Fluoropyrimidine chemotherapy can cause serious adverse effects including myelosuppression, gastrointestinal and skin toxicity. Dihydropyrimidine dehydrogenase gene (DPYD) variations can increase risk of fluoropyrimidine-related toxicity. DPYD testing allows clinicians to individualise dosing based on genotype. Testing is recommended internationally, however anecdotal evidence suggested inconsistency in Australian practice. From 1st November 2025, DPYD testing was introduced onto the Medicare Benefits Schedule (MBS) improving accessibility for Australians. This study evaluated DPYD testing practices and dosing individualisation in patients commencing fluoropyrimidine chemotherapy at a private day oncology clinic pre- and post-MBS listing.
A retrospective audit of DPYD testing was conducted at a private day oncology clinic from 1 May 2025 to 30 April 2026. Patients commenced on capecitabine and 5-fluorouracil were included. Data collected from electronic prescribing software and medical records included diagnosis, therapeutic intent, DPYD testing status, genetic variation and fluoropyrimidine dosing at cycles 1 and 2. Dose adjustments were assessed for appropriateness against eviQ and international guidelines. Statistical analysis explored the correlation between DPYD testing and therapeutic intent (palliative versus curative). Ethics approval was obtained.
A total of 102 patient treatments were included. Prior to MBS listing, 33.9% (19/56) of fluoropyrimidine patients received DPYD testing, with one patient having a genetic variation. Post-MBS listing, 56.5% (26/46) of fluoropyrimidine patients received testing. Genetic variation was found in three patients. Fluoropyrimidine doses followed recommended guidelines. Pre‑MBS listing, DPYD testing was strongly associated with curative-intent capecitabine treatment (φ=0.73, p<0.001); this association was no longer observed following MBS listing. Clinicians cited uncertain clinical utility and turnaround time as barriers to testing.
DPYD testing increased by 67% following MBS listing. Fluoropyrimidines were appropriately dosed according to recommended guidelines for patients with DPYD genetic variation. Addressing barriers through providing further education and professional endorsement may improve testing rates and support safer fluoropyrimidine prescribing.