Association of early tumor shrinkage with progression-free survival in patients with metastatic colorectal cancer treated with bevacizumab-based chemotherapy: HGCSG0802.

Abstract

749 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 cetuximab. We investigated association of ETS with progression free survival (PFS) in pts with unresectable colorectal liver metastases (CLM) from HGCSG0802 observational cohort study in pts with mCRC treated with first-line bevacizumab (BV)-based chemotherapy. Methods: The objective of HGCSG0802 was to evaluate PFS, OS, time to treatment failure (TTF), response rate (RR), safety and so on. The key eligibility criteria were evaluable lesions, older than 20 years old, ECOG PS 0-2. In this analysis, association of ETS at 8 weeks from the start of chemotherapy with pts characteristics, PFS and TTF was evaluated. Pts characteristics were compared using Student-t test, chi-square test and Fisher’s exact test. PFS and TTF were analyzed with Kaplan-Meier method and compared using log-rank test. Univariate analysis for the association of pts characteristics with PFS and TTF was performed using log-rank test, and multivariate analysis was performed using Cox proportional hazards model. Results: Of 108 pts (the full analysis set), 74 pts with CLM were evaluable for ETS. Forty-nine pts (66.2%) had ETS ≥20%. The pts characteristics between ETS ≥20% and <20% were well balanced. The median PFS was 7.3 months in ETS <20% versus 10.0 months in ETS ≥20% (HR 0.55; p=0.025). In multivariate analysis for PFS, there was no significant difference between ETS ≥20% and <20% (HR 0.585; p=0.066). The median TTF (ETS <20% v ≥20%) was 5,1 months vs. 7.7 months (HR 0.46; p=0.003). In multivariate analysis for TTF, there was significant difference between ETS ≥20% and <20% (HR 0.509; p=0.017). Conclusions: In this analysis, ETS ≥20% might be positive predictive marker for PFS and TTF in pts with CLM receiving first-line BV-based chemotherapy.