Surgical Perspectives on the Updated ASTRO Guideline on Partial Breast Irradiation for Breast Cancer

This is an executive summary of the most recent American Society for Radiation Oncology (ASTRO) guidelines on use of partial breast irradiation in early-stage breast cancer.In the conscientious pursuit of "right-sizing" the management of patients with early-stage breast cancer, there has been an emphasis on judicious de-escalation of therapy. A component of this paradigm shift is partial breast irradiation (PBI), an approach characterized by targeted radiation therapy (RT) to lumpectomy cavity margins rather than to the whole breast (i.e., whole breast irradiation [WBI]) after breast conservation surgery (BCS). The American Society for Radiation Oncology (ASTRO) recently completed a revision of its evidence-based guidelines for the application of PBI.1To accomplish this, recent PBI data were reviewed by panel members, including representatives of the American Society for Radiation Oncology (ASTRO), in collaboration with the American Society of Clinical Oncology (ASCO), and the Society of Surgical Oncology (SSO), which provided representatives and peer reviewers. The guideline was approved by the ASTRO Board of Directors and endorsed by the Canadian Association of Radiation Oncology, European Society for Radiotherapy and Oncology, Royal Australian and New Zealand College of Radiologists, and the Society of Surgical Oncology.The recommendations focused on indications for PBI as an alternative to WBI and technical considerations specific to PBI. This editorial provides a summary and comments on the updated ASTRO PBI guidelines, offering insights into the implications of these findings for clinical practice and multidisciplinary decision-making while underscoring technical considerations for optimal incorporation of PBI into patient care.

Ribosomal Protein L9 Maintains Stemness of Colorectal Cancer via an ID-1 Dependent Mechanism

The identification of therapeutic target genes that are functionally involved in stemness is crucial to effectively cure patients with metastatic carcinoma. We have previously reported that inhibition of ribosomal protein L9 (RPL9) expression suppresses the growth of colorectal cancer (CRC) cells by inactivating the inhibitor of DNA-binding 1 (ID-1) signaling axis, which is functionally associated with cancer cell survival. In addition to cell proliferation, ID-1 is also involved in the maintenance of cancer stemness. Thus, we aimed in this study to investigate whether the function of RPL9 could correlate with CRC stem cell-like properties. Here, we demonstrated that siRNA silencing of RPL9 reduced the invasiveness and migrative capabilities of HT29 and HCT116 parental cell populations and the capacity for sphere formation in the HT29 parental cell population. CD133+ cancer stem cells (CSCs) were then separated from CD133- cancer cells of the HT29 parental cell culture and treated with RPL9-specific siRNAs to verify the effects of RPL9 targeting on stemness. As a result, knockdown of RPL9 significantly suppressed the proliferative potential of CD133+ colorectal CSCs, accompanied by a reduction in CD133, ID-1, and p-IκBα levels. In line with these molecular alterations, targeting RPL9 inhibited the invasion, migration, and sphere-forming capacity of CD133+ HT29 CSCs. Taken together, these findings suggest that RPL9 promotes CRC stemness via ID-1 and that RPL9 could be a potential therapeutic target for both primary CRC treatment and the prevention of metastasis and/or recurrence.

Efficacy and safety of biosimilar trastuzumab (CT-P6) in routine clinical practice in the Republic of Korea: a real-world post-marketing surveillance study

BACKGROUND

The trastuzumab biosimilar CT-P6 is approved for human epidermal growth factor receptor 2 (HER2)-positive early breast cancer (EBC), metastatic breast cancer (MBC), and metastatic gastric cancer (MGC). The objective of this post-marketing surveillance (PMS) study was to evaluate the real-world safety and effectiveness of CT-P6 in patients with HER2-positive cancers.

RESEARCH DESIGN AND METHODS

This open-label, observational, prospective, PMS study collected data via investigator surveys from 35 centers in the Republic of Korea (5 October 2018-4 October 2022). Eligible patients with HER2-positive EBC, MBC, or MGC started CT-P6 treatment during routine clinical practice, followed by 1-year observation. Evaluations included adverse events (AEs), adverse drug reactions (ADRs), and effectiveness.

RESULTS

Safety was analyzed in 642 patients (494 EBC, 94 MBC, 54 MGC). Overall, 325 (50.6%) patients experienced 1316 AEs, and 550 ADRs occurred in 199 (31.0%) patients. Unexpected ADRs occurred in 62 (9.7%) patients. Unexpected ADRs and ADRs of special interest did not raise any new safety signals. Among trastuzumab-naïve patients, 34/106 (32.1%) with EBC achieved pathological complete response; 30/74 (40.5%) MBC and 24/49 (49.0%) MGC patients achieved complete or partial response.

CONCLUSIONS

In a real-world setting, CT-P6 demonstrated safety and efficacy findings consistent with previous CT-P6 studies.

Lazertinib versus Gefitinib as First-Line Treatment for EGFR-mutated Locally Advanced or Metastatic NSCLC: LASER301 Korean Subset

PURPOSE

This subgroup analysis of the Korean subset of patients in the phase 3 LASER301 trial evaluated the efficacy and safety of lazertinib versus gefitinib as first-line therapy for epidermal growth factor receptor mutated (EGFRm) non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Patients with locally advanced or metastatic EGFRm NSCLC were randomized 1:1 to lazertinib (240 mg/day) or gefitinib (250 mg/day). The primary endpoint was investigator-assessed progression-free survival (PFS).

RESULTS

In total, 172 Korean patients were enrolled (lazertinib, n=87; gefitinib, n=85). Baseline characteristics were balanced between the treatment groups. One-third of patients had brain metastases (BM) at baseline. Median PFS was 20.8 months (95% confidence interval [CI], 16.7 to 26.1) for lazertinib and 9.6 months (95% CI, 8.2 to 12.3) for gefitinib (hazard ratio [HR], 0.41; 95% CI, 0.28 to 0.60). This was supported by PFS analysis based on blinded independent central review. Significant PFS benefit with lazertinib was consistently observed across predefined subgroups, including patients with BM (HR, 0.28; 95% CI, 0.15 to 0.53) and those with L858R mutations (HR, 0.36; 95% CI, 0.20 to 0.63). Lazertinib safety data were consistent with its previously reported safety profile. Common adverse events (AEs) in both groups included rash, pruritus, and diarrhoea. Numerically fewer severe AEs and severe treatment-related AEs occurred with lazertinib than gefitinib.

