt;70 years: HR = 3.53, 95% CI 1.67 – 7.46), tumor size (vs T1, T3-4: HR = 2.79, 95% CI 1.45 – 5.37), positive lymph nodes (HR = 2.04, 95% CI: 1.10 – 3.77), use of radiotherapy (HR = 0.54, 95% CI 0.33 – 0.91) and endocrine therapy (HR = 0.31, 95% CI 0.12 – 0.77). On further analysis, the inferior RFS, DRFS and OS in older patients (&gt;70 years) were driven largely by non-breast cancer deaths rather than relapses. Use of endocrine therapy was also associated with superior DRFS (HR = 0.26, 95% CI 0.09 – 0.73) but not OS. In a subgroup analysis, use of chemotherapy was associated with improved DRFS (HR = 0.25, 95% CI 0.08 – 0.82) and OS (HR = 0.07, 95% CI 0.01 – 0.37) with a trend in RFS (HR = 0.41, 95% CI 0.14 – 1.24) for lymph node-positive PMBC; no differences in outcomes were observed for the lymph node-negative subgroup. Conclusions: Larger tumor size, lymph node positivity and ethnicity were significant factors for RFS in PMBC. Use of endocrine therapy was associated with superior RFS and DRFS, while chemotherapy was associated with better DRFS and OS for lymph-node positive PMBC.

Citation Format: Ryan Tan, Whee Sze Ong, Kyung-Hun Lee, Seri Park, Jabed Iqbal, Yeon Hee Park, Jeong-Eon Lee, Jong Han Yu, Ching-Hung Lin, Yen-Shen Lu, Makiko Ono, Takayuki Ueno, Yoichi Naito, Tatsuya Onishi, Geok hoon Lim, Su-Ming Tan, Han-Byoel Lee, Jiwon Koh, Han Suk Ryu, Wonshik Han, Veronique Kiak Mien Tan, Fuh-Yong Wong, Seock-Ah Im, Puay Hoon Tan, Yoon-Sim Yap. Prognostic factors in non-metastatic hormone receptor-positive HER2-negative mucinous breast cancer: an international multicentre cohort study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-36.

Abstract P6-02-14: Contralateral breast cancer risk in patients with or without BRCA mutation

Background: Patients who carry mutated BRCA1 or BRCA2 genes have a significantly increased risk of breast cancer and developing contralateral breast cancer (CBC). In this study, we aimed to investigate the acceptance rate of BRCA1/2 testing in Korean breast cancer patients and to determine the risk of CBC in Korean patients with BRCA 1/2 germline mutations. Methods: This study included 13,109 patients with first primary breast cancer who were treated at Seoul National University Hospital from January 2005 to December 2018. These patients were divided into high-risk for BRCA1/2 mutation group and low-risk group. High risk patients were defined as those who were eligible for BRCA testing per Korean National Health Insurance Service. The high-risk group was further classified into three groups; BRCA1/2 mutation carrier, BRCA 1/2 non carrier and BRCA/12 untested. Results: Among the 4,446 high-risk patients, 962 (21.7%) patients underwent BRCA1/2 testing. The testing rate varied among different indications (47.8% of patients with a family history, 23.3% of patients under 40 years of age, and 13.0% of patients with triple negative breast cancer). The risk of the CBC in BRCA mutation group was higher than other groups (p value &lt; 0.001). The 10-year cumulative risk of CBC was 11.0% BRCA1 mutation carrier and 7.4% for BRCA2 mutation carrier. In the BRCA1/2 non-carriers, the cumulative risk of CBC was 5.7%. Interestingly, the CBC risk for BRCA1/2 non-carriers significantly higher than BRCA1/2 untested group and the low-risk group (p &lt; 0.001). When compared to the BRCA1/2 untested group, the relative risk for CBC was 6.7-fold increase for the BRCA1/2 mutation carrier group (95% CI = 3.65-12.22, p &lt; 0.001), and 2.3-fold increase for the BRCA1/2 non-carriers group (95% CI = 1.44-3.83, p &lt; 0.001). The relative risk for CBC in high-risk group also depended on subtype of breast cancer and family history. Hormone receptor negative breast cancer patients had a 1.5-fold (95% CI = 1.02-2.31, p = 0.04) increased risk of CBC and patients with one or more 1st degree relative with breast cancer had 2.4-fold increased risk (95% CI = 1.55-3.67, p &lt; 0.001). Conclusion: About one out of five Korean breast cancer patients, who are eligible for the BRCA1/2 testing, undergo testing for BRCA1/2 germline mutations. We observed increased CBC risk not only for the BRCA1/2 mutation carriers but also for the BRCA1/2 non-carriers. At present, we are conducting multi-gene panel testing for the BRCA1/2 non-carriers to understand the mechanisms of the increased CBC risk.

Citation Format: Eunhye Kang, Ji-Jung Jung, Hyunsu Yeoh, Changjin Lim, Jang-il Kim, Jung Whan Chun, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Contralateral breast cancer risk in patients with or without BRCA mutation [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-02-14.

Role of Doppler US and elastography prior to biopsy to identify candidates for avoidance of surgery following neoadjuvant chemotherapy for breast cancer

PURPOSE

This study aimed to evaluate the role of Doppler ultrasound (US) and elastography to identify residual breast cancer for patients showing near complete response following chemotherapy on magnetic resonance imaging (MRI).

