The prognostic effects of somatic mutations in ER-positive breast cancer

More than 50 genes are recurrently affected by somatic mutation in estrogen receptor positive (ER+) breast cancer but prognostic effects have not been definitively established. Primary tumor DNA was therefore subjected to targeted sequencing from 625 postmenopausal (UBC-TAM series) and 328 premenopausal hormonal receptor-positive (HR+) patients (MA12 trial). Independent validation of prognostic interactions were achieved with public data from the METABRIC study. Associations between MAP3K1 and PIK3CA with luminal A status and TP53 mutations with Luminal B/Non-luminal tumors were observed, validating the methodological approach. In UBC-TAM, NF1 frame-shift nonsense (FS/NS) mutations were validated as poor outcome drivers. For MA12, poor outcomes associated with PIK3R1 mutation were similarly validated. DDR1 mutations were strongly associated with poor prognosis in UBC-TAM with false-discovery correction (q=0.0003). In conclusion, the tail of uncommon recurrent somatic mutations should be further explored to create a more complete explanation of the highly variable outcomes that typify ER+ breast cancer.