Relative dose intensity of first-line triplet chemotherapy in metastatic colorectal cancer

Purpose: Relative dose intensity (RDI) is a measurement of chemotherapy (CT) dose defined as the actual dose received divided by the standard calculated dose during a set period. The study objective was to assess the impact of a RDI ≥ 80% on response and survival of patients treated in first line CT by FOLFOXIRI or FOLFIRINOX ± Bevacizumab (BV) for an unresectable metastatic colorectal cancer (mCRC).

Materials and methods: It was a retrospective, non-interventional, multicenter study calculating RDI from the first cycles of CT to the first CT-scan evaluation (CT-scan1). Objective response and disease control rates (ORR and DCR), progression-free survival (PFS) and overall survival (OS) were compared between patients with RDI ≥ 80% and <80% and results were adjusted for age, gender, ECOG, tumor location, number of metastatic sites, RAS and BRAF status, the CT regimen, the use of BV, the delay from C1 to CT scan1.

Results: Among 152 screened patients, 100 met inclusion criteria, with a mean (± standard deviation) age at 59.0 (± 10.7) years. The ECOG performance status was 0-1 in 96 (96%) patients; metastases were synchronous in 95 (95%), RAS and BRAF were mutated in 60 (60%) and 22 (22%), respectively. ORR was observed in 51 (51%) at CT-scan1 with median PFS and OS of 10.5 and 21.9 months, respectively. A RDI ≥ 80% was observed in 44 (44%) patients without impact on ORR (ORa: 1.04, 95% CI: 0.37 to 2.89, p = 0.94) but was significantly associated to improved PFS and OS with HRa 0.50 (95%CI: 0.29 to 0.87, p = 0.013) and 0.52 (95% CI: 0.29 to 0.91, p = 0.023), respectively.

Conclusion: Our results suggest a low level of FOLFOXIRI or FOLFIRINOX +/- BV exposure in first-line mCRC is associated with a significant trend on PFS and OS.