CONCLUSION

Consistent with results for the overall LASER301 population, this analysis showed significant PFS benefit with lazertinib versus gefitinib with comparable safety in Korean patients with untreated EGFRm NSCLC, supporting lazertinib as a new potential treatment option for this patient population.

Genomic analysis of plasma circulating tumor DNA in patients with heavily pretreated HER2 + metastatic breast cancer

We explored accumulated genomic alterations in patients with heavily treated HER2 + metastatic breast cancer enrolled in the KCSG BR18-14/KM10B trial. Targeted sequencing was performed with circulating tumor DNAs (ctDNAs) collected before the treatment of 92 patients. ctDNAs collected at the time of disease progression from seven patients who had a durable response for > 12 months were also analyzed. Sixty-five genes were identified as pathogenic alterations in 99 samples. The most frequently altered genes were TP53 (n = 48), PIKCA (n = 21) and ERBB3 (n = 19). TP53 and PIK3CA mutations were significantly related with shorter progression free survival (PFS), and patients with a higher ctDNA fraction showed a worse PFS. The frequency of homologous recombination deficiency (HRD)-related gene mutations was higher than that in matched tumor tissues, and these mutations tended to be associated with shorter PFS. New pathogenic variants were found at the end of treatment in all seven patients, including BRCA2, VHL, RAD50, RB1, BRIP1, ATM, FANCA, and PIK3CA mutations. In conclusion, TP53 and PIK3CA mutations, as well as a higher ctDNA fraction, were associated with worse PFS with trastuzumab and cytotoxic chemotherapy. The enrichment of HRD-related gene mutations and newly detected variants in ctDNA may be related to resistance to treatment.

Dual Biomarker Combining DNA Damage Repair Gene Mutations and PD-L1 Expression for Immune Checkpoint Inhibitors in Non-small Cell Lung Cancer

BACKGROUND/AIM

Immune checkpoint inhibitors (ICIs) improve long-term survival in advanced non-small cell lung cancer (NSCLC) and require robust predictive biomarkers for the selection of responders. This study investigated the optimal implementation of DNA damage repair (DDR) gene mutations to predict response to ICIs in real-world NSCLC patients.

PATIENTS AND METHODS

We retrospectively reviewed 55 advanced NSCLC patients who had undergone targeted high-throughput sequencing and received ICIs. Patients with two or more DDR gene mutations were defined as DDR2 positive.

RESULTS

The patients' median age was 68 (range=44-82) years, and 48 (87.3%) were men. Seventeen patients (30.9%) showed ≥50% high programmed death-ligand 1 (PD-L1) expression. Ten patients (18.2%) received an ICI-chemotherapy combination as first-line therapy, and 38 (69.1%) received ICI monotherapy as more than second-line therapy. Fourteen patients (25.5%) were DDR2-positive. The objective response rate of patients with DDR2-positive or PD-L1 ≥50% was 45.5%, and that of patients with DDR2-negative and PD-L1 <50% was 11.1% (p=0.007). In the PD-L1 low expression subgroup (<50%), patients with DDR2-positive had improved progression-free survival (PFS) and overall survival (OS) after ICIs compared to those with DDR2-negative (PFS: 5.8 vs. 1.9 months, p=0.026, OS: 14.4 vs. 7.2 months, p=0.078). DDR2-positive patients or those with PD-L1 ≥50% (24, 43.6%) had statistically significant improvement in PFS and OS after ICIs compared to DDR2-negative and those with PD-L1 <50% (PFS: 4.4 vs. 1.9 months, p=0.006, OS: 11.6 vs. 7.2 months, p=0.037).

CONCLUSION

A dual biomarker combining DDR gene mutations and PD-L1 expression improves the prediction of response to ICIs in advanced NSCLC.

Abstract 2439: RPL27 augments growth and stemness properties in colorectal cancer through PLK1 signaling

Background: In 2020, colorectal cancer (CRC) had the second highest mortality rate worldwide and was the third most common cancer type among various carcinomas, accounting for 10.0% and 9.4% of all carcinomas, respectively. Although the expression of ribosomal protein L27 (RPL27) is upregulated during CRC development, oncogenic roles of RPL27 have not yet been elucidated. We aimed in this study to investigate the effect of RPL27 targeting on CRC growth and whether RPL27 gained an extra-ribosomal function during CRC development.

Methods: Human CRC cell lines, HCT116 and HT29, were transfected with RPL27-specific siRNA and tested for growth inhibition and apoptotic induction using MTS, FACS and Western blotting. To obtain insights into the molecular changes in response to RPL27 knockdown, global changes in gene expression were examined using RNA sequencing.

Results: We observed that inhibition of RPL27 expression suppresses CRC cell growth and long-term colony formation through an induction of apoptotic cell death. Targeting RPL27 also significantly inhibited the growth of human CRC xenografts in nude mice. Noticeably, polo-like kinase 1 (PLK1), which is known to play an important role in mitotic cell cycle progression and stemness, was commonly down-regulated in both HCT116 and HT29 cells with RPL27 depletion. Western blot analysis confirmed that RPL27 silencing reduces the levels of PLK1 protein and G2/M-associated regulators, such as p-CDC25C, CDK1, and cyclin B1. Reflecting these molecular responses, knockdown of RPL27 reduced the migration and invasion abilities of CRC cells. In terms of CSC phenotypic changes, RPL27 knockdown suppressed sphere forming capacity of isolated CD133+ CSC population accompanying with the reduction in CD133 and PLK1 levels.

Conclusion: Taken together, these findings indicate that RPL27 contributes to promotion of CRC growth and stemness through PLK1 signaling and that targeting RPL27 could be a next-line therapeutic strategy for both primary CRC treatment and prevention of metastasis and/or recurrence.

Citation Format: Keon Uk Park, Ilseon Hwang, Hun Mo Ryoo, Yun-Han Lee, So-Young Park. RPL27 augments growth and stemness properties in colorectal cancer through PLK1 signaling [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 2439.

A Phase 2 Study of Palbociclib for Recurrent or Refractory Advanced Thymic Epithelial Tumors (KCSG LU17-21)

INTRODUCTION

Thymic epithelial tumors (TETs) are rare but are the most common tumors of the anterior mediastinum. Platinum-based combination chemotherapy is the standard of care for such tumors and is associated with a 50% to 90% objective response rate (ORR) in metastatic disease. Nevertheless, there is no standard chemotherapeutic option after failure of platinum-based combination chemotherapy. Genetic alterations associated with the cell cycle, including pRB, p16^INK4A, and cyclin D1, are most often observed in TETs. On the basis of these results, we conducted a phase 2 trial to evaluate the efficacy and safety of palbociclib in patients with recurrent or refractory advanced TETs.

