Tumor Location Impacts Treatment Outcomes in Metastatic Colorectal Cancer

09/25/17

Recent research has uncovered an association between tumor origin and mortality among patients receiving systemic chemotherapy plus biologic therapy for metastatic colorectal cancer, published in JAMA Surgery (online September 20, 2017; doi:10.1001/jamasurg.2017.3466).

Metastatic colorectal cancer is often times treated with biologic therapies – such as bevacizumab or cetuximab. Recent research has led many to believe that right-sided or left-sided primary tumor origin may have an effect on response to biologic therapy and survival.

Mayada A Aljehani, MSPH, Epidemiology Program, Loma Linda University School of Public Health (California), and colleagues conducted a study to evaluate the association of tumor origin with mortality in patients receiving systemic chemotherapy plus bevacizumab or cetuximab for metastatic colorectal cancer. Researchers used a diverse population-based data set of 11,905 patients, 4632 of whom received chemotherapy plus bevacizumab or cetuximab.

Patients were stratified by tumor origin in the left vs right sides. The primary outcome was mortality hazards by tumor origin, assessed for patients receiving chemotherapy alone or chemotherapy plus biologic therapy.

Results of the comparison showed that patients receiving chemotherapy plus bevacizumab benefited from reduced mortality regardless of tumor origin, compared with those who received chemotherapy alone. Chemotherapy plus cetuximab was shown to reduce mortality only among patients with left-sided tumors; the combination was associated with significantly higher mortality for right-sided tumors (HR, 1.31; 95% CI, 1.14-1.51; P < .001).

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Furthermore, researchers found that among those receiving chemotherapy plus biologic therapy (either bevacizumab or cetuximab), right-sided origin was associated with higher mortality than left-sided origin.

A subgroup analysis for patients with wild-type KRAS tumors showed similar data supporting favorable results for patients with left-sided origin after biologic therapy.

Researchers concluded that there is a significant association between primary tumor site and response to biologic therapy in metastatic colorectal cancer. These findings support the use of tumor origin in stratification for research and guidelines for treatment of such disease, they wrote.—Zachary Bessette