Skin patches which deliver oestrogen into the blood may be a cheaper and safer treatment for prostate cancer than current therapies, a study says.The main treatment is injections of a chemical to cut levels of testosterone - the driving force of many prostate cancers - but it causes side effects.The Imperial College London study in the Lancet Oncology compared patches and injections in 254 patients.It found patches were safe and should avoid menopause-like side effects.'Effective treatments'Using oestrogen to treat prostate cancer is an old treatment.Both oestrogen and testosterone are very similar chemically, so ramping up the levels of oestrogen in the body can reduce the amount of testosterone produced - and slow prostate cancer growth.However, taking oral oestrogen pills caused significant health problems by overdosing the liver. The organ then produced chemicals which caused blood clots, heart attacks and strokes.The preferred treatment is injections of a drug, LHRHa, which reduces the production of both oestrogen and testosterone. However, this has side effects similar to the menopause in women - resulting in poor bone health and diabetes.Prof Paul Abel, from Imperial College London, said: "We're not claiming this is equivalent to current therapies yet, but it does look like we are getting castration levels of testosterone."However, the researchers need to follow patients for longer."The next step is to test if the oestrogen patches are as effective at stopping the growth of prostate cancer as the current hormone treatments, we're now testing this in over 600 patients."Kate Law, from the charity Cancer Research UK which part funded the study, said: "More men than ever are surviving prostate cancer thanks to advances in research, but we still urgently need to find more effective treatments and reduce side effects."This trial is an important step towards better and kinder treatments that could bring big benefits to men with prostate cancer in the future."Dr Iain Frame, director of research at Prostate Cancer UK, said: "It is unclear as yet if hormone patches could be an effective alternative to hormone injections, but we await with anticipation the results of the further trials planned which could in time offer men hope for the future."