A retrospective analysis found that the location of the primary tumor within the colon predicts survival and may help inform optimal treatment selection for patients with metastatic colorectal cancer.

The data show that patients whose primary tumors originate on the left side of the colon—including the descending colon, sigmoid colon and rectum—survive significantly longer than those whose tumors originate on the right side, or the cecum and ascending colon.

Researchers retrospectively evaluated data from the phase III CALGB/SWOG 80405 clinical trial, a federally funded clinical trial designed to compare Avastin (bevacizumab) and Erbitux (cetuximab) in combination with chemotherapy as initial therapy for metastatic colorectal cancer.