Colorectal Tumor Location Influences Length of Survival

Drug efficacy varies in colorectal cancer dependent on where the tumor is located.

The primary location of tumors in the colon is associated with the length of survival in metastatic colorectal cancer patients, a recent study found.

The retrospective analysis presented at the 2016 American Society of Clinical Oncology Annual Meeting used data from the federally-funded phase 3 CALGB/SWOG 80405 clinical trial that compared bevacizumab and cetuximab in combination with chemotherapy as an initial treatment for metastatic colorectal cancer.

Data was identified from 293 patients with right-sided primary tumors and 732 patients with left-sided primary tumors. Participants eligible for the analysis were disqualified if they had a mutated KRAS gene.

The left side of the colon includes the descending colon, sigmoid colon, and rectum, while the right side include the cecum and ascending colon. The results of the study showed that patients with left-side tumors had a longer median overall survival of 33.3 months compared with patients who have right-side tumors at 19.4 months.

In the left-side arm, patients given cetuximab lived 36 months, while the right-side arm lived 16.7 months. Similar results were seen among patients who received bevacizumab and had an overall survival of 31.4 months for left-side tumors and 24.2 months for right-side tumors.

There was no significant advantage found within the study for overall or progression-free survival in patients who received cetuximab or bevacizumab. However, the findings suggest that drug efficacy may differ depending on the location of the primary tumor.

Right-side tumors treated with bevacizumab showed longer survival (24.2 months) than cetuximab (16.7 months). Left-side tumor patients treated with cetuximab had longer overall survival at 36 months compared with bevacizumab at 31.4 months.

“While previous studies had suggested that tumor location may impact clinical colorectal cancer outcomes, the effect we observed in this analysis appears to be far greater than we expected,” said lead study author Alan P. Venook, MD. “These findings will likely change the way we approach colorectal cancer treatment and research, even as we seek to more deeply understand the biology driving the difference in outcomes between right- and left-sided cancers.”