Clinical and Biomarker Findings of Neoadjuvant Pembrolizumab and Carboplatin Plus Docetaxel in Triple-Negative Breast Cancer: NeoPACT Phase 2 Clinical Trial

Importance

Addition of pembrolizumab to anthracycline-based chemotherapy improves pathologic complete response (pCR) and event-free survival (EFS) in triple-negative breast cancer (TNBC). The efficacy of anthracycline-free chemoimmunotherapy in TNBC has not been assessed.

Objective

To assess the efficacy of the anthracycline-free neoadjuvant regimen of carboplatin and docetaxel plus pembrolizumab in TNBC.

Design, Setting, and Participants

This was an open-label phase 2 clinical trial including a single group of patients with stage I to III TNBC enrolled at 2 sites who received neoadjuvant carboplatin and docetaxel plus pembrolizumab every 21 days for 6 cycles. Participants were enrolled from 2018 to 2022.

Intervention or Exposure

Carboplatin (with an area under the free carboplatin plasma concentration vs time curve of 6) and docetaxel (75 mg/m2) plus pembrolizumab (200 mg) every 21 days for 6 cycles. Myeloid growth factor support was administered with all cycles.

Main Outcomes and Measures

Primary end point was pathologic complete response (pCR) defined as no evidence of invasive tumor in breast and axilla. The secondary end points were residual cancer burden, EFS, toxicity, and immune biomarkers. RNA isolated from pretreatment tumor tissue was subjected to next-generation sequencing. Specimens were classified as positive or negative for the 44-gene DNA damage immune response (DDIR) signature and for the 27-gene tumor immune microenvironment (TIM; DetermaIO) signature using predefined cutoffs. Stromal tumor-infiltrating lymphocytes (sTILs) were evaluated using standard criteria. Programmed cell death-ligand 1 (PD-L1) testing was performed using a standard immunohistochemical assay.

Results

Among the eligible study population of 115 female patients (median [range] age, 50 [27-70] years) who enrolled from September 2018 to January 2022, 39% had node-positive disease. pCR and residual cancer burden 0 + 1 rates were 58% (95% CI, 48%-67%) and 69% (95% CI, 60%-78%), respectively. Grade 3 or higher immune-mediated adverse events were observed in 3.5% of patients. sTILs, PD-L1, DDIR, and TIM were each predictive of pCR in multivariable analyses. The areas under curve for pCR were 0.719, 0.740, 0.699, and 0.715 for sTILs, PD-L1, DDIR, and TIM, respectively. Estimated 3-year EFS was 86% in all patients; 98% in pCR group and 68% in no-pCR group.

Conclusions and Relevance

The findings of the phase 2 clinical trial indicate that neoadjuvant carboplatin and docetaxel plus pembrolizumab shows encouraging pCR and 3-year EFS. The regimen was well tolerated, and immune enrichment as identified by various biomarkers was independently predictive of pCR. These results provide data on an alternative anthracycline-free chemoimmunotherapy regimen for patients who are not eligible for anthracycline-based regimens and support further evaluation of this regimen as a chemotherapy de-escalation strategy in randomized studies for TNBC.

Trial Registration

ClinicalTrials.gov Identifier: NCT03639948.

ctDNA and residual cancer burden are prognostic in triple-negative breast cancer patients with residual disease

Triple-negative breast cancer (TNBC) patients with residual disease (RD) after neoadjuvant systemic therapy (NAST) are at high risk for recurrence. Biomarkers to risk-stratify patients with RD could help individualize adjuvant therapy and inform future adjuvant therapy trials. We aim to investigate the impact of circulating tumor DNA (ctDNA) status and residual cancer burden (RCB) class on outcomes in TNBC patients with RD. We analyze end-of-treatment ctDNA status in 80 TNBC patients with residual disease who are enrolled in a prospective multisite registry. Among 80 patients, 33% are ctDNA positive (ctDNA+) and RCB class distribution is RCB-I = 26%, RCB-II = 49%, RCB-III = 18% and 7% unknown. ctDNA status is associated with RCB status, with 14%, 31%, and 57% of patients within RCB-I, -II, and -III classes demonstrating ctDNA+ status (P = 0.028). ctDNA+ status is associated with inferior 3-year EFS (48% vs. 82%, P < 0.001) and OS (50% vs. 86%, P = 0.002). ctDNA+ status predicts inferior 3-year EFS among RCB-II patients (65% vs. 87%, P = 0.044) and shows a trend for inferior EFS among RCB-III patients (13% vs. 40%, P = 0.081). On multivariate analysis accounting for T stage and nodal status, RCB class and ctDNA status independently predict EFS (HR = 5.16, P = 0.016 for RCB class; HR = 3.71, P = 0.020 for ctDNA status). End-of-treatment ctDNA is detectable in one-third of TNBC patients with residual disease after NAST. ctDNA status and RCB are independently prognostic in this setting.

