The cancer vaccine is not a "cure" for prostate cancer
A "vaccine" which harnesses the body's own immune system to fight prostate cancer has been approved for use by US drug regulators.
Provenge - which is designed to be used in men with advanced disease - is the first of its kind to be accepted by the Food and Drug Administration.
Each dose has to be individually tailored and it is an expensive treatment at $93,000 per patient.
It will add to, rather than replace, existing treatments, said experts.
Doctors have been working on therapies that prompt the immune system to fight tumours for decades.
Potential success stories include an experimental vaccine for melanoma which is in the late stages of development.
This latest therapy is made by collecting special blood cells from each patient that help the immune system recognise cancer as a threat.
These are then mixed with a protein found on most prostate cancer cells and a substance which kick-starts the immune response.
The drug is not a "cure" but is used in advanced prostate cancer that has spread to other sites in the body and is no longer responding to standard hormone treatment.
Clinical trials showed that the treatment extended the lives of patients by four months.
This compares with an average of three months with chemotherapy.
Dr Phil Kantoff, an oncologist at the Dana-Farber Cancer Institute who helped run the studies of Provenge said: "The big news here is that this is the first immunotherapy to win approval, and I suspect within five to ten years immunotherapies will be a big part of cancer therapy in general."
Prostate cancer accounts for about 12% of male deaths from cancer in the UK and is the second most common cause of cancer death in men.
In older men aged 85 and over, the disease is the most common cause of all deaths from cancer.
John Neate, chief executive of The Prostate Cancer Charity, said: "The news that this type of immunotherapy may offer additional survival benefit is promising."
But he added: "There are still questions to answer, even if the treatment fulfils its early promise.
"At present, we believe there are currently no laboratories in Europe equipped to undertake this treatment.
"Furthermore, this treatment is not currently approved in the UK and it will still be some years before doctors know enough about its long term effectiveness and side effects to be confident about its potential place in the armoury against advanced prostate cancer."
Dr Chris Parker, Cancer Research UK's prostate cancer expert said: "We hope this approval will open new avenues of research into using a patient's own immune system to treat cancer."