Patients with RAS wild-type metastatic colorectal cancer (mCRC) with left-sided tumors had a better prognosis than those with right-sided tumors, according to a study published in JAMA Oncology. 1

In a retrospective analysis, researchers led by Sabine Tejpar, MD, of the University Hospital Gasthuisberg in Belgium evaluated data from patients with RAS wild-type mCRC through the CRYSTAL (Cetuximab Combined With Irinotecan in First-line Therapy for Metastatic Colorectal Cancer; Identifier:

NCT00154102) and FIRE-3 (FOLFIRI Plus Cetuximab Versus FOLFIRI Plus Bevacizumab as First-Line Treatment For Patients With Metastatic Colorectal Cancer; Identifier: NCT00433927) trials.

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Patients were examined by whether they had left-sided tumors, defined as patients whose tumors originated in the splenic fixture, descending colon, sigmoid colon or rectum, or right-sided tumors, defined as tumors in the appendix, cecum ascending colon, hepatic flexure, or transverse colon. Researchers assessed for progression-free and overall survival, as well as objective response rate according to tumor location and treatment.

Patients with left-sided tumors had superior progression-free survival, overall survival and objective response rate in contrast with those with right-sided tumors.

RELATED: Alternative Metrics of Response Correlate With OS in FIRE-3 Trial

Among left-sided tumor patients, treatment with FOLFIRI plus cetuximab had significantly improved overall survival in contrast with those treated with FOLFIRI and FOLFIRI plus bevacizumab.

Patients with right-sided tumors who had a poor prognosis, however, experienced limited efficacy benefits with the addition of cetuximab to FOLFIRI in the CRYSTAL study. Comparable outcomes were found between the FOLFIRI plus cetuximab and FOLFIRI plus bevacizumab groups in FIRE-3.


  1. Tejpar S, Stintzing S, Ciardiello F, et al. Retrospective analyses of the CRYSTAL and FIRE-3 trials. JAMA  Oncol. 2016 Oct 10. doi:10.1001/jamaoncol.2016.3797 [Epub ahead of print]