Suboptimal Adherence to Hereditary Cancer Risk Management Guidelines: A Cohort Study of High-Risk Individuals in Newfoundland and Labrador, Canada.

Hereditary cancer syndromes (HCSs), including BRCA 1/2-associated hereditary breast and ovarian cancer (HBOC) and Lynch syndrome (LS), confer substantial lifetime cancer risks, yet adherence to recommended risk-management strategies remains variable. This population-based retrospective cohort study examined cancer prevention practices, outcomes, and predictors of cancer occurrence among 476 BRCA and LS carriers identified through the Provincial Medical Genetics Program in Newfoundland and Labrador, Canada (2001-2022). Linked genetic, surgical, screening, and cancer registry data were evaluated, with adherence assessed during two intervals (2018-2020 and 2020-2022) based on NCCN guidelines. Participants were predominantly female (69%), with a mean age of 48.5 years at genetic testing; nearly 70% of primary cancers were already diagnosed at the time of testing. BRCA carriers demonstrated higher uptake of breast MRI (58-61%) and risk-reducing salpingo-oophorectomy (63-66%) compared with LS carriers' colonoscopy uptake (42-44%). In univariate analyses, non-adherence during 2018-2020 was associated with increased odds of cancer after testing (OR ≈ 4.43, p < 0.001); this remained significant in the multivariate model (OR = 8.70; p = 0.0004). Individuals who did not follow recommended risk-management guidelines had nearly nine times greater odds of developing cancer after genetic testing than those who fully adhered to guidelines. Older age at referral (OR = 1.07/year, p < 0.001) also increased the odds of developing cancer. Study findings indicate that late referral and pre-existing cancers diminish the preventive impact of guideline-based risk management. System-level initiatives to promote earlier genetic testing, enhance cascade outreach, and strengthen surveillance pathways are needed to optimize cancer prevention and earlier cancer detection in high-risk populations.