https://www.selleckchem.com/products/Cyclopamine.html © The Author(s) 2020. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.Importance The increasing use of germline genetic testing may have unintended consequences on treatment. Little is known about how women with pathogenic variants in cancer susceptibility genes are treated for breast cancer. Objective To determine the association of germline genetic testing results with locoregional and systemic therapy use in women diagnosed with breast cancer. Design, Setting, and Participants For this population-based cohort study, data from women aged 20 years or older who were diagnosed with stages 0 to III breast cancer between 2014 and 2016 were accrued from the Surveillance, Epidemiology and End Results (SEER) registries of Georgia and California. The women underwent genetic testing within 3 months after diagnosis and were reported to the Georgia and California SEER registries by December 1, 2017. Exposures Pathogenic variant status based on linked results of clinical germline genetic testing by 4 laboratories that did most such testing in the studied regions. Main Outcomes and Measurethogenic variants were more likely to receive bilateral mastectomy for a unilateral tumor (61.7% vs 24.3%; OR, 5.52, 95% CI, 4.73-6.44), less likely to receive postlumpectomy radiotherapy (50.2% vs 81.5%; OR, 0.22, 95% CI, 0.15-0.32), and more likely to receive chemotherapy for early-stage, ER/PR-positive disease (38.0% vs 30.3%; OR, 1.76 (95% CI, 1.31-2.34). Similar patterns were seen with pathogenic variants in other breast cancer-associated genes (ATM, CDH1, CHEK2, NBN, NF1, PALB2, PTEN, and TP53) but not with variants of uncertain significance. Conclusions and Relevance Women with pathogenic variants in BRCA1/2 and other breast cancer-associated genes were found to have distinct patterns of breast cancer treatment; these may be less concordant with practice guidelines, particularly