Impact of early tumor shrinkage on clinical outcome in wild-type-KRAS colorectal liver metastases treated with cetuximab

Abstract

Background and Aim: To evaluate the impact of early tumor shrinkage (ETS) on long-term outcome in patients with wild-type Kirsten rat sarcoma viral oncogene homolog (KRAS) unresectable colorectal liver metastases (CLM) receiving cetuximab plus chemotherapy. Methods: A total of 138 patients in a randomized controlled trial (70 in armA received cetuximab plus chemotherapy, 68 in armB received chemotherapy alone), as previously reported (Ye etal., 2013) were included into this analysis. The cut-off date updated for overall survival (OS) was June 2014. ETS was defined as a ≥20% reduction of the longest diameters of the target lesions compared with baseline at the first evaluation (8 weeks). Outcome measures were progression-free survival (PFS) and OS. Results: There were 132 patients available for evaluation, and ETS occurred more frequently in armA than that in armB (P=0.003). ETS was associated with longer OS (armA: 35.7 vs 19.5 months, P<0.001; armB 28.7 vs 18.7 months, P=0.01) and PFS (armA: 13.4 vs 4.2 months, P<0.001; armB 7.0 vs 4.2 months, P=0.001) compared with patients with no-ETS. Among patients with ETS, there was a significant difference between armA and armB in PFS (P=0.03), but not in OS (P=0.19). All 23 patients who underwent liver surgery achieved ETS. In armA, for patients without liver surgery, patients observed ETS also gained an increased survival benefit over those no-ETS in OS (P=0.02) and PFS (P<0.001). ETS was an independent predictor of improved OS (hazard ratio 0.56, P=0.007). Conclusion: ETS may serve as a predictor of favorable outcome in patients with wild-type KRAS CLM receiving cetuximab plus chemotherapy.