Enzalutamide shows promise for advanced androgen receptor-positive TNBC
medwireNews: Patients with locally advanced or metastatic triple-negative breast cancer (TNBC) that is positive for the androgen receptor (AR) could benefit from treatment with the AR inhibitor enzalutamide, phase II trial results suggest.
In the intention-to-treat (ITT) population of 118 women who received enzalutamide 160 mg/day, the primary endpoint of clinical benefit rate at 16 weeks was achieved by 25%, while 33% of 78 evaluable participants – those with tumor AR levels of at least 10% and one or more post-baseline assessments – derived a clinical benefit at this timepoint.
The corresponding rates at 24 weeks were 20% and 28%, report Tiffany Traina (Memorial Sloan-Kettering Cancer Center and Weill Medical College of Cornell University, New York, USA) and fellow investigators.
As reported in the Journal of Clinical Oncology, the median progression-free survival was 2.9 months in the ITT population and 3.3 months in the evaluable subgroup, with median overall survival times of 12.7 and 17.6 months, respectively.
The toxicity profile was as expected, say the researchers, and fatigue was the only treatment-related adverse event of grade 3 or worse observed in more than 2% of participants.
Noting that “TNBC has the poorest outcomes of the three major subtypes of breast cancer,” with the use of targeted agents meeting with little success, Traina et al say that the current data “support and build upon the findings from others that there seems to exist a subset of patients with androgen-driven TNBC who may benefit from an AR-targeted agent.”
They say that although the AR inhibitors bicalutamide and abiraterone acetate have also shown activity in prior advanced TNBC trials, there is a role for enzalutamide in this setting and additional development of the drug is warranted. The study authors explain that enzalutamide has been shown to be superior to bicalutamide in patients with prostate cancer, and that the need for concurrent prednisone with abiraterone acetate could limit its efficacy as prednisone-induced stimulation of the glucocorticoid receptor, expressed in around a quarter of TNBCs, could lead to tumor growth.
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