Prognostic significance of primary tumor localization in patients with metastatic colorectal cancer: Is it beneficial to select targeted treatment? Real-life experience from Turkey.

Purpose: The purpose of this study was to investigate the prognostic value,and the effect of primary tumor location on targeted therapy selection in patients with metastatic colorectal cancer (mCRC).

Methods: A total of 201 patients with de novo mCRC who received first line treatment were retrospectively analyzed. Clinicopathological features, treatment outcomes, the primary tumor surgery, metastasectomies/local therapies and survivals were evaluated in terms of both RAS mutation status and primary tumor sidedness.

Results: Tumor localization showed 140 (69.7%) patients with left-sided and 61 (30.3%) with right-sided tumors. Median progression-free survival (PFS) and overall survival (OS) were significantly shorter in patients with right-sided tumor than those with left-sided tumors (10.1 vs 12.9 months, p=0.005; 25 vs 44.4 months, p=0.008, respectively). In addition,the median OS interval of patients receiving anti-VEGF containing regimen was better than those treated with anti-EGFR containing regimen (50.7 vs. 26.9 months, p=0.001). Multivariate analysis indicated that age (HR:0.41,p=0.045), primary tumor resection (HR:0.41,p=0.037) and primary tumor localization (HR:0.38,p=0.021) for PFS and age (HR:0.39, p=0.09), the presence of BRAF mutation (HR:0.59,p=0.019) and the type of targeted therapy (HR:3.16,p=0.025) for OS were independent prognostic factors.

Conclusions: Our results showed that primary tumor location is a prognostic factor in mCRC patients regardless of RAS status. Primary tumor location before treatment decision may be a simple indicator predicting survival and in choosing targeted agent.