(ChemotherapyAdvisor) – Patients with KRAS wild-type metastatic colorectal cancer who are receiving capecitabine- and cetuximab-based first-line therapy experience early tumor shrinkage that correlates with prolonged progression-free survival and overall survival, as well as cetuximab-induced skin toxicity, according to the results of a study presented at the 2012 American Society of Clinical Oncology Annual Meeting.
The present analysis, for the first time, evaluates the correlation of early tumor shrinkage with outcome parameters in patients undergoing capecitabine-based therapy, and also aims to correlate the predictive value of ETS and cetuximab-induced skin toxicity, wrote lead author Dominik Paul Modest, MD, of Klinikum Grosshadern and Comprehensive Cancer Center, Munich, Germany.
Patients in this study were randomized to receive either capecitabine/oxaliplatin (CAPOX) plus cetuximab or capecitabine/irinotecan (CAPIRI) plus cetuximab as first-line treatment of metastatic colorectal cancer. ETS was defined as a relative change of ≥20% in the sum of the longest diameters of target lesions compared to baseline, the authors wrote.
Tumors from 63 patients (71% KRAS wild-type (wt), 100% skin reactions) developed ETS, 58 tumors did not develop early tumor shrinkage (53% KRAS wt, 86% skin reactions). Early tumor shrinkage was associated with prolonged progression-free survival (8.9 vs. 4.7 months, P<0.001, hazard ratio, 0.37) and overall survival (31.6 vs. 15.8 months, P=0.005, hazard ratio, 0.48) in patients with KRAS wt tumors but not in patients with KRAS mutant metastatic colorectal cancer. Early tumor shrinkage occurred more frequently with CAPOX- vs. CAPIRI-based therapy (P=0.05). There was a highly significant correlation between the occurrence of early tumor shrinkage and cetuximab-related skin toxicity of any grade (1–3) (P=0.002). Early tumor shrinkage was documented more frequently in patients with liver metastasis (P=0.09), metastatic involvement of <2 organs (P=0.09), KRAS wild-type tumors (P=0.06), and no previous adjuvant chemotherapy (P=0.06).
The investigators concluded that patients with KRAS wild-type mCRC who are receiving capecitabine- and cetuximab-based first-line therapy experienced early tumor shrinkage that correlates with prolonged progression-free survival and overall survival, as well as cetuximab-induced skin toxicity.