Impact Of Cetuximab Sequence On Progress-Free Survival (Pfs) And Overall Survival (Os) In Patients With Ras Wild-Type Metastatic Colorectal Cancer (Mcrc): A Real-World Study.

e16042 Background: Cetuximab provides a clear clinical benefit in the treatment in patients with RAS wild-type mCRC irrespective of treatment line, but the best sequence is still under investigation. Methods: Patients with RAS wild-type mCRC (2011-2019) who received cetuximab therapy were retrospectively analyzed. They were stratified based on the cetuximab treatment sequence, into the 1st, 2nd, 3rd or later-lines groups. The primary objective was to investigate the impact on Cetuximab sequence (2nd vs. 3rd and later-line) in PFS and OS. As for patients received the 3rd or later-line cetuximab with irinotecan therapy after refractory to the prior 1st and 2nd-line combined chemotherapy with fluoropyrimidine, oxaliplatin, and irinotecan, they will get another PFS of 2nd-line chemotherapy (PFSchemo) besides the PFS of 3rd or later-line cetuximab compared with the cetuximab 2nd-line used patients. We combined the PFSchemo to the PFS of 3rd or later-line cetuximab, then compared with PFS of 2nd -line cetuximab to evaluate the primary objective in PFS. As for the OS of primary objective, we calculated it from start of the 2nd-line of treatment. The secondary objective was to compare the efficacy of cetuximab sequence (1st vs. 2nd and later-lines) in OS calculated from start of the 1st-line of treatment. Results: In total, 193 patients were included: 106 in the 1st, 41 in the 2nd, and 46 in the 3rd-line groups. No difference was observed in baseline characteristics as sex,age,site of primary tumour,number of metastatic sites in the three groups. The median PFS of the 2nd-line and 3rd or later-line groups were 7.1 (95% CI 6.39-7.80) and 13.87 months(95% CI 11.44-16.29) respectively. PFS of the 3rd or later-line group was significantly longer than that of the 2nd-line group (hazard ratio[HR], 0.552; 95% CI, 0.349 to 0.871; P = 0.01). Median OS was 17.8 months (95% CI 13.5-22.1) in the 2nd-line and 27.4 months (95% CI 20.69-34.16) in the 3rd or later-line group (HR, 0.597; 95% CI 0.341 to 1.043; P = 0.07) from start of 2nd-line therapy. The median OS was 28.17 months (95% CI 22.11-34.22) in the 1st-line group and 33.10 months (95% CI 26.88-39.31) in the 2nd and later-lines group (HR, 0.724; 95% CI 0.507 to 1.304; P = 0.075) calculated from the 1st-line of therapy. Conclusions: In a real-world cohort we found that later-line especially 3rd or later-line therapy of cetuximab, may be more benefit for patients with RAS wild type mCRC, as 3rd or later-line use of cetuximab give one more line therapy chance.