Impact of tissue-based genomic profiling on clinical decision making in the management of patients with metastatic breast cancer at academic centers

Background: Genomic profiling can identify targetable mutations; however, the impact of tissue-based genomic profiling on clinical decision making for patients with metastatic breast cancer has not been well characterized. Methods: Patients with stage IV breast cancer who had undergone genomic profiling between 7/2013 and 3/2015 were identified at three academic cancer centers. Genomic analysis was determined to have impacted clinical decision if (A) a patient was enrolled onto a genotype-matched clinical trial or (B) prescribed off-label an FDA-approved therapy targeting an identified mutation. The frequency of mutated genes was determined. Results: A total of 117 patients with stage IV breast cancer were identified. Median age was 46 (25–75). Fifty-three patients (45%) had ER-positive/HER2-negative disease, 50 (43%) had ER-negative/HER2-negative disease, and 14 (12%) had ER-any/HER2-positive disease. Median number of previous therapies received prior to genomic profiling was 2 (range 0–15), and median follow-up after testing was obtained after 5.8 months (range 0–24.4 months). Commercial reports indicated that 85 (73%) patients had at least one mutation targetable by an FDA-approved medication, and 112 (96%) patients had at least one clinical trial available; however, clinical management was only affected in 11 patients (9%). The most frequent mutations observed were those in TP53, FGF, PI3KCA, MYC, ZNF, FGFR, CCND, ARID1A, GATA3, and MAP; frequencies of these mutations varied by clinical subtype. Conclusions: Tumor genomic profiling affected clinical management in a minority of patients with metastatic breast cancer, thus these data do not support the routine use of genomic profiling outside of a clinical trial.