New York, Oct 14 (IANS) Men with prostate cancer who are treated with testosterone-lowering drugs are twice as likely to develop dementia within five years as compared to prostate cancer patients whose testosterone levels are not tampered with, say researchers including one of Indian-origin.

"The risk is real and, depending on the prior dementia history of the patient, we may want to consider alternative treatment," said senior author of the study Nigam Shah, Associate Professor at Stanford University School of Medicine.

Testosterone can promote the growth of prostate tumors, and so clinicians have used androgen deprivation therapy (ADT) to lower testosterone and other androgens in prostate cancer patients since the 1940s.

The team looked at records from Stanford Medicine's clinical-research data warehouse for nearly 10,000 patients with prostate cancer. 

Of the 1,829 who received androgen deprivation therapy, 7.9 percent developed dementia within five years, compared with 3.5 percent of those not treated with androgen deprivation therapy, said the study published in the journal JAMA Oncology.

The researchers, however, cautioned that prostate cancer patients who are receiving ADT should not make changes to their medications without talking to their physicians.

The new retrospective study of patient records took only a few weeks, Shah said. 

But retrospective studies of patient medical records are not meant to replace randomised clinical trials, he added.