Common drugs to treat prostate cancer could treble the risk of heart death among those with a history of cardiac problems, a study suggests.
One in three men with prostate cancer is put on hormone thereapy to shrink tumours and lower the risk of the disease returning.
Prostate cancer is the most common cancer in men in the UK, developed by around one third of men over the age of 50. Each year about 40,000 men are diagnosed and around 10,000 die.
Around 14,000 cases a year are suitable for androgen deprivation therapy (ADT), which works by reducing levels of male hormone in the body, to prevent them from stimulating cancer cells.
The Harvard study tracked 5,000 men with the disease, with an average age of 70, one third of whom were put on ADT. The research found that among those with a history of heart problems, risks of heart death rose sharply after undergoing the treatment.
Men who had previously had a heart attack or suffered congestive heart failure had three times the risk of heart-related deaths compared to men who were not on the therapy, according to the study.
Overall, their risk of dying from a heart-related problem within five years was 7 percent - compared with 2 percent among those who were not on the therapy, the study found.
Dr Paul Nguyen, from Harvard Medical School, said prostate cancer patients with a history of heart disease needed to weigh up the pros and cons of hormone treatment.
"While androgen deprivation therapy can be a life-saver for men with prostate cancer and significantly increase the cure rates when used with radiation for aggressive disease, this study also raises the possibility that a small subgroup of men who have significant heart disease could experience increased cardiac death on ADT" he said.