Correlative analyses of RET RET and RAS mutations in a phase 3 trial of cabozantinib in patients with progressive, metastatic medullary thyroid cancer

摘要

BACKGROUND Cabozantinib significantly prolonged progression‐free survival (PFS) versus a placebo in patients with progressive, metastatic medullary thyroid cancer (MTC; P ??.001). An exploratory analysis of phase 3 trial data evaluated the influence of rearranged during transfection ( RET ) and RAS (HRAS, KRAS, and NRAS) mutations on cabozantinib clinical activity. METHODS Patients (n?=?330) were randomized to cabozantinib (140?mg/day) or a placebo. The primary endpoint was PFS. Additional outcome measures included PFS, objective response rates (ORRs), and adverse events in RET and RAS mutation subgroups. RESULTS Among all study patients, 51.2% were RET mutation–positive (38.2% with RET M918T), 34.8% were RET mutation–unknown, and 13.9% were RET mutation–negative. Sixteen patients were RAS mutation–positive. Cabozantinib appeared to prolong PFS versus the placebo in the RET mutation–positive subgroup (hazard ratio [HR], 0.23; 95% confidence interval [CI], 0.14‐0.38; P ??.0001), the RET mutation–unknown subgroup (HR, 0.30; 95% CI, 0.16‐0.57; P ?=?.0001), and the RAS mutation–positive subgroup (HR, 0.15; 95% CI, 0.02‐1.10; P ?=?.0317). The RET M918T subgroup achieved the greatest observed PFS benefit from cabozantinib versus the placebo (HR, 0.15; 95% CI, 0.08‐0.28; P ??.0001). The ORRs for RET mutation–positive, RET mutation–negative, and RAS mutation–positive patients were 32%, 22%, and 31%, respectively. No PFS benefit was observed in patients lacking both RET and RAS mutations, although the ORR was 21%. The safety profile for all subgroups was similar to that for the overall cabozantinib arm. CONCLUSIONS These data suggest that cabozantinib provides the greatest clinical benefit to patients with MTC who have RET M918T or RAS mutations. However, a prospective trial is needed to confirm the relation between genetic variation and the response to cabozantinib. Cancer 2016;122:3856–3864. ? 2016 American Cancer Society.