Impact of low versus negative estrogen/progesterone receptor status on clinico-pathologic characteristics and survival outcomes in HER2-negative breast cancer

Triple-negative breast cancer (TNBC) is classically defined by estrogen receptor (ER) and progesterone receptor (PR) immunohistochemistry expression <1% and absence of HER2 amplification/overexpression. HER2-negative breast cancer with low ER/PR expression (1–10%) has a gene expression profile similar to TNBC; however, real-world treatment patterns, chemotherapy response, endocrine therapy benefit, and survival outcomes for the Low-ER group are not well known. 516 patients with stage I-III HER2-negative breast cancer and ER/PR expression ≤10% who were enrolled in a multisite prospective registry between 2011 and 2019 were categorized on the basis of ER/PR expression. TNBC (ER and PR < 1%) and Low-ER (ER and/or PR 1–10%) groups comprised 87.4% (n = 451) and 12.6% (n = 65) of patients, respectively. Demographic, clinical, and treatment characteristics, including prevalence of germline BRCA1/2 mutation, racial and ethnic distribution, and chemotherapy use were not different between TNBC and Low-ER groups. No difference was observed in recurrence-free survival (RFS) and overall survival (OS) between TNBC and Low-ER groups (3-year RFS 82.5% versus 82.4%, respectively, p = 0.728; 3-year OS 88.0% versus 83.4%, respectively, p = 0.632). Among 358 patients receiving neoadjuvant chemotherapy, rates of pathologic complete response were similar for TNBC and Low-ER groups (49.2% vs 51.3%, respectively, p = 0.808). The HER2-negative Low-ER group is often excluded from TNBC clinical trials assessing novel treatments (immunotherapy and antibody-drug conjugates), thus limiting efficacy data for newer effective therapies in this group. Given that HER2-negative Low-ER disease displays clinical characteristics and outcomes similar to TNBC, inclusion of this group in TNBC clinical trials is encouraged.

Clinical and biomarker results of neoadjuvant phase II study of pembrolizumab and carboplatin plus docetaxel in triple-negative breast cancer (TNBC) (NeoPACT)

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Background: Addition of pembrolizumab to anthracycline-taxane-platinum chemotherapy improves pathologic complete response (pCR) and event free survival (EFS) in TNBC. Aim of this study was to assess the efficacy of the anthracycline free neoadjuvant regimen of pembrolizumab plus carboplatin plus docetaxel (Cb+D) in TNBC. Methods: In this multicenter study, eligible patients with stage I-III TNBC received carboplatin (AUC 6) + docetaxel (75 mg/m2) + pembrolizumab (200 mg) every 21 days x 6 cycles. The primary endpoint was pCR (no evidence of invasive tumor in breast and axilla). Secondary endpoints were residual cancer burden (RCB), EFS, toxicity, and immune response biomarkers. RNA isolated from pretreatment tumor tissue was subjected to next generation sequencing. Samples were classified as DNA Damage Immune Response (DDIR) signature and DetermaIO signature positive/negative using predefined cutoffs. Evaluation of stromal tumor infiltrating lymphocytes (sTILs) was performed using standard criteria. Results: 117 patients were enrolled from September 2018 to January 2022. 18% were African American, 39% had node positive disease, 88% had stage II/III disease and 15% had ER/PR 1-10%. Pathologic response information is available for 105 patients. pCR and RCB 0+1 rates were 60% (95% CI 51%-70%) and 71% (95% CI 62%-80%), respectively. Treatment related adverse events led to discontinuation of any trial drug in 12% of patients. Immune adverse events were observed in 28% of patients (Grade ≥3=6%). 47% of patients had sTILs ≥30%, 48% were DetermaIO positive, and 61% DDIR positive. The table describes the impact of these biomarkers on pCR and RCB. The areas under the prediction curve (AUC) for pCR were 0.660, 0.709, and 0.719 for DDIR, sTILs, and DetermaIO respectively. At a median follow up of 21 months, 2-year EFS is 88% in all patients; 98% in pCR group and 82% in no pCR group. Conclusions: Neoadjuvant pembrolizumab plus Cb+D regimen yields pCR of 60% and 2-year EFS of 88% in the absence of adjuvant pembrolizumab. The regimen was well tolerated, and no new toxicity signals were noted. Immune enrichment identified by sTILs or DetermaIO signature was associated with high pCR rates approaching or exceeding 80%. PD-L1 and additional biomarker analyses are ongoing. Clinical trial information: NCT03639948. [Table: see text]

Abstract P2-01-05: Impact of post-treatment ctDNA and residual cancer burden (RCB) on outcomes in patients with triple-negative breast cancer (TNBC) and residual disease

