P-219 Real-life experience with chemotherapy plus biologics in first-line treatment of right-sided, RAS wild-type, metastatic colon cancer: A multicenter Onco-Colon Turkey study

Prognosis of metastatic right-sided colon cancer (mrCC) is poor compared to left-sided counterparts. There is ambigous data for the first-line treatment choice of anti-EGFR or anti-VEGF monoclonal antibody (mAb) in RAS type mrCC. Our aim was to study the real-life experience (onco-colon registry Turkey) of doublet chemotherapy backbone plus antiEGFR or antiVEGF mAbs in RAS wild-type mrCC. Data of mrCC patients treated with a first-line regimen between 2016 and 2019 from 28 centers were recorded. Treatment regimens were as follows: FOLFOX (XELOX), FOLFIRI plus panitumumab (6 mg/kg on d1), cetuximab (500 mg/m2 on d1, iv) or bevacizumab (5 mg/kg on d1, iv) every 2 weeks. There were 210 (19.7%) right-sided of 1065 metastatic colorectal cancer (mCRC) patients treated with first-line FOLFOX/FOLFIRI plus panitimumab/cetuximab or bevacizumab regimens. Four patients treated with triplet chemotherapy backbone (5-fluorouracil, oxaliplatin and irinotecan) were excluded from the analysis. The median age was 62 (26-84). Thirty-five percent of patients were female. BRAF mutation and MSI-h status rates were 9,1% and 20%. The proportion of patients receiving treatment including panitumumab, cetuximab and bevacizumab was 19%, 27% and 54%, respectively. The median follow-up time was 18,7 months(mo’s) (2-73). Overall response rate was 46.8% (CR: 5.2%). Median treatment cycles was 6 (1 to 30) and 26,2% of the patients were given maintenance treatment with a median of 6 cycles (1 to 27). Second-line treatment was given to 56,2% of patients. Median PFS was 9,8 months (95% CI; 8,8- 10,8) and OS was 24,6 months (95% CI; 20,1-29,2). Response type was the only statistically significant parameter in multivariate cox regression analysis for progression free survival (p: 0.000). Complete and partial responders had longer PFS durations (21.2 and 11.2 mo’s) compared to stable and progressive disease (9.9 and 3.3 mo’s) patients (p:0.000). PFS in anti-EGFR treated group was numerically longer with oxaliplatin compared to the irinotecan treated group (11.7 vs 8.7 mo’s; p:0.093), but PFS duration was similar in bevacizumab and oxaliplatin or irinotecan treated patients (9.9. vs 9.7 mo’s). Metastatectomy rate was higher in anti-EGFR treated group (9.8% vs 17.2%). Biologic treatment and chemotherapy backbone and response type were statistically significant parameters in multivariate cox regression analysis for overall survival (OS, p < 0.05). Patients treated with panitimumab (32.8 mo’s) and cetuximab (28.7 mo’s) lived longer compared to bevacizumab (21.7 mo’s; p:0.047). Patients treated with oxaliplatin (26 mo’s) had longer survival than irinotecan (18.8) based chemotherapy backbone (p:0.045). ORR was similar in anti-VEGF and anti-EGFR mAb treated patients (44.2% and 44.3%). OS was longer with oxaliplatin (anti-EGFR vs anti-VEGF; 32.8 vs 22.8 mo’s) compared to irinotecan (anti-EGFR vs anti-VEGF; 18.8 vs 19.3 mo’s) based regimens. Anti-EGFR and oxaliplatin based treatment regimens and treatment responders were positive prognostic factors for OS in RAS wild-type mrCC patients.