Early tumor shrinkage in patients with metastatic colorectal cancer receiving first-line treatment with cetuximab combined with either CAPIRI or CAPOX: An analysis of the AIO KRK 0104 trial.

3588 Background: This study investigated the impact of early tumor-shrinkage (ETS) on progression-free (PFS) and overall survival (OS) in patients with metastatic colorectal cancer (mCRC) treated within the AIO KRK-0104-trial. ETS was previously shown to be a predictor of treatment response to cetuximab. The present analysis, for the first time, evaluates the correlation of ETS with outcome parameters in patients undergoing capecitabine-based therapy. It also aims to correlate the predictive value of ETS and cetuximab-induced skin toxicity. Methods: The AIO KRK0104 trial was performed as a randomised study comparing capecitabine/oxaliplatin (CAPOX) plus cetuximab to capecitabine/irinotecan (CAPIRI) plus cetuximab in the first-line treatment of mCRC. 121 patients were available for evaluation of ETS at 6 weeks. ETS was defined as a relative change of ≥20% in the sum of the longest diameters of target lesions compared to baseline. Results: Tumors of 63 patients (71% KRAS wild-type (wt), 100% skin reactions)...