Abstract P2-09-06: Genetic counseling and genetic testing for germline BRCA1/2 mutations among high risk breast cancer patients in Jordan: A study of 500 patients

Abstract

Abstract Introduction: Breast Cancer is the most common cancer worldwide and so in our region. In Jordan, almost 50% of patients are diagnosed before the age of 50. Knowledge of BRCA1/2 mutations has significant clinical impact on the management and prevention of breast cancer. In this study, we evaluate the prevalence of germline mutations in BRCA1/2 among high-risk Jordanian patients selected as per the updated NCCN guidelines. Methods: Jordanian breast cancer patients, stages I-IV, with a selected high-risk profile treated at our institution were invited to participate. Blood samples were obtained for DNA extraction, and BRCA sequencing and dosage analysis were performed at Leeds Cancer Center, Leeds-United Kingdom. BRCA1/2 mutations were classified as pathogenic/likely pathogenic and variant of uncertain significance (VUS). Clinical and pathological data were obtained from patients' medical records and a detailed 3-generation family history was also obtained by a genetic counselor. Results: A total of 517 patients were enrolled, genetic testing and counseling have been completed for all. Median age at diagnosis was 39 (range: 20-78) years. Among the whole group, 72 (13.9%) patients had pathogenic or likely pathogenic BRCA1 (n=24, 4.6%) or BRCA2 (n=48, 9.3%) mutations, while 53 (10.3%) others had VUS. Among 333 younger (≤40 years) patients, pathogenic/likely pathogenic mutations were observed in 44 (13.2%) patients and 36 (10.8%) others had VUS. Among 242 patients who had one or more close relatives with breast cancer, diagnosed at age 50 years or younger, 40 (16.5%) had pathogenic/likely pathogenic mutations (Table). Twenty (35.1%) of the 57 patients with triple-negative (TN) disease had pathogenic/likely pathogenic mutations; 16 (28.1%) were in BRCA1. Rate was significantly higher (55.6%, p <0.0001) among those with two family members with breast cancer at any age (n=9). However, compared to older patients, mutation rates were not higher among 37 TN-patients who were 40 years or younger. Conclusions: BRCA1/2 mutations are not uncommon and may contribute to the pathogenesis of familial breast cancer among Jordanians. Young age, per se, has the weakest association with positive BRCA1/2 mutations while TN-disease, especially when associated with positive family history, has significantly higher mutation rate. The establishment of Clinical Cancer Genetics program made running such culturally-sensitive genetic testing and counseling more acceptable even in societies like ours. Table: Rates of positive BRCA1/2 mutation across different indications for testingVariableTotalPositive BRCA mutations*BRCA1BRCA2BRCA1/2P-ValueAge (years)≤4033315 (4.5%)29 (8.7%)44 (13.2%)0.53>401849 (4.9%)19 (10.3%)28 (15.2%)Age ≤ 50 years with one or more close relative with breast cancer at any ageYes2428 (3.3%)32 (13.2%)40 (16.5%)0.1No27516 (5.8%)16 (5.8%)32 (11.6%)Age ≤ 60 with triple negative diseaseYes5716 (28.1%)4 (7.0%)19 (35.1%)<0.001No4628 (1.7%)44 (9.6%)53 (11.3%)Any age with at least 2 breast cancer primariesYes574 (7.0%)4 (7.0%)8 (14.0%)0.98No46020 (4.3%)44 (9.6%)64 (13.9%)Any age with 2 or more close relatives with breast cancerYes1157 (6.1%)21 (18.3%)28 (24.3%)<0.001No40217 (4.2%)27 (6.7%)44 (10.9%)Any age with one or more close relatives with invasive ovarian cancer diagnosed at any ageYes192 (10.5%)4 (21.1%)6 (31.6%)0.023No49822 (4.4%)44 (8.8%)66 (13.3%)All Patients51724 (4.6%)48 (9.3%)72 (13.9%)*Positive mutations: Pathogenic/Likely Pathogenic Citation Format: Hikmat Abdel-Razeq, Lama Abujamous, Amal Al-Omari, Abdelghani Tbakhi, Dima Jadaan. Genetic counseling and genetic testing for germline BRCA1/2 mutations among high risk breast cancer patients in Jordan: A study of 500 patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-09-06.