METHODS

This is a phase 2, multicenter, open-label, single-arm study of palbociclib monotherapy in patients with recurrent or metastatic advanced TETs who failed one or more cytotoxic chemotherapies. The patients received 125 mg of oral palbociclib daily for 21 days, followed by a 7-day break. The primary end point was progression-free survival (PFS). The secondary end points were ORR, duration of response, overall survival, and safety.

RESULTS

Between August 2017 and October 2019, a total of 48 patients were enrolled. The median number of previous chemotherapies was one (range: one to four), and 21 (43.7%) of 48 patients received thymectomy. By the WHO classification, the patients were type A (n = 1), type B1 (n = 2), type B2 (n = 8), type B3 (n = 13), thymic carcinoma (n = 23), and unknown (n = 1). With a median follow-up of 14.5 months (range: 0.8-38.2), the median number of cycles of palbociclib monotherapy was 10 (range: 1-40). The ORR was 12.5% (four partial responses in thymoma and two partial responses in thymic carcinoma). The PFS at 6 months was 60.2%, and the median PFS was 11.0 months (95% confidence interval: 4.6-17.4). The median overall survival was 26.4 months (95% confidence interval: 17.4-35.4). The most common treatment-related adverse events of any grade were neutropenia (62.5%), anemia (37.5%), and thrombocytopenia (29.1%), and the most common grade 3/4 treatment-related hematologic adverse event was neutropenia (41.7%). Neutropenia above grade 3 was reversible, and there were no cases with neutropenic fever.

CONCLUSIONS

Palbociclib monotherapy was well tolerated and had encouraging efficacy in patients with TETs who failed platinum-based combination chemotherapy.

A randomized Phase 2 study to compare erlotinib with or without bevacizumab in previously untreated patients with advanced non-small cell lung cancer with EGFR mutation

BACKGROUND

This study evaluated whether an addition of bevacizumab to erlotinib improves clinical outcomes in patients with advanced EGFR-mutated non-small cell lung cancer (NSCLC).

METHODS

This is an open-label, multicenter, randomized Phase 2 study in South Korea. Chemonaïve patients with Stage IIIB/IV NSCLC with EGFR 19 deletion or L858R mutation were eligible. Asymptomatic brain metastasis (BM) was enrolled without local treatment. Patients received either erlotinib plus bevacizumab or erlotinib.

RESULTS

Between December 2016 and March 2019, 127 patients were randomly assigned to receive erlotinib plus bevacizumab (n = 64) or erlotinib (n = 63). Fifty-nine (46.5%) patients had baseline BM. Fewer patients in the erlotinib plus bevacizumab arm received radiotherapy for BM than in the erlotinib arm (10.3% vs. 40.0%). A trend toward longer progression-free survival (PFS) was observed in the erlotinib plus bevacizumab arm compared with the erlotinib alone arm; however, it was not statistically significant (median PFS, 17.5 months vs. 12.4 months; hazard ratio [HR], 0.74; 95% CI, 0.51-1.08; p = .119). The unplanned subgroup analysis showed a longer PFS with erlotinib plus bevacizumab in patients with BM (median PFS, 18.6 months vs. 10.3 months; HR, 0.54; 95% CI, 0.31-0.95; p = .032). Grade 3 or worse adverse events occurred in 56.6% of the erlotinib plus bevacizumab arm and 20.6% of the erlotinib arm.

CONCLUSIONS

Although it was not statistically significant, a trend to improvement in PFS was observed in patients with erlotinib plus bevacizumab compared to erlotinib alone.

PLAIN LANGUAGE SUMMARY

A randomized Phase 2 study compared erlotinib with or without bevacizumab in previously untreated patients with advanced non-small cell lung cancer with EGFR mutation. The erlotinib plus bevacizumab failed to improve median progression-free survival compared with the erlotinib alone. However, the progression-free survival benefit from erlotinib plus bevacizumab was found in patients with brain metastasis with no severe hemorrhagic adverse effects.

Comparison of Treatment Patterns and Clinical Outcomes by Gender in Locally Advanced Head and Neck Squamous Cell Carcinoma (KCSG HN13-01)

We aimed to compare treatment modalities and outcomes by gender in patients with locally advanced head and neck squamous cell carcinoma (LA-HNSCC). We characterized the sex-specific differences and compared the overall survival (OS) between male and female patients in a multicenter cohort of LA-HNSCC. To minimize the observed confounding, propensity score matching was utilized. The study included 445 patients; 385 (86.5%) were men and 60 (13.5%) were women. In terms of age, smoking habits, drinking habits, and primary tumor locations, there was a significant imbalance in sex before the matching. Propensity score matching yielded 60 patient pairs, with no statistical difference between the sexes in terms of their characteristics. As for the treatment strategies, there were no significant differences between the sexes before (p = 0.260) and after (p = 0.585) the propensity score matching. When comparing the survival probabilities between the sexes, OS was not significantly different in the overall (HR 1.02; 95% CI 0.59-1.76; p = 0.938) and propensity-score-matched population (HR 1.46; 95% CI 0.68-3.17; p = 0.331). These results suggest that there was no difference in prognosis by gender in the treatment modalities and outcomes of LA-HNSCC in real-world practice.

Clinical Implications of BRCA Mutations in Advanced Biliary Tract Cancer

INTRODUCTION

Current standard chemotherapy for biliary tract cancer (BTC) has limited survival benefits, and the need for targeted therapies is increasing. This study investigated the genetic profiles and clinical implications of BRCA mutations in patients with advanced BTC.

METHODS

Targeted high-throughput sequencing was performed on samples obtained from 25 patients with advanced BTC who had received palliative first-line platinum-based chemotherapy.

