Pharmacogenetic‐guided dosing for fluoropyrimidine (DPYD) and irinotecan (UGT1A128) chemotherapies for patients with cancer (PACIFIC‐PGx): A multicenter clinical trial

PACIFIC‐PGx evaluated the feasibility of implementing pharmacogenetics (PGx) screening in Australia and the impact of DPYD/UGT1A1 genotype‐guided dosing on severe fluoropyrimidine (FP) and irinotecan‐related toxicities and hospitalizations, compared to historical controls. This prospective single arm trial enrolled patients starting FP/irinotecan for any cancer between 7 January 2021 and 25 February 2022 from four Australian hospitals (one metropolitan, three regional). During the accrual period, 462/487 (95%) consecutive patients screened for eligibility for DPYD and 50/109 (46%) for UGT1A1 were enrolled and genotyped (feasibility analysis), with 276/462 (60%) for DPYD and 30/50 (60%) for UGT1A1 received FP/irinotecan (safety analysis). DPYD genotyping identified 96% (n = 443/462) Wild‐Type, 4% (n = 19/462) Intermediate Metabolizers (50% dose reduction), and 0% Poor Metabolizers. UGT1A1 genotyping identified 52% (n = 26/50) Wild‐Type, 40% (n = 20/50) heterozygous, and 8% (n = 4/50) homozygous (30% dose reduction). Key demographics for the FP/irinotecan safety cohorts included: age range 23–89/34–74 years, male 56%/73%, Caucasian 83%/73%, lower gastrointestinal cancer 50%/57%. Genotype results were reported prior to cycle‐1 (96%), average 5–7 days from sample collection. PGx‐dosing for DPYD variant allele carriers reduced high‐grade toxicities compared to historic controls (7% vs. 39%; OR = 0.11, 95% CI 0.01–0.97, p = 0.024). High‐grade toxicities among Wild‐Type were similar (14% vs. 14%; OR = 0.99, 95% CI 0.64–1.54, p = 0.490). PGx‐dosing reduced FP‐related hospitalizations (−22%) and deaths (−3.7%) compared to controls. There were no high‐grade toxicities or hospitalizations for UGT1A1*28 homozygotes. PGx screening and prescribing were feasible in routine oncology care and improved patient outcomes. Findings may inform expanded PGx programs within cancer and other disease settings.