Controversial breast cancer trials set to commence

A natural hormone considered harmful by some scientists is being tested for potential use in breast cancer treatment.

The University of Liverpool and Cancer Research UK Cambridge Institute (CRUK-CI), in collaboration with the University of Adelaide, will conduct clinical trials early next year to test the effectiveness of progesterone in slowing the growth of cancerous tumours. Progesterone is a naturally occurring sex steroid that is being coupled with the breast cancer drug Tamoxifen to attack tumours.

The controversy centres on the different effects in women of the naturally occurring hormone compared with synthetic forms (progestins) designed to mimic its actions. Some, but not all, progestins have been linked with increased breast cancer risk when used in menopausal hormone therapy, leading to concerns in the scientific community about the use of these drugs.

Writing in the journal Nature Reviews Cancer, University of Adelaide researchers claimed that progesterone when used in menopausal hormone therapy does not increase breast cancer risk. Additionally, they argued in the journal Nature that the new treatment method would be safe and suitable.

“There is no evidence in the literature that progesterone produces risk in laboratory studies or hormone studies,” said Professor Wayne Tilley, director of the university’s Dame Roma Mitchell Cancer Research Laboratories.

“That is why we believe it is a safe agent and, when you couple that with the research we published last year, it shows that if you combine progesterone with hormone therapy and oestrogen, you can alter the way a cancer cell grows.

“In particular, progesterone can reprogram oestrogen action in the breast in a way that results in oestrogen receptor action improving breast cancer outcomes. Because of this unique interaction of the two natural female sex hormones in the breast, we see great potential benefits in adding progesterone to existing drugs that target the oestrogen receptor, thereby helping to switch off the growth of cancer cells.”

The first trial with the University of Liverpool will test the potential benefit of combining progesterone treatment with Tamoxifen in premenopausal women with breast cancer. The second, initiated by the CRUK-CI, will evaluate whether a particular progestin, Megace, provides added therapeutic benefit when combined with a current oestrogen receptor target treatment, compared to the target treatment alone.

Professor Tilley said although the trials are being conducted in a pretreatment space for therapeutic treatment, he is interested in the possibility of whether it could be used in high-risk women as well.

“There is no really good treatment and we are hoping to create a niche for this therapeutic strategy,” he said.

“Sometimes women who responded initially to hormone therapies end up building a resistance to it eventually.

“Hopefully the paper and these trials show people its [progesterone’s] potential and how safe it is.”

This is a modified version of a story published by The Lead South Australia under Creative Commons.