Findings on an androgen receptor inhibitor, maintenance chemotherapy were presented during Monday's sessions on triple-negative breast cancer

Studies presented at the 2015 meeting of the American Society of Clinical Oncology (ASCO) included several on triple-negative breast cancer. Below we report on a trial of enzalutamide, an androgen receptor inhibitor medicine, and a study of maintenance chemotherapy in people with early-stage, hormone receptor-negative breast cancer. 

Androgen Receptor Inhibitor

In breast cancer, we most often talk about estrogen, progesterone and HER2 receptors. But another receptor, the androgen receptor, may play a role in breast cancer as well.

In what is now the largest breast cancer study of a medicine that targets the androgen receptor, researchers gave study participants – women with metastatic, androgen receptor-positive, triple-negative breast cancer – enzalutamide (Xtandi), an androgen receptor inhibitor FDA approved for use in men with prostate cancer. They also used a new test, called PREDICT AR, with the hope it would identify the participants who would most benefit from the treatment.

Lead researcher Tiffany A. Traina, MD, of Memorial Sloan Kettering Cancer Center, in New York City, reported that median progression free survival was 8 weeks in participants whose cancers were PREDICT AR-negative, but 16.1 weeks in participants who were PREDICT AR-positive. This suggests that enzalutamide hormonal therapy has activity in triple-negative breast cancers, and the PREDICT AR correctly identifies people whose cancers would benefit from the treatment.

Data about overall survival, or OS, the time from start of treatment until death from any cause, is not yet available.

Because enzalutamide showed activity in AR-positive triple-negative breast cancers, it deserves further study, some ASCO attendees said.

Maintenance Therapy With Low-Dose Chemotherapy

Maintenance therapies are treatments that are given to help keep breast cancer from coming back after initial therapy. Hormonal therapies, such as tamoxifen and aromatase inhibitors, used in hormone-positive breast cancer, are examples of maintenance therapies.

These researchers wanted to test a low-dose chemotherapy regimen in women with hormone-negative, early-stage breast cancer who had already had standard chemotherapy treatment. The regimen was given as pills for one year and was made up of the medicines cyclophosphamide (Cytoxan) and methotrexate. Researchers looked at breast cancer-free survival in that group and in a control group of participants who received no further treatment after standard chemotherapy.

Lead researcher Marco Colleoni, MD, of the European Institute of Oncology in Milan, Italy, reported that though breast cancer-free survival was higher in the group that received the study medicine, especially among participants who had triple-negative, node-positive breast cancer, it was not a statistically significant difference. That means the difference could be because of chance.

Check out our previous coverage of ASCO 2015, including studies presented on Saturday related to surgery and preventing hair loss and studies presented Monday related to hormone receptor-positive breast cancer. Don’t forget to join us for our annual ASCO webinar on Thursday, June 4.