Pharmacogenetics testing (DPYD and UGT1A1) for fluoropyrimidine and irinotecan in routine clinical care: Perspectives of medical oncologists and oncology pharmacists

Background Despite robust evidence and international guidelines, to support routine pharmacogenetic (PGx) testing, integration in practice has been limited. This study explored clinicians' views and experiences of pre-treatment DPYD and UGT1A1 gene testing and barriers to and enablers of routine clinical implementation. Methods A study-specific 17-question survey was emailed (01 February-12 April 2022) to clinicians from the Medical Oncology Group of Australia (MOGA), the Clinical Oncology Society of Australia (COSA) and International Society of Oncology Pharmacy Practitioners (ISOPP). Data were analysed and reported using descriptive statistics. Results Responses were collected from 156 clinicians (78% medical oncologists, 22% pharmacists). Median response rate of 8% (ranged from 6% to 24%) across all organisations. Only 21% routinely test for DPYD and 1% for UGT1A1. For patients undergoing curative/palliative intent treatments, clinicians reported intent to implement genotype-guided dosing by reducing FP dose for DPYD intermediate metabolisers (79%/94%), avoiding FP for DPYD poor metabolisers (68%/90%), and reducing irinotecan dose for UGT1A1 poor metabolisers (84%, palliative setting only). Barriers to implementation included: lack of financial reimbursements (82%) and perceived lengthy test turnaround time (76%). Most Clinicians identified a dedicated program coordinator, i.e., PGx pharmacist (74%) and availability of resources for education/training (74%) as enablers to implementation. Conclusion PGx testing is not routinely practised despite robust evidence for its impact on clinical decision making in curative and palliative settings. Research data, education and implementation studies may overcome clinicians' hesitancy to follow guidelines, especially for curative intent treatments, and may overcome other identified barriers to routine clinical implementation.