A new treatment for breast cancer patients with hormone receptor (HR ) early stage disease who are at a high risk of recurrence has been shown to reduce the risk by 25%, according to a study led by The Royal Marsden NHS Foundation Trust.

The results of the monarchE study presented at the European Society for Medical Oncology Virtual Congress (ESMO) and published simultaneously in the Journal of Clinical Oncology (JCO) on Sunday 20 September 2020, have been described as one of the most promising breakthroughs for patients with this type of breast cancer in the last 20 years.

The global randomised Phase III study with 5,637 patients in 38 countries tested if patients taking the CDK 4/6 inhibitor abemaciclib along with hormone therapy following standard of care treatments (chemotherapy, surgery and/or radiotherapy) would reduce the risk of recurrence compared with the standard hormone treatment alone.

Approximately 70% of breast cancer patients have hormone receptor positive tumours, and of those a proportion of patients will have a higher risk of relapsing in the first two of years.

Patients with disease that has spread to lymph nodes, a large tumour size at the time of diagnosis, or an increased cellular proliferation (determined by high grade of the tumour, or number of dividing cells) were considered to be at "high risk" of recurrence and recruited to the study.

The study found a 25% reduction in recurrence of cancer when abemaciclib was added to the standard hormone therapy compared to the hormone therapy alone for two years.

During this time 11.3% of patients in the control group had a relapse of their cancer compared with 7.8% of those in the abemaciclib group.

Professor Stephen Johnston, Consultant Medical Oncologist at The Royal Marsden and Professor of Breast Cancer Medicine at The Institute of Cancer Research, said: "The monarchE research has given us a confidence that we will soon be to offer our high risk HR patients a greater chance of keeping them cancer free.

"While there have been many advances in other early breast cancer subtypes such as HER2 positive disease, there has been no significant advancements for the large group of patients who have hormone receptor positive breast cancer since the late 1990s when aromatase inhibitors were introduced. This research could potentially save many lives in the future."

Patient Sarah Ryder, 57, said: "When I was referred to The Royal Marsden last year and Professor Johnston told me about the monarchE trial I was so pleased to be part of something that could potentially save my life. By that stage my cancer had spread to 23 lymph nodes and I honestly did not feel much hope.

"The trial has helped me believe in a future again. I can see my daughter grow up, go off to university next year and maybe have a family of her own one day."

Source: The Royal Marsden NHS Foundation Trust

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