Testosterone may offer hope of cure for prostate cancer
A man with advanced, treatment-resistant prostate cancer may have been "cured" by an experimental therapy that involves shocking tumours to death with testosterone.
Other seriously ill men taking part in the same trial showed responses that astounded scientists. Tumours were seen to shrink and in several patients progress of the disease was halted.
Levels of Prostate Specific Antigen (PSA), a blood marker used to monitor prostate cancer, fell in the majority of the 47 participants.
One individual whose PSA levels dropped to zero after three months and shows no remaining trace of the disease after 22 cycles of treatment appears to be cured, said the researchers
All the men taking part in the pilot trial had completed at least three cycles of "bipolar androgen therapy" (BAT) which involves alternately flooding and starving the body of the male hormone testosterone.
The treatment is revolutionary because testosterone is generally assumed to fuel prostate cancer. For decades men with advanced and spreading prostate cancer have been treated by cutting off the supply of testosterone or blocking its effects.
A common therapy is a form of chemical castration using an injected drug. Upping testosterone in a man with prostate cancer is generally considered to be pouring petrol on a fire.
Yet laboratory experiments have hinted that blasting tumours with high levels of the hormone can suppress or even kill prostate cancer cells.
Professor Sam Denmeade, from Johns Hopkins University School of Medicine in Baltimore, USA, who led the study, said: "We think the results are unexpected and exciting.
"We are still in the early stages of figuring out how this works and how to incorporate it into the treatment paradigm for prostate cancer.
"Thus far we have observed dramatic PSA response in a subset of men: PSA levels declined in about 40pc of men and in about 30pc of men levels fell by more than 50pc.
"Some men also have objective responses with a decrease in the size of measurable disease, mostly in lymph nodes. Many of the men have stable disease that has not progressed for more than 12 months.
"I think we may have cured one man whose PSA dropped to zero after three months and has remained so now for 22 cycles. His disease has all disappeared."
The men received high dose injections of testosterone once every 28 days. At the same time, they were given a drug that stopped testosterone being produced naturally by the testicles.
"Our goal is to shock the cancer cells by exposing them rapidly to very high followed by very low levels of testosterone in the blood," said Prof Denmeade.