Abstract P6-09-02: Associations between hereditary cancer panel predisposition genes and breast cancer histological subtypes

Background: Clinical panel testing has become routine practice for patients that are diagnosed with breast cancer at a young age and/or have a personal or family history of cancer. Associations with known breast cancer genes and breast cancer subtypes have been previously identified, such as BRCA1 associations with estrogen receptor negative (ER-) and triple negative (ER-/PR-/HER2-) breast cancers. However, the cancer predisposition genes associated with each of the four clinical subtypes of breast cancer have not been fully defined. We evaluated 24,901 Caucasian female breast cancer cases receiving clinical panel testing for 23 cancer predisposition genes and assessed associations between mutations in each gene and breast cancer subtypes.

Methods: Germline hereditary cancer multigene panel testing results for cancer predisposition genes were obtained for 24,901 Caucasian female breast cancer cases evaluated by a clinical testing laboratory. Information on tumor histology, personal and family history of cancer, age at diagnosis, and previous genetic testing was provided by clinical care providers of patients receiving clinical cancer genetic testing. Breast cancer cases were classified into clinical breast cancer subtypes based on estrogen/progesterone hormone receptor status (HR) and HER2 status: Luminal A (HR+/HER2-), Luminal B (HR+/HER2-), HER2 subtype (HR-/HER2+), and Triple Negative (HR-/HER2-). The frequency of pathogenic or likely pathogenic mutations observed in each subtype was compared against the Exome Aggregation Consortium (ExAC) non-TCGA non-Finnish European population to estimate risks.

Results: ATM was associated with moderate risks (odds ratio (OR)>2.0) of Luminal A, Luminal B, and HER2 subtypes of breast cancer, but was not associated with the Triple Negative subtype. PALB2 was associated with moderate risk for Luminal B subtype, but high risk (OR>5.0) for Luminal A, HER2, and triple negative subtypes. TP53 was associated with high risks for Luminal B and HER2 tumors. NBN, MRE11A, and RAD50 were not associated with any subtype of breast cancer.

Conclusions: Identifying associations between inherited mutations (odds ratio (OR)>2.0) and breast cancer subtypes can inform clinical risk management, treatment options, and therapeutic development efforts.

Citation Format: Lilyquist J, Laduca H, Hu C, Na J, Polley EC, Hart SN, Pesaran T, Tippin-Davis B, Goldgar DE, Dolinsky JS, Couch FJ. Associations between hereditary cancer panel predisposition genes and breast cancer histological subtypes [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-09-02.

Abstract OT3-02-01: Development of cell-free nucleic acid-based tests for early detection of breast cancer: The STRIVE study

Background:

Mammography (digital 2D or digital 3D/tomosynthesis) is the cornerstone of current screening strategies for breast cancer, but new approaches are needed to further reduce the proportion of cancers diagnosed at advanced stages and more effectively identify those women in need of additional testing and biopsies. Circulating cell-free nucleic acids (cfNAs) shed from tumors, isolated from peripheral blood, and analyzed with ultra-deep and broad sequencing of cancer-associated genes, have great potential for early cancer detection. The ultimate goal is to develop blood cfNA cancer screening tests for use in conjunction with established risk factors and/or radiographic features for improved cancer detection. Development of these tests requires large, well-annotated cohorts of asymptomatic participants with adequate volumes of prediagnostic blood. The STRIVE Study cohort was recently established to train and validate cfNA-based tests for early detection of breast cancer.

Eligibility criteria and trial design: The STRIVE Study is a new prospective, multi-ethnic mammography cohort that will recruit 120,000 subjects from 15+ US breast cancer screening centers (including Mayo Clinic and Sutter Health sites). Eligibility criteria require only that a participant has a scheduled routine screening mammogram at a participating center and has not received a biopsy prior to the research blood draw. Participants are recruited within 28 days of screening mammography (digital or tomosynthesis), consent electronically, provide blood samples, and complete an on-line risk factor questionnaire. Participants will be followed for all cancer diagnoses, cancer recurrences, and death for at least 5 years. Pertinent medical record information, imaging findings (including breast density), and follow-up data will be transferred electronically to a central database throughout the study period. Additional blood samples will be collected from participants with abnormal mammogram results, or who are diagnosed with cancer, to document and better understand the evolution of cfNA signals. Recruitment began in February 2017.

