HRT patches to treat prostate cancer – here’s how it works

Women’s HRT patches can treat prostate cancer just as effectively as standard hormone injections – but with fewer of the worst side-effects – according to a large UK trial published in the New England Journal of Medicine. The finding could change how men with prostate cancer that has spread beyond the gland are treated for years to come.

Standard treatment has long relied on shutting down testosterone, the fuel that drives many tumours, through regular injections that turn off the body’s own hormone production. They are effective, but they are blunt tools, dragging down oestrogen as well as testosterone and taking a heavy toll on quality of life with hot flushes, brittle bones and metabolic problems. Now, in an elegant twist of biology, the very hormone patches used to ease menopause symptoms in women are being repurposed to treat prostate cancer in men.

The idea sounds counterintuitive at first. Why would giving oestrogen to men help control a cancer fed by testosterone? The answer lies in feedback loops.

Oestradiol, the form of oestrogen in standard HRT patches, signals to the brain that there is plenty of sex hormone around. The brain then dials down its instructions to the testes to make testosterone, so levels of the male hormone fall just as effectively as with injections designed to switch production off directly. In other words, you can arrive at the same hormonal destination by a more subtle route.

In the new trial, more than 1,300 men, with an average age of about 72, were randomly allocated to either the standard hormone injections or to skin patches delivering oestradiol, identical to those used for menopausal symptoms. Many also received radiotherapy and sometimes chemotherapy, reflecting how these cancers are treated in routine practice.

After three years, the proportion of men alive without the cancer progressing was almost identical in the two groups: 87% in the patch arm and 86% with injections. Essentially, a dead heat for effectiveness.

Where the approaches really diverged was in how men felt. Because injections strip away oestrogen as well as testosterone, they create a kind of sudden “male menopause”, complete with hot flushes, night sweats and thinning bones.

In the trial, almost nine in ten men on injections reported hot flushes. Among those wearing patches, less than half did.

Bone health also favoured the patches, with fractures roughly twice as common in the injection group. Men on patches, however, paid a different price: more than 80% developed breast tissue swelling, compared with about 40% of those on injections. This gynaecomastia, as it’s called, is rarely dangerous, but it can be very uncomfortable and for some men deeply unwelcome.

Those trade-offs go to the heart of modern cancer care. It is no longer enough just to count years of survival. As more people live for longer with their disease controlled, the quality of those years matters just as much. Prostate cancer is already the most common cancer in UK men, with around 64,000 new cases and 12,000 deaths each year.

Many of those men will spend years on hormone therapy. If two treatments tame the tumour equally well, the one that lets you sleep through the night without wrestling with hot flushes, preserves your bones and can be applied at home rather than in a clinic starts to look very attractive.

The practical advantages of patches are easy to appreciate. Injections require repeated trips to hospital or GP surgeries and can be painful. Patches are simply stuck on the skin and replaced at home, with oestradiol absorbed steadily into the bloodstream.

This “transdermal” delivery – through the skin rather than the stomach – avoids the liver processing the hormone and appears to blunt some of the heart and clotting risks historically linked to oestrogen tablets taken by mouth. That is important because earlier attempts decades ago to treat prostate cancer with oestrogen pills fell out of favour when they were linked to more heart attacks and strokes. The current research essentially resurrects that old idea with a safer formulation and route.

The trial is part of a broader shift towards re-examining assumptions in oncology. For years, the focus in prostate cancer has been on newer, more targeted drugs and immunotherapies. Yet here we have a relatively cheap, widely available hormone patch being asked to do double duty: easing menopausal symptoms in one half of the population and quietly disabling a common male cancer in the other.

It is a reminder that innovation is not always about glamorous new molecules. Sometimes it is about taking an existing tool and using human physiology more cleverly.

None of this means that injections will vanish. For some men, breast swelling from patches may be intolerable despite the benefits. For others, the familiarity and simplicity of a regular injection still appeals. There will also be questions about which patients are best suited to this approach, how it interacts with newer generations of hormonal drugs and whether long-term effects on the heart remain reassuring.

Regulatory approval is still needed

Regulators will need to approve oestradiol patches specifically for prostate cancer, not just menopause, before health systems such as the NHS can routinely offer them in this way. Cost-effectiveness analyses and real-world data will follow.

What the study does immediately is widen the menu of choices. Instead of a single standard hormone therapy pathway, men with prostate cancer may soon be able to sit down with their doctors and weigh the trade-offs in a more personal way: fewer hot flushes and better bones with a high chance of breast swelling, or more traditional injections with their own set of problems. That conversation may feel more like choosing between HRT options in the menopause clinic than the old, paternalistic model of cancer care where one default protocol is imposed.

It is also a striking example of how women’s health and men’s health intersect. For years, debates around HRT have focused on its risks and benefits for women navigating menopause, with strong views on both sides. Now, the same patches are being recast as a potential life-prolonging treatment for men.

It is hard not to see a poetic symmetry there: a therapy designed to buffer women from the hormonal upheavals of midlife, helping men withstand the hormonal upheaval we deliberately induce to control prostate cancer. As more evidence accumulates, the humdrum little square of adhesive on the skin may come to symbolise a new, gentler chapter in how we use hormones against one of our most common cancers.

Justin Stebbing does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.