RESEARCH ARTICLE The Prognostic Significance of Metabolic Response Heterogeneity in Metastatic Colorectal Cancer

Background Tumoral heterogeneity is a major determinant of resistance in solid tumors. FDG-PET/CT can identify early during chemotherapy non-responsive lesions within the whole body tumor load. This prospective multicentric proof-of-concept study explores intra-individual meta-bolic response (mR) heterogeneity as a treatment efficacy biomarker in chemorefractory metastatic colorectal cancer (mCRC). Methods Standardized FDG-PET/CT was performed at baseline and after the first cycle of combined sorafenib (600mg/day for 21 days, then 800mg/day) and capecitabine (1700 mg/m/day administered D1-14 every 21 days). MR assessment was categorized according to the pro-portion of metabolically non-responding (non-mR) lesions (stable FDG uptake with SUV-max decrease <15%) among all measurable lesions. Results Ninety-two patients were included. The median overall survival (OS) and progression-fre