Abstract P3-05-43: Germline Testing Results in Patients with Genomic Tumor Profiling
Authors: Beitsch Peter , Wernecke Chloe , Patel Rakesh , Rosen Barry , Brown Eric , Compagnoni Gia , Grady Ian , Gold Lindsay , Whitworth Pat , Smith Linda Ann , Wirga Mariusz , Reitherman Richard , Cai Steven , Nguyen Toan , Traina Valerie , Holmes Dennis , Baron Paul , Krautheim Brittany , Peled Anne , Taylor Walt , Bontempo Kelly , Bentley Brenna , Ortega Krista , Ahmadi Pouyan 
Published: March 2023

Abstract
Background: With the rise of genomic testing, more clinicians are using panels to understand the genetic profile of breast cancer to help aid in clinical management. However, little is known about the relationship between the results of genomic tests and the likelihood of identifying an underlying germline variant, and how this should integrate into clinical decision making. Methods: Data was obtained from the Informed Genetics Annotated Patient Registry (iGAP), an IRB-approved, multi-centered longitudinal registry designed to capture biomarker test results and their impact on treatment practices and outcomes. Two genomic tumor profiling tests were studied - MammaPrint recurrence risk and Blueprint molecular subtypes, including Luminal type A, Luminal type B, Basal, and HER 2 type. Of the 3400 patients currently enrolled in the registry, 528 have been diagnosed with breast cancer and underwent tumor profiling by both MammaPrint and BluePrint as well as germline genetic testing, including analyses of 24 cancer susceptibility genes (ATM, BARD1, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, NBN, PALB2, PTEN, STK11, TP53, APC, BMPR1A, CDK4, EPCAM, MLH1, MSH2, MSH6, MUTYH, PMS2, RAD51C, RAD51D, SMAD4). Differences in positive germline variant rates were tested for with two-sided, Chi-Square tests using the prop.test function in R. Results: 231 (44.17%) were classified as High-Risk for recurrence on MammaPrint, with a 0.13 PVs detected per patient tested (positive germline variant (PV) Rate), 269 (51.34%) were identified as having a Low-Risk, with a 0.0849 PV rate, and 23 (4.4%) Ultra-Low-Risk, with a 0.0455 PV rate. There is not a significant difference between the High-Risk and Low-Risk for recurrence (p=0.09). 45 (8.54%) Basal molecular subtype identified by BluePrint panel, with a 0.1778 PV rate, 292 (55.41%) classified as Luminal A type, with a 0.0819 PV rate, 171 (32.45%) Luminal B with 0.1078 PV rate, and 13 (2.47%) HER2 Type with 0.07 PV rate. There was a significant difference between Basal and Luminal A PV rates (p=0.042), but no other statistically significant differences were found. Conclusions: Patients with a Basal molecular subtype have a significantly higher likelihood of having a germline pathogenic variant compared to Luminal A subtype. There was a trend that did not reach statistical significance for MammaPrint High Risk to have a higher likelihood of germline pathogenic result compared to MammaPrint Low Risk. This data adds another parameter for germline testing in those breast cancer patients who fall outside of current NCCN testing criteria.
Citation Format: Peter Beitsch, Chloe Wernecke, Rakesh Patel, Barry Rosen, Eric Brown, Gia Compagnoni, Ian Grady, Lindsay Gold, Pat Whitworth, Linda Ann Smith, Mariusz Wirga, Richard Reitherman, Steven Cai, Toan Nguyen, Valerie Traina, Dennis Holmes, Paul Baron, Brittany Krautheim, Anne Peled, Walt Taylor, Kelly Bontempo, Brenna Bentley, Krista Ortega, Pouyan Ahmadi. Germline Testing Results in Patients with Genomic Tumor Profiling [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 P3-05-43.