RESULTS

Of the 25 patients, 16 (64.0%) were younger than 65 years of age and 16 (64.0%) were male. The BTC cases consisted of intrahepatic cholangiocarcinoma (9, 36.0%), extrahepatic cholangiocarcinoma (5, 20.0%), and gallbladder cancer (11, 44.0%). The median overall survival (OS) and progression-free survival (PFS) of all patients were 11.9 months (95% confidence interval [CI]: 9.2-14.6) and 5.6 months (95% CI: 3.8-7.3), respectively. Genomic alterations in TP53 (52.0%), BRCA (36.0%), ATM (32.0%), ERBB2 (24.0%), NOTCH1 (20.0%), and FGFR3 (20.0%) were frequently reported. TP53 and ATM mutations were associated with OS (TP53: hazard ratio [HR] 2.719, 95% CI: 1.074-6.881, p = 0.035; ATM: HR 2.780, 95% CI: 1.091-7.082, p = 0.032). Patients with BRCA mutations had a slightly improved PFS compared to those with intact BRCA (6.7 months [range, 2.7-10.7 months] vs. 5.3 months [range, 3.6-7.0 months], p = 0.090). However, there was no significant difference in OS between groups (BRCA mutant vs. intact: 10.6 months [range, 3.6-17.6 months] vs. 11.9 months [range, 7.5-16.3 months], p = 0.252). BRCA mutations were significantly associated with PFS in the multivariate analysis (HR 0.150, 95% CI: 0.034-0.655, p = 0.012).

CONCLUSION

This study demonstrated that BRCA mutations might have a role as predictive biomarkers for palliative first-line platinum-based chemotherapy in patients with advanced BTC.

Phase II study to investigate the efficacy of trastuzumab biosimilar (Herzuma®) plus treatment of physician's choice (TPC) in patients with heavily pretreated HER-2+ metastatic breast cancer (KCSG BR 18–14/KM10B)

We investigated the efficacy and safety of a trastuzumab biosimilar, Herzuma®, in combination with treatment of physician's choice (TPC) in patients with HER2+ metastatic breast cancer (MBC) who had failed at least two HER2 directed chemotherapies.

•

Treatment of HER2-positive breast cancer is rapidly evolving with the development of new agents. However, treatment options are still limited after progression with proven anti-HER2 therapies.

•

The combination of chemotherapy with a trastuzumab biosimilar, Herzuma®, was effective and safe in patients with heavily pre-treated HER2+ MBC.

•

Duration of response to previous anti-HER2 therapy, PIK3CA and ERBB2 mutations were associated with clinical efficacies of trastuzumab biosimilar plus chemotherapy.

Totality outcome of afatinib sequential treatment in patients with EGFR mutation-positive non-small cell lung cancer in South Korea (TOAST): Korean Cancer Study Group (KCSG) LU-19-22

Background

Irrespective of the first-line epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor chosen, acquired resistance to therapy is inevitable. Therefore, a key consideration when assessing therapeutic choices is the availability of subsequent treatment options following disease progression. We assessed clinical outcomes in patients who received first-line afatinib treatment with various second-line treatments including osimertinib for patients acquiring the T790M mutation.

Methods

A total of 737 EGFR mutation-positive (EGFR M+) non-small cell lung cancer (NSCLC) patients receiving first-line afatinib treatment were categorized by second-line treatment: T790M+ sequentially treated with osimertinib (cohort A, n=116); T790M− given chemotherapy or others (cohort B, n=143); patients with unknown T790M status (cohort C, n=111); and patients who were undergoing afatinib treatment at the time of data collection, were dead, had discontinued afatinib treatment due to serious adverse events or were lost to follow-up (cohort D, n=367). The primary outcomes were total time on treatment (TOT) and TOT for first-line (TOT-1) and second-line treatments (TOT-2). Secondary outcomes were objective response rates (ORR), overall survival (OS), and central nervous system (CNS) efficacy.

Results

Median total TOT in cohorts A, B, C, and D were 35.10 months [95% confidence interval (CI): 30.09–43.53 months], 18.80 months (95% CI: 16.92–20.20 months), 12.00 months (95% CI: 10.22–14.98 months), and 42.60 months (95% CI: 30.95–59.23 months), respectively. The ORR of patients given afatinib was 75.7%. In patients with initial brain metastasis without local treatment, the CNS response rate was 67.0% and CNS progression-free survival was 24.70 months (95% CI: 19.84–33.15 months).

Conclusions

This study showed that sequential approach of afatinib followed by second line treatment is an effective therapeutic strategy for EGFR M+ NSCLC patients.

A randomized phase II study comparing erlotinib with or without bevacizumab in patients with advanced non–small cell lung cancer (NSCLC) with EGFR mutation

9107

Background: Synergistic anti-tumor effect of double blocking EGFR and VEGF pathways is proven by preclinical and clinical data. This study evaluated whether an addition of bevacizumab to erlotinib improves clinical outcomes in patients (pts) with untreated advanced EGFR-mutated NSCLC. Methods: This is an open-label, multi-center, randomized phase II study conducted in South Korea. Key eligibility was age ≥ 19 years old, untreated stage IIIB/IV NSCLC, EGFR exon 19 deletion or exon 21 L858R mutation, and ECOG performance status of 0 or 1. Asymptomatic brain metastasis (BM) was permitted without local treatment. Pts were randomly assigned to receive either oral erlotinib (E) 150 mg/day alone or erlotinib plus bevacizumab (E+B) at 15 mg/kg intravenously every 3 weeks. Primary endpoint was progression-free survival (PFS) with secondary endpoints including response rate (RR), overall survival (OS), and toxicity. Results: Between Dec 16, 2016, and Mar 8, 2019, a total of 127 pts were randomly assigned to receive E (n=63) or E+B (n=64). Median follow-up duration was 38.9 months. Fifty-nine (46.5%) pts had baseline BM. While the prevalence of baseline BM was similar between both arms (45.3% vs. 47.6%), more pts of the E arm received radiotherapy for BM before the study enrollment, compared to the E+B arm (40.0% vs. 10.3%). A trend toward improved PFS was observed with the E+B arm compared to the E arm (median PFS, 17.5 months vs 12.4 months; hazard ratio [HR] = 0.74 [95% confidence interval (CI), 0.51–1.08], P= 0.119). The RR was similar between both arms (85.9% vs. 83.9%; P= 0.746). The most significant PFS benefit from the E+B was found in the subgroup with baseline BM (median PFS, 18.6 months vs 10.3 months; HR = 0.54 [95% CI, 0.31–0.95], P= 0.032). The 12-month and 24-month cumulative central nervous system (CNS) progression rate was 4.4% and 6.8% in the E+B arm compared to 15.1% and 32.5% in the E arm. Thus, the E+B arm significantly reduced the risk for CNS progression than the E arm (HR = 0.33 [95% CI, 0.11–0.93], P= 0.035). Grade 3 or worse adverse events occurred in 56.6% of the E+B arm while 20.6% of the E arm. The E+B arm tended to increase the incidence or severity of some erlotinib-related adverse effects: grade 3 skin rash (17.2% vs. 4.8%) and any grade paronychia (60.9% vs. 46.0%), and oral mucositis (51.6% vs. 33.3). At the time of disease progression, more pts in the E arm showed EGFR T790M positivity (82% vs. 64%) and received 3rd generation EGFR tyrosine kinase inhibitor as the 2nd line therapy (58% vs. 22%) compared to the E+B arm. OS data are immature (events: 34%, HR = 1.24 [95% CI, 0.68–2.26]). Conclusions: A trend to improvement in PFS was observed with the combination of erlotinib and bevacizumab vs. erlotinib alone in advanced EGFR-mutated NSCLC. Especially, the PFS benefit from this combination was most significant in the pts with BM. Clinical trial information: NCT03126799.

