New therapies are being developed for patients in the late stage of prostate cancer, when in 90 per cent of cases the tumour has spread to the bones, writes Victoria Lambert
When prostate cancer spreads into the bones or lymph nodes, oncologists turn to “holding” therapies aimed at extending life by months or even years. However, there are treatments newly available or being trialled which look promising.
“The gold standard at this stage of disease is hormone therapy. We know testosterone acts as a fuel for cancer, so we aim to switch it off and so slow down the cancer’s growth,” says nurse specialist John Robertson of Prostate Cancer UK.
Up until this year, a patient with advanced prostate cancer would be treated with a regime including anti-androgens, which block the effect of testosterone, GNrH agonists such as Zolodex, which stop the production of testosterone, steroids or a different hormone-oestrogen and chemotherapy, which aims to hold the cancer in check. There is also a new hormone therapy, called abiraterone (branded as Zytiga), to add to the mix.
“If prostate cancer cells can’t get natural testosterone, they produce their own form of synthetic hormone. Abiraterone stops the cancer doing that, and it seems to be effective when chemotherapy and other hormones have stopped working,” says Mr Robertson.
Best of all, abiraterone has been passed by the National Institute for Health and Clinical Excellence (NICE) for men who have had chemo and so is available now. It is currently being trialled to see if it is useful for men who have not had chemotherapy.
Other therapies are creating interest. Cabzitaxel (known as Jevtana), a type of chemotherapy not passed by NICE due to its side effects and cost, is back in trials to be evaluated at a lower dose.
If we can offer Radium 223 plus MDV 3100 next year; it could make a significant difference for men with advanced prostate cancer
But Mr Robertson is more excited about a hormone blocker called MDV 3100. “We’re hoping for licensing and NICE evaluation next year. It seems to improve survival outcomes by some 4.8 months. We may be able to use these drugs consecutively, one after another, to extend life. Alternately, there may be benefits by combining them,” he says.
Another area of development is immunotherapy. A promising US drug called silpeulicil (Provenge) primes the body’s immune system to attack prostate cancer. But it is expensive and only available in one UK trial.
A treatment called Prostvac stimulates the immune system in a different way. It is a vaccine developed using a genetically engineered fowl pox virus, which is injected into the patient. A small US trial has suggested improved survival of up to eight months. A much larger global trial is now underway, but Mr Robertson suspects it will be four or five years before we know if it is affordable and useful in the UK.
The most exciting new therapy may be home-grown. At the Royal Marsden Hospital in London, a global trial led by consultant clinical oncologist Dr Chris Parker, has developed a new form of radiotherapy for bone secondaries from prostate cancer.
Dr Parker explains: “Radium 223 is a similar chemical to calcium; when we inject it into the vein, the body takes it naturally to where it needs to make new bone, including areas where cancer has spread to bone. It is a way of delivering radiation precisely to areas where needed and, once it gets there, it kills the cancer cells.”
Targeted radiotherapy is not new. Doctors already use a chemical called Strontium 89 to do the same job. “Strontium gives off ‘beta’ radiation which travels much further than the cancer cells, destroying healthy tissue such as bone marrow in the same area,” says Dr Parker.
“Radium 223 gives off ‘alpha’ radiation which only travels a few microns so it is less toxic. In our trial of 900 men, it improved survival by 30 per cent plus quality of life increased and the chance of fractures was reduced,” he adds.
Although Radium 223 has not been licensed or approved by NICE yet, experts are hopeful it will be available next year. “If we can offer Radium 223 plus MDV 3100 next year, it could make a significant difference for men with advanced prostate cancer,” says Mr Robertson.
Until then, if available treatments have failed, men with advanced disease can still apply to the Cancer Drugs Fund (CDF) which provides ring-fenced funding for cancer drugs rejected by NICE or not yet approved.
Prostate Cancer UK “strongly believes” that provisions should be put in place so that, if the CDF is terminated in 2014 as planned, this will not lead to a reduction in the budget available for cancer drugs.