METHODS

Between September 2016 and January 2018, 40 breast cancer patients who showed near complete response (either tumor size ≤0.5 cm or lesion-to-background parenchymal signal enhancement ratio ≤1.6) on MRI following neoadjuvant chemotherapy were prospectively enrolled. After excluding seven women who did not undergo Doppler US and elastography, 33 women (median age, 49 years; ranges, 32 to 67 years) were analyzed. On the day of surgery, women underwent Doppler US and elastography for tumor bed prior to US-guided core needle biopsy. Histopathologic results of biopsy and surgery were evaluated. Negative predictive value (NPV) and false negative rate (FNR) of biopsy and the combined Doppler US and elastography were analyzed, respectively.

RESULTS

After surgery, nine women had residual cancers and 24 women had pathologic complete response. The NPV and FNR of biopsy were 92% (24 of 26) and 22% (2 of 9), respectively. The NPV and FNR of combined Doppler US and elastography were 100% (14 of 14) and 0% (0 of 9), respectively. All of nine women with residual cancers had positive vascularity or elasticity. Two women with false-negative biopsy results, having 0.3 cm or 2.5 cm ductal carcinoma in situ at surgery, showed positive vascularity or elasticity.

CONCLUSION

Tumor bed showing positive vascularity or elasticity indicates residual breast cancer for patients showing near complete response on MRI following chemotherapy.

Protocol for the postoperative radiotherapy in N1 breast cancer patients (PORT-N1) trial, a prospective multicenter, randomized, controlled, non-inferiority trial of patients receiving breast-conserving surgery or mastectomy

Background

Postoperative radiotherapy (PORT) could be useful for pN1 breast cancer patients who have undergone breast-conserving surgery (BCS) or mastectomy. However, the value of regional nodal irradiation (RNI) for BCS patients, and the indications for post-mastectomy radiotherapy (PMRT) for pN1 breast cancer mastectomy patients, have recently been challenged due to the absence of relevant trials in the era of modern systemic therapy. “PORT de-escalation” should be assessed in patients with pN1 breast cancer.

Methods

The PORT-N1 trial is a multicenter, randomized, phase 3 clinical trial for patients with pN1 breast cancer that compares the outcomes of control [whole-breast irradiation (WBI) and RNI/PMRT] and experimental (WBI alone/no PMRT) groups. PORT-N1 aims to demonstrate non-inferiority of the experimental group by comparing 7-year disease-free survival rates with the control group. Female breast cancer patients with pT1-3 N1 status after BCS or mastectomy are eligible. Participants will be randomly assigned to the two groups in a 1:1 ratio. Randomization will be stratified by surgery type (BCS vs. mastectomy) and histologic subtype (triple-negative vs. non-triple-negative). In patients who receive mastectomy, dissection of ≥5 nodes is required when there is one positive node, and axillary lymph node dissection when there are two or three positive nodes. Patients receiving neoadjuvant chemotherapy are not eligible. RNI includes a “high-tangent” or wider irradiation field. This study will aim to recruit 1106 patients.

Discussion

The PORT-N1 trial aims to verify that PORT de-escalation after BCS or mastectomy is safe for pN1 breast cancer patients in terms of oncologic outcomes and capable of reducing toxicity rates. This trial will provide information crucial for designing PORT de-escalation strategies for patients with pN1 breast cancer.

Trial registration

This trial was registered at ClinicalTrials.gov (NCT05440149) on June 30, 2022.

Retrospective Cohort Study on the Longterm Oncologic Outcomes of Sentinel Lymph Node Mapping Methods (Dye-Only Versus Dye and Radioisotope Mapping) in Early Breast Cancer: A Propensity Score-Matched Analysis

Purpose

In sentinel lymph node (SLN) biopsy (SLNB) during breast cancer surgery, SLN mapping using dye and isotope (DUAL) may have lower false-negative rates than the dye-only (DYE) method. However, the longterm outcomes of either method are unclear. We aimed to compare longterm oncological outcomes of DYE and DUAL for SLNB in early breast cancer.

Materials and Methods

This retrospective single-institution cohort study included 5,795 patients (DYE, 2,323; DUAL, 3,472) with clinically node-negative breast cancer who underwent SLNB and no neoadjuvant therapy. Indigo carmine was used for the dye method and Tc99m-antimony trisulfate for the isotope. To compare longterm outcomes, pathologic N0 patients were selected from both groups, and propensity score matching (PSM), considering age, pT stage, breast surgery, and adjuvant treatment, was performed (1,441 patients in each group).

Results

The median follow-up duration was 8.7 years. The median number of harvested sentinel nodes was 3.21 and 3.12 in the DYE and DUAL groups, respectively (p=0.112). The lymph node-positive rate was not significantly different between the two groups in subgroups of similar tumor sizes (p>0.05). Multivariate logistic regression revealed that the mapping method was not significantly associated with the lymph node-positive rate (p=0.758). After PSM, the 5-year axillary recurrence rate (DYE 0.8% vs. DUAL 0.6%; p=0.096), and 5-year disease-free survival (DYE 93.9% vs. DUAL 93.7%; p=0.402) were similar between the two groups.

Conclusion

Dye alone for SLNB was not inferior to dual mapping regarding longterm oncological outcomes in early breast cancer.