Dose Modification of Etoposide plus Platinum in Elderly Patients with Extensive-Disease Small-Cell Lung Cancer

BACKGROUND

Elderly patients with extensive-disease small-cell lung cancer (ED-SCLC) have a high risk of chemotherapy toxicity due to multiple comorbidities and poor performance status. Although dose modification is often used to avoid toxicity in elderly patients with ED-SCLC, there is little data on the effect of initial dose-reduced chemotherapy on survival outcomes.

METHODS AND PATIENTS

We retrospectively reviewed 100 elderly patients with ED-SCLC who received first-line etoposide plus platinum chemotherapy between January 2006 and December 2020.

RESULTS

The median age was 74 years. Eighty-nine patients (89%) had a history of smoking, and 38 (38%) had chronic lung disease. Thirty-four patients (34%) received dose-reduced etoposide plus platinum in the first cycle. The dose-reduced group had significantly higher age, lower body mass index, and poor ECOG PS. There were no significant differences in survival outcomes between the dose-reduced and full-dose chemotherapy [median overall survival (OS), 4.9 vs. 6.5 months, p=0.440; median progression free survival (PFS), 3.7 vs. 4.6 months, p=0.272]. In multivariate analyses, dose reduction in the first cycle (hazard ratio 0.519, 95% CI 0.269-1.000, p=0.050) was significantly associated with OS. Following subgroup analysis of 59 patients who received minimum four cycles, no significant differences in survival outcomes between the two groups (median OS, 10.9 vs. 9.4 months, p=0.817; median PFS, 6.3 vs. 6.5 months, p=0.902) was noted.

CONCLUSIONS

The dose-reduced chemotherapy with first-line etoposide plus platinum had non-inferior survival outcomes compared to the full-dose chemotherapy in elderly patients with ED-SCLC.

Abstract P5-16-03: Phase II study of trastuzumab biosimilar (Herzuma®) plus gedatolisib in patients with HER-2 positive metastatic breast cancer who progressed after 2 or more HER-2 directed chemotherapy (BR 18-13, KM-10A): Interim analysis

Background: Prognosis of patients with HER-2 positive metastatic breast cancer (MBC) has been revolutionized with the development of monoclonal antibodies targeting HER-2 and antibody-drug conjugate, but resistance to anti-HER-2 therapy is inevitable ultimately. PI3K-AKT-mTOR pathway aberration is known to be one of the key resistance mechanisms. BR18-13(KM-10A) study is a phase 2 clinical trial evaluating efficacy and safety of Herzuma® (trastuzumab biosimilar) plus Gedatolisib (dual PI3K/mTORC inhibitor) in patients with HER-2 positive MBC who progressed after multiple lines of therapy. Methods: Patients with HER-2 positive MBC with known PIK3CA pathologic mutation or amplification whose disease progressed after more than 2 HER-2 directed therapy were enrolled in the study. They received Herzuma® (8mg/kg IV for 1st cycle loading dose, and then 6mg/kg IV every 3 weeks) plus Gedatolisib (180mg on D1, 8, 15 of every 21 days). We evaluated efficacy of the combination treatment as interim analysis. The data cutoff of this interim analysis was June 8, 2021. Results: 17 patients were enrolled and followed for a median of 6.2 months. At data cutoff, 17 patients were eligible for response assessment. All patients were confirmed to have pathologic PIK3CA aberrations: 9 kinase mutations (H1047X), 5 helical mutations (E545X), 2 other point mutations, and 1 amplification. Overall, response rate was 64.7% and disease control rate was 82.4%. Eleven patients reached partial response (PR) as their best response, three were stable disease (SD), and three had progressive disease (PD). Two patients who have reached PR remain on investigational treatment until the data cutoff point, and the longest one is on treatment for 12.0 months. The median progression-free survival assessed in data cutoff time was 5.9 months. One patient ended treatment due to CNS disease progression, but her visceral metastatic lesions were decreased with experimental treatment. No fatal adverse events related to trial medication were reported. Conclusion: In this phase 2 study, Trastuzumab biosimilar plus Gedatolisib presented 64.7% of response rate with manageable toxicity in patients with HER-2 positive MBC with PIK3CA mutation. Clinical trial information: NCT03698383 Acknowledgement: this research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &Welfare, Republic of Korea (Grant number: HI17C2206).

Citation Format: Ju Won Kim, Hee Kyung Ahn, Jong Gwon Choi, Yee Soo Chae, Gyeong-Won Lee, Keon Uk Park, Eunmi Lee, Sung Hoon Sim, Jee Hyun Kim, Yeon Hee Park, Miso Kim, Jin Hyun Park, Jeong Eun Kim, Han Jo Kim, Mi Sun Ahn, So Yeon Oh, Min Hwan Kim, Su-Jin Koh, Kyoung Eun Lee, Myoung Joo Kang, Jae Ho Byun, Joo Young Ha, Jung Hye Kwon, Joo Young Jung, Su Ee Lee, Inhae Park, Kyong Hwa Park. Phase II study of trastuzumab biosimilar (Herzuma®) plus gedatolisib in patients with HER-2 positive metastatic breast cancer who progressed after 2 or more HER-2 directed chemotherapy (BR 18-13, KM-10A): Interim analysis [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 P5-16-03.

RPL17 Promotes Colorectal Cancer Proliferation and Stemness through ERK and NEK2/β-catenin Signaling Pathways

Aims: Ribosomal protein L17 (RPL17), a 60S subunit component, is up-regulated in colorectal cancer (CRC). However, its oncogenic role in CRC progression remains unexplored. Thus, we aimed to investigate the effect of RPL17 targeting on CRC in vitro and in vivo and whether RPL17 gained an extra-ribosomal function during CRC development.

