On World Cancer Day 2026 we would like to highlight the results of the PIONEER trial. The results have recently been published in the journal ‘Nature’, a high ranking medical journal.
About three out of four breast cancers are known as ‘ER-positive’. This means the cancer cells use oestrogen to grow. To stop this, doctors give medicines that lower oestrogen levels. These treatments work well, but they can cause unwanted effects such as hot flushes, joint pain, and maybe bone loss.
Doctors already use low doses of megestrol to help women cope with hot flushes, a common side-effect of anti-oestrogen treatment. This means many women can stay on their cancer medicine more comfortably. Megestrol acts like the hormone progesterone.
In the PIONEER trial, post-menopausal women with ER-positive breast cancer were treated two weeks before their surgery with either an anti-oestrogen drug alone (Letrozole), or with the same drug plus megestrol (Megace).
After two weeks, the women who received both medicines showed a bigger drop in tumour growth than those who got only the anti-oestrogen treatment.
Early results suggest adding megestrol could make treatment more effective and also help reduce the side-effects that cause some women to stop taking their medication. The researchers did point out that longer follow-up and more studies with more people in the period after surgery are needed to strengthen these findings.
The study was coordinated by the University of Cambridge. Our Breast Cancer Research Unit at Aberdeen Royal Infirmary was one out of 9 units participating in this UK-wide study UK. Local Principal Investigator Miss Beatrix Elsberger (Consultant Breast Surgeon) would like to thank NHS Grampian breast cancer patients, who took part in this study and helped gaining new valuable knowledge. You can read more about these results here: https://crukcambridgecentre.org.uk/news/hot-flush-treatment-has-anti-breast-cancer-activity-study-finds