Targeting CLK4 inhibits the metastasis and progression of breast cancer by inactivating TGF-β pathway

Triple-negative breast cancer (TNBC) represents the most aggressive subtype of breast cancer that is highly resistant to current therapeutic options. According to the public databases Oncomine and KM plotter, the CLK4 expression is correlated with poor patient survival in TNBC, especially in mesenchymal-like TNBC (MES-TNBC) that has strong metastatic potential. Therefore, we investigated the potential involvement of CLK4 in the metastasis and progression of MES-TNBC. In the MES-TNBC cell lines, the CLK4 expression was elevated. Notably, the RNAi-mediated silencing of CLK4 reduced the expression of multiple epithelial-mesenchymal transition (EMT) genes that mediate metastasis. Furthermore, CLK4 silencing reduced both the invasive behaviors of the cultured cells and tumor metastasis in the mouse xenograft model. It is also noteworthy that CLK4 silencing repressed the invasive and cancer stem cell (CSC) properties that are induced by the TGF-β signaling. Importantly, the pharmacological inhibition of CLK4 potently repressed the invasion and proliferation of MES-TNBC cell lines and patient-derived cells, which demonstrates its clinical applicability. Collectively, our results suggest that CLK4 plays a crucial role in invasion and proliferation of MES-TNBC, especially in the processes that are induced by TGF-β. Also, this study characterizes CLK4 as a novel therapeutic target in breast cancer.

Abstract 6373: Spheroid culture of ER+ breast cancer patient-derived tumor cells enriches cancer stem-likecells with EpCAM-/CD49f+and high ALDH activity and poor prognostic gene signatures

Background: Cancer stem-like cells (CSCs) represent a critical subset of the tumor population, which contributes to tumor recurrence, metastasis and therapy resistance. Spheroid culture is unique method for CSC enrichment. Patient-derived breast cancer cells (PDBCCs) has provided an invaluable tool in preclinical and translational research. The objective of this study is to characterize the immunophenotype and transcriptomes of PDBCCs grown in the adherent monolayer and spheroid condition.

Methods: PDBCCs were harvested from residual tumor of fresh surgical specimens of patients with ER-positive subtype (8 cases). The adherent monolayer(M) and spheroid(S) culture of PDBCCs were applied on collagen I-coated plate and an ultra-low attachment polymer-X coated plate. Flow cytometry and immunocytochemistry was performed by using fluorescent-dye conjugated antibodies for EpCAM, CD49f, CD24, CD44, and cytokeratin. ALDEFLUOR® assay to detect ALDH activity was used. Total RNA-sequencing was applied to investigate differentially expressed genes (DEGs), followed by GO and KEGG pathway enrichment analysis. Real-time RT-PCR was performed to evaluate BCSC-related RNA levels. The Kaplan-Meier Plotter online database was used to evaluate the prognostic value of DEGs (2-fold change, p&lt;0.05).

Results: Under adherent monolayer condition, more than 95% of PDBCCs passaged for up to 5 passages on collagen I-coated plate sustained EpCAM+/cytokeratin+/fibroblast marker_ phenotype. On polymer-X coated plates, PDBCCs formed compact multicellular spheroids with a diameter of less than 300 µm. As compared with monolayer, CSCs with EpCAM-/CD49f+ phenotype (M vs S; 0.16±0.06 vs 2.34±0.65, p=0.015) and high ALDH activity (M vs S; 0.73±0.43 vs 7.05±1.48, p=0.038) were significantly increased by spheroid culture. In whole-transcriptome analysis (3 cases) between spheroid and monolayer, a total of 561 DEGs were identified, including 290 upregulated and 271 downregulated DEGs (2- fold change, p&lt;0.05) in spheroid. The upregulated and downregulated DEGs in spheroids were enriched in 8 and 19 KEGG pathways, respectively. In recurrence-free survival analysis based on the Kaplan-Meier Plotter database of the genes corresponding to Oncotype Dx, Mammaprint, and Prosigna and top 30 ranked DEGs identified in spheroids, 15 upregulated and 14 downregulated DEGs were associated with poor prognosis of breast cancer patients.

Conclusion: Spheroid culture of PDBCCs with ER+ subtype enriches CSCs and poor prognostic gene signatures. Future studies to explore the specific molecular mechanisms underlying these observations may provide new molecular targets for the development of therapies for targeting CSCs in breast cancer patient.

Citation Format: Hoe Suk Kim, Seungyeon Ryu, So-Hyun Yoon, Sangeun Lee, Junhyuk Song, Yoonjung Choi, Moonjou Baek, Han-Byoel Lee, Sangyong Jon, Daeyoup Lee, Wonshik Han. Spheroid culture of ER+ breast cancer patient-derived tumor cells enriches cancer stem-likecells with EpCAM-/CD49f+and high ALDH activity and poor prognostic gene signatures [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6373.

Abstract 6039: Application of triple negative breast cancer patient-derived organoid and xenograft model for drug screening

Background: Breast cancer Patient Derived Organoids (PDOs) and patient-derived xenografts (PDXs) which recapitulate the tumor heterogeneity and molecular signatures of original tumor tissue, are useful tools to enable greater precision of both approved and experimental medicines through personalized therapeutic approaches. We focus on use of ex vivo PDOs, PDX-derived organoids (PDXOs), and vivo PDXs models for drug testing and personalized therapy. In this study, we investigated the oncogenic role and therapeutic potency of targeting WEE1 in breast cancer.

