Abstract PO5-08-01: Investigating the Link between APC I1307K Mutation and Breast Cancer in Arab Population
Authors: Sharaf Baha' , Hani Hira Bani , Zayed Anas , Barbar Maha , Hushki Ahmad , Abdel-Razeq Rashid , Titi Mohammad , Al-Halalsheh Reem , Mahafdah Suleiman , Abdel-Razeq Hikmat 
Published: May 2024

Background: Identifying asymptomatic individuals with an increased risk of hereditary breast cancer may significantly enhance early detection and prevention strategies and may inform treatment decision of patients who carry such variants. The APC I1307K missense mutation is known to be unrelated to conditions such as familial adenomatous polyposis (FAP), attenuated FAP, or gastric adenocarcinoma. However, individuals of Ashkenazi Jewish ancestry who carry this variant, have increase risk of colon cancer compared to the general population. The association of this variant with other cancer types, such as breast cancer, and in individuals of other ancestries, like Arabs, remains unknown. In this study, we investigate the potential association between APC gene (I1307K variant) and breast cancer risk.

Method: Over a course of 18 months, all newly diagnosed patients with solid tumors were offered to participate in a universal germline genetic screening study, utilizing a standard 21-gene or an investigational 84-gene panel testing. A retrospective analysis was conducted on the 153 patients within the study group who carry the APCI1307K missense variant irrespective of cancer type. Patients were classified as meeting the criteria or not meeting the criteria of the National Comprehensive Cancer Network (NCCN) v.1.2020. Data were extracted from electronic medical records and our institutional cancer registry. Descriptive statistics test was employed.

Results: Among the screened cancer patients (n=3400), 153 (4.5%) were tested positive for the APC I1307K missense mutation are included in this analysis. Median age at cancer diagnosis was 52 (range,19-80) years, and 99 (64.7%) were female. Breast cancer was the most common primary tumor (n=67, 43.8%) followed by colorectal (n=38, 24.8%), lung (n=7, 4.6%) and pancreatic cancer (n=6,3.9%). Among the 67 breast cancer patients included, 16 (23.9%) were not eligible for genetic testing as per the NCCN guidelines, and were tested as part of the universal genetic testing study. Among the patients with breast cancer, 53 (79.1%) had screening colonoscopy and 9 (17.0%) were found to have polyps (range, 1-3); 8 (88.9%) were low-grade dysplasia, while the other 44 (83.0%) had completely normal colonoscopy.

On the other hand, among the 38 patients with colorectal cancer, 21 (55.3%) had tumors presenting as polyps, or exhibited concomitant polyps (range, 1-3), or displayed abnormalities in the background that were polypoid in nature. Notably, 24 (63.2%) of patients with colorectal cancer, have a family history of breast cancer.

Conclusions: APC I1307K variant is unexpectedly common among our cohort of Arab patients. Individuals who carry this variant may face an elevated risk of developing breast cancer; potentially contributing to hereditary and familial cases, and such patients are at higher risk for colorectal cancer, too.

Citation Format: Baha' Sharaf, Hira Bani Hani, Anas Zayed, Maha Barbar, Ahmad Hushki, Rashid Abdel-Razeq, Mohammad Titi, Reem Al-Halalsheh, Suleiman Mahafdah, Hikmat Abdel-Razeq. Investigating the Link between APC I1307K Mutation and Breast Cancer in Arab Population [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-08-01.