A type of drug known as selective oestrogen receptor modulators (SERMs) cuts incidences of breast cancer by 38% in women at increased risk of the disease, new research has revealed.
One incidence of breast cancer would be prevented for every 42 women who took a SERM for five years and followed for a further five, according to a study published in The Lancet.
Researchers from Queen Mary University of London analysed the records of more than 83,000 women to review the effectiveness of four specific SERMS - tamoxifen, raloxifene, arzoxifene, and lasofoxifene.
Tamoxifen is widely used to treat oestrogen receptor positive (ER positive) breast cancer, while the others are used to treat osteoporosis.
The greatest reduction in breast cancer incidence was seen during the first five years, with 376 breast cancer cases versus 594 for those who were not taking a SERM – a 42% drop, the Cancer Research UK study found.
A benefit continued to be felt in the five years after the women had stopped taking the drug, researchers discovered.
There were 211 breast cancer cases in women who had taken a SERM compared with 258 in those who had not – a 25% decrease – but there was no effect on breast cancer deaths.
SERMS work by locking on to the oestrogen receptor, the part of the breast cancer cell that causes the cell to grow.
While they are effective in reducing incidence of breast cancer, all four drugs were found to sharply increase the risk of blood clots such as deep vein thrombosis.
The drugs also led to a reduction in the risk of fractures, although Tamoxifen was linked to an increase in endometrial cancers, with the increase in cases falling after women stopped taking it.
The direct comparison of tamoxifen with raloxifene showed that raloxifene is less effective than tamoxifen, but has fewer side-effects.
No effect was noted for ER-negative breast cancers but the reduction of ER-positive breast cancer was 51%.
Professor Jack Cuzick, lead researcher based at the Queen Mary University of London, said: “These are very encouraging results and pave the way for more widespread use of these drugs in high risk women in a manner similar to the way statins and blood pressure lowering drugs are used to reduce the risk of heart disease and stroke.”
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