Introduction: Residual disease (RD) after neoadjuvant chemotherapy (NACT) is associated with high risk of recurrence in TNBC. RCB classification is prognostic in patients with RD. Recent studies show that post-NACT circulating cell-free tumor DNA (ctDNA) also provides prognostic information in patients with RD. Most TNBC patients with RD receive adjuvant therapy after surgery (chemotherapy and/or radiation), thus ctDNA status at completion of all adjuvant therapy (end of treatment, EOT) may be a better indicator of long-term prognosis. Furthermore, the impact of EOT ctDNA status on prognosis in context of RCB is of interest. Utilizing data from a prospective registry, the objective of this study was to investigate the impact of EOT ctDNA status and RCB class on outcomes in TNBC patients with RD. We hypothesized that RCB and EOT ctDNA status may provide complementary prognostic information. Methods: Study population included TNBC patients with RD post-NACT and available EOT plasma samples who were enrolled in an IRB-approved multisite prospective registry between 2011 and 2018. EOT samples were collected after completion (1-6 months) of all curative treatment (local and systemic). ctDNA was isolated and subjected to next generation sequencing (QIAseq 275-gene Human Comprehensive Cancer Panel on an Illumina NextSeq 550). Samples demonstrating pathogenic/likely pathogenic variant(s) with 3-40% allelic frequencies were considered ctDNA positive. Variants with allelic frequencies ≥40% were included in ctDNA positive status only if not present in ClinVar8/dbSNP9 as a known germline variant. The impact of EOT ctDNA status and RCB on event-free survival (EFS) and overall survival (OS) were estimated according to the Kaplan-Meier method and compared among groups by log-rank test, followed by Cox regression analysis. Results: For 47 TNBC patients with RD and available EOT plasma sample, the median age was 47 years, and 43% had node-positive disease at diagnosis. RCB class distribution was as follows: RCB I=28%, RCB II=49%, RCB III=15%, RCB unknown=8%. 45% of patients received adjuvant chemotherapy (59% with RCB II-III received adjuvant chemotherapy), and 68% received adjuvant radiation. EOT ctDNA was positive in 34% (16/47) of patients and was associated with higher T stage (p=0.012), TNM stage (p=0.033) and trend toward higher RCB class (p=0.078). ctDNA positivity rates in RCB I, II and III classes were 23%, 30% and 71%, respectively. Among all patients, 3-year EFS and OS were 71% and 73%, respectively. Table 1 provides 3-year EFS and OS by ctDNA status in all patients and by RCB class. ctDNA positive status was associated with inferior EFS and OS. Conclusion: EOT ctDNA positivity was noted in one-third of TNBC patients with residual disease and was highly prognostic, with almost half of patients with ctDNA positivity suffering an EFS event by 3 years. Patients with RCB III had very poor outcome (3-year EFS ≤20%) regardless of ctDNA status. However, in RCB classes I/II, ctDNA provided further prognostic utility, as ctDNA negative patients with RCB I/II had excellent outcomes (3-year EFS &gt;90%). These findings should be confirmed in other studies and provide insights into the role of ctDNA for patient stratification/selection in residual disease adjuvant therapy intensification trials for TNBC.

3-year EFS3-year OSAll patients: ctDNA positive vs ctDNA negative56% vs 78%, HR 3.02 (95% CI: 1.01-9.01), p=0.03856% vs 82%, HR 3.05 (95% CI: 1.02-9.13), p=0.037RCB I/II: ctDNA positive vs ctDNA negative73% vs 92%, HR 4.38, p=0.07873% vs 92%, HR 3.03, p=0.159RCB III: ctDNA positive vs ctDNA negative0% vs 20%, HR 1.67, p=0.5610% vs 20%, HR 1.30, p=0.765

Citation Format: Priyanka Sharma, Shane R Stecklein, Bruce F Kimler, Rachel Yoder, Kelsey Schwensen, Joshua M Staley, Qamar J Khan, Anne P O'Dea, Lauren E Nye, Manana Elia, Jaimie Heldstab, Trisha Home, Stephen Hyter, Kamilla Isakova, Harsh B Pathak, Andrew K Godwin. Impact of post-treatment ctDNA and residual cancer burden (RCB) on outcomes in patients with triple-negative breast cancer (TNBC) and residual disease [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 P2-01-05.

Residual cancer burden after neoadjuvant chemotherapy and long-term survival outcomes in breast cancer: a multicentre pooled analysis of 5161 patients

BACKGROUND

Previous studies have independently validated the prognostic relevance of residual cancer burden (RCB) after neoadjuvant chemotherapy. We used results from several independent cohorts in a pooled patient-level analysis to evaluate the relationship of RCB with long-term prognosis across different phenotypic subtypes of breast cancer, to assess generalisability in a broad range of practice settings.

METHODS

In this pooled analysis, 12 institutes and trials in Europe and the USA were identified by personal communications with site investigators. We obtained participant-level RCB results, and data on clinical and pathological stage, tumour subtype and grade, and treatment and follow-up in November, 2019, from patients (aged ≥18 years) with primary stage I-III breast cancer treated with neoadjuvant chemotherapy followed by surgery. We assessed the association between the continuous RCB score and the primary study outcome, event-free survival, using mixed-effects Cox models with the incorporation of random RCB and cohort effects to account for between-study heterogeneity, and stratification to account for differences in baseline hazard across cancer subtypes defined by hormone receptor status and HER2 status. The association was further evaluated within each breast cancer subtype in multivariable analyses incorporating random RCB and cohort effects and adjustments for age and pretreatment clinical T category, nodal status, and tumour grade. Kaplan-Meier estimates of event-free survival at 3, 5, and 10 years were computed for each RCB class within each subtype.

