Prognostic importance of tumor location and anti-EGFR therapy in patients with K-RAS wild type metastatic colorectal cancer.

PURPOSE: To compare anti-EGFR and anti-VEGF agents in patients with K-RAS wild-type metastatic colorectal cancer (mCRC) with regards to tumor location. METHODS: 450 patients diagnosed with mCRC, who applied to our center were included in this retrospective study. Of 450 patients, 303 underwent K-RAS mutation tests, assessed as having right-sided or left-sided mCRC and grouped according to localization of right and left colon. Sixty-five Patients with K-RAS wild-type mCRC, who were treated with first line anti-EGFR or anti-VEGF containing combination therapies of fluorouracil with leucovorin and either irinotecan or oxaliplatin were compared. RESULTS: 393 (87%) out of 450 mCRC patients had left-sided colon cancers, and 57(13%) had right-side colon cancers. K-RAS analysis was performed in 303 of 450 patients with mCRC, 186 (61.4%) patients had K-RAS wild-type and 117 (38,6%) had K-RAS mutant. Median survival for right-sided cancers was 23.3 months and 29.4 months for left-sided cancers (p=0.309). Median progression-free survival (PFS) was 10.4 months (95% CI 7.3-13.4) in the anti-EGFR containing regimens group and 9.7 months (8.2-11.1) in the anti-VEGF containing regimens group (p=0.037); however, median overall survival (OS) was 18.4 months (95% CI 11.7-25.1) in the anti-EGFR containing regimens group and 19.3 months (95% CI 15.7-22.9) in the anti-VEGF containing regimens group (p=0.635). CONCLUSION: Addition of anti-EGFR in left sided K-RAS wild-type mCRC regarding PFS was beneficial, however there was no difference in terms of OS.