Abstract

Abstract Background: Next-generation sequencing (NGS) of cell-free DNA (cfDNA) is increasingly being utilized to assess somatic genomic alterations in patients with breast cancer. We investigated the clinical use of such testing in breast cancer care in a major healthcare system with both academic and community-based practices. We also explored the observed genomic landscape in the analyzed patient cohort and whether treatment plans were modified based on the results. Methods: A retrospective review of cfDNA NGS results (Guardant360) ordered at the University of Pittsburgh Medical Center for patients with breast cancer from 7/2015-3/2017 was performed. Test ordering patterns, the landscape of genomic alterations identified, and clinical use of select results were assessed. Results: During this period 95 samples were submitted, 73 (77%) ordered by academic center providers and 22 (25%) from community providers. Alterations were detected in 88 samples (93%) with a median of 3 alterations per test. Five patients had serial samples ordered assessing dynamic cfDNA across clinical treatment and progressions, leaving 84 unique patients in the dataset. The average patient age was 57, and 95% of patients were female. Patients were most often observed to have alterations in TP53 (51%), PIK3CA (44%), and ESR1 (26%). Additional clinical data were collected for 48 patients with mutations or amplifications in PIK3CA, ESR1, and/or ERBB2 (HER2) to assess for clinical use of genomic information. Results were used to change clinical care in 13 (27%) of these cases. Community providers were more likely to use genomic results to guide clinical management in these cases (9/16, 56%) than academic providers (4/32, 12.5%), p=0.001. Of this patient subset, those with tests ordered by an academic provider had more lines of prior therapy at the time of testing vs. those in the community (average 5.9 vs 3.4 respectively, p=0.019). Conclusions: CfDNA NGS analysis for somatic genomic alterations in breast cancer is being ordered clinically by both academic and community practices within this healthcare system. Results for a subset of clinically annotated patients were acted on more frequently by community-based ordering providers, which may be related to patients tested at academic sites having had more lines of prior treatment. Citation Format: Thomas RA, Klar N, Kiedrowski L, Nagy RJ, Lee AV, Brufsky A. Utilization of cell-free circulating tumor DNA for management of breast cancer: Practices in academic and community oncology [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-13.

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