The impact of dose reduction and time delay in irinotecan- and oxaliplatin-based chemotherapies on outcomes in metastatic colorectal cancer.

Abstract

631 Background: This study was designed to evaluate the influence of dose reduction and schedule modification on outcomes in patients with metastatic colorectal cancer (mCRC). Methods: Pooled datasets from two previous phase II trials of FOLFIRI (CCOG-0502; n = 36) and mFOLFOX6 (CCOG-0704; n = 30) in patients with mCRC were analyzed retrospectively. The RDIs of irinotecan and oxaliplatin were compared to response rate (RR), disease control rate (DCR), progression-free survival (PFS) and overall survival (OS). To assess the effects of dose reduction and time delay, we defined ‘dose index (DI)’ as the ratio of the actual delivered total dose to the planned total dose and ‘time index (TI)’ as the ratio of the planned duration to the actual duration of therapy. Relative dose intensity (RDI) was computed by multiplying DI by TI. DI and TI of irinotecan and oxaliplatin were compared to response rate (RR), disease control rate (DCR) and progression-free survival (PFS). Results: In patients receiving FOLFIRI therapy, the median DI and TI of irinotecan were 0.92 and 0.90, respectively. RRs were 59% vs. 12% in the higher vs. lower DI groups (p < 0.01), and 35% vs. 35% in the higher vs. lower TI groups (p = 1.00), respectively. Median PFS was 10.2 vs. 5.0 months in the higher vs. lower DI groups (p < 0.01), and 6.1 vs. 6.7 months in the higher vs. lower TI groups (p = 0.48), respectively. In mFOLFOX6 therapy, the median DI and TI of oxaliplatin were 0.97 and 0.82, respectively. RRs were 44% vs. 36% in the higher vs. lower DI groups (p = 0.65), and 44% vs. 36% in the higher vs. lower TI groups (p = 0.65), respectively. Median PFS was 7.7 vs. 6.7 months in the higher vs. lower DI groups (p = 0.13), and 8.5 vs. 5.9 months in the higher vs. lower TI groups (p = 0.02), respectively. Multivariate analyses showed that DI of irinotecan (HR 8.48; 95% CI, 2.94-24.51, p < 0.01) and TI of oxaliplatin (HR 2.74; 95% CI, 1.02-7.33, p = 0.04) were the independent prognostic factors for PFS. Conclusions: Dose reductions in irinotecan and time delays in oxaliplatin could have significant impact on PFS in patients receiving FOLFIRI and FOLFOX6, respectively.