A standard treatment for prostate cancer may change as a result of a new Canadian study that supports "drug holidays" for patients receiving hormone therapy.
The research suggests patients who received continuous treatment through androgen-suppressing drugs (testosterone, a type of androgen, is known to fuel prostate cancer) had the same survival rate as those who received intermittent treatment (they took the drugs initially and then took a break of sometimes months or even years before taking another dose).
The results of the study – led by the Canadian Cancer Society-funded NCIC Clinical Trials Group at Queen's University in Kingston, Ont. – were published this week in the New England Journal of Medicine.
What's more, those who took the drug holidays had a better quality of life than their continuous-therapy counterparts, and intermittent treatment is vastly cheaper than continuous treatment.
Androgen-suppression therapy is commonly given to prostate cancer patients following radiation or surgery, and the standard approach is to keep giving patients the drugs for their entire lives. As a result of the usual