The Predictive Role of Primary Tumour Sidedness in Metastatic Colorectal Cancer Treated With Targeted Agents.

Abstract

The aim of our study was to assess the predictive role of primary tumour sidedness (PTS) in patients with metastatic colorectal cancer (mCRC) harbouring wild-type RAS and treated with targeted agents. The cohort included 178 patients treated with first-line chemotherapy plus cetuximab, panitumumab or bevacizumab. We observed longer progression-free survival (PFS) and overall survival (OS) in patients with left-sided (L-CRC) compared to right-sided tumours (R-CRC) treated with anti-EGFR mAbs (p=0.0033 and p=0.0037), while there was no difference in patients treated with bevacizumab (p=0.076 and p=0.56). Finally, we observed longer PFS and OS in patients with L-CRC treated with anti-EGFR mAbs and those with R-CRC treated with bevacizumab compared to the reverse combination (p=0.0002 and p=0.011). PTS is a predictive factor for anti-EGFR mAbs, not for bevacizumab. Superior survival was observed when anti-EGFR mAbs were used for L-CRC and bevacizumab for R-CRC.