Primary Aims: To train and validate a cfNA blood-based test to identify breast cancer overall in a cohort of women undergoing screening mammography.

Statistical Methods: The study will be divided into a training phase (1/3 of participants) and an independent clinical validation phase (remaining 2/3 of participants). In the training phase, statistical machine learning techniques will be used to develop algorithms incorporating cfNA signals, clinical characteristics, or radiological features. In the validation phase, the prespecified locked algorithm developed from the training phase will be clinically validated in an independent group of women.

Contact information for people with a specific interest in the trial: Additional details regarding the STRIVE Study are available on the ClinicalTrials.gov website (NCT03085888). For site-specific questions, please call 844-366-9738 for the Mayo Clinic and 1-855-578-7483 for Sutter Health.

Citation Format: Liu MC, Cummings S, Vachon CM, Kerlikowske K, Couch FJ, Morris EA, Olson JE, Polley EC, Conners AL, Ellis RL, Patel B, Maimone IV S, Zhang N, Hamilton S, Clarke CA, Allen BA, Maddala T, Hartman A-R. Development of cell-free nucleic acid-based tests for early detection of breast cancer: The STRIVE study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT3-02-01.

Abstract PD1-01: Triple negative breast cancer predisposition genes

Background: Germline cancer testing panels provide an effective method for identifying individuals at increased risk for breast cancer. However, estimates of risk for triple negative breast cancer (TNBC) (estrogen receptor-negative, progesterone receptor-negative, HER2-negative) associated with pathogenic mutations in panel genes have not been established. We sought to define the genes that contribute to TNBC.

Methods:Germline hereditary cancer multigene panel testing results were obtained for 8,753 TNBCs evaluated by a clinical testing laboratory. Associations between pathogenic mutations in individual genes and TNBC were assessed by comparing mutation frequencies in TNBCs and in the Exome Aggregation Consortium, non-Finn European, non-Cancer Genome Atlas reference controls.

Results: Inactivating mutations in 21 known cancer predisposition genes were identified in 14.6% of TNBCs. BRCA1, BRCA2, PALB2, BARD1, and RAD51D alterations were associated with high risks (odds ratio(OR)>5.0) of TNBC and variants in BRIP1, RAD51C, MSH6, and TP53 were associated with moderate risks (OR>2). In contrast, ATM, CHEK2, NBN, and RAD50 yielded no clinically relevant risks of TNBC. Pathogenic mutations in these established non-BRCA1/2 TNBC susceptibility genes were detected in 6.3% of TNBCs. Similar trends were observed among African American TNBCs. Overall, 5.5% of TNBCs with pathogenic mutations did not meet NCCN clinical testing criteria for BRCA1/2 due to a lack of significant family history and diagnosis over the age of 60.

Conclusions: The identification of genes associated with elevated risk of TNBC will improve understanding of the etiology of this aggressive form of breast cancer and inform risk management of individuals receiving panel testing. The high frequency of pathogenic variants suggests that all patients with TNBC, regardless of age of diagnosis or family history of cancer, should be considered for multigene panel testing.

Citation Format: Couch FJ, Shimelis H, LaDuca H, Hu C, Hart SN, Polley EC, Pesaran T, Tippin-Davis B, Goldgar DE, Dolinsky JS. Triple negative breast cancer predisposition genes [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD1-01.

