In this trial, we will investigate whether and to what extent metformin is effective, well tolerated and safe in combination with radiotherapy for patients with prostate cancer who have a recurrence after removal of the prostate gland. Up to now, patients in this situation have been offered radiotherapy with or without hormonal treatment. We aim to find out whether the addition of metformin to the standard treatment can delay the progression of the disease and possibly help cure prostate cancer patients. To do so, the trial participants will be divided into two groups: group A will be given radiotherapy in combination with metformin, and Group B will receive the same radiotherapy without the medication. The patients who are given metformin in addition to radiotherapy will be chosen at random. This trial will be conducted at in more than 20 hospitals in Switzerland, Germany and France.
Metformin is a well-known and widely prescribed medication taken in tablet form by patients with diabetes to control the blood levels of glucose (sugar). Several trials have shown that metformin can potentially halt the growth of tumour cells as well as increase the efficacy of the radiation treatment. However, as not enough is known about the efficacy of combining radiotherapy and metformin for patients with prostate cancer who have a recurrence after removal of the prostate gland, the trial will investigate this question.