Methods: Fresh surgical specimens of primary TNBC breast tumor (N=3) were used for PDOs. PDOs and PDX-derived organoids (PDXOs) were cultured in previously reported media compositions based on ECM hydrogel. PODs and PDXOs were subjected to drug screening for 22 anticancer drugs including chemoreagents and targeted drugs in the 3D HTS system. Drug sensitivity was tested in triplicate in different concentration ranges for 7 days. The IC50 for each drug was calculated by a sigmoidal dose-response curve, using the GraphPad Prism 9 program. For drug screening in PDXs models, PDOs were injected into the fourth mammary fat pads of NOD.Cg-Prkdcscid Il2rgtm1wjl/SzJ mice. WEE1 inhibitor (AZD1775) was administered by oral gavage (AZD1775, 30 mg/kg) for 3 weeks. Immunostaining of ER, PR, Her2, CK5 and Ki67 was performed in PODs, PODXs and PDX tumor tissues.

Results: All PDOs, PDXs, and PDXOs were ER-, PR- and HER2- negative. PDOs and PDXOs (172T, 185T, 207T) showed differential response to 22 anticancer drugs. In PDOs and PDXOs models, 172T and 207T PDOs and PDXOs are highly sensitive to AZD1775, but 185T PDOs and PDXOs less sensitive or never respond to treatment with AZD1775 (10 µM). In PDX models, treatment with AZ1775 decreased tumor growth (P&lt;0.0079) as well as distance metastasis in 207T-PDX mice, whereas in 172T- and 185T-PDX mice, the tumor growth and metastasis were not reduced compared with the vehicle group.

Conclusion: Consequently, PDOs, PDXOs and PDXs recapitulated immunohistological signatures of original tumor tissues. The results of WEE1 inhibitor response between PDOs, PDXOs and PDXs were consistent. This study may provide a preclinical tool to screen drug responses to standard-of-care and newly identified drugs.

Citation Format: Seungyeon Ryu, Hoe Suk Kim, Jung Eun KIM, So-Hyun Yoon, Sangeun Lee, Moonjou Baek, Han-Byoel Lee, Dong Woo Lee, Bosung Ku, Wonshik Han. Application of triple negative breast cancer patient-derived organoid and xenograft model for drug screening [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6039.

Abstract 2369: The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression

Basal-like breast cancer (BLBC) is an aggressive malignancy with a poor prognosis. Persistent activation of NRF2 and STAT3 is considered to stimulate the aggressive behavior of BLBC. An online database, NRF2-ome predicted the possibility of interplay between NRF2 and STAT3 based on domain motif interactions. However, cooperation between NRF2 and STAT3 and its implications for breast cancer progression remain elusive. Immunoprecipitation and in situ proximity analyses revealed that NRF2 and STAT3 directly interact with each other, which predominantly occurred in the nucleus of human breast cancer cells. After confirming the physical interaction between STAT3 and NRF2, we examined whether this could influence the expression or stability of each transcription factor. While silencing of NRF2 failed to alter the STAT3 expression, STAT3 knockdown facilitated degradation of NRF2. Of note, silencing of STAT3 did not affect the mRNA expression of NRF2, suggesting that STAT3-induced accumulation of NRF2 is attributable to stabilization of the preexisting protein. As the NRF2-STAT3 complex was found to accumulate predominantly in the nucleus, we speculate that NRF2 could bind to a functionally active phosphorylated form of STAT3 (P-STAT3Y705). The substitution of Y705 of STAT3 with the non-phosphorylatable phenylalanine (STAT3Y705F) abolished interaction with NRF2. Notably, the dimeric form, but not a monomeric form, of STAT3 interacts directly with the Neh1 and Neh3 domains of NRF2. Next, we investigated the functional significance of STAT3- NRF2 interaction in BLBC growth in vivo. STAT3 knockdown significantly reduced expression of NRF2 in the xenograft tumor tissues derived from MDA-MB-231 human breast cancer cells. Tumors derived from cells transfected with the non-specific control siRNA showed a pronounced interaction between STAT3 and NRF2, whereas such interaction was abolished in the STAT3-silenced xenograft tumor. Analysis of the TCGA multi-omics data showed that high levels of STAT3 and NRF2 mRNA transcripts were correlated with elevated expression of P-STAT3Y705 and NRF2 target proteins in breast cancer patients. Next generation RNA sequencing analysis identified the gene encoding interleukin-23A (IL-23A) upregulated by concurrent binding of STAT3 and NRF2 to its promoter. IL-23A is markedly overexpressed in BLBC, compared with other subtypes of breast cancer. Combined silencing of NRF2 and STAT3 inhibited BLBC growth to a greater extent than that achieved with single siRNA transfection. IL-23A depletion by siRNA also showed the similar phenotypic changes to those caused by double knockdown of both transcription factors. In conclusion, these findings suggest that the STAT3-NRF2 interaction accelerates BLBC growth and progression by augmenting IL-23A expression, which underscores the importance of subtype-specific molecular pathways in human breast cancer.

Citation Format: Su-Jung Kim, Soma Saeidi, Nam-Chul Cho, Seung Hyeon Kim, Han-Byoel Lee, Wonshik Han, Hye-Kyung Na, Young-Joon Surh. The NRF2 and dimeric STAT3 complex coordinately regulates IL-23 expression: Implications for breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2369.