Abstract S2-01: Breast cancer risks associated with mutations in cancer predisposition genes identified by clinical genetic testing of 60,000 breast cancer patients

Clinical genetic testing panels are broadly used to gather information about cancer predisposition in individuals with personal and/or family history of breast cancer. However, the involvement of several of the genes on clinical testing panels in predisposition to breast cancer, such as MRE11A and RAD50, has recently come into question. In addition, accurate risk estimates for breast and other cancer are not well defined for the majority of genes on testing panels. We studied 60,000 women diagnosed with breast cancer who were tested for germline cancer predisposing mutations using hereditary cancer gene panels. Information on personal and family cancer history, age of diagnosis, and ethnicity of patients was obtained from test requisition forms. Greater than 90% met National Comprehensive Cancer Network HBOC testing criteria. To estimate gene-specific risks for breast cancer, case-control analyses were performed comparing the frequencies of pathogenic mutations from Caucasian cancer cases with frequencies from Caucasian, non-Finnish, non-TCGA controls from the Exome Aggregation Consortium (ExAC) database. Mutations were detected in 9% of breast cancer patients. Twelve genes displayed a significant association (p<0.05) with breast cancer. Nine of these genes, including ATM, RAD51D, NF1, and MSH6, were associated with moderate risk (RR>2.0) of breast cancer and three genes (BRCA1, BRCA2, PALB2) were associated with high risk (RR>5.0) of breast cancer. Cumulative age-dependent risk models were developed for each gene. This large clinical testing dataset of 60,000 women with breast cancer provides useful data for many predisposition genes previously lacking risk estimates, and should prove useful for clinical risk management of patients with inherited mutations in these genes.

Citation Format: Couch FJ, Hu C, Lilyquist J, Shimelis H, Akinhanmi M, Na J, Polley EC, Hart SN, McFarland R, LaDuca H, Huether R, Goldgar DE, Dolinsky JS. Breast cancer risks associated with mutations in cancer predisposition genes identified by clinical genetic testing of 60,000 breast cancer patients [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 S2-01.

Abstract P5-09-03: Associations between breast cancer subtypes and mutations in cancer predisposition genes identified by clinical genetic testing of breast cancer patients

Clinical genetic testing of individuals with a personal or family history of breast and ovarian cancer using panels for BRCA1/2 and other candidate cancer predisposition genes has become routine clinical practice. Several of the genes on hereditary cancer testing panels have been strongly associated with specific subtypes of breast cancer. In particular, individuals with germline mutations in BRCA1 predominantly develop estrogen receptor (ER)-negative and triple negative (TN) (estrogen receptor negative, progesterone receptor negative, HER2 negative) breast tumors. In contrast, CHEK2 and ATM mutations have been associated with ER-positive breast cancer. In this study, associations between mutations in panel genes and breast cancer subtypes were evaluated. A cohort of 60,000 breast cancer patients tested for germline cancer predisposing mutations using hereditary cancer gene panels was utilized. Information on personal and family cancer history, age of diagnosis, tumor pathology, and ethnicity of patients was obtained from test requisition forms or by follow up with ordering health care providers. Mutations in each gene were combined into four histological subtypes (triple negative; HER2 positive; ER-positive,HER2-positive; and ER-positive,HER2 negative). Associations for each subtype were estimated by case-control analyses comparing the frequencies of pathogenic mutations in each subtype with frequencies from non-TCGA controls from the Exome Aggregation Consortium (ExAC) database. In addition, case-case analyses were conducted to assess enrichment of gene mutations in specific breast cancer subtypes. Among the observed associations between genes and breast cancer subtypes, mutations in CHEK2 and ATM were highly enriched in luminal breast cancers and BARD1 was specifically associated with TN breast cancer. Refining the spectrum of pathological correlates with mutations in hereditary breast cancer genes will aid gene specific cancer risk management, and may accelerate the development of novel gene-specific therapeutic interventions.

Citation Format: Couch FJ, Lilyquist J, Na J, Hu C, Polley EC, Shimelis H, Akinhanmi M, McFarland R, LaDuca H, Goldgar DE, Dolinsky JS. Associations between breast cancer subtypes and mutations in cancer predisposition genes identified by clinical genetic testing of breast cancer patients [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 P5-09-03.