Breast Cancer: Do We Have a New Target?

Currently, chemotherapy is the only standard drug therapy for those with “triple negative” breast cancer. By triple negative, we mean that the cancer does not have estrogen receptors (it is ER negative), progesterone receptors (PR negative), or HER2 receptors (HER2 negative). Of the major groups of breast cancer, triple negative has the worst survival overall.

However, when we interrogate triple negative breast cancer cells with molecular assays, we find that there are distinct subjects of the entity. One subset expresses a receptor for “male hormone”; cancer cells that have these androgen receptors (AR-positive) have been shown to have a modest response to drugs that block androgen receptors. Examples of these AR-inhibitors include a abiaterone acetate and bicalutamide, drugs that we sometimes use to help manage prostate cancer in men.

Now researchers have conducted a study looking at enzalutamide, another androgen receptor inhibitor (that is sometimes used for prostate cancer that has spread to distant sites). How well did the drug work for patients with metastatic (spread to distant sites) androgen receptor positive, triple negative breast cancer? Certainly not extraordinary results, but at the 16 week mark the drug led to clinical benefit for 25 percent of patients; for the subgroup with androgen receptor over 10 percent, the clinical benefit was 33 percent. The most common severe side effect was treatment-related fatigue.

My take: The study did achieve its primary endpoint. Subsets of triple negative breast cancer may benefit from strategies targeting the androgen receptor in the future.

I am Dr. Michael Hunter, and I invite you to follow me (below) and to learn more here: Wellness!

My background? I have degrees from Harvard, Yale, and the University of Pennsylvania. I help folks with cancer in the Seattle area, serving as a radiation oncologist. Thank you for joining me today.


* above is the human androgen receptor ligand binding domain

Reference: J Clinical Oncology 2018 Jan 26; or try the web by clicking here: Targeting the Androgen Receptor in Triple-Negative Breast Cancer