Abstract PO1-08-04: Universal Germline Genetic Testing for Breast Cancer: Implementation in a Rural Practice and Impact on Shared Decision Making

Abstract Background: Prior work from our group has shown a high rate of familial breast cancer (BC) among rural BC patients (pts), with 33% reporting > 1 first-degree family members with BC and 55% meeting NCCN germline genetic testing (GGT) criteria (Shelton CH et al. NC Med. J; 2022). In 2018, we increased GGT to include all BC pts and observed: 1) many pts were out-of-criteria per NCCN guidelines but had actionable pathogenic germline variants (PGVs) and 2) knowledge of GGT factored significantly into shared decision making by providers and patients, including for positive and negative results. Beginning in 2019, concurrent with the recommendation from the American Society of Breast Surgeons, we expanded this model of universal GGT to an IRB-approved study to measure the impact of prospective testing on shared decision-making. Herein we report the real-world implementation of universal GGT for patients with BC and genetics-informed treatment decision-making in a rural community practice. Methods: From 2019-2022 all BC pts at a small, rural community hospital were offered GGT. Demographics, clinical features, and GGT results were collected along with clinician-reported clinical recommendations for treatment based on GGT results. Descriptive statistics and two-tailed Fisher’s exact test were employed and significance was set at p< 0.05. Results: 210 BC pts were offered GGT and 192 (91%) underwent testing [97% female, 95% non-Hispanic White, mean age at diagnosis of 62, 75% Stage I], with all but 7 pts completing GGT before primary treatment decisions. 104 (54%) of patients were in-criteria (IC) and 88 (46%) out-of-criteria (OOC) with NCCN GGT guidelines. PGVs were identified in 25 pts (13%) and 15 genes, most commonly BRCA1/2 (5 pts), PALB2 (3), monoallelic MUTYH (3) and ATM, BARD1, CHEK2 (2 pts each). PGV frequencies were 15% in IC and 11% in OOC patients (p=0.495). 46 (24%) pts had only a variant of uncertain significance (VUS) results. 70% of patients had > 1 clinical management change based on their GGT results. Changes in breast surgery, uptake of risk-reducing bilateral salpingo-oophorectomy, surveillance and clinical follow-up were significantly higher in patients with PGV compared to those with VUS/negative results (p < 0.0001). Compared to those with negative results, patients with PGVs in BRCA1 and BRCA2 were significantly more likely to undergo bilateral mastectomy (BLM) while those with PGVs in other genes or with VUS were not significantly more likely to elect for BLM than those with negative results. Clinicians reported that return of GGT reinforced their recommendation for 73/138 (53%) of patients who underwent breast-conserving therapy. GGT results aided in radiation therapy strategy for 54% of pts, most often resulting in dose de-escalation (accelerated fractionation) for negative/VUS pts (Table). Conclusions: Universal GGT for patients with BC was successfully implemented in a rural community practice with >90% uptake. Treatment was enhanced in those with clinically actionable PGVs and de-escalated in those without PGVs. Universal GGT for patients with BC is feasible to implement as the standard of practice within rural populations, enabling optimization of clinical care to patients’ genetic profile and may reduce unnecessary healthcare resource utilization. Universal Germline Genetic Testing for Breast Cancer: Implementation in a Rural Practice and Impact on Shared Decision Making Changes in Radiation Therapy Strategy based on GGT Citation Format: Charles Shelton, Sarah Nielsen, Antonio Ruiz, Lauren Shelton, Karen Freas, Sarah Poll, Brandie Heald, Daniel Pineda-Alvarez, Edward Esplin, Rachel Ellsworth, Hannah Montgomery. Universal Germline Genetic Testing for Breast Cancer: Implementation in a Rural Practice and Impact on Shared Decision Making [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 PO1-08-04.