Methods: RPL17-specific siRNAs complexed with cationic lipids were transfected to CRC cells to silence target gene expression and then real-time RT-PCR and western blotting were applied to observe the change of expression or activity of genes or proteins of interest. Cell proliferation assay, clonogenic assay and cell cycle analysis were used to determine the in vitro effects of RPL17siRNAs on CRC cell growth, and a subcutaneous xenograft assay was applied to test the effect of RPL17siRNAs on in vivo tumor growth. RNA sequencing and western blotting were used to investigate the underlying mechanisms. Sphere-forming assay, invasion assay and migration assay were used to evaluate the effects of RPL17siRNAs on CRC stemness.

Results: siRNA-mediated inhibition of RPL17 expression suppressed CRC cell growth and long-term colony formation by inducing apoptotic cell death. Similarly, targeting RPL17 effectively suppressed tumor formation in a mouse xenograft model. RNA sequencing of RPL17-silenced CRC cells revealed the same directional regulation of 159 (93 down- and 66 up-regulated) genes. Notably, NIMA-related kinase 2 (NEK2), which functionally cooperates with extracellular-regulated protein kinase (ERK) and plays a pivotal role in mitotic progression and stemness maintenance, was down-regulated. RPL17 silencing reduced NEK2, β-catenin, and p-ERK protein levels. These molecular alterations reflected the reduction in sphere-forming capacity, expression of stem cell marker genes, migration, and invasion. Reversely, RPL17 overexpression increased the ability of long-term colony formation, migration, and invasion.

Conclusion: Our findings indicate that RPL17 promotes CRC proliferation and stemness via the ERK and NEK2/β-catenin signaling axis, and targeting RPL17 could be the next molecular strategy for both primary CRC treatment and prevention of secondary tumor formation.

Characteristics and treatment patterns in older patients with locally advanced head and neck cancer (KCSG HN13-01)

BACKGROUND/AIMS

Treatment decisions for locally advanced head and neck squamous cell carcinoma (LA-HNSCC) are complicated, and multi-modal treatments are usually indicated. However, it is challenging for older patients to complete treatments. Thus, we investigated disease characteristics, real-world treatment, and outcomes in older LA-HNSCC patients.

METHODS

Older patients (aged ≥ 70 years) were selected from a large nationwide cohort that included 445 patients with stage III-IVB LA-HNSCC from January 2005 to December 2015. Their data were retrospectively analyzed and compared with those of younger patients.

RESULTS

Older patients accounted for 18.7% (83/445) of all patients with median age was 73 years (range, 70 to 89). Proportions of primary tumors in the hypopharynx and larynx were higher in older patients and older patients had a more advanced T stage and worse performance status. Regarding treatment strategies of older patients, 44.5% of patients received concurrent chemoradiotherapy (CCRT), 41.0% underwent surgery, and 14.5% did not complete the planned treatment. Induction chemotherapy (IC) was administered to 27.7% (23/83) of older patients; the preferred regimen for IC was fluorouracil and cisplatin (47.9%). For CCRT, weekly cisplatin was prescribed 3.3 times more often than 3-weekly cisplatin (62.2% vs. 18.9%). Older patients had a 60% higher risk of death than younger patients (hazard ratio, 1.6; p = 0.035). Oral cavity cancer patients had the worst survival probability.

CONCLUSION

Older LA-HNSCC patients had aggressive tumor characteristics and received less intensive treatment, resulting in poor survival. Further research focusing on the older population is necessary.

Usefulness of cyclic thermal therapy and red blood cell scintigraphy in patients with chemotherapy-induced peripheral neuropathy

Background

Pharmacological and non-pharmacological therapies have been used to treat patients with chemotherapy-induced peripheral neuropathy (CIPN). However, the effect of therapies in cancer patients has yet to be investigated comprehensively. We hypothesized that cyclic thermal therapy would improve blood flow and microcirculation and improve the symptoms driven by CIPN.

Methods

The criteria of assessment were blood volume in region of interest (ROI) in the images, and European Organization for Research and Treatment of Cancer-Quality of Life Questionnaire-Chemotherapy-Induced Peripheral Neuropathy 20 questionnaire scores. The blood volume was quantified by using red blood cell (RBC) scintigraphy. All patients were treated 10 times during 10 days. The thermal stimulations, between 15° and 41°, were repeatedly delivered to the patient's hands.

Results

The total score of the questionnaires, the score of questions related to the upper limbs, the score of questions closely related to the upper limbs, and the score excluding the upper limbs questions was decreased. The blood volume was decreased, and the variance of blood volume was decreased. During cooling stimulation, the blood volume was decreased, and its variance was decreased. During warming stimulation, the blood volume was decreased, and its variance was decreased.

Conclusions

We suggest that cyclic thermal therapy is useful to alleviate CIPN symptoms by blood circulation improvement. RBC scintigraphy can provide the quantitative information on blood volume under certain conditions such as stress, as well as rest, in peripheral tissue.

Totality outcome of afatinib sequential treatment in patients with EGFR mutation-positive NSCLC in Korea: KCSG LU-19-22

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Background: While osimertinib showed impressive efficacy and safety profile in 1st-line setting for EGFR mutation-positive (EGFR M+) NSCLC patients, there are no standard targeted therapy following progression. Thus, interest has been growing on sequential treatment of osimertinib as 2nd-line treatment for patients acquiring T790M resistance mutation after 2nd generation EGFR TKIs. We did a retrospective study to support the hypothesis that sequential approach of afatinib followed by osimertinib represents a practical treatment option in ‘real-world’ practice. Methods: In this non-interventional, multicenter study, EGFR M+ NSCLC patients had to start 1st-line afatinib treatment ≥ 13 months prior to data entry. They were categorized into 4 cohorts according to 2nd-line treatments with retesting results: T790M+ patients sequentially treated with osimertinib in cohort A, T790M patients treated with chemotherapy or other treatments in cohort B, and patients with unknown mutation status in cohort C. Cohort D included patients who were still ongoing with afatinib. Primary outcome was the time on treatment (TOT) of patients receiving 1st-line afatinib (TOT-1) followed by 2nd-line treatments (TOT-2). Secondary endpoints were acquisition rate of T790M after progression, objective response rates of afatinib (ORR-1) and 2nd-line treatments (ORR-2), and overall survival (OS). Results: Among a total of 761 enrolled patients, 737 patients excluding 24 screening failures were allocated into cohort A (n=116), B (n=143), C (n=111), and D (n=367). Median age was 62 years (22 - 90) with 53.05% of female proportion. Brain metastasis was discovered in 38.94% at initial diagnosis. Regarding genotypes of EGFR mutations, del19 was 57.53%, 31.48% for L858R, 7.33% for uncommon mutations, and 3.66% for compound mutation. Median TOTs in cohort A, B, C, and D were 35.09 months (95% CI, 30.09 to 43.53), 18.76 months (95% CI, 16.92 to 20.20), 12.02 months (95% CI, 10.22 to 14.98), and 42.61 months (95% CI, 30.95 to 59.23), respectively. Particularly, in cohort A, median TOT-1 and TOT-2 were 17.43 months (95% CI, 15.21 to 19.32) and 11.04 months (95% CI, 7.10 to 14.13), respectively. Retesting was attempted in 262 of 370 patients (70.81%) with 44.27% of T790M detection rate. ORR-1 and -2 in cohort A, B, and C were 84.48% and 56.03%, 82.52% and 29.08%, 54.95% and 21.70%, respectively and 68.94% of ORR for cohort D. Median OS has was not reached. Conclusions: These data suggest that, in real-world practice, sequential afatinib followed by osimertinib be a feasible and effective therapeutic strategy for EGFR M+ NSCLC patients acquiring T790M during the period of afatinib treatment. Of note, median TOT in cohort D is over 3.5 years, suggesting that 1st-line afatinib potentially allow certain patients to maintain long-term, chemotherapy-free state. Further analysis is currently being undertaken and will be presented.

