Abstract 1250: Impact of homologous recombination repair or mismatch repair gene alteration on first-line FOLFOX chemotherapy in advanced colorectal cancer patients: K-MASTER project

Abstract Purpose: Homologous recombination repair (HRR) and mismatch repair (MMR) alteration is known to have a good response to platinum-based chemotherapy in both breast and ovarian cancer. However, HRR/MMR alteration and response for 1L FOLFOX chemotherapy in advanced colorectal cancer (CRC) is not fully understood. Methods: From 2017 to 2021, a number of 1,225 advanced CRC patients with available HRR/MRR alteration data were registered in K-MASTER project. After excluding missing data, adjuvant chemotherapy alone, other chemotherapeutic regimen, 390 patients who received 1L FOLFOX chemotherapy were finally analyzed. Targeted sequencing was conducted using Cancer Scan panel, FIRST panel, and K-MASTER Cancer (v1.0 or v1.1) panel for tumor tissue. If tumor tissue was not available, liquid biopsy was performed. HRR gene defined as follow; ATM, ATR, BARD1, BRCA1, BRCA2, BRIP1, CHEK2, FANCA, FANCD2, FANCG, PALB2, RAD50, RAD51. MMR gene defined as below; MLH1, MSH2, PMS2, MSH6, POLE, ARID1A. Results: Among 340 patients, 79 patients harbored HRR/MMR alteration. The median progression free survival (PFS) was 5.6 months vs 5.7 months in HRR/MMR alteration and wild-type group, respectively (hazard ratio (HR)=1.19, p-value=0.21). The median overall survival (OS) was comparable between two group (40.6 months vs 34.5 months, respectively; HR=0.71, p-value=0.17). Multivariate cox-proportional hazard model also showed HRR/MRR alteration status was not an independent factor for both PFS and OS (Both p-value>0.05). Conclusions: Patients harbored HRR/MRR alteration may not be sensitive for 1L oxaliplatin-based chemotherapy than wild-type. The effective treatment targeting high genomic instability populations warrants further investigation in CRC. Table 1. Baseline clinical characteristics and survival outcomes HRR/MMR alteration (n = 79) HRR/MMR wild-type (n = 261) P-value Age, year 58.5 ± 12.4 59.1 ± 12.8 0.710 Primary tumor resection, n (%) 70 (88.6%) 241 (92.3%) 0.298 Prior neoadjuvant or adjuvant chemotherapy, n (%) 10 (12.7%) 27 (10.3%) 0.212 Clinical stage IV, n (%) 71 (91.0%) 240 (92.7%) 0.855 Combined target agents, n (%) 54 (68.4%) 183 (70.1%) 0.811 HRR/MMR variants, n (%) N/A HRR mutation alone 38 (48.1%) - MMR mutation alone 30 (38.0%) - HRR+MMR mutation 11 (13.9%) - Median PFS (95% CI), months 5.6 (4.9-6.3) 5.7 (5.5-5.9) 0.215 Median OS (95% CI), months 40.6 (39.5-41.8) 34.5 (29.3-39.8) 0.175 Citation Format: Myung Han Hyun, Jwa Hoon Kim, Ah Reum Lim, Jae Sook Sung, Hee-Joon Chung, Yeul Hong Kim, Soohyeon Lee. Impact of homologous recombination repair or mismatch repair gene alteration on first-line FOLFOX chemotherapy in advanced colorectal cancer patients: K-MASTER project [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1250.