FOLFOXIRI-bevacizumab or FOLFOX-panitumumab for the treatment of left-sided metastatic colorectal cancer without RAS/BRAF mutations.

This study compared the use of chemotherapy and bevacizumab (Avastin) or panitumumab (Vectibix) for the treatment of left-sided metastatic colorectal cancer (mCRC) without BRAF/RAS mutations (permanent changes in genes). The study found that both treatment options are effective for these patients. 

Patients who are diagnosed with mCRC have disease that has spread to other areas. A distinct group of these patients has cancer that began in the left side of the large intestine. This is termed left-sided mCRC. Genetic changes in RAS and BRAF proteins can often occur to promote mCRC growth and spread. mCRC tumors that do not have these genetic changes are termed RAS/BRAF wild-type (wt) mCRC.

Patients who have left-sided RAS/BRAF wt mCRC have limited treatment options. Treatment includes a combination of targeted therapy and chemotherapy. Bevacizumab is a targeted therapy that stops the formation of new blood vessels in the tumor. This starves the tumor and it stops growing and spreading. Panitumumab is a targeted therapy that blocks signals that tell the cancer cells to grow and divide. Bevacizumab can be used in combination with chemotherapy regimens such as FOLFOXIRI (folinic acid, fluorouracil, oxaliplatin, and irinotecan). Panitumumab is used together with FOLFOX (folinic acid, fluorouracil, and oxaliplatin).

It is not yet clear which treatment option gives patients with RAS/BRAF wt mCRC a better outcome.

This study analyzed the results of 5 different clinical trials. Overall, 317 patients with left-sided RAS/BRAF wt mCRC were included in the study. 185 patients were given FOLFOX+ panitumumab (Group 1). 132 patients were given FOLFOXIRI + bevacizumab (Group 2). The average follow-up time was 39.6 months.

The average survival without cancer growing or spreading was similar between group 1 (11.4 months) and 2 (13.3 months). The average overall survival was also similar between group 1 (30.3 months) and group 2 (33.1 months). 77% of group 1 and 73% of group 2 responded to treatment. 

59% of patients in group 2 and 46% of patients in group 1 reported serious side effects. The most common serious side effect was low white blood cell count (48% in group 2 and 26% in group 1).

This study found that patients with RAS/BRAF wt mCRC treated with FOLFOX+ panitumumab and FOLFOXIRI + bevacizumab had similar outcomes.

This study combined data from 5 clinical trials. This meant that the treatments were not randomized. The criteria for choosing patients for each clinical trial were different. The sample size was small in each individual trial. A clinical trial directly comparing the 2 treatments would give clearer results.