Diabetes treatment metformin could reduce treatment side effects for men with advanced prostate cancer

Some side effects of treating advanced prostate cancer could be reduced by a common type 2 diabetes medication, according to research we supported. 

The study found that weight gain, cholesterol levels and blood sugar levels were all reduced in men taking metformin. 

Men on the treatment were also less likely to have metabolic syndrome – a group of health problems that increase the risk of type 2 diabetes and heart disease. 

The results suggest that prescribing metformin alongside existing cancer treatments could help men who are newly diagnosed with advanced cancer live healthier lives. 

We’re also funding a team who will analyse the trial results further, to see whether metformin could even extend the lives of some of these men with advanced cancer. 

However, the treatment is not currently licensed for prostate cancer, meaning NHS doctors may not be able to prescribe it right away. 

Finding the best treatments for men with advanced cancer

The research was part of a much larger trial called STAMPEDE, funded by Cancer Research UK and the Medical Research Council, which aims to improve treatments for men with advanced prostate cancer.  

For example, hormone therapy has helped to extend the lives of thousands of men with prostate cancer worldwide. But, because these treatments affect the body’s metabolism, they can cause side effects that come with their own health risks. 

These challenges led the researchers to metformin, which, as a treatment for type 2 diabetes, changes the way that the body processes energy.  

Metformin is also a cheap and widely used treatment that generally has mild side effects - minimising the potential drawbacks of adding it to men’s treatments.  

Reduced side effects for men on metformin

For this study, the team recruited men who were newly diagnosed with advanced prostate cancer.  

Half the men were given the current standard treatment for their disease (hormone therapy, with some also having radiotherapy and/or chemotherapy), and half were given the standard treatment plus metformin. 

The researchers found that the men who were given metformin alongside their existing treatments gained half as much weight (2 kg compared to 4.4 kg), and had lower cholesterol and blood sugar levels, than men who didn't take the diabetes drug. They also had fewer signs of metabolic syndrome. 

The main drawback to adding metformin was that more men experienced diarrhoea, but most men continued taking it for the length of the study. 

Funding more research into metformin and prostate cancer

The research also looked at whether metformin could extend the lives of men with advanced prostate cancer.  

That’s because cancer is especially energy-hungry, needing extra fuel to keep growing and spreading – suggesting that metformin’s ability to change the way the body processes energy might slow the growth of the disease. 

The researchers did find some evidence of this. They saw that men on metformin lived around six months longer on average, and that these men’s cancers seemed to take longer to start growing again.  

They also found evidence that men whose cancer had spread more at diagnosis may have benefited more from metformin than men whose cancer had spread less. 

Unfortunately, given the number of men on the trial, these differences weren’t big enough for the team to say that these findings were due to metformin and not down to chance. In other words, the results weren’t ‘statistically significant’. This means that bodies like the NHS could not use the results to change the way prostate cancer is treated. 

However, we are funding further analysis of the trial data (including men’s scans, blood tests and tumour samples) to see whether the any specific groups of men did consistently better on metformin.  

This kind of analysis can tease out benefits that might not be obvious when trials look at the ‘average’ man.  

For example, another part of the wider STAMPEDE trial looked at whether giving men docetaxel chemotherapy alongside hormone therapy helps extend their lives. Although the initial results suggested the chemotherapy gave men limited benefit, a later analysis that we funded showed that some men with advanced prostate cancer benefited much more than others. 

Dr Hayley Luxton, our Head of Research Impact & Engagement, said: “Hormone therapy has helped thousands of men with advanced prostate cancer, but the side effects can be hard for men to manage, and can even put them at risk of other conditions. 

“Metformin is cheap, widely available and already used safely by millions. If further analysis confirms its benefits, it could be a game-changer for men starting treatment for advanced prostate cancer. 

“By supporting this research – and the deeper analysis that’s now underway – we’re helping to uncover kinder, smarter ways to treat prostate cancer.” 

This research is only possible because of you.

To help support more vital research that could improve the lives of men with prostate cancer, please consider donating today.

Thank you.

Donate now