The ARB trial is investigating whether the hormone treatment enzalutamide is a useful treatment for women with breast cancer before they have surgery. The trial is for women with breast cancer that has oestrogen receptors (oestrogen receptor positive) or breast cancer that has androgen receptors but doesn’t have receptors for the hormones progesterone and oestrogen, or for the protein HER2 (triple negative breast cancer).

Enzalutamide is a hormone therapy that targets androgens and it is already used to treat men with prostate cancer. Researchers are hoping to find out if it would be useful for women with triple negative breast cancer. Some triple negative breast cancers have androgen receptors on the surface of the cancer cells (called androgen positive) and most oestrogen positive breast cancers also have androgen receptors.

The receptors allow the cancer cells to use androgen to grow, but enzalutamide blocks the androgens from signaling to the cancer cells to grow. Another type of hormone therapy called exemestane is sometimes used to shrink oestrogen positive breast cancer before surgery. Doctors want to know whether adding enzalutamide to exemestane will shrink it further.



  • Find out if enzalutamide can slow or shrink the growth of androgen positive triple negative breast cancer
  • Learn more about the side effects of enzalutamide
  • Find out whether enzalutamide and exemestane is better than exemestane alone for oestrogen positive breast cancer

Inclusion criteria


Patients may be eligible for the ARB trial if:

  • They have breast cancer that is oestrogen receptor (ER) positive and are post-menopausal
  • Their breast cancer has androgen receptors, but doesn’t have receptors for the hormones progesterone and oestrogen, or for the protein HER2 (triple negative breast cancer)
  • Have invasive breast cancer
  • Have a breast cancer of any size that can be felt on examination or a cancer that measures at least 1cm by ultrasound or MRI scan
  • Are well enough to be up and about for at least half the day (performance status 0, 1 or 2)
  • Have satisfactory blood test results
  • They are at least 18 years old

Patients are not eligible for this trial if:

  • They have inflammatory breast cancer
  • They have had hormone therapy in the last 4 weeks including any drug that targets androgens or stop androgens from being made in the body
  • Are having or have had any other treatment for your breast cancer
  • Are having any experimental drugs. You must have finished taking part in any other trial investigating new drugs 4 weeks before joining this trial
  • Have had a fit (seizure) or you have lost consciousness for any reason in the last year
  • Have had a mini stroke (TIA or trans ischemic attack) in the last year
  • Have certain heart problems, for example a heart attack in the last 6 months or you have a significant irregular heart rhythm
  • Have had treatment for another cancer in the last year. You can take part if you have had another cancer, including another primary breast cancer and it was successfully treated over a year ago
  • Are allergic to the drugs used in this trial
  • Have any other serious medical condition or mental health problems that the trial team think could affect you taking part

Further information


For more information please visit the Cancer Research website here.