Panitumumab is associated with improved survival in metastatic colorectal cancer without KRAS or RAS mutations

This study investigated the effect of panitumumab (Vectibix) in overall survival of patients with metastatic colorectal cancer without a KRAS or RAS mutation. Researchers suggested that panitumumab significantly improved survival in these patients. 

Panitumumab is a therapy that targets a particular receptor (the EFGR receptor) on a cancer cell. This blocks the cell from growing, and eventually causes cell death. This therapy is effective alone and combined with chemotherapy in patients with metastatic colorectal cancer (spread to other areas of the body). A previous study reported that patients treated with panitumumab plus best supportive care (BSC; treatment to relieve the symptoms) had a significant improvement in overall survival. This improved survival was reported in patients without a particular mutation (permanent genetic change present in more aggressive cancers) in the KRAS gene (KRAS exon 2) when compared with patients with the mutation.

It is not clear whether or not this KRAS mutation, or mutations in the same family of genes (RAS mutations), can predict who could benefit from this treatment.

The objective of this study was to evaluate the impact of panitumumab in the overall survival of patients with metastatic colorectal cancer. Additionally this study examined whether the KRAS or RAS mutation could predict response to treatment.

337 patients with metastatic colorectal cancer were included. 83% of patients did not have a KRAS mutation.17% had another type of RAS mutation. Patients were randomly assigned to treatment with panitumumab and BSC (group 1) or BSC alone (group 2). The average follow-up period was 41 weeks for group 1 and 25.5 weeks for group 2.

Average overall survival (time from treatment until death from any cause) was 10 months for group 1. Overall survival was 6.9-7.4 months for group 2, depending on the type of mutation. Patients in group 1 had a 27% to 30% improvement in the odds of a better overall survival,

Patients in group 1 had a 49% improvement in the odds of a better progression-free survival (time from treatment to disease progression). The objective response rate (ORR; disease response rate to the treatment) was 27% in group 1 and 1.6% in group 2. 

Patients with a RAS mutation did not benefit from panitumumab treatment.  

This study showed that panitumumab improved overall survival in patients with metastatic colorectal cancer without a KRAS or RAS mutation. Additionally, this study confirmed that the KRAS or RAS mutation may predict outcomes of metastatic colorectal cancer patients treated with panitumumab.