A phase II study of palbociclib for recurrent or refractory advanced thymic epithelial tumor (KCSG LU17-21)

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Background: Thymic epithelial tumors (TETs) are rare but the most common tumor of the anterior mediastinum. Platinum-based combination chemotherapy is standard of care which is associated with a 50%-90% overall response rate (ORR) in metastatic disease. However, there is no standard chemotherapeutic option after failure of platinum-based combination chemotherapy. Genetic alterations associated with cell cycle including pRB, p16INK4A, and cyclin D1 are commonly observed in TETs. Based on these results, we conducted a phase II trial to evaluate the efficacy and safety of palbociclib in patients with recurrent or refractory advanced TETs. Methods: This is a phase II multicenter, open-label, single arm study of palbociclib monotherapy in patients with recurrent or metastatic advanced TETs who failed one or more cytotoxic chemotherapy. Patients receive oral palbociclib 125mg daily for 21 days followed by a 7-day break. The primary endpoint was the progression-free survival (PFS) rate at 6 months (H0 = 30% vs H1 = 48%). Results: Between August 2017 and October 2019, 48 patients were enrolled. The median number of previous chemotherapy was 1 (range: 1-4) and 21 (43.7%) of 48 patients received thymectomy. By WHO classification, Type A (n = 1), Type B1 (n = 2), Type B2 (n = 8), Type B3 (n = 13), Type C (n = 23), and unknown (n = 1). With medial follow-up of 14.5 months (range 0.8-38.2), the median cycle of palbociclib was 10 (range 1-40). The PFS at 6 months was 60% and the median PFS was 11.0 months (95% CI: 4.6-17.4). Six of 48 patients (12.5%) achieved partial response. The median overall survival was 26.4 months (95% CI: 17.4-35.4). The most common adverse events of any grade included neutropenia (62.5%), anemia (37.5%) and thrombocytopenia (29.1%). Conclusions: Palbociblib monotherapy is well tolerable and encouraging efficacy in patients with TETs who failed platinum-based combination chemotherapy. Updated results will be presented. Clinical trial information: NCT03219554.

Induction Chemotherapy as a Prognostication Index and Guidance for Treatment of Locally Advanced Head and Neck Squamous Cell Carcinoma: the Concept of Chemo-Selection (KCSG HN13-01)

Purpose

Certain patient subgroups who do not respond to induction chemotherapy (IC) show inherent chemoresistance in locally advanced head and neck squamous cell carcinoma (LA-HNSCC). This study aimed to assess the prognostic value of IC, and role of IC in guiding the selection of a definitive locoregional therapy.

Materials and Methods

Out of the 445 patients in multi-institutional LA-HNSCC cohort, 158 (36%) receiving IC were enrolled. The study outcome was to assess overall survival (OS) through IC responsiveness and its role to select subsequent treatments.

Results

Among 135 patients who completed subsequent treatment following IC, 74% responded to IC (complete response in 17% and partial response in 58%). IC-non-responders showed 4.5 times higher risk of mortality than IC-responders (hazard ratio, 4.52; 95% confidence interval, 2.32 to 8.81; p < 0.001). Among IC-responders, 84% subsequently received definitive concurrent chemoradiotherapy (CCRT) and OS was not differed by surgery or CCRT (p=0.960). Regarding IC-non-responders, 54% received CCRT and 46% underwent surgery, and OS was poor in CCRT (24-month survival rate of 38%) or surgery (24-month survival rate of 63%).

Conclusion

Response to IC is a favorable prognostic factor. For IC-responders, either surgery or CCRT achieved similar survival probabilities. For IC-non-responder, multidisciplinary approach was warranted reflecting patients’ preference, morbidity, and prognosis.

Prognostic effects of cytokine levels on patients treated with taxane and zoledronic acid for metastatic breast cancer in bone (BEAT-ZO) (KCSG BR 10-13)

Advanced breast cancer frequently metastasizes to the skeleton causing major mobility issues and hazards to quality of life. To manage osteolytic bone metastasis, bone-modifying agents and chemotherapy are recommended as the standard of care. Here, we investigated serologic biomarkers that might be associated with prognosis in breast cancer patients treated with zoledronic acid (ZA) and taxane-based chemotherapy. We collected serum samples from breast cancer patients with bone metastasis who received taxane plus ZA as palliative treatment. Fourteen biomarkers of angiogenesis, immunogenicity, and apoptosis were assessed, and the correlation between serum cytokine levels and patient's prognosis was statistically analyzed. Sixty-six patients were enrolled, and samples from 40 patients were analyzed after laboratory quality control. Patients with low baseline PDGF-AA, high IFN-γ, low MCP-2, low TGF-β1, and low TNF-α were significantly associated with longer progression-free survival (PFS). Decreasing VEGF and TNF-α and increasing FGF-2 and PDGF-AA in the early treatment phase indicated longer PFS. In univariate and multivariate analyses, low TGF-β1 and TNF-α and high IFN-γ at baseline were associated with a significantly low hazard ratio for disease progression. Further, we designed a risk score with TGF-β1, TNF-α, and IFN-γ levels, which could prognosticate patients for PFS. In conclusion, serum cytokine level, such as TGF-β1, TNF-α, and IFN-γ, could be a potential prognostic biomarker for breast cancer patients with bone metastasis treated with ZA and taxane-based chemotherapy.