Abstract 6241: Macc1 regulates breast cancer progression and metastasis via remodeling tumor immune microenvironment

Although the established cancer cell lines exhibit less degrees of intratumoral heterogeneity when compared to human solid tumors, studies have suggested that, even within the same cancer cell line, substantial degree of heterogeneity may exist. In this study, we have performed single cell cloning experiment using 4T1 mouse mammary carcinoma cell line and compared the phenotypes of different clones. When compared to the parental 4T1 cell line, one clone (C12) showed markedly different phenotype by exhibiting less aggressive features in vitro and significantly slower tumor growth and metastasis in vivo. The tumor tissue of the C12 showed significant alteration in immune microenvironment as higher number of recruited immune cells including T and B cells. RNA sequencing of the C12 clones and parental 4T1 cells identified Macc1 as a significantly up-regulated gene in parental 4T1 cells. Metastasis-associated colon cancer 1 (MACC1) has been associated with poor prognosis and the promotion of metastasis within several types of cancer, especially colon cancer. The gene encoding the hepatocyte growth factor (HGF) receptor, MET, is a transcriptional target of MACC1. Next, we established Macc1-silenced 4T1 cells using the parental 4T1 cells and observed that Macc1-silencing resulted in a similar phenotype seen in the C12 clone; decreased cell proliferation and migration in vitro and slow tumor growth and metastasis in vivo. To mimic the metastasis in vitro, intravasation was determined as which tumor cells were co-cultured with HUVEC, human umbilical vein endothelial cells. We discovered tumor cell penetration into HUVEC cells was blocked in Macc1-silencing 4T1 group. According to CD45, CD3, and CD19 immunohistochemistry, we also defined immune cells, especially T and B cells, were highly infiltrated in Macc1-silencing tumor like as C12 clone tumor. These results were also reconstructed in EMT6, another TNBC mouse cell line model. In this study, we show that MACC1 can regulate tumor progression and metastasis by remodeling of immune microenvironment.

Citation Format: Hye-Youn Son, Woo Hang Heo, Song Bin Li, Mingji Quan, Yu Jeong Her, Kyu-Jin Lee, Ju Hee Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Macc1 regulates breast cancer progression and metastasis via remodeling tumor immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 6241.

Effect of neoadjuvant versus adjuvant chemotherapy on ipsilateral breast tumor recurrence after breast-conserving surgery and whole-breast irradiation

604

Background: Early Breast Cancer Trialists’ Collaborative Group conducted a large meta-analysis and reported that patients who underwent neoadjuvant chemotherapy (NAC) had higher ipsilateral breast tumor recurrence (IBTR) rate than those with adjuvant chemotherapy. However, since the study was conducted with patients treated two decades ago, the results could not reflect the advance in treatments and IBTR rate was much higher than in recent studies, Thus, we investigated the association between chemotherapy settings and IBTR rates in breast cancer patients. Methods: We retrospectively reviewed the data of 5,307 patients who underwent breast conserving surgery followed by whole breast irradiation between January 2004 and December 2018 in a single institution. Patients who underwent mastectomy or omitted chemotherapy were excluded. Results: The 1,473 patients who underwent NAC showed significantly higher IBTR rate than the 3,564 patients who underwent adjuvant chemotherapy (10-year risk: 4.5% vs. 4.0%; log-rank p=0.045, hazard ratio 1.42 [95%CI,1.01-1.99]). The difference was more evident for patients with hormone receptor (HR) positive and human epidermal growth factor receptor-2 (HER2) negative tumor (unadjusted p=0.001, hazard ratio 2.27 [95%CI,1.37-3.74; adjusted p=0.002, hazard ratio 2.80 [95%CI,1.45-5.42]], and the statistical significance was still remained after 1:1 propensity score matching (p=0.026). In contrast, patients with other subtypes did not show significant differences between two groups. Conclusions: Patients who underwent NAC for HR+/HER2- tumors carry increased risk of IBTR than those who underwent adjuvant chemotherapy. Our observation supports the need for considering tumor subtypes in initial treatment. In addition, more intensive surveillance would be needed for patients with HR+/HER2- tumors after NAC.

A randomized, prospective, multicenter trial of 3D printing, a patient-specific surgical guide for breast-conserving surgery after neoadjuvant chemotherapy: Comparative evaluation according to the presence or absence of surgical guide

576

Background: To obtain a clear resection margin during breast-conserving surgery (BCS) after neoadjuvant chemotherapy (NCT), accurate targeting of the location and assessment extent of the tumor are essential. However, conventional targeting methods such as USG/MMG guided hook wire insertion have disadvantages in that they could only localize the tumor, not reflecting its extent. To assess this problem, we developed an MRI-based 3D printed breast surgical guide (3DP-BSG) and conducted a multicenter randomized clinical study to prove its clinical effectiveness. Methods: In this multicenter, randomized (1:1), controlled trial (KCT0004469), we assigned 566 patients who underwent NCT and planned to undergo BCS, to use customized 3DP-BSG for lumpectomy, or not to use 3DP-BSG for lumpectomy. We assumed that 3DP-BSG group achieve non-inferior outcomes compared with control group with conventional targeting method. The primary endpoint was the margin positivity of the first resected margin. Under the assumption that the proportion of margin positivity would be 23% in both groups, a total of 438 patients were calculated to have 80% power to establish non-inferiority with a margin of 10% at a one-sided significance level of 0.05. Efficacy was assessed in the intention-to-treat (ITT) population. Results: Between 2019 and 2021, 282 (49.8%) patients were assigned to 3DP-BSG group, and 284 (50.2%) patients were assigned to control group with conventional targeting method. The median age was 51 years. In the ITT analysis, first resected margin was positivity in 5 (2.1%) of 235 patients in 3DP-BSG group and 7 (2.9%) of 244 patients in control group (difference -1.15 [95% CI -3.58 to -1.28], pnon-inferiority <.0001). In the analysis of population excluding patients assessed as complete response (CR), first resected margin was positivity in 5 (3.40%) of 147 patients in 3DP-BSG group and 7 (4.8%) of 145 patients in control group (difference -1.43 [95% CI -5.25 to -2.40], pnon-inferiority <.0001). Most of the cases, marked areas with 3DP-BSG were partially different from those with conventional targeting method, and there were some cases where completely different areas were marked. In most of these cases, pathological CR made it difficult to compare the accuracy of the targeting methods, but in one case, a malignant tumor was diagnosed only in the 3DP-BSG targeting region. Even lesions that have been incorrectly targeted by conventional methods can be properly removed using 3DP-BSG, which is believed to be helpful in surgery. Conclusions: Lumpectomy using 3DP-BSG showed non-inferiority compared to the conventional targeting group, and the surgeon's satisfaction was higher by quantitatively presenting the extent of initial tumor. Clinical trial information: KCT0004469.

