Genetic testing and surgical treatment after breast cancer diagnosis: Results from a national online cohort.

BACKGROUND: Genetic testing for hereditary breast cancer has implications for breast cancer decision-making. We examined genetic testing rates, factors associated with testing, and the relationship between genetic testing and contralateral prophylactic mastectomy (CPM). METHODS: Patients with breast cancer (2000-2015) from The Health of Women Study were identified and categorized as low, moderate, or high-likelihood of the genetic mutation using a previously published scale based on period-relevant national guidelines incorporating age and family history. Genetic testing and CPM rates were compared using univariate and multivariate logistic regression. RESULTS: Among 4170 patients (median age 56-years), 38% were categorized as high-likelihood of having a genetic mutation. Among high-likelihood women, 67% underwent genetic testing, the odds of which were increased among women of higher-education and White-race (p < .001). Among 2028 patients reporting surgical treatment, 385 (19%) chose CPM. CPM rate was highest among mutation-positive women (41%), but 26% of women with negative tests still underwent CPM. Independent of test result, genetic testing increased the odds of CPM on multivariate analysis (adjusted-OR: 1.69; 95% CI: 1.29-2.22). CONCLUSIONS: Genetic testing rates were higher among women at high-likelihood of mutation carriage, but one-third of these women were not tested. Racial disparities persisted, highlighting the need to improve testing in non-White populations. CPM rates were associated with mutation-carriage and genetic testing, but many women chose CPM despite negative testing, suggesting that well-educated women consider factors other than cancer mortality in selecting CPM.