Pharmacokinetically guided 5-fluorouracil dosing reduces severe toxicity and improves response rates in colorectal cancerTailored dosing of 5-fluorouracil improves safety for colorectal cancer

BACKGROUND: Body surface area (BSA)-based 5-fluorouracil (5-FU) dosing remains the standard in colorectal cancer despite substantial interpatient pharmacokinetic variability, which may lead to underexposure, treatment failure, or severe toxicity. This systematic review and meta-analysis evaluated whether pharmacokinetically guided 5-FU dosing improves efficacy and safety compared with conventional BSA-based dosing. METHODS: PubMed/MEDLINE, Embase, and Scopus databases were searched from inception to the final search date. The search identified 1,802 records: PubMed/MEDLINE, 47; Embase, 118; and Scopus, 1,637 records. Comparative randomized and non-randomized studies evaluating pharmacokinetically guided, area under the curve-guided, or therapeutic drug monitoring-based 5-FU dosing versus BSA-based dosing in colorectal cancer were included. Random-effects models were employed. The risk of bias was assessed using RoB 2 and ROBINS-I, and the certainty of evidence was evaluated using GRADE. RESULTS: Five studies comprising 809 unique patients were included. Across the primary severe-toxicity analysis, the pooled denominator was 1,338 reported observations, including 625 in the PK-guided 5-FU dosing arm and 713 in the BSA-based 5-FU dosing arm, because one study reported severe toxicity by treatment cycle rather than by patient. PK-guided dosing was associated with lower severe or grade ≥ 3 toxicity (RR 0.50, 95% CI 0.33-0.76; P = 0.001; I²=79%). PK-guided dosing was also associated with a higher objective response rate (RR 1.50, 95% CI 1.24-1.80; P < 0.0001) and disease control rate (RR 1.18, 95% CI 1.07-1.30; P = 0.001). Severe diarrhea was reduced (RR 0.33, 95% CI 0.18-0.62; P = 0.0006), whereas mucositis, neutropenia/leukopenia, and hand-foot syndrome were not significantly different between dosing strategies. CONCLUSION: PK-guided 5-FU dosing was associated with lower severe toxicity and diarrhea and higher objective response and disease-control rates than conventional BSA-based dosing. However, the evidence was derived from a small and clinically heterogeneous group of studies, and progression-free or overall-survival benefits could not be established. The findings apply predominantly to metastatic colorectal cancer treated with infusional 5-FU within FOLFOX- or FOLFIRI-based regimens. CLINICAL TRIAL REGISTRATION: Not applicable. This study was a systematic review and metaanalysis, and not a clinical trial.