Spatial epitranscriptomics reveals A-to-I editome specific to cancer stem cell microniches

Epitranscriptomic features, such as single-base RNA editing, are sources of transcript diversity in cancer, but little is understood in terms of their spatial context in the tumour microenvironment. Here, we introduce spatial-histopathological examination-linked epitranscriptomics converged to transcriptomics with sequencing (Select-seq), which isolates regions of interest from immunofluorescence-stained tissue and obtains transcriptomic and epitranscriptomic data. With Select-seq, we analyse the cancer stem cell-like microniches in relation to the tumour microenvironment of triple-negative breast cancer patients. We identify alternative splice variants, perform complementarity-determining region analysis of infiltrating T cells and B cells, and assess adenosine-to-inosine base editing in tumour tissue sections. Especially, in triple-negative breast cancer microniches, adenosine-to-inosine editome specific to different microniche groups is identified.

The spatial context of epitranscriptomic features in the tumour microenvironment remains poorly understood. Here, a method for transcriptomic and epitranscriptomic analysis of immunofluorescence-stained tissue, Select-seq, is applied to stem cell-like microniches in triple negative breast cancer.

HER2 expression, copy number variation and survival outcomes in HER2-low non-metastatic breast cancer: an international multicentre cohort study and TCGA-METABRIC analysis

BACKGROUND

HER2-low breast cancer (BC) is currently an area of active interest. This study evaluated the impact of low expression of HER2 on survival outcomes in HER2-negative non-metastatic breast cancer (BC).

METHODS

Patients with HER2-negative non-metastatic BC from 6 centres within the Asian Breast Cancer Cooperative Group (ABCCG) (n = 28,280) were analysed. HER2-low was defined as immunohistochemistry (IHC) 1+ or 2+ and in situ hybridization non-amplified (ISH-) and HER2-zero as IHC 0. Relapse-free survival (RFS) and overall survival (OS) by hormone receptor status and HER2 IHC 0, 1+ and 2+ ISH- status were the main outcomes. A combined TCGA-BRCA and METABRIC cohort (n = 1967) was also analysed to explore the association between HER2 expression, ERBB2 copy number variation (CNV) status and RFS.

RESULTS

ABCCG cohort median follow-up was 6.6 years; there were 12,260 (43.4%) HER2-low BC and 16,020 (56.6%) HER2-zero BC. The outcomes were better in HER2-low BC than in HER2-zero BC (RFS: centre-adjusted hazard ratio (HR) 0.88, 95% CI 0.82-0.93, P < 0.001; OS: centre-adjusted HR 0.82, 95% CI 0.76-0.89, P < 0.001). On multivariable analysis, HER2-low status was prognostic (RFS: HR 0.90, 95% CI 0.85-0.96, P = 0.002; OS: HR 0.86, 95% CI 0.79-0.93, P < 0.001). These differences remained significant in hormone receptor-positive tumours and for OS in hormone receptor-negative tumours. Superior outcomes were observed for HER2 IHC1+ BC versus HER2-zero BC (RFS: HR 0.89, 95% CI 0.83-0.96, P = 0.001; OS: HR 0.85, 95% CI 0.78-0.93, P = 0.001). No significant differences were seen between HER2 IHC2+ ISH- and HER2-zero BCs. In the TCGA-BRCA and METABRIC cohorts, ERBB2 CNV status was an independent RFS prognostic factor (neutral versus non-neutral HR 0.71, 95% CI 0.59-0.86, P < 0.001); no differences in RFS by ERBB2 mRNA expression levels were found.

CONCLUSIONS

HER2-low BC had a superior prognosis compared to HER2-zero BC in the non-metastatic setting, though absolute differences were modest and driven by HER2 IHC 1+ BC. ERBB2 CNV merits further investigation in HER2-negative BC.

Polygenic risk scores for prediction of breast cancer risk in Asian populations

PURPOSE

Non-European populations are under-represented in genetics studies, hindering clinical implementation of breast cancer polygenic risk scores (PRSs). We aimed to develop PRSs using the largest available studies of Asian ancestry and to assess the transferability of PRS across ethnic subgroups.

METHODS

The development data set comprised 138,309 women from 17 case-control studies. PRSs were generated using a clumping and thresholding method, lasso penalized regression, an Empirical Bayes approach, a Bayesian polygenic prediction approach, or linear combinations of multiple PRSs. These PRSs were evaluated in 89,898 women from 3 prospective studies (1592 incident cases).

