mFOLFOX plus panitumumab is associated with an improved tumor response in metastatic colorectal cancer patients

This study investigated the tumor response and overall survival in colorectal cancer patients treated with mFOLFOX6 and bevacizumab (Avastin) or panitumumab (Vectibix). Researchers suggested that mFOLFOX+panitumumab is associated with an improved response. 

The standard treatment for metastatic (spread to other parts of the body) colorectal cancer is chemotherapy. Chemotherapy is used in these patients to reduce symptoms and prolong survival. Chemotherapy agents attack cancer cells, slowing down cancer progression.

Different chemotherapies can be used and are often combined to increase effectiveness. mFOLFOX6 chemotherapy combines 5-fluorouracil, leucovorin and oxaliplatin. More recently, targeted therapies like bevacizumab or panitumumab, which block the effect of proteins involved in tumor growth, have been shown to be effective.

More aggressive tumors can have mutations (permanent changes) such as KRAS, NRAS or BRAF. The outcomes of patients with these mutations are in general poorer and treatment less efficient. 

Prior studies suggested that mFOLFOX6 plus panitumumab was associated with a longer overall survival when compared to mFOLFOX6 plus bevacizumab in patients with the BRAF mutation. However, this study did not determine the tumor response of these two lines of treatment.

The objective of this study was to determine the tumor response and overall survival associated to the two treatments mFOLFOX+panitumumab (group 1) and mFOLFOX+bevacizumab (group 2).

This study included information about 326 metastatic colorectal cancer patients. Of these, 233 underwent RAS mutation analysis. Of 233, 156 had non-mutated tumors (RAS and BRAF negative) and 14 had RAS-negative and BRAF-positive tumors.

Patients were randomized to group 1 or group 2. The average follow-up time was of 134.1 weeks for group 1 and 115.7 for group 2.

BRAF positive patients from group 1 had a 32% improvement in the odds of a longer progression-free survival (time from treatment to progression). These patients also had a 24% improvement in the odds of a better survival when compared to patients from group 2.

Patients from group 1 with RAS and BRAF negative tumors had an improved survival of 41.3 months when compared to group 2 (28.9 months).

Patients from group 1 had a 41% improvement in the odds of a better duration of response. These patients were more likely to see a 30% decrease in tumor size.

This study concluded that mFOLFOX+panitumumab treatment is associated with increased PFS and OS and improved tumor response in patients without a RAS mutation.