Long-Term Outcomes of 5-Fluorouracil-Related Early-Onset Toxicities: A Retrospective Cohort Study.

Objectives: We aimed to determine whether the occurrence of early-onset toxicities due to 5-fluorouracil (5-FU) in treatment-naive patients undergoing their first cycle of FOLFOX/FOLFIRINOX was associated with decreased overall survival, increased risk of treatment cessation, and hospitalization.

Methods: This was a retrospective cohort study using patient information from community oncology practices. Patients who received their first dose of 5-FU from 1 January 2015 through 1 August 2023 were included. The occurrence of an early-onset 5-FU-related toxicity (during 5-FU infusion or up to 96 h after infusion completion) in the first cycle of FOLFOX/FOLFIRINOX was the explanatory variable. The primary endpoint was overall survival (OS); secondary endpoints included early treatment cessation and early hospital admission.

Results: In total, 3988 patients were included; the median age was 62.9 years and 57.5% were male. Early-onset toxicities were observed in 19.1%, with vomiting, thrombocytopenia, and diarrhea being most common. Patients with early-onset toxicities had a median OS of 2.5 years [95% CI 2.2 to 2.9] compared with 5.3 years [95% CI 4.7 to 5.8] in patients without early-onset toxicities (p < 0.001). The occurrence of early-onset toxicities was associated with an adjusted hazard ratio of 1.61 [95% CI 1.44 to 1.80] and was also significantly associated with early treatment cessation (odds ratio [OR] 1.53, 95% CI 1.30 to 1.80) and early hospital admission (OR 8.69, 95% CI 3.45 to 24.18).

Conclusions: Early-onset toxicities related to 5-FU during the first cycle of FOLFOX/FOLFIRINOX treatment were associated with poor outcomes. Early recognition and prompt intervention are pertinent to improve outcomes in patients receiving fluoropyrimidine chemotherapy.