FINDINGS

We analysed participant-level data from 5161 patients treated with neoadjuvant chemotherapy between Sept 12, 1994, and Feb 11, 2019. Median age was 49 years (IQR 20-80). 1164 event-free survival events occurred during follow-up (median follow-up 56 months [IQR 0-186]). RCB score was prognostic within each breast cancer subtype, with higher RCB score significantly associated with worse event-free survival. The univariable hazard ratio (HR) associated with one unit increase in RCB ranged from 1·55 (95% CI 1·41-1·71) for hormone receptor-positive, HER2-negative patients to 2·16 (1·79-2·61) for the hormone receptor-negative, HER2-positive group (with or without HER2-targeted therapy; p<0·0001 for all subtypes). RCB score remained prognostic for event-free survival in multivariable models adjusted for age, grade, T category, and nodal status at baseline: the adjusted HR ranged from 1·52 (1·36-1·69) in the hormone receptor-positive, HER2-negative group to 2·09 (1·73-2·53) in the hormone receptor-negative, HER2-positive group (p<0·0001 for all subtypes).

INTERPRETATION

RCB score and class were independently prognostic in all subtypes of breast cancer, and generalisable to multiple practice settings. Although variability in hormone receptor subtype definitions and treatment across patients are likely to affect prognostic performance, the association we observed between RCB and a patient's residual risk suggests that prospective evaluation of RCB could be considered to become part of standard pathology reporting after neoadjuvant therapy.

FUNDING

National Cancer Institute at the US National Institutes of Health.

Clinical and Biomarker Results from Phase I/II Study of PI3K Inhibitor Alpelisib plus Nab-paclitaxel in HER2-Negative Metastatic Breast Cancer

PURPOSE

PIK3CA mutations are common in breast cancer and promote tumor progression and treatment resistance. We conducted a phase I/II trial of alpelisib (α-specific PI3K inhibitor) plus nab-paclitaxel in patients with HER2-negative metastatic breast cancer (MBC).

PATIENTS AND METHODS

Eligible patients had HER2-negative MBC with any number of prior chemotherapies. Phase I was 3+3 dose-escalation design with three dose levels of alpelisib (250, 300, and 350 mg) daily plus nab-paclitaxel 100 mg/m2 administered on days 1, 8, and 15 every 28 days. Phase II was according to Simon's two-stage design. PIK3CA mutations in tumor/circulating tumor DNA (ctDNA) were assessed. Primary endpoints were recommended phase II dose (RP2D) and objective response rate (ORR). Additional endpoints included safety, pharmacokinetics, progression-free survival (PFS), and association of PIK3CA mutation with outcomes.

RESULTS

A total of 43 patients were enrolled (phase I, n = 13 and phase II, n = 30). A total of 84% had visceral disease and 84% had prior taxane. No dose-limiting toxicities occurred in phase I. RP2D was alpelisib 350 mg daily plus nab-paclitaxel 100 mg/m2 on days 1, 8, and 15. Hyperglycemia (grade 3, 26% and grade 4, 0%), neutropenia (grade 3, 23% and grade 4, 7%), diarrhea (grade 3, 5% and grade 4, 0%), and rash (grade 3, 7% and grade 4, 0%) were the most common adverse events. Among 42 evaluable patients, ORR was 59% (complete response, 7% and partial response, 52%), 21% of whom had response lasting >12 months; median PFS was 8.7 months. A total of 40% of patients demonstrated tumor and/or ctDNA PIK3CA mutation; patients with tumor/ctDNA mutation demonstrated better PFS compared with those without mutation (11.9 vs. 7.5 months; HR, 0.44; P = 0.027). Patients with normal metabolic status had longer PFS compared with prediabetic/diabetic patients (12 vs. 7.5 months; P = 0.014). No pharmacokinetics interactions were detected.

CONCLUSIONS

The alpelisib plus nab-paclitaxel combination was well tolerated and shows encouraging efficacy, especially in patients with PIK3CA-mutated tumor/ctDNA. The impact of metabolic status on response to this combination merits further investigation.

