Finally, pooled analysis of all 3 trials suggested that only the G12A KRAS allele was significantly associated with a negative treatment effect on OS....The results from this retrospective analysis of three phase 3 trials indicate that patients with MT KRAS codon 12 or 13 mCRC tumors are unlikely to benefit from panitumumab therapy.

The treatment effect on PFS in the wild-type (WT) KRAS group (hazard ratio [HR], 0.45; 95% CI: 0.34 to 0.59) was significantly greater (P < .0001) than in the mutant group (HR, 0.99; 95% CI, 0.73 to 1.36). Median PFS in the WT KRAS group was 12.3 weeks for panitumumab and 7.3 weeks for BSC. Response rates to panitumumab were 17% and 0%, for the WT and mutant groups, respectively. WT KRAS patients had longer overall survival (HR, 0.67; 95% CI, 0.55 to 0.82; treatment arms combined)....Table 2. Distribution of KRAS Mutations By Treatment Arm.