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 German AIO KRK 0104 trial.

PURPOSE: 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 as first-line therapy. Moreover, correlations of ETS with clinical characteristics and prognostic markers were evaluated.

PATIENTS AND METHODS: In total, 121 patients were included into this analysis. Patients were treated with cetuximab combined with either CAPIRI or CAPOX. ETS at six weeks was defined as a relative change of ≥ 20% in the sum of the longest diameters of target lesions compared to baseline. Survival times were compared between patients with ETS ≥ 20% versus no-ETS.

RESULTS: ETS ≥ 20% was observed in 59% of all patients with KRAS wild-type tumors. In these patients ETS ≥ 20% was associated with higher overall response rate (82% vs. 19%, p < 0.001). Also, PFS (8.9 vs. 4.7 months, p < 0.001) and OS (31.6 vs. 15.8 months, p = 0.005) were significantly superior in ETS ≥ 20% of patients compared to no-ETS. In patients with KRAS mutant mCRC ETS ≥ 20% neither had an effect on PFS nor OS. Cetuximab-induced skin toxicity correlated with the occurrence of ETS ≥ 20% (p = 0.002).

CONCLUSION: In patients with KRAS wild-type tumors treated with cetuximab plus capecitabine-based chemotherapy ETS ≥ 20% is an important predictor of favorable outcome.