Panitumumab-FOLFIRI: Effective Second-line Treatment for Metastatic Colorectal Cancer

By William B. Ershler, MD

Synopsis: This report details the long-term outcomes from a dataset culled in a previous industry-sponsored study that displayed non-significant results linking panitumumab-FOLFIRI to increased survival rates regarding KRAS metastatic colorectal cancer when compared with FOLFIRI alone.

Source: Peeters M, et al. Final results from a randomized, Phase 3 study of FOLFIRI ± panitumumab for second-line treatment of metastatic colorectal cancer. Ann Oncol2014;25:107-116.

Coupled with chemotherapy, certain agents that have had success combating otherwise-chemorefractory colorectal cancers have often targeted epidermal growth factor receptors (EGFRs). The presence of the KRAS gene in tumors is perhaps the most established predictive biomarker for the effect anti-EGFR chemicals can have for mCRC patients. Panitumumab itself is a fully humanized monoclonal antibody that inhibits downstream cell signaling by binding to the EGFR of cancerous tumor cells. Panitumumab has shown the tendency to inhibit tumor growth and angiogenesis as well as even induce tumor cell apoptosis.

Designed to discern the relative benefit of using panitumumab in conjunction with FOLFIRI, study 20050181 has just now borne long-term results. An international phase 3 trial, study 20050181 randomly assigned patients with prior history of mCRC treatment to groups of equal size: one group was treated with FOLFIRI, while the test group received a joint treatment of Panitumumab and FOLFIRI. Treatments were conducted every two weeks, and progression-free survival and overall survival rates were gleaned through analysis of tumor KRAS status.

The 1186 patients were randomly assigned to groups and then categorized by both their treatment and their tumor specificities. Though wild-type KRAS tumor patients saw an improvement in treatments with panitumumab, quality of life data was not completely procured. As such, the study fails to provide sufficient evidence of any statistically significant or meaningful deviations or improvements between the panitumumab-FOLFIRI treatments and the FOLFIRI-alone treatments.