Romidepsin (HDACi) plus cisplatin and nivolumab triplet combination in patients with metastatic triple negative breast cancer (mTNBC)

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Background: Histone deacetylase inhibitors (HDACi) upregulate genes involved in antigen presentation machinery and increase expression of natural killer group 2, member D ligands (NKG2DL), thus resulting in enhanced tumor cell recognition and response to PD-1/CTLA-4 blockade. Cisplatin and HDACi combination synergistically induces cytotoxicity, apoptosis, and DNA damage. This phase I-II trial investigated combination of romidepsin (HDACi) plus cisplatin and nivolumab (PD-1 inhibitor) in mTNBC. Patients and Methods: Eligible patients had mTNBC with any number of prior chemotherapies. Phase I was 3+3 dose-escalation design with three dose levels of romidepsin (8, 10, 12mg/m2, D2, 9) plus cisplatin 75mg/m2 D 1 every 21 days. Phase II treatment included romidepsin plus cisplatin plus nivolumab 360mg every 21 days and was designed according to Simon’s two stage minimax design. Primary endpoints were recommended phase 2 dose (RP2D) and objective response rate (ORR). Additional endpoints included safety, PFS, and pharmacokinetics. Results: 51 patients were enrolled (N=13 phase I, N=38 phase II) between 2015-2020. 69% had received ≥1 prior metastatic chemotherapy, 47% had prior platinum, 53% had liver metastasis, 12% had BRCA1/2 mutation, and 11% had PD-L1 positive disease. There were no dose limiting toxicities in phase I. The RP2D was romidepsin 12mg/m2 D2,9 + cisplatin 75mg/m2 D1 + nivolumab 360mg D1 every 21 days. Thrombocytopenia (G3:27%, G4:0%), neutropenia (G3:25%, G4:0%), anemia (G3:22%, G4:0%), nausea (G3:22%, G4:0%), and vomiting (G3:20%, G4:0%) were the most common grade 3/4 adverse events. 21% of patients had immune AEs (G3-4:8%). Among 34 evaluable phase II patients, ORR was 44% (Table), median PFS was 4.4 months, and 1-year PFS was 23%. Median OS was 10.3 months and 1-year OS was 43%. No pharmacokinetic interactions were detected with co-administration of romidepsin-cisplatin-nivolumab. Conclusions: The triplet combination of romidepsin plus cisplatin and nivolumab was well tolerated and shows encouraging efficacy in pretreated mTNBC, including in patients with PD-L1 negative disease and in those with liver metastasis. Correlative biomarker work is ongoing. This combination warrants further evaluation in larger studies. Clinical trial information: NCT02393794 .[Table: see text]

Abstract PS6-04: Impact of low versus negative estrogen/progesterone receptor status on clinico-pathologic characteristics and survival outcomes in HER2 negative breast cancer

Background: Triple negative breast cancer is defined by lack of expression of ER/PR (immunohistochemistry expression &lt;1%) and absence of HER2 gene amplification. However, data regarding endocrine therapy benefit in patients with low levels (1-10%) of ER/PR expression are lacking. Furthermore, gene expression studies show tremendous similarities between HER2 negative tumors with low and negative ER/PR status. Accordingly, the 2020 ASCO/CAP guideline designates that ER expression of 1-10% be reported as a distinct “ER low positive” category. Utilizing data from a prospective registry, the aim of this study was to determine the impact of low versus negative ER/PR status on clinico-pathologic characteristics and survival outcomes in patients with HER2 negative breast cancers. Methods: 516 subjects with stage I-III HER2 negative breast cancer and ER/PR IHC ≤10% were enrolled in an IRB-approved multisite prospective registry between 2011 and 2019. Demographic, clinical, pathologic, and treatment information was collected, and patients were followed for recurrence and survival. Patients were categorized according to ER/PR expression into two groups: TNBC (ER and PR &lt;1%) and Low-ER (ER and/or PR 1-10%). Recurrence free survival (RFS) and overall survival (OS) were estimated according to the Kaplan-Meier method and compared among groups by log-rank test, followed by Cox regression analysis. Results: TNBC and Low-ER groups comprised 451/516 (87.4%) and 65/516 (12.6%) patients, respectively. Demographic, clinical, pathologic, and treatment characteristics of the two groups are described in Table 1. Median follow-up was 39 months. Three-year RFS was 82% for both TNBC and Low-ER groups (p=0.70). Three-year OS was 88% and 83% for TNBC and Low-ER groups, respectively (p=0.63). Twenty percent of patients in the Low-ER group received adjuvant endocrine therapy, and endocrine therapy use did not impact outcomes in the Low-ER group (RFS: p=0.32; OS: p=0.88). On multivariate analysis, T stage, nodal status, and age significantly impacted RFS (T stage 3/4 vs 1/2, HR=2.7, p&lt;0.001; nodal status positive vs negative, HR=2.4, p&lt;0.001; age above vs below median, HR=1.8, p=0.006) and OS (T stage 3/4 vs 1/2, HR=3.6, p&lt;0.001; nodal status positive vs negative, HR=2.8, p&lt;0.001; age above vs below median, HR=1.026, p=0.01). For patients who received neoadjuvant chemotherapy, achievement of pathological complete response (pCR) was associated with superior RFS (3-year RFS of 95% and 67% in those with and without pCR, respectively, HR=0.18, p&lt;0.001). Conclusions: Patients with TNBC and Low-ER HER2 negative breast cancer present with similar clinico-pathologic characteristics, including prevalence of germline BRCA1/2 mutation. Prognosis and rate of pCR (with neo-adjuvant chemotherapy) in patients with Low-ER HER2 negative breast cancer is similar to those with TNBC. The role and efficacy of adjuvant endocrine therapy in patients with Low-ER breast cancer is unclear. These findings support consideration for inclusion of patients with Low-ER disease along with TNBC for future clinical trial eligibility and planning.

