Experimental treatment shows promise in small prostate cancer trial
Scientists have achieved promising results from a small prostate cancer trial involving an experimental drug.
Two patients were treated at the Mayo Clinic in the US, both of whom had prostate cancer that was deemed to be inoperable because their tumours were aggressive and had spread to the abdominal areas.
They received standard hormone and radiation therapy, along with an experimental drug called MDX-010 or ipilimumab, which is designed to boost the immune system's ability to fight cancer.
The drug is given through the blood and builds on the anti-tumour action of hormone therapy, causing more tumour cells to die than with hormone therapy alone.
Researchers found that both patients experienced consistent falls in their levels of prostate specific antigen (PSA) - a protein that can indicate the progression of prostate cancer - over the following weeks.
After a number of weeks, both of the patients were said to be eligible for surgery on their tumour, during which surgeons found that the experimental treatment regime had been even more effective than first thought.
Lead researcher and urologist Dr Eugene Kwon revealed: "The goal of the study was to see if we could modestly improve upon current treatments for advanced prostate cancer.
"However, we were startled to see responses that far exceeded any of our expectations."
Co-investigator Dr Michael Blute revealed that, when surgeons operated, they found that the men's tumours had shrunk "dramatically".
"I had never seen anything like this before. I had a hard time finding the cancer. At one point the pathologist (who was working during surgery) asked if we were sending him samples from the same patient," he revealed.
Dr Kwon described the treatment as "one of the holy grails of prostate cancer research".
"We've been looking for this for years," he added.
Writing in the Mayo Clinic's publication Discovery's Edge, the researchers noted that further studies will be needed to validate the results.
However, Dr Blute noted: "This could have significant implications for other forms of cancer, including hormone-sensitive forms such as breast and ovarian cancer."
Professor Malcolm Mason, Cancer Research UK prostate cancer specialist, said: "These case reports are extremely interesting and encouraging. Ipilimumab might potentially be a strong stimulator of the immune system, and it seems logical that it might also be effective in prostate cancer and early phase trials with this drug in prostate cancer have suggested that it might be active.
"But caution is needed, as earlier trials with this drug in other types of cancer were less successful than reported here, and its true value can only become clear through large-scale randomised clinical trials, two of which are already underway. The other cautionary note is that both men received hormone therapy, which in some instances causes dramatic reductions in tumour size by itself.
"Recently, there has been an upsurge of interest in the use of vaccine therapies for prostate cancer, following the recent announcement of the results of a clinical trial of a vaccine called 'Provenge', which prolonged survival in patients with very advanced prostate cancer by around four months."