London: A man with advanced prostate cancer is believed to have been cured after doctors "shocked" his tumour to death with huge amounts of testosterone.
The result has been described as "unexpected" and "exciting", as most prostate cancer therapies work by depriving tumours of the hormone, which cancer uses as a fuel.
Other men taking part in the trial also showed responses that astounded scientists, with tumours shrinking and the progress of their disease halted.
Levels of Prostate Specific Antigen (PSA), a blood marker used to monitor prostate cancer, fell in most of the 47 participants. One individual whose PSA level dropped to zero after three months, and who shows no remaining trace of the disease after 22 cycles of treatment, appears to be cured, the researchers said.
Professor Sam Denmeade, from Johns Hopkins University School of Medicine in Baltimore in the US, who led the study, said: "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. 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.
"Many of the men have stable disease that has not progressed for more than 12 months. I think we may have cured one man - his disease has all disappeared."
All the patients had spreading cancer that was resistant to treatment with two of the latest hormone therapy drugs, abiraterone and enzalutamide.
The trial involved three cycles of "bipolar androgen therapy" (BAT), which involves alternately flooding the body with, and starving it, of testosterone.
The men received high-dose injections once every 28 days. At the same time, they were given a drug that stopped testosterone from being produced naturally.
Dr Matt Hobbs, deputy director of research at Prostate Cancer UK, said: "This research is intriguing because it offers a hint that - somewhat unexpectedly - for some men whose cancers have reached that 'hormone-resistant' stage, it may be possible to kill or stop growth of the cancer cells."
The early findings from the study were presented at a symposium on Molecular Targets and Cancer Therapeutics in Munich.
Telegraph, London