Table 1. Demographic, clinical, pathologic, and treatment characteristicsCharacteristics - N (%)All N=516TNBC (ER & PR &lt;1%) n=451Low-ER (ER or PR 1-10%) n=65pAge at diagnosis, years - median (range)53 (23-97)54 (23-97)51 (28-76)0.61RaceWhite386 (75%)335 (74%)51 (79%)0.69Black101 (20%)89 (20%)12 (19%)Asian8 (2%)8 (2%)0 (0%)Menopausal statusPre214 (42%)181 (41%)33 (51%)0.25Post295 (58%)263 (59%)32 (49%)Histological gradeI2 (0.4%)2 (0.4%)0 (0%)0.82II86 (17%)76 (17%)10 (15%)III428 (83%)373 (83%)55 (85%)T stageT1-2446 (87%)388 (87%)58 (89%)0.56T3-467 (13%)60 (13%)7 (11%)N statusPositive177 (34%)158 (35%)19 (29%)0.36Negative339 (66%)293 (65%)46 (71%)TNM stageI179 (35%)150 (33%)29 (44%)0.10II263 (51%)232 (52%)31 (48%)III74 (14%)69 (15%)5 (8%)Germline BRCA1/2 mutationYes70 (14%)64 (14%)6 (9%)0.53No357 (69%)309 (69%)48 (74%)Unknown89 (17%)78 (17%)11 (17%)ChemotherapyNeoadjuvant357 (69%)318 (71%)39 (60%)0.23Adjuvant147 (29%)123 (27%)24 (37%)None12 (2%)10 (2%)2 (3%)Surgery typeMastectomy308 (60%)275 (61%)33 (51%)0.10Lumpectomy205 (40%)173 (39%)32 (49%)Adjuvant endocrine therapyYes20 (4%)7 (2%)13 (20%)&lt;0.001No496 (96%)444 (98%)52 (80%)pCR (in patients with neoadjuvant chemotherapy, n=357)176 (49%)157 (49%)19 (49%)0.94

Citation Format: Rachel Yoder, Bruce F Kimler, Joshua M Staley, Kelsey Schwensen, Yen Y Wang, Karissa Finke, Anne O'Dea, Lauren Nye, Manana Elia, Gregory Crane, Richard McKittrick, Robert Pluenneke, Sheshadri Madhusudhana, Larry Beck, Roberto Rodriguez, Anuj Shrestha, Larry Corum, Mark Marsico, Andrew K Godwin, Qamar Khan, Priyanka Sharma. Impact of low versus negative estrogen/progesterone receptor status on clinico-pathologic characteristics and survival outcomes in HER2 negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-04.

Abstract GS4-07: Assessing prognosis after neoadjuvant therapy: A comparison between anatomic ypAJCC staging, residual cancer burden class and neo-bioscore