RESULTS

The best performing PRS (genome-wide set of single-nucleotide variations [formerly single-nucleotide polymorphism]) had a hazard ratio per unit SD of 1.62 (95% CI = 1.46-1.80) and an area under the receiver operating curve of 0.635 (95% CI = 0.622-0.649). Combined Asian and European PRSs (333 single-nucleotide variations) had a hazard ratio per SD of 1.53 (95% CI = 1.37-1.71) and an area under the receiver operating curve of 0.621 (95% CI = 0.608-0.635). The distribution of the latter PRS was different across ethnic subgroups, confirming the importance of population-specific calibration for valid estimation of breast cancer risk.

CONCLUSION

PRSs developed in this study, from association data from multiple ancestries, can enhance risk stratification for women of Asian ancestry.

Abstract P3-18-12: Achieving negative margin after repeated attempts for lumpectomy does not nullify the risk of ipsilateral breast tumor recurrences

Introduction: Currently, the widely accepted principle in managing lumpectomy margins in early breast cancer patients is to avoid the presence of tumor cell at the margin. The presence of tumor cells on lumpectomy margin can represent two different aspects of local control in breast cancer. One aspect is related to the potential technical failure that may lead to an incomplete resection of the tumor. The other aspect of positive margin is associated with a biologic nature of the tumor. For example, some tumors show features of extensive intraductal component which often result in positive lumpectomy margins and may lead to increased risk of local recurrence after breast conservation surgery. Therefore, the two-fold increase of IBTR risk with positive margin would be the reflection of the combined effect of both technical failure and the biologic features.In this study, we aimed to address this issue by investigating the IBTR rates of patients in whom negative margins were achieved by initial lumpectomy or by re-excision. Our assumption was if the IBTR rates of the two groups are identical, then the two-fold increase of IBTR risk is mostly caused by the technical incomplete resection and therefore the measures to achieve negative margins would be justified. Methods: We retrospectively reviewed the data of 5,633 patients who underwent breast conservation surgery and whole breast irradiation for invasive breast cancer between January 2004 and December 2018 from Seoul National University Hospital. During the period, a total of 828 patients had positive lumpectomy margin after their initial surgery. Among them, thirty-five patients who did not undergo re-operation were excluded due to the small sample size. Results: The median age of the studied patients was 49 years old (19-92), and nearly two third of the patients had T1 tumors (64.3%). 4,293 patients (76.7%) were node negative and 4,332 patients (77.4%) had hormone receptor positive tumors. During the median follow-up period of 76.6 ( ± 44.6) months, a total of 121 patients (2.2%) experienced IBTR. Patients who underwent re-excision to achieve negative margins experienced significantly higher rate of IBTR compared to patients in whom the margins were clear at the first lumpectomy (p=0.031, HR: 1.61; 95% C.I., 1.04-2.48). The survival curves began to separate around 4-5 years after surgery (98.5% vs 98.0% at 5 year and 97.4% vs 94.7% at 10 years of follow-up). The survival difference was more clearly observed for younger patients (p=0.033, HR 1.72; 95% C.I., 1.04-2.85 for age less than 50). When the patients were divided according to their hormone receptor and HER2 amplification status, we observed significant difference in HR+/HER2- and HR-/HER2- subtypes while the HER2-amplified tumors showed no significant differences.By using Cox regression analysis, we adjusted for other significant predictors of IBTR such as age, histologic grade, lymphovascular invasion, hormone receptor status, HER2 amplification status, and Ki-67 levels. The results of the Cox regression analysis showed that re-excision to achieve negative margin is significantly associated with the risk of IBTR after adjusting for these variables (p=0.023, HR: 1.72; 95% C.I., 1.08-2.74). Conclusion: Patients who underwent re-excision after lumpectomy for initial positive margin carry increased risk of developing IBTR even they achieve final negative margin when compared to patients with initially negative lumpectomy margin. Our observation indicate that a substantial proportion of the increasing risk of IBTR associated with positive lumpectomy margin can be attributed to the biologic characteristics of the tumor rather than technical incomplete resection.

Citation Format: Jong Ho Cheun, Hong-Kyu Kim, Han-Byoel Lee, Wonshik Han, Hyeong-Gon Moon. Achieving negative margin after repeated attempts for lumpectomy does not nullify the risk of ipsilateral breast tumor recurrences [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-12.

Abstract P3-18-14: Assessment of quality of life and objective cosmetic outcome of breast conserving surgery with or without latissimus dorsi mini-flap in breast cancer

