Impact of American Society of Breast Surgeons (ASBS) guidelines on genetic testing (GT) rates among patients with breast cancer (BC).

e22537 Background: Identifying patients with pathogenic germline genetic variants can inform clinical decision-making and risk assessment. Previous studies have suggested low rates of GT in BC patients overall and disproportionately lower rates of GT among black patients. This may be explained in part by clinicians failing to understand the current National Comprehensive Cancer Network (NCCN) GT guidelines, which are complex. In February 2019, the ASBS released updated guidelines recommending GT for all patients with a personal history of BC. The objective of this study was to evaluate the impact of the ASBS guideline change on GT utilization for all BC patients, and for black BC patients in particular. Methods: This retrospective cohort study included 4386 BC patients who were diagnosed and/or treated at the Siteman Cancer Center (SCC) in St. Louis, MO from January 1, 2017 to December 31, 2020. The pre-guideline period included those patients diagnosed between January 1, 2017 and July 25th, 2019 and the post-guideline period included those diagnosed between July 26, 2019 and December 31, 2020. Within the study period, Myriad Genetics was used almost exclusively for GT by breast oncologists and surgeons at SCC. Myriad data was queried to identify all BC patients at SCC with GT. Data including self-reported race/ethnicity, BC subtype (triple negative breast cancer (TNBC) vs other), insurance type (public vs private), and family history of BC (yes vs no) was collected from the electronic medical record (EMR) independently by authors. Multivariate logistic regression analyses and difference in difference (DiD) analyses were performed to compare GT rates pre- and post-guideline change. Results: There was no significant difference in the rate of GT among BC patients pre- vs post-guideline change (17% vs 14.8%, p = 0.05). Similarly, there was no significant difference in GT rates pre- vs post-guideline change for non-Hispanic black (NHB) (14.6% vs 13.1%) and non-Hispanic white (NHW) subgroups (17.8% vs 15.2%) using DiD analysis (p = 0.96). Patients with a family history of BC (odds ratio (OR) 1.41, 95% confidence interval (CI) 1.17-1.69, p < 0.01) and TNBC (OR 1.47, 95% CI 1.15-1.86, p < 0.01) were more likely to receive GT. Patients aged greater than 50 years (OR 0.44, 95% CI 0.37-0.54, p < 0.001) and those with public insurance were less likely to receive GT (OR 0.82, 95% CI 0.67-1.02, p = 0.07). DiD analyses identified no significant differences pre- and post-guideline change for these subgroups. Conclusions: Despite the recent broadening of GT guidelines by ASBS, GT rates remain low among patients with BC. We found no significant impact of the guideline change on the uptake of GT among our population of BC patients overall or by race/ethnicity, family history, BC subtype, age, or insurance status. Multidisciplinary efforts are needed to improve guideline implementation and uptake of GT in BC patients.