Early Tumor Shrinkage (ETS) For the Prediction of Efficacy in Metastatic Colorectal Cancer (MCRC): Post-Hoc Analysis from an Irinotecan-Based Randomized First-Line Trial

ABSTRACT Background Early tumor shrinkage (ETS) has been highlighted as a favorable prognostic factor related to progression-free survival (PFS) and overall survival (OS) in cytotoxic chemotherapy with or without cetuximab. We investigated ETS ≥20% and Material and methods Data from a randomized phase III study comparing FUFIRI vs. mIROX in 479 pts were evaluated. ETS has been defined as at least 20% shrinkage between the sum of baseline diameters (RECIST) and the first remission control imaging according to Piessevaux et al. As in our study one cycle consisted in 50 days of treatment our time interval was 7.2 weeks. ETS assessment was possible in 201 pts. PFS and OS for ETS ≥ 20% and Results Baseline characteristics between ETS ≥20% and Conclusion In this irinotecan-based study the presence of ETS ≥20% was associated with a significant benefit in PFS and OS. Pts with ETS Disclosure C. Giessen: Travel support: Roche. S. Stintzing: honoraria and financial support for research, Merck Serono. All other authors have declared no conflicts of interest.