Introduction : Latissimus dorsi mini-flap (LDMF) with breast conserving surgery (BCS) was introduced as a useful volume replacement technique when the tumor is located in upper or outer portion of breast and the tumor size is large requiring extensive excision of breast tissue. However few studies have assessed quality of life (QoL) and objective cosmetic outcome of LDMF in breast cancer surgery. We tried to evaluate those in patients who underwent BCS with or without LDMF. Methods : This study was a prospective, single-center cohort study of patients who underwent LDMF and BCS between 2011 and 2018. As a control, patients who underwent BCS without any volume replacement and the tumor size equal to or greater than 2.5cm on the upper or upper outer of the breast on preoperative imaging. Breast Q questionnaire and body photo were taken at least 1 year after surgery. Two breast surgeons and one plastic surgeon who did not performed LDMF assessed the cosmetic outcome of the patients with photo. Results : 62 patients were in the BCS with LDMF group and 58 patients were in BCS-only group. Pathologic tumor size was significantly larger in LDMF group than BCS-only group (LDMF 3.89cm vs BCS-only 2.92cm, p= 0.001 ). Psychosocial well-being (P= 0.024), physical well-being (P= 0.000), and satisfaction with surgeon (p= 0.006) were significantly better in the BCS-only group than in the LDMF group respectively. But, there were no significant difference in neither sexual well-being (p= 0.286) nor satisfaction for breast (p=0.278) between BCS and LDMF group. In the physicians assessment, there was no significant difference in the cosmetic outcome score between the two groups (LDMF 2.56/4 vs. BCS-only 2.58/4, p= 0.884). Conclusion : In conclusion, physician assessed cosmetic outcome of LDMF was equivalent to that of BCS without LDMF although the tumor size was significantly larger in patients with LDMF. Some inferiority of QoL might be due to postoperative pain or arm movement discomfort. We are planning to evaluate objective cosmetic results using BCCT.core software.

Citation Format: Jang-il Kim, Yireh Han, Changjin Lim, Jong-Ho Cheun, Ji Gwang Jung, Hong Kyu Kim, Han-Byoel Lee, Hyeong-Gon Moon, Wonshik Han. Assessment of quality of life and objective cosmetic outcome of breast conserving surgery with or without latissimus dorsi mini-flap in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-14.

Abstract P5-02-02: Development of automated 3D high-throughput drug screening platform for patient-derived breast cancer organoids

Background Patient-derived cancer organoids, which reliably conserve original features of tumors, are emerging as an excellent model for predicting therapy response and drug screening. Developing optimized 3D high-throughput drug screening platform to establish patient-derived cancer organoids and simultaneously perform drug screening is essential for personalized medicine. Methods We established normal breast organoids (n=4) and breast cancer organoids (n=10) from 20 fresh surgical specimen (normal 7, tumor 13 cases). A number (500-2000) of normal and cancer cells were automatically dispensed with the ASFA™ Spotter ST and organoids were generated by hydrogel hanging-drop culture on Cellvitro™ Pillar platform (Medical & Bio Decision, South Korea). Organoids were subjected to drug screening for 17 anticancer drugs including chemoreagents and targeted drugs in the 3D HTS system. Drug sensitivity was tested in triplicate in different concentration ranges for 5 days. Drug cytotoxic effect was assessed by calcein AM staining. Acquisition and analysis of high-content 3D organoid images were peformed using ASFA™ SCANNER (Medical & Bio Decision, South Korea). The IC50 for each drug was calculated by a sigmoidal dose-response curve, using the GraphPad Prism 9 program. We analyzed a drug response index (DRI) using a prediction alogorithm to evalute drug sensitivity (DRI&lt;-0.5) and resistance (DRI&gt;0.5). Results We summarized the DRI value of patient-derived breast organoids of 7 drugs (Table 1). 6 tumor organoids (2T, 6T, 8T, 10T, 13T, 15T) showed high sensitivity to Docetaxel, Doxorubicin, Paclitaxel, and Gemcitabin while 4 tumor organoids (1T, 9T, 14T, 16T) were less sensitive and resistant. 2 tumor organoids (10T, 16T) were sensitive to Tamoxifen and 2 tumor organoids (6T, 8T) show high sensitivity to palbociclib and erlotinib. Normal organoids show less sensitivity and resistance to chemotherapeutic drugs.

Drug response index &gt;0.5 : resistancy top 30%, Drug response index &lt;-0.5 : sensitivity top 30%. Conclusions Herein, we developed the hydrogel hanging-drop culture on Cellvitro™ Pillar platform for easily and rapidly high-throughput drug screening in patient-derived organoids using a small number of cells by testing clinically actionable drugs at different concentrations. There were different drug response indeces for each individual organoids to chemoreagents and targeted drugs. We anticipate that 3D high-throughput drug screenings platform based on patient-derived organoids can provide the information to predict drug response and allow for finding more appropriate therapy for individual patients.

Table 1.DRI values of patient-derived breast organoids of 7 drugs.Patient No.Tumor/NormalDocetaxelPaclitaxelDoxorubicinTamoxifenGemcitabinePalbociclibErlotinib1TTumor1.051.261.080.060.590.26-2TTumor-0.64-0.72-0.60-0.08-0.79--6TTumor-0.98-0.99-2.330.00-1.44-2.31-1.608TTumor-0.32-0.50-0.250.64-1.07-1.47-0.669TTumor1.050.980.610.870.430.610.4410TTumor-0.84-0.77-0.78-1.680.790.610.0913TTumor-0.87-0.430.560.70-0.510.611.1714TTumor0.861.261.180.481.81--15TTumor-1.59-1.45-1.41--0.71-0.13-16TTumor1.051.261.18-1.70-1.22-2NNormal1.051.260.650.741.810.610.7810NNormal1.05-0.910.810.870.880.610.084NNormal-0.31-0.25-0.530.25-0.190.61-1.575NNormal1.051.130.380.75-0.630.610.10

Citation Format: Jungeun Kim, Hoe Suk Kim, Ga Yeon Kim, Kyung hyeun Park, Seung yeon Ryu, Sangeun Lee, Dong Woo Lee, Bosung Ku, Han-Byoel Lee, Wonshik Han. Development of automated 3D high-throughput drug screening platform for patient-derived breast cancer organoids [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-02-02.