Background: Pathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) in patients with breast cancer is associated with improved survival. Further assessment of the extent of residual disease, using the pathological anatomic American Joint Committee on Cancer staging method (ypStage) or the Residual Cancer Burden (RCB) method, have been shown to add prognostic information for patients with residual disease. Neo-Bioscore, an alternate system to classify response to NAC, includes clinical stage at diagnosis and biology and defines eight prognostic groups. The goal of this study was to compared three scoring systems (anatomic ypStage (7th ed), RCB Class and Neo-Bioscore) and assess whether RCB Class and Neo-Bioscore provide additional prognostic value in the context above anatomic ypStage, the most commonly used method for post-neoadjuvant residual disease assessment. Methods: Data from 5161 patients treated with NAC was pooled from 12 sites. Patients without clinical and pathological staging were excluded, as were patients with HER2+ breast cancer who did not receive neoadjuvant HER2-targeted therapy, leaving 3730 for analysis. PCR was defined as no residual invasive tumor in breast and nodes, i.e. RCB-0 or ypT0/Tis and ypN0. Patients with discordant pCR status by RCB Class vs ypStage (n=9) were excluded. Associations between each scoring system and event-free survival (EFS) were evaluated using the log rank test. EFS at 5 years was estimated using the Kaplan Meier method. Associations between Neo-Bioscore and EFS were assessed in the pCR group. For patients with residual disease, we assessed RCB and Neo-Bioscore within each ypStage. Analysis was performed overall and within subtype. Subgroups with &lt;5 patients were excluded from the survival analyses. Results: ypAJCC staging, RCB class and Neo-Bioscore were all associated with EFS in the overall population and within each subtype (log rank p&lt;0.0001). Of note, 13 patients with a Neo-Bioscore of 7 all recurred or died within 19 months of follow-up. Overall, 34% (1264/3721) of patients achieved a pCR. Their Neo-Bioscore ranges from 0-5, where 3% (37/1264) has a Neo-Bioscore of 5 despite achieving pCR. The Neo-Bioscore was not associated with EFS in case of a pCR, with EFS estimates at 5 years of 95%, 94%, 92%, 93%, 90% and 92% for Neo-Bioscores 0-5 respectively. As HR and HER2 status are components of the score, the range of Neo-Bioscore in the pCR group differs by subtype. However, similar to the overall analysis, the Neo-Bioscore was not prognostic within subtypes in case of pCR. Overall, among the patients who did not achieve pCR, both RCB class and Neo-Bioscore were associated with EFS within ypStages I, II and III. However, the ypStage within which RCB and Neo-Bioscore are prognostic is different for each subtype. RCB class was prognostic in ypStage I in both HR+ subtypes: patients with ypStage-I/RCB-I had significantly improved survival compared to patients with ypStage-I/RCB-II (5-year EFS: 100% vs 83% in HR+HER2- and 95% vs 77% in HR+HER2+). In contrast, for patients with triple negative breast cancer, RCB class was prognostic within ypStage II and III. Analysis by clinical stage and the components of the three systems that contribute most to prognosis will be presented. Conclusions: The degree of response to NAC adds important information to pCR versus residual disease. The Neo-Bioscore was not prognostic among patients with pCR, suggesting that clinical stage (including subtype and grade) adds little information in the setting of a pCR. In contrast, both RCB and Neo-Bioscore provide additional prognostic information to the conventional ypAJCC staging among non-pCR patients, suggesting that clinical stage, tumor biology as well as extent of residual disease all contribute to prognosis in the setting of residual disease after NAC.

Citation Format: Marieke EM van der Noordaa, Christina Yau, Sonal Shad, Marie Osdoit, Tessa G Steenbruggen, Diane de Croze, Anne-Sophie Hamy, Marick Lae, Fabien Reyal, Maria Del Monte-Millán, Miguel Martin, Sara Lopez Tarruella, I-SPY 2 TRIAL Consortium, Judy C Boughey, Matthew Goetz, Tanya Hoskin, Rebecca Gould, Vincent Valero, Gabe Sonke, Maartje van Seijen, Jelle Wesseling, John Bartlett, Stephan Edge, Mi-Ok Kim, Jean Abraham, Carlos Caldas, Helena Earl, Elena Provenzano, Stephen-John Sammut, David Cameron, Ashley Graham, Peter Hall, Lorna MacKintosh, Fang Fan, Andrew K Godwin, Kelsey Schwensen, Priyanka Sharma, Angela DeMichele, Janet Dunn, Louise Hiller, Larry Hayward, Jeremy Thomas, Kimberley Cole, Lajos Pusztai, Laura van 't Veer, Fraser Symmans, Laura Esserman. Assessing prognosis after neoadjuvant therapy: A comparison between anatomic ypAJCC staging, residual cancer burden class and neo-bioscore [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS4-07.

Abstract PD13-02: Site of recurrence after neoadjuvant therapy: A multi-center pooled analysis

Background: Achieving a pathologic complete response (pCR) has been shown on the patient level to predict excellent long-term event-free survival outcomes. Residual cancer burden (RCB) quantifies the extent of residual disease for patients who did not achieve pCR. We have previously observed in the I-SPY 2 TRIAL that while metastatic events outside the central nervous system (CNS) were dramatically reduced in the setting of pCR, the incidence of CNS metastasis remained similar across RCB classes, raising the possibility that these CNS events may be independent of response in the breast. In this study, we evaluate the type and sites of recurrences by RCB in a large pooled dataset, which allows for analysis within subtype, to validate these findings. Methods: 5161 patients pooled across 12 institutions/trials with available RCB and event-free survival (EFS) data were included in this analysis. EFS was calculated as the interval between treatment initiation, and locoregional recurrence, distant recurrence or death from any cause; patients without event are censored at time of last follow-up. The median follow-up is 4.6 years. We summarized the EFS event type, further sub-dividing the distant recurrence events (DR) by their site of relapse (CNS-only, CNS and other sites, Non-CNS). We used a competing risk (Fine-Gray) model to assess which of these site-specific relapses differ between RCB classes and estimated the cumulative incidence of CNS-only and non-CNS events at 5 years. Analyses were performed across the entire study population and within HR/HER2 defined subtypes. Results: Among the 5161 subjects, there were 1164 EFS events, including 92 (7.9%) local recurrences (without distant recurrence and/or death) and 1072 distant recurrence-free survival (DRFS) events. Among the DRFS events, 158 patients died without a distant recurrence. 914 experienced distant recurrences, including 90 (9.8%) with CNS-only, 145 (15.9%) with CNS and other sites, 664 (72.6%) with non-CNS distant recurrence; 15 (1.6%) patients had missing recurrence site information. Table 1 summarizes the cumulative incidence of CNS-only and non-CNS recurrence at 5 years and the proportion of CNS-only recurrences among DR events by RCB class overall and within each HR/HER2 subtypes. The incidence of CNS-only recurrences was low and similar across RCB classes. In contrast, the incidence of non-CNS recurrences increases with increasing RCB. As a result, CNS-only recurrences are proportionally higher within the RCB-0 and RCB-I than in the RCB-II and RCB-III groups, largely because of the low DR event rate and relative low frequency of non-CNS recurrence events within the RCB-0 and RCB-I classes. Overall, 27% of the recurrences in the setting of pCR (RCB-0) are due to CNS-only recurrences.Conclusions: Consistent with previous studies, our large pooled analysis confirmed that CNS-only recurrences are uncommon but appear similar across RCB groups, independent of response, suggesting that the CNS is a treatment sanctuary site. In contrast, non-CNS recurrence rates increase as RCB increases. These findings suggest that inclusion of CNS-only recurrences as an outcome event may impact the association between neoadjuvant therapy response and long-term outcomes in the context of current therapies. Novel therapies that cross the blood brain barrier will be needed to impact CNS recurrence rates.

