Prostate Cancer Drug Xtandi Shows Promise for Treating Advanced, AR+ Triple-Negative Breast Cancer

The gist: A prostate cancer drug called Xtandi (aka enzalutamide) might also help treat women with advanced, androgen receptor-positive triple-negative breast cancer (TNBC). More research will need to be done to see whether Xtandi outperforms standard chemotherapy for these patients.

“Preliminary results from a Phase II trial of Astellas’ Xtandi (enzalutamide) show positive benefits for the prostate cancer drug when used as a single therapy to treat women with advanced androgen-receptor positive, triple-negative breast cancer.

“But Novartis’ bid to prove benefits for Afinitor (everolimus) as a first-line treatment for women with HER2-positive advanced breast cancer failed, after a Phase III trial found no benefit in this group of patients. [See more here.]

“The data from both studies were presented at the San Antonio Breast Cancer Symposium in Texas. The trial involving Xtandi is the largest to date in patients with androgen-receptor positive triple-negative breast cancer, and the first to report objective responses to a hormonal therapy.

“The study found that out of 26 women evaluated, 11 showed a clinically significant benefit after 16 weeks and 9 showed benefit after 24 weeks. More data is due in 2015 from a further 76 women enrolled in the study, but so far researchers have observed positive responses in one woman and partial positive responses in three more women in this group.”