Clinical Benefits and Utility of Pretherapeutic DPYD and UGT1A1 Testing in Gastrointestinal Cancer: A Secondary Analysis of the PREPARE Randomized Clinical Trial.

Importance: To date, the clinical benefit and utility of implementing a DPYD/UGT1A1 pharmacogenetic-informed therapy with fluoropyrimidines and/or irinotecan have not been prospectively investigated. Objective: To examine clinically relevant toxic effects, hospitalizations, and related costs while preserving treatment intensity and efficacy outcomes in patients with gastrointestinal cancer. Design, Setting, and Participants: This nonprespecified secondary analysis stems from Pre-Emptive Pharmacogenomic Testing for Preventing Adverse Drug Reactions (PREPARE), a multicenter, controlled, open, block-randomized, crossover implementation trial conducted from March 7, 2017, to June 30, 2020, and includes data from Italy according to a sequential study design. The study population included 563 patients (intervention, 252; control [standard of care], 311) with gastrointestinal cancer (age ≥18 years) who were eligible for fluoropyrimidine and/or irinotecan treatment. Data analysis for the present study was performed from May 27 to October 10, 2024. Interventions: Participants with actionable variants (DPYD*2A, DPYD*13, .DPYD c.2846A>T, and DPYD c.1236G>A for fluoropyrimidines, and UGT1A1*28, UGT1A1*6, and UGT1A1*27 for irinotecan) received drug or dose adjustments based on Dutch Pharmacogenetics Working Group recommendations. Main Outcomes and Measures: The primary outcome was clinically relevant toxic effects (National Cancer Institute Common Terminology Criteria for Adverse Events grade ≥4 hematologic, grade ≥3 nonhematologic, or causing hospitalization, fluoropyrimidines and/or irinotecan causally related). Secondary outcomes included hospitalization rates, toxic effect management costs, intensity of treatment, quality-adjusted life-years, and 3-year overall survival. Results: Overall, 1232 patients were enrolled in Italy, with 563 included in this analysis (317 [56.3%] men; median age, 68.0 [IQR, 60.0-75.0] years). In the intervention arm, carriers of any actionable genotype exhibited a 90% lower risk of clinically relevant toxic effects compared with the control arm (odds ratio, 0.1; 95% CI, 0.0-0.8; P = .04). They also presented higher toxic effect management costs per patient ($4159; 95% CI, $1510-$6810) compared with patients in the intervention arm ($26; 95% CI, 0-$312) (P = .004) and a higher rate of hospitalization (34.8% vs 11.8%; P = .12). The differences were not significant among all patients. Three-year overall survival did not differ significantly between arms, while quality-adjusted life-years significantly improved in the intervention arm. The pharmacogenetics-informed approach did not manifest a detrimental effect on treatment intensity in actionable genotype carriers. Conclusions and Relevance: In this secondary analysis of PREPARE, pretreatment application of DPYD- and UGT1A1-guided treatment appeared to increase safety and reduce hospitalizations and related costs in patients with gastrointestinal cancer. Clinical benefit did not appear to be affected. Trial Registration: ClinicalTrials.gov Identifier: NCT03093818.