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Incidence of germline BRCA mutation in patients with ER-low positive/PR negative/HER-2 neu negative tumors.
General Poster Session B: Risk Assessment, Prevention, Early Detection, Screening, and Systemic Therapy
Background: The 2011 ASCO/CAP guidelines recommend that breast cancers with estrogen receptor (ER) staining as low as 1% on immunohistochemistry be considered ER-positive. In practice, there remains significant variability in what clinicians consider ER-positive versus ER-negative. Current NCCN guidelines recommend that patients under age 60 with triple-negative breast cancer (TNBC) be referred for genetic counseling and consideration of germline BRCA mutation testing. With the 2011 ASCO/CAP guidelines, the definition of TNBC has changed to exclude patients with ER low-positive (1-9%) tumors; hence patients with ER-low positive tumors (formerly considered ER negative) may not be referred for genetic counseling and BRCA testing. This may lead to “undertesting” of appropriate patients. The incidence of BRCA germline mutations in patients with ER-low positive versus ER-negative (0%) tumors is unknown. We sought to identify whether the incidence of BRCA mutation differed between patients with ER-negative/PR-negative/HER-2 neu negative tumors and patients with ER-low positive/PR-negative/HER-2 neu negative tumors. Methods: We performed a review of a prospectively maintained research database of all patients with ER < 10%, PR 0% and HER-2 neu–negative breast cancers who were referred for genetic risk assessment and testing for BRCA mutation at UT MD Anderson Cancer Center. Results: Of 144 patients who underwent BRCA mutation testing, 22 (15%) had ER-low positive tumors while 122 (85%) had ER-negative tumors. Among patients with ER-low positive tumors, 7 of 22 (31.8%) were found to have a deleterious BRCA 1/2 mutation, while 33 of 122 (27%) with ER-negative tumors were found to have a deleterious BRCA 1/2 mutation. The incidence of deleterious BRCA 1/2 mutation in patients with ER-low positive tumors versus those with ER-negative tumors was not statistically significantly different (p = 0.6457). Conclusions: The rate of deleterious BRCA 1/2 germline mutations in ER-negative versus ER-low positive (1-9%) breast cancer is similar. Therefore, we strongly recommend that BRCA testing continue to be offered to women under age 60 with tumors that are ER-low positive/PR-negative/HER-2 neu negative.