Omitting the 5-fluorouracil bolus in metastatic colorectal cancer: impact on survival and toxicity in a retrospective multicentre cohort
Clinical Oncology Department, Faculty of Medicine, Menoufia University, Al Minufya, Egypt
Tropical Medicine Department, Faculty of Medicine, Menoufia University, Al Minufya, Egypt
Medical Oncology Department, National Cancer Institute, Cairo, Egypt
Radiation Oncology Department, South Egypt Cancer Institute, Assiut University, Assiut, Egypt
Clinical Pharmacology Department, Faculty of Medicine, Menoufia University, Al Minufya, Egypt
Contemp
Oncol (Pozn) 2026; 30 (2)
Introduction
The clinical value of the 5-fluorouracil (5-FU) bolus in modern multidrug regimens for metastatic colorectal cancer (mCRC) is uncertain, with concerns about added haematologic toxicity. This study assessed the impact of omitting the 5-FU bolus on survival and toxicity in patients receiving mFOLFOX6-based chemotherapy.
Material and methods
In this retrospective multicentre cohort, 267 mCRC patients treated between June 2020 and June 2024 at Menoufia University Hospitals and the National Cancer Institute, Cairo University, received either bolus-free nbFOLFOX (n = 141) or standard mFOLFOX6 (n = 126), with or without bevacizumab or anti-epidermal growth factor receptor therapy. Progression-free survival (PFS) and overall survival were analysed using Kaplan-Meier and Cox models.
Results
Bolus omission produced a statistically significant but clinically small PFS improvement (mean 10.029 vs. 9.319 months; hazard ratio [HR] 1.532, 95% CI: 1.194–1.967; p = 0.001). Overall survival was similar between groups (mean 21.7 vs. 20.7 months; median 20.667 vs. 20.633 months; HR 1.242, 95% CI: 0.966–1.597; p = 0.089). Multivariate analysis identified bolus inclusion as an independent predictor of inferior PFS (HR 1.433, p = 0.006). High grade neutropenia was significantly reduced with nbFOLFOX (14.9% vs. 25.4%, p = 0.019).
Conclusions
Omitting the 5-FU bolus does not compromise survival and reduces haematologic toxicity, supporting individualised treatment decisions, particularly in settings of drug shortages or high toxicity risk.
Keywords
colorectal neoplasms, treatment outcome, fluorouracil, antineoplastic combined chemotherapy protocols, drug administration schedule
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