Landscape of somatic mutations in different subtypes of advanced breast cancer with circulating tumor DNA analysis.

It is particularly important to provide precise therapies and understand tumor heterogeneity based on the molecular typing of mutational landscape. However, the landscape of somatic mutations in different subtypes of advanced breast cancer (ABC) is largely unknown. We applied target-region capture deep sequencing to determine the frequency and spectrum of common cancer-related gene mutations in circulating tumor DNA (ctDNA) among different ABC subtypes and analyze their association with clinical features. In this retrospective study of 100 female advanced breast cancer patients, 96 (96.0%) had somatic genomic alterations in ctDNA, including copy number variants and point mutations. The results revealed that different subtypes of ABC have distinct features in terms of genetic alterations. Multivariate regression analyses revealed that the number of somatic mutations increased with the line of endocrine therapy and the fractions of trunk mutations was positive associated with the line of target therapy.