BACKGROUND: It is unclear whether the American Society of Breast Surgeons' (ASBrS) guideline to offer genetic testing (GT) to all patients with breast cancer (BC) impacted contralateral prophylactic mastectomy (CPM) rates. We sought to describe the trends of GT and CPM rates and to determine predictors of CPM uptake. METHODS: After retrospective review of two prospectively maintained institutional databases, we identified patients with unilateral stage 0-III BC who underwent surgery between January 2016 and July 2020. Trends in GT and CPM rates were described and multivariable logistic regression determined factors associated with CPM utilization. RESULTS: Among 6062 women identified, 3242 (53.4%) had GT. From January 2016 to July 2020, GT rates increased significantly from 46.3% to 70.1% (p <
0.001), but were not impacted by release of the guidelines. The proportion of pathogenic/likely pathogenic variants (PVs) detected in BC-related genes did not change significantly (p = 0.115). Overall, 782/6062 (12.9%) patients underwent CPM. There was no significant change in the CPM rate (p = 0.527), including before (p =0.298) and after (p = 0.220) guideline release. The factors significantly associated with increased CPM rates were PVs in a BC-related gene, increasing number of relatives with BC, first-degree relative with ovarian cancer, younger age, and cT2-3 tumors (all p <
0.05). Conversely, GT alone did not impact CPM (adjusted odds ratio 1.152, 95% confidence interval 0.85-1.55
p = 0.350 untested compared with GT with negative results). CONCLUSIONS: Despite increasing GT rates, CPM rates were stable over time and were not associated with GT, indicating that offering GT to more patients does not necessarily increase CPM rates.