Cabergoline Suppresses Postpartum Breast Cancer by Enhancing Mammary Gland Involution in Brca1-Mutant Mice and Is Associated with Reduced Risk in Younger Women

Breast cancer that arises in the postpartum period often carries a poor prognosis and urgently requires chemoprevention strategies, particularly for women at elevated risk. Here, we report that a single post-lactation dose of cabergoline, a dopaminergic agonist that blocks prolactin secretion, delays the onset and reduces the incidence of postpartum mammary cancer in K14-Cre; Brca1F/F, Trp53F/F mice. In these mice, cabergoline treatment remodels the mammary gland by potentiating involution, reducing ductal area and proliferation, and reversing T cell exhaustion, potentially through modulation of ion channel expression. Notably, independent retrospective studies in two large cohorts of European women showed that cabergoline treatment was associated with a lower incidence of postpartum breast cancer, with a meta-analysis indicating an approximate 69% reduction in risk. Our work underscores the importance of targeting postlactational involution as a strategy for the prevention of postpartum breast cancer and positions cabergoline as a novel, low-risk chemoprevention strategy.