Experimental vaccine extends life of men with prostate cancer
Mon, 01 Feb 2010 12:00:39 +0000
A vaccine that primes the immune system to attack prostate cancer can extend the lives of men in the advanced stages of the disease, researchers say. Men who had the experimental vaccine lived on average 8 to 9 months longer than men who had inactive, placebo injections.
What do we know already?
About 35,000 men are diagnosed with prostate cancer each year in the UK, making it the most common cancer in men. Some cases of prostate cancer are so slow-growing that they won’t do any harm, but about 20 or 30 percent of men are diagnosed with a more aggressive form of the disease that’s already started to spread around the body.
Some types of prostate cancer grow more quickly when they have a supply of testosterone. Hormone treatments, such as drugs to switch off the production of testosterone or surgery to remove the testicles, can be used to treat these cancers. However, hormone treatments can stop working over time. Chemotherapy is sometimes used as a fall-back treatment.
Researchers have been looking for new ways to attack prostate cancer when hormone treatment doesn’t work. One option is immunotherapy, which uses a vaccine to encourage the man’s immune system to attack prostate cancer cells. A new study of 125 men has looked at a treatment called the PROSTVAC-VF vaccine.
What does the new study say?
Men who had the vaccine lived an average of 8.5 months longer than men who didn’t. After about three years, 30 percent of the men who’d been vaccinated were still alive, compared with 17 percent of men who’d had a placebo injection.
Strangely, there was no difference between the two groups in the likelihood of their cancer spreading. The vaccinated men were just as likely to have their cancer spread further around their bodies after treatment, but for some reason, were less likely to die of it.
The most common side effect was irritation at the spot where men had the injection. Some men felt sick, tired, or got a temperature. One man stopped having the injections because he got swelling in his lips. Another developed a problem with clots in his blood and had a heart attack, which the researchers say was “possibly related to treatment”.
How reliable are the findings?
There are still lots of questions about treating prostate cancer with a vaccine. The men in the study had advanced disease that was resistant to treatment with hormones. We don’t know if the vaccine would have similar effects for different stages of prostate cancer.
Another issue is that the men who had placebo injections did less well than expected, based on the stage of their illness. We don’t know what other treatment the men were getting, so it could have been that more men in the vaccine group were having chemotherapy. The placebo group also included slightly more men whose cancer had already spread to their bones, which is linked to a worse outcome.
Where does the study come from?
The research appeared in the Journal of Clinical Oncology, published by the American Society of Clinical Oncology.
The trial began with funding from a company called Therion Biologics, and from the US National Cancer Institute. Ongoing funding came from a second company, called BN ImmunoTherapeutics. Several of the researchers worked for these companies or owned stock in them.
What does this mean for me?
We’re still a long way from vaccines being a practical treatment for prostate cancer. The new study is a phase II trial; a type of study that looks at how well a drug works for a medium-sized group of patients, normally a couple of hundred. If phase II trials are successful, it usually leads to larger studies that can give a better idea of how well a treatment works.
Since the vaccine shows promise, researchers are planning a phase III trial involving about 600 people. If the drug works in larger studies – and is reasonably safe – the manufacturer can apply to the UK or European drug regulator for permission to market the drug.
Once a new drug is launched, there’s also the question of whether the National Institute for Health and Clinical Excellence (NICE) approves it for use on the NHS. That will only happen if NICE thinks it represents good value for money.
