Abstract P5-08-28: Incidence of germline BRCA1- and BRCA2-mutated breast cancer in the US
Authors: Kim R , Peterson A , Isherwood A , Uppal H , Barlev A 
Published: March 2017

Background: Breast cancer is the most common cancer and second leading cause of cancer death among women in the United States (US).1 Inherited mutations in germline breast cancer susceptibility gene 1 and 2 (gBRCAm) are associated with increased risk of developing cancers, including breast cancer.2 No published reports of gBRCAm incidence within an unselected US breast cancer population are available based on a comprehensive literature review (CLR). The main objective of this analysis is to estimate the incidence of gBRCAm breast cancer in the US.

Methods: For this analysis the Surveillance, Epidemiology, and End Results (SEER) Program 18 registries captured incidence of breast cancer by stage, age and gender.3 The size of the US population was based on United Nation's population projections and standardized to the 2010 population.4 Age-specific gBRCAm distribution and gBRCAm-specific hormonal subtype for estrogen-receptor and progesterone-receptor (ER/PR), and human epidermal growth factor receptor-2 (HER2) estimates were determined from a CLR.5-8 Tumor cells negative for ER/PR and HER2 are referred to as triple-negative breast cancer (TNBC).

Results: In 2016, it is projected that approximately 250,000 individuals will be diagnosed with invasive breast cancer (all genders). Median age range of the population with invasive breast cancer is 65-69 years and 99% are females. Majority (72%) of female invasive breast cancer cases are ER/PR+ whereas 11% of cases are TNBC. Corroborating with current publications, gBRCAm is estimated at 5% for individuals less than 50 years old and 1% among all ages. Median age range of the gBRCAm cohort is 40-44 years. After applying currently available gBRCAm specific literature parameters, the majority (55%) of gBRCAm diagnoses are TNBC.

Conclusion: In the US, patients with gBRCAm represent a small proportion (1%) of all breast cancer tissues evaluated. Majority of gBRCAm patients are diagnosed with TNBC (55%) and are younger (median age range 40-44 years) than overall breast cancer population. Age differences noticed in gBRCAm may have been due to disparity in genetic screening practices among breast cancer population in the US rather than a reflection of gBRCAm expressions. These estimates of gBRCAm incidence are driven by limited reports on an unselected population of breast cancer gBRCAm cohort; therefore sensitivity analysis is required to assess the robustness of these estimates.

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3. Surveillance, Epidemiology, and End Results (SEER) Program (www.seer.cancer.gov) Research Data (1973-2013), National Cancer Institute, DCCPS, Surveillance Research Program, Surveillance Systems Branch, released April 2016, based on the November 2015 submission.

4. United Nations Population Division. World Population Prospects, the 2015 Revision. http://esa.un.org/unpd/wpp/.

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8. Spurdle AB et al. Breast Cancer Res. 2014;16:3419.

Citation Format: Kim R, Peterson A, Isherwood A, Uppal H, Barlev A. Incidence of germline BRCA1- and BRCA2-mutated breast cancer in the US [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-28.