Silencing CDCA8 Suppresses Hepatocellular Carcinoma Growth and Stemness via Restoration of ATF3 Tumor Suppressor and Inactivation of AKT/β-Catenin Signaling

Simple Summary

Although the overexpression of CDCA8 is frequently observed in hepatocellular carcinoma (HCC) tissues, the functions of CDCA8 during HCC development remain to be clarified. The aim of our study was to investigate if targeting CDCA8 could affect liver tumor phenotypes in vitro and in vivo and to identify underlying molecular mechanisms to exert its therapeutic effect. We found that silencing of CDCA8 by siRNA inhibits the growth of parental cancer cell culture and mice tumors and suppresses stemness of CD133⁺ cancer stem cell population through the common responses of the upregulation of the tumor suppressive ATF3/GADD34 functional pathway and inactivation of the Akt/β–catenin signaling axis. These findings suggest CDCA8 as a novel therapeutic target for both primary HCC treatment and the prevention of metastasis or recurrence providing mode of action performed by a CDCA8 inhibitor.

Abstract

Big data analysis has revealed the upregulation of cell division cycle associated 8 (CDCA8) in human hepatocellular carcinoma (HCC) and its poorer survival outcome. However, the functions of CDCA8 during HCC development remain unknown. Here, we demonstrate in vitro that CDCA8 silencing inhibits HCC cell growth and long-term colony formation and migration through the accumulation of the G2/M phase cell population. Conversely, CDCA8 overexpression increases the ability to undergo long-term colony formation and migration. RNA sequencing and bioinformatic analysis revealed that CDCA8 knockdown led to the same directional regulation in 50 genes (25 down- and 25 upregulated). It was affirmed based on protein levels that CDCA8 silencing downregulates the levels of cyclin B1 and p-cdc2 and explains how it could induce G2/M arrest. The same condition increased the protein levels of tumor-suppressive ATF3 and GADD34 and inactivated AKT/β–catenin signaling, which plays an important role in cell growth and stemness, reflecting a reduction in sphere-forming capacity. Importantly, it was demonstrated that the extent of CDCA8 expression is much greater in CD133⁺ cancer stem cells than in CD133⁻ cancer cells, and that CDCA8 knockdown decreases levels of CD133, p-Akt and β-catenin and increases levels of ATF3 and GADD34 in the CD133⁺ cancer stem cell (CSC) population. These molecular changes led to the inhibition of cell growth and sphere formation in the CD133⁺ cell population. Targeting CDCA8 also effectively suppressed tumor growth in a murine xenograft model, showing consistent molecular alterations in tumors injected with CDCA8siRNA. Taken together, these findings indicate that silencing CDCA8 suppresses HCC growth and stemness via restoring the ATF3 tumor suppressor and inactivating oncogenic AKT/β–catenin signaling, and that targeting CDCA8 may be the next molecular strategy for both primary HCC treatment and the prevention of metastasis or recurrence.

Abstract PS11-39: Phase II pilot study of trastuzumab biosimilar (herzuma®) plus gedatolisib in patients with HER-2 positive metastatic breast cancer who progressed after 2 or more HER-2 directed chemotherapy [KM-10A/KCSG18-13 interim analysis]

Background: Prognosis of patients with HER-2 positive metastatic breast cancer (MBC) has been revolutionized with the development of dual antibodies targeting HER-2 and antibody-drug conjugate, but resistance to anti-HER-2 therapy is inevitable ultimately. PI3K-AKT-mTOR pathway aberration is known to be one of the resistance mechanisms. This randomized phase 2 pilot study evaluated safety and efficacy of Herzuma® (trastuzumab biosimilar) plus Gedatolisib (dual PI3K/mTORC inhibitor) in patients with HER-2 positive MBC who progressed after multiple lines of therapy. Methods: Patients with HER-2 positive MBC with known PIK3CA pathologic mutation or amplification whose disease progressed after more than two HER-2 directed therapy were enrolled in the study. They received Herzuma® (8mg/kg IV for 1st cycle loading dose, and then 6mg/kg IV every 3 weeks) plus Gedatolisib (180mg on D1, 8, 15 of every 21 days). We evaluated efficacy of the combination treatment as interim analysis. The data cutoff of this interim analysis was Aug 4, 2020. Results: As a pilot study, 15 patients were enrolled and followed for a median of 2.3 months. At data cutoff, 11 patients were eligible for response assessment. All patients were confirmed to have pathologic PIK3CA aberrations: H1047R, H1047L, E542Q, E542K, E453K, N345K, and PIK3CA amplification. Five patients reached partial response (PR) as their best response, three were stable disease (SD), and three had progressive disease (PD). All patients who have reached PR remain on investigational treatment at the data cutoff point, and the longest one is on treatment for 7.8 months. One of the SD patients ended treatment due to disease progression, and the other two have been undergoing treatment. Overall, response rate was 45.5% and disease control rate was 72.7%. No fatal adverse events related to trial medication were reported. Conclusion: In this phase 2 pilot study, Trastuzumab biosimilar plus Gedatolisib presented 45.5% of response rate with manageable toxicity in patients with HER-2 positive MBC with PIK3CA aberration. Clinical trial information: NCT03698383 Acknowledgement: this research was supported by a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &Welfare, Republic of Korea (Grant number: HI17C2206).

Citation Format: Ju Won Kim, Hee Kyung Ahn, Jong Gwon Choi, Yee Soo Chae, Gyeong Won Lee, Keon Uk Park, Eun Mi Lee, Sung Hoon Sim, Jee Hyun Kim, Yeon Hee Park, Mi So Kim, Jin Hyun Park, Jeong Eun Kim, Han Jo Kim, Mi Sun Ahn, So Yeon Oh, Min Hwan Kim, Su-Jin Koh, Kyoung Eun Lee, Myoung Joo Kang, Jae Ho Byun, Joo young Ha, Jung Hye Kwon, Joo Young Jung, Su Ee Lee, In Hae Park, Kyong Hwa Park. Phase II pilot study of trastuzumab biosimilar (herzuma®) plus gedatolisib in patients with HER-2 positive metastatic breast cancer who progressed after 2 or more HER-2 directed chemotherapy [KM-10A/KCSG18-13 interim 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 PS11-39.