Table 1: Cumulative Incidence of CNS Only and non-CNS Distant Recurrences at 5 years and proportion of CNS-only events among DR eventsRCB Class0IIIIIIpOverall (5161)N16766622017806Cum. Inc. CNS Only2%2%2%1%0.627Cum. Inc. Non-CNS3%6%16%27%&lt;0.001# CNS-Only / # DR events (%)26/96 (27%)14/74 (19%)39/443 (9%)11/301 (4%)HR-HER2- (1774)N770212590202Cum. Inc. CNS Only2%3%2%4%0.298Cum. Inc. Non-CNS4%11%19%42%&lt;0.001# CNS-Only / # DR events (%)13/50 (26%)6/32 (19%)13/148 (9%)8/111 (7%)HR-HER2+ (572)N3766710029Cum. Inc. CNS Only1%5%5%0%0.022Cum. Inc. Non-CNS2%5%18%38%&lt;0.001# CNS-Only / # DR events (%)4/17 (24%)3/10 (30%)6/31 (19%)0/13 (0%)HR+HER2+ (858)N31317229182Cum. Inc. CNS Only1%1%2%0%0.37Cum. Inc. Non-CNS2%3%15%26%&lt;0.001# CNS-Only / # DR events (%)3/10 (30%)2/16 (12%)7/68 (10%)0/29 (0%)HR+HER2- (1957)N2172111036493Cum. Inc. CNS Only3%2%1%0.2%0.087Cum. Inc. Non-CNS5%4%13%20%&lt;0.001# CNS-Only / # DR events (%)6/19 (32%)3/16 (19%)13/196 (7%)3/148 (2%)

Citation Format: Sonal Shad, Marieke van der Noordaa, Marie Osdoit, Diane de Croze, Anne-Sophie Hamy, Marick Lae, Fabien Reyal, Miguel Martin, María Del Monte-Millán, Sara López-Tarruella, I-SPY 2 TRIAL Consortium, Judy C Boughey, Matthew P Goetz, Tanya Hoskin, Rebekah Gould, Vicente Valero, Gabe Sonke, Tessa G Steenbruggen, Maartje van Seijen, Jelle Wesseling, John Bartlett, Stephen Edge, Mi-Ok Kim, Jean Abraham, Carlos Caldas, Helena Earl, Elena Provenzano, Stephen-John Sammut, David Cameron, Ashley Graham, Peter Hall, Lorna Mackintosh, Fan Fang, Andrew K Godwin, Kelsey Schwensen, Priyanka Sharma, Angela DeMichele, Janet Dunn, Louise Hiller, Larry Hayward, Jeremy Thomas, Kimberly Cole, Lajos Pusztai, Laura Van't Veer, Fraser Symmans, Laura Esserman, Christina Yau. Site of recurrence after neoadjuvant therapy: A multi-center pooled analysis [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD13-02.

Epidurography as a Diagnostic Aid in Canine Lumbosacral Compressive Disease: 47 Cases(1981–1986)

Epidurograms were performed on 47 dogs with clinical signs consistent with lumbosacral compressive disease. Thirtyeight abnormal epidurograms were identified. Epidurograms were considered abnormal when complete obstruction of cranial forward flow or dorsal deviation over the lumbosacral junction were present. Dorsal laminectomies were performed on 28 dogs with abnormal epidurographic findings. Surgical findings included: disc herniation (17), connective tissue nerve root entrapment (5), fibrous connective tissue mass (3), no abnormality (2), and instability (1). The strong correlation between abnormal epidurographic signs and compressive lumbosacral lesions seen at surgery (93%) suggests that epidurography can be a valuable aid in the diagnosis of lumbosacral compressive lesions.