Cross-sectional analysis of prevalence of targetable genomic alterations in young women with advanced breast cancer

Approximately 5% of breast cancers are diagnosed in women younger than 40 years, who tend to have worse clinical outcomes than older women with breast cancer. Cross-sectional analysis using comprehensive genomic profiling of tumor tissue compared prevalence of targetable genomic alteration in 2049 advanced breast cancer (aBC) patients younger than 30 years (1.37%), 30-39 years (7.76%), and older than 39 years (90.87%) at the time of diagnosis. Breast tumors were less likely to be ER-positive in younger women (54% of patients younger than 30 years and 60% of patients 30-39 years versus 69.4% of patients older than 39 years) and more likely to be triple negative (43%, 33%, and 26.1%, respectively). Younger women had higher rates of BRCA1 mutations (17.9%, 10.1%, and 2.6%, respectively) but lower rates of CDH1 mutations (7.1%, 5.0%, and 15.4%, respectively) and PIK3CA mutations (17.9%, 17.6%, and 40.0%, respectively). The authors conclude that these findings contribute to the growing literature demonstrating unique genetic profiles among young women diagnosed with aBC compared to older women.