Abstract P6-02-12: Underutilization and disparities in germline genetic testing for breast cancer patients diagnosed in Chile

Abstract Introduction 10% of Breast Cancer (BC) cases are thought to carry a germline pathogenic variant (PV) in a susceptibility gene. Most clinicians utilize the National Comprehensive Cancer Network (NCCN) guidelines criteria to both identify these patients and, in those who test positive, to provide adequate follow-up and/or surgery recommendations. In Chile, BC Guidelines, established in 2004, defined treatment strategies for invasive BC (iBC) which significantly reduced mortality. However, these guidelines do not define strategies for germline genetic testing nor contemplate coverage for those who needs them. Thus, we face many obstacles to genetic testing implementation such as out-of-pocket cost and lack of genetic counsellors. The aim of the study is to determine how many BC Chilean patients are at risk according to international guidelines, how many are being tested and what are their clinical characteristics. Methods Retrospective analysis of a prospective database of iBC patients treated in a public hospital (PH) and in an Academic Private Centre (AC) in Santiago, Chile from January 2012 to March 2022. All patients who had enough information (age, family history (FH), BC subtype) for NCCN Version 2.2022 categorization were included. Patients whose only indication for germline testing was the potential use of PARP-inhibitors were excluded. Clinical characteristics were extracted from clinical charts. Results 4,365 iBC patients met criteria. 51.1% were treated in PH and 49.9% in a AC. 2,260 patients (51.8%) fulfilled NCCN criteria for germline testing, distributed unevenly between PH (46.0%) vs. AC (56.9%, p=0.0001). Compared to PH, patients in AC were diagnosed at younger age (54 vs 56 years, p=0.0001) and were more likely to report FH (69.4% vs. 53.7%, p=0.0001). No difference between BC subtypes was reported. Considering only those fulfilling criteria, germline genetic testing was performed in 326 patients (14.4%) with a significant difference according to UH vs AC (18.7% vs. 9.1%, p= 0.0001). 58% of these tests were performed in the last 3 years. Multivariate logistic regression showed that being diagnosed before 46 (HR=5.3, p=0.0001); FH (HR=2.2, p=0.0001); localized vs. metastatic disease (HR=3.7, p=0.001); triple negative (TN) BC (HR=1.8, p=0.0001) and being treated in AC (HR=1.9, p=0.0001) were independently associated with germline genetic testing being performed in patients fulfilling NCCN criteria. 82 PV were documented, being the most frequent BRCA1/2 (18.1%) followed by PALB2 (1.8%) and ATM (1.2%). Being diagnosed with TNBC (HR=3.8, p=0.0001) and having a first-degree relative with cancer (HR=4.4, p=0.0001) were the only factors associated with carrying a pathogenic BRCA1/2 mutation. Conclusion In Chile, less than 20% of iBC patients who meet NCCN criteria for germline testing are being tested. In this sample of our Public Health System, where over 80% of the Chilean population is treated, fewer than 1 in 10 individuals fulfilling criteria have undergone testing. New evidence suggests that probably a wider span than suggested by NCCN of patients should be counselled and tested, deepening even further the underutilization of germline testing in Chile. Lack of knowledge and training in oncology providers and out-of-pocket costs might influence these results. National guidelines are urgently needed. Citation Format: FRANCISCO ACEVED, Benjamin Walbaum, Lidia Medina, Tomas Merino, Paula Reyes, Militza Petric, Francisco Dominguez, Paulina Gonzalez, CÉSAR SÁNCHEZ. Underutilization and disparities in germline genetic testing for breast cancer patients diagnosed in Chile [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-02-12.