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Panitumumab in Combination With Chemotherapy Significantly Improves Progression-Free Survival
Further, the addition of Vectibix to chemotherapy also improved response rate in the KRAS wild-type patient population as measured by blinded central review (55 percent versus 48 percent in the FOLFOX only arm).
"I am very pleased with the outcome of this high quality trial which demonstrated that Vectibix improved progression-free survival and appeared to be well tolerated as a first-line metastatic colorectal cancer treatment in a selected patient population," said Jean-Yves Douillard, director Clinical and Translational Research, Medical Oncology Branch, Centre R Gauducheau, France and the study's principal investigator. "This is the first prospective Phase 3 data to demonstrate the importance of KRAS mutation as a predictive biomarker for Vectibix treatment in the first-line setting, providing definitive support for the use of the KRAS biomarker for selection of patients eligible for anti-EGFR therapy."
Importantly, in patients with tumors harboring activating KRAS mutations, PFS was significantly inferior in the Vectibix arm. For patients with mutant KRAS tumors, median PFS was 7.3 months with Vectibix in combination with FOLFOX vs. 8.8 months with FOLFOX alone (hazard ratio 1.29, p=0.02). These data confirm previous findings when oxaliplatin-based chemotherapy and an anti-epidermal growth factor receptor (EGFR) antibody are combined in patients bearing tumors with activating KRAS mutations.
Consistent with the PFS data, an interim analysis of overall survival, a secondary endpoint, demonstrated a reduction in overall survival in patients with KRAS mutant tumors receiving Vectibix. The median overall survival for patients with KRAS wild-type mCRC has not yet been reached. Long-term follow-up for survival continues and the primary analysis is expected in the fourth quarter of 2009.
Adverse event rates were comparable across arms with the exception of known toxicities associated with anti-epidermal growth factor receptor (EGFR) therapy such as rash, diarrhea and hypomagnesemia. Vectibix-related grade 3 infusion reactions were reported for two patients (less than 1 percent).
Originally designed to compare the treatment effect in the overall population, the study was amended to analyze outcomes with respect to the presence or absence of activating mutations in KRAS in the tumor itself. Tumor KRAS status was ascertained in 93 percent of the 1,183 patients enrolled in the trial, the highest percentage ever reported. Tumor KRAS tests were finalized after the completion of enrollment and prior to the primary analysis.