CompletedPhase IVInterventional

A trial looking at metformin for early prostate cancer patients undergoing surgery

Prostate cancer is the most common cancer in UK men. Doctors have found that conditions affecting blood sugar and weight may raise the risk of developing it. Metformin is an inexpensive, widely used medicine for type 2 diabetes. Early research suggests it might also slow down prostate cancer growth, but doctors need to understand how it works inside cancer cells. This study invites men who have recently been diagnosed with early prostate cancer and are already scheduled for surgery. Participants are randomly chosen to take either metformin tablets or dummy tablets (a placebo) each day until the night before their operation. After surgery, scientists examine the removed prostate tissue to check for changes in the cancer cells. Taking part does not delay your planned operation, and it could help doctors develop new ways to treat prostate cancer in the future.

At a glance

Status

Completed

Phase

Phase IV

Enrolment target

105

Start

22 Aug 2015

Estimated completion

06 Feb 2020

Prostate cancer

What is this study about?

Prostate cancer develops in the prostate gland, which sits just below the bladder in men. While age and family history are well-known risks, doctors have also discovered links between prostate cancer and metabolic health. Conditions like high blood sugar, excess body weight, and high blood pressure can create an environment in the body that may encourage cancer cells to grow.

Metformin is a well-established tablet taken by millions of people worldwide to manage type 2 diabetes. Over the years, doctors noticed that people taking metformin often had lower rates of certain cancers, including prostate cancer. Researchers now want to find out whether metformin can directly attack prostate cancer cells or stop them from multiplying.

This trial is known as a 'window of opportunity' study. It uses the natural waiting period between a cancer diagnosis and planned surgery. By giving participants metformin or a dummy tablet during this window, doctors can compare the tumour tissue removed during surgery with tissue from the original biopsy. This allows scientists to see exactly what biological changes the drug causes inside the tumour.

Taking part will not change the timing or type of surgery you receive. Instead, it provides valuable biological clues that could help researchers discover whether an everyday diabetes medicine can become an effective, low-cost cancer treatment in the years ahead.

Key takeaways

Tests whether the diabetes drug metformin has anti-cancer effects in prostate tissue.
Designed for men awaiting surgery for newly diagnosed, localised prostate cancer.
Participants take daily tablets (metformin or a dummy pill) until the night before surgery.
Does not delay or replace your planned NHS surgical treatment.
Common side effects are mild stomach upsets, which are managed with dose adjustments.

Who may be eligible?

You may be eligible for this study if you are a man aged 18 or over and were diagnosed with early, localised prostate cancer through a biopsy within the past six months. You must have already chosen surgery (a radical prostatectomy) to treat your cancer, and you must not have had any previous prostate cancer treatments, such as hormone therapy, radiotherapy, or earlier operations. You also need to be able to swallow tablets and have satisfactory blood test results.

You cannot take part if you already have type 1 or type 2 diabetes, or if you have ever taken metformin in the past. The study is also not suitable for men with serious heart, liver, or kidney problems, or those who have had another active cancer requiring treatment in the past five years.

Because of the way the drug is processed, you must agree not to drink alcohol while taking the study tablets. If you are sexually active and able to father a child, you must also agree to use condoms throughout the study and for 16 weeks after your final dose.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a man aged 18 or over.
I was diagnosed with localised prostate cancer by biopsy within the last 6 months.
I have chosen surgery (radical prostatectomy) and have had no prior prostate cancer treatment.
I do not have diabetes and have never taken metformin.
I do not have severe kidney, liver, or heart problems.
I am willing to avoid alcohol and use condoms during the study and for 16 weeks after.

Answer every question to see your result.

What does participation involve?

If you decide to join, a computer will randomly place you into one of two groups: one group takes metformin tablets, and the other takes matching dummy tablets (placebo). Neither you nor your doctor will know which tablet you are taking. You will take the tablets each day, gradually increasing the dose during the first week, and record each dose in a simple diary. You stop taking them the evening before your surgery.

Taking part involves around three extra hospital visits. These include a screening check to confirm you are suitable, a visit to start the tablets, and a check-up the week before your operation. Where possible, the team will arrange these alongside your routine hospital appointments. At these visits, staff will check your blood pressure, pulse, weight, and waist size, and take standard blood samples.

During your planned surgery, the surgical team will save a small portion of the removed prostate tissue. This, along with samples from your original biopsy, will be securely sent to partner research laboratories for specialised testing. Your final trial visit will happen 8 to 10 weeks after your operation, alongside your normal post-surgery clinic appointment. After that, your involvement ends and your standard NHS care continues as normal.

Potential risks and benefits

This trial is designed to build scientific knowledge, so taking part is unlikely to cure or directly improve your own cancer. However, your participation could help future patients by showing whether metformin is an effective cancer fighter. Metformin is generally very safe, but it can cause mild stomach upsets, nausea, or diarrhoea. Starting on a low dose helps prevent this, and your doctor can lower your dose if needed. A very rare but serious blood condition called lactic acidosis can occur, but doctors minimise this risk by excluding anyone with kidney or heart problems. You are completely free to leave the trial at any time, and doing so will never affect your normal NHS cancer treatment.

Locations (3)

Guy's and St Thomas' Hospitals
City only
London, England
The Royal Marsden Hospital
Approximate
London, England
Royal Gwent Hospital
Approximate
Newport, Wales

Common questions

Will taking part delay my cancer surgery?

No. The trial is designed to fit entirely within the normal waiting time between your diagnosis and your planned operation date.

Can I choose whether I receive metformin or the dummy pill?

No. A computer randomly decides which tablet you receive to keep the study results completely fair and unbiased.

Do I have to pay for the study tablets or tests?

No. All study medication and trial-related tests are provided completely free of charge through the NHS research team.

Why do I need to use condoms during and after the study?

Because the exact effects of the medicine on sperm are not fully proven, using condoms protects your partner from potential risks during the trial and for 16 weeks afterwards.

What happens if I get an upset stomach from the tablets?

You should tell the research team straight away. They can adjust your dose or give you medicine to help settle your stomach.

How to find out more

Harriet Wylie

harriet.wylie@kcl.ac.uk +44 (0)20 7188 7188 x52985 Official trial record

Always speak to your GP or specialist before deciding to take part in a study.