Evaluating consistency and variation in mainstream germline cancer genetic and genomic testing

Background Mainstreaming, in which genetic testing is shifted outside clinical genetics, can improve access to genetic testing. This is being explored in several countries, including Canada, the USA and the UK. However, standardised practice within a jurisdiction helps ensure equitable high-quality access. This study aimed to evaluate consistency in the implementation of cancer genetics mainstreaming across Ontario, Canada. Methods Adult cancer genetics centres in Ontario were emailed an online survey in June 2025, which was completed by mainstreaming implementation leads. Results were anonymised and analysed in aggregate. Results Of 18 centres contacted, 13 responded; 12/13 reported having implemented cancer genetics mainstreaming. All mainstreaming centres offered pathways for breast, ovarian, prostate and pancreatic cancers, primarily based on personal history criteria. Most centres did not mainstream for other cancer sites but were planning to expand. A 19-gene hereditary breast/ovarian/prostate panel was most commonly ordered. There was variation in the timepoint of genetics service involvement. Turnaround times for expedited results were relatively consistent (median 21 days, IQR 18–22), whereas turnaround times for routine results varied widely (median 50 days, IQR 36–94). Conclusion Across Ontario, centres were generally consistent in mainstreaming the most common indications. Opportunities to improve quality and equity include reducing variability in routine turnaround time, standardising management pathways for negative results and streamlining ordering to align with eligibility criteria. Some centres cited limited genetics knowledge as an implementation barrier, though engagement improved over time. Ongoing evaluation of mainstreaming can support consistent access to care.