Survival and relative dose intensity of 5-fluorouracil, oxaliplatin and irinotecan in real-life treatment of metastatic colorectal cancer

Introduction
Combinations of 5-fluorouracil/leucovorin (5-FU/LV) with oxaliplatin (FOLFOX) or irinotecan (FOLFIRI) are part of standard treatments for metastatic colorectal cancer (mCRC). For these molecules, the impact of a low relative dose intensity (RDI) on survival is not sufficiently known in real-life.

Material and methods
Data were collected retrospectively from patients treated in our center for an unresectable mCRC with FOLFOX or FOLFIRI as a first-line treatment. To study the impact on progression-free survival (PFS) and overall survival (OS), patients were divided into high and low RDI according to the median RDI of 5-FU on one end, and the median RDI of oxaliplatin or irinotecan (OXA-IRI) on the other.

Results
In our population of 75 patients, the median age was 67.1 years and 77% of patients were treated with FOLFIRI. Patients with high RDI for OXA-IRI had better PFS compared to patients with low RDI (hazard ratio [HR], 0.58; p = 0.03). There was no statistically significant difference in PFS for patients with high RDI for 5-FU (HR, 0.66; p = 0.09). No difference was found in overall survival according to the RDI of OXA-IRI (HR, 0.72; p = 0.18) or 5-FU (HR, 0.77; p = 0.29). RDI had no significant impact on toxicities.

Conclusions
Our analysis suggests that a low RDI of oxaliplatin and irinotecan has a negative effect on PFS. RDI had no significant effect on OS in our cohort. The clinical benefit of maintaining high RDI in these patients appears low.