PreOperative Endocrine Therapy for Individualised Care With Abemaciclib

In women with hormone sensitive early breast cancer, taking a hormone therapy (also known as endocrine therapy) for at least five years after surgery is very effective at reducing the risk of the cancer returning. However, for some women their cancer may eventually become resistant to these drugs. POETIC-A Registration part will identify those who have a higher risk of developing resistance to standard endocrine therapy (ET). At least 8000 women diagnosed with early stage breast cancer will enter the Registration stage from 80 centres. Study doctors will use aromatase inhibitors (AIs), a type of ET, to treat the cancer for between 2 weeks and 6 months before surgery. A sample will be taken from the cancer during surgery and the study laboratory will measure a biological marker called Ki67. If the level of Ki67 does not drop after 2 weeks of AI treatment, the patient is likely to be less sensitive to endocrine therapy, and the study doctor will explore additional treatments after surgery in the POETIC-A Treatment part. Everyone who agrees to join the Treatment stage (2032 patients) will be randomly put into one of the 2 treatment groups; Group1: ET only; or Group2: ET plus a new drug called abemaciclib. The first aim of the Treatment stage is to confirm whether abemaciclib given in combination with ET is more effective than giving ET alone in preventing the cancer coming back. The study laboratory will perform a second test on the cancer sample, called an AIR-CIS test. This test aims to find out if particular groups of patients based on their tumour biology are more suitable for treatment with abemaciclib. Patients in Group 2 will receive ET plus abemaciclib for 2 years. Patients in both groups will have regular study visits during this period.