Real-world cancer care utilization among patients with breast cancer with germline variants of uncertain significance.

10512 Background: Receipt of variant of uncertain significance (VUS) results from germline genetic testing (GGT) is common, but should not influence treatment or surveillance interventions. We examined treatment and surveillance uptake among breast (BC) patients (pts) undergoing GGT. Methods: GGT (Invitae Corporation) and insurance claims (Komodo Healthcare Map) data were assembled for female pts with ICD code(s) for BC or DCIS from 2015-2023, GGT 1 year of claims pre- and post-GGT. Inclusion/exclusion criteria followed prior work (PMID 32027353). Genes analyzed for VUS and positive (>1 pathogenic germline variant, PGV) results were those with high ( > 50%; BRCA1/ 2, CDH1, PALB2, PTEN, TP53) or moderate (20-50%; ATM, BARD1, CHEK2, NF1, STK11, RAD51C/D) BC risk. Multivariable logistic regression models of the association between GGT results and interventions included race/ethnicity, age, family history, local/distant metastasis, and log-transformed time from BC dx to GGT. Chi-square tests were used to compare demographics of VUS pts to other pts. Significance was set to p < 0.05. Results: The cohort consisted of 19,334 pts (2005 VUS, 16,062 negative, 1,267 positive): 68% White, 25% lymph node involvement, 63% cancer family history, 28% Medicare/Medicaid, mean (SD) age at testing: 53 (11) and mean (SD) days from dx to GGT: 37 (25). VUS pts were more likely to be non-White (p < 0.001). VUS pts were not more likely than negative pts to undergo BC-related therapies or surveillance, except for (anthracycline) chemotherapy (Table). In contrast, positive pts had significantly greater odds than negative pts of bilateral mastectomy, platinum/anthracycline chemotherapy, PARP inhibitors, and breast MRI. Conclusions: In a contemporary, real-world cohort of nearly 20,000 BC patients, receipt of BC-related interventions was similar in VUS and negative pts. VUS results do not appear to prompt guideline-discordant management, though the finding of increased anthracycline use needs further study. Table: see text