Observational cohort study of first-line bevacizumab with oxaliplatin or irinotecan and fluoropyrimidines in metastatic colorectal cancer: HGCSG0802—Analysis of early tumor shrinkage (ETS).

Abstract

753 Background: It was reported that early tumor shrinkage (ETS) was associated with better overall survival (OS) in patients (pts) with metastatic colorectal cancer (mCRC) receiving first line chemotherapy. We investigated association of ETS with progression-free survival (PFS) and OS in pts with mCRC treated with first-line bevacizumab (BV)-based chemotherapy (HGCSG0802). Methods: The objective of HGCSG0802 was to evaluate PFS, OS, response rate (RR), safety and so on. The key eligibility criteria were evaluable lesions, older than 20 years old, ECOG PS 0-2. This analysis evaluated the association of ETS at 8 weeks from the start of chemotherapy with pts characteristics, PFS and OS. To identify factors associated with ETS, if there were clinical variables with p < 0.2 in univariate analysis, we planned a multivariate analysis using the logistic regression model. To identify predictive and prognostic factors, a multivariate analysis was performed using Cox proportional hazard model with backward elimination for variables with p < 0.2 in univariate analysis. Results: Of 108 pts (the full analysis set), 99 pts were evaluable for ETS. Sixty-eight pts (68.7%) had ETS ≥20%. The pts characteristics between ETS ≥20% (ETS) and <20% (Non-ETS) were well balanced. In univariate analysis to identify factors associated with ETS, there were no clinical variables with p < 0.2. The median PFS and OS were 7.3/18.3 months in Non-ETS versus 10.0/25.2 months in ETS (HR 0.529; p=0.006 and HR 0.627; p=0.107). In multivariate analysis for PFS and OS, although there was no significant difference between ETS and Non-ETS for OS (HR 0.709; p=0.186), there was significant difference for PFS (HR 0.524; p=0.006). Conclusions: ETS was observed in 68.7% (68/99) and non-ETS in 31.3% (31/99) of patients with metastatic colorectal cancer received bevacizumab combined first line chemotherapy. In univariate analysis, it could not identify any factors associated with ETS. In the results of multivariate analysis, ETS showed an independent predictive impact, but not prognostic impact. Clinical trial information: UMIN000018935.