Phase II Study of Dehydroepiandrosterone in Androgen Receptor‐Positive Metastatic Breast Cancer

LESSONS LEARNED. The androgen receptor (AR) is present in most breast cancers (BC), but its exploitation as a therapeutic target has been limited. This study explored the activity of dehydroepiandrosterone (DHEA), a precursor being transformed into androgens within BC cells, in combination with an aromatase inhibitor (to block DHEA conversion into estrogens), in a two‐stage phase II study in patients with AR‐positive/estrogen receptor‐positive/human epidermal growth receptor 2‐negative metastatic BC. Although well tolerated, only 1 of 12 patients obtained a prolonged clinical benefit, and the study was closed after its first stage for poor activity. BACKGROUND. Androgen receptors (AR) are expressed in most breast cancers, and AR‐agonists have some activity in these neoplasms. We investigated the safety and activity of the androgen precursor dehydroepiandrosterone (DHEA) in combination with an aromatase inhibitor (AI) in patients with AR‐positive metastatic breast cancer (MBC). METHODS. A two‐stage phase II study was conducted in two patient cohorts, one with estrogen receptor (ER)‐positive (resistant to AIs) and the other with triple‐negative MBC. DHEA 100 mg/day was administered orally. The combination with an AI aimed to prevent the conversion of DHEA into estrogens. The main endpoint was the clinical benefit rate. The triple‐negative cohort was closed early. RESULTS. Twelve patients with ER‐positive MBC were enrolled. DHEA‐related adverse events, reported in four patients, included grade 2 fatigue, erythema, and transaminitis, and grade 1 drowsiness and musculoskeletal pain. Clinical benefit was observed in one patient with ER‐positive disease whose tumor had AR gene amplification. There was wide inter‐ and intra‐patient variation in serum levels of DHEA and its metabolites. CONCLUSION. DHEA showed excellent safety but poor activity in MBC. Although dose and patient selection could be improved, high serum level variability may hamper further DHEA development in this setting.