Phase 3 trial finds effective treatment for premenopausal breast cancer



Between 20-50% of all breast cancers worldwide are diagnosed in women under 50 years old. Doctors have prescribed different drugs and different endocrine therapy protocols for premenopausal breast cancer patients compared with postmenopausal breast cancer patients. Researchers have recently questioned this line of thinking.

Patients can have different types of breast cancer. Patients that have estrogen-receptor positive breast cancer often continue to take daily medications after all treatment has ended. The purpose of this is to affect the sex hormone estrogen. Health professionals refer to this as endocrine therapy.

For the first time, an international group of researchers looked at whether drugs and endocrine therapy given to postmenopausal women can help premenopausal women. The researchers recently published their findings in the The Lancet.

Ribociclib stops the normal processes of cancer cells

The new drug in question for premenopausal women is called ribociclib. It stops some of the normal processes of the cancer cell. The researchers combined this drug with the usual endocrine therapy treatments that are given to premenopausal and postmenopausal women.

A total of 672 patients were enrolled in the clinical trial. All were premenopausal patients with advanced breast cancer. The patients were randomly placed into one of two treatment groups. One group received ribociclib and endocrine therapy. The other group received a placebo and endocrine therapy. A placebo is a pill that has no treatment effect. Researchers give placebo pills so that the patients do not know which treatment group they are in.

The patients continued to take their treatments until one of the following occurred: their breast cancer got worse it was making them sick; they or their doctor chose to stop it for other reasons.

Doctors monitored whether the breast cancer was growing with a CT scan or MRI. The patients had the CT or MRI every eight weeks for the first 18 months. After this time, they had it every year. The patients stopped having the CT or MRI if the breast cancer was getting worse or they made a decision to stop.

Researchers followed the patients for on average 19 months. They recorded how long the patients lasted without the breast cancer getting any worse. The patients that received ribociclib lasted on average 23.8 months. However, the patients that received the placebo lasted on average13 months.

Patients receiving ribociclib had lower white blood cell counts that those patients that did not. This affects their ability to fight infections. However, the doctors were able to manage these complications by adjusting the patient’s dose of ribociclib.

Ribociclib with any type of endocrine therapy is helpful in premenopausal breast cancer patients

The researchers made two important conclusions from the study. The first is that giving ribociclib with any type of endocrine therapy is helpful in stopping breast cancer progression in premenopausal patients. The second is these results show for the first time how helpful frontline endocrine therapy is in the fight against advanced breast cancer in premenopausal women.

Written by Nicola Cribb, VetMB DVSc Dip.ACVS


  1. Romero D. Expanding ribociclib use. Nat Rev ClinOncol. 2018:1. doi:10.1038/s41571-018-0051-x.
  2. Tripathy D, Im S-A, Colleoni M, et al. Ribociclib plus endocrine therapy for premenopausal women with hormone-receptor-positive, advanced breast cancer (MONALEESA-7): a randomised phase 3 trial. Lancet Oncol. 2018. doi:10.1016/S1470-2045(18)30292-4.