CHICAGO, IL–Enzalutamide may represent a novel therapeutic option in patients with triple-negative breast cancer who would otherwise receive cytotoxic chemotherapy, a study presented at the 2015 American Society of Clinical Oncology (ASCO) annual meeting has shown.
“We hypothesized that enzalutamide will have activity in advanced androgen receptor (AR)-positive triple-negative breast cancer,” said Tiffany A. Traina, MD, medical oncologist at Memorial Sloan Kettering Cancer Center in New York, NY.
For the open-label, phase II study, researchers tested 404 samples of advanced AR-positive triple-negative breast cancer for androgen receptor immunohistochemistry. Of those, 118 patients were treated with single-agent enzalutamide 160 mg/day orally and only 75 were evaluable.
Results showed that 35% (95% CI: 24, 46) and 29% (95% CI: 20, 41) experienced clinical benefit at 16 and 24 weeks, respectively, meaning patients achieved a complete response, partial response, or stable disease.
Researchers found that median progression-free survival was 14.7 weeks (95% CI: 8, 19). Median progression-free survival was 16.1 weeks (95% CI: 13.3, 27.4) in those who were PREDICT AR-positive compared with 8 weeks (95% CI: 7.4, 12.6) in those who were AR-negative in an intent to treat analysis.“PREDICT AR and line of therapy were the only variables significantly and independently associated with outcome,” Dr. Traina noted.
In regard to safety, the most common adverse events associated with enzalutamide treatment were fatigue, nausea, decreased appetite, constipation, and diarrhea. “The only grade 3 treatment-related adverse event was fatigue,” Dr. Traina added
The findings suggest that clinical outcomes were superior in patients with advanced triple-negative breast cancer who tested positive for an androgen-related gene signature.
Dr. Traina concluded, “A novel genomic diagnostic assay, PREDICT AR, may identify triple-negative breast cancer patients who benefit from enzalutamide treatment…Results from this phase II study support continued development of enzalutamide in patients with PREDICT AR-positive TNBC.”
Enzalutamide is currently approved by the U.S. Food and Drug Administration for the treatment of men with metastatic castration-resistant prostate cancer.
1. Traina TA, Miller K, Yardley DA, et al. Results from a phase 2 study of enzalutamide (ENZA), an androgen receptor (AR) inhibitor, in advanced AR+ triple-negative breast cancer (TNBC). J Clin Oncol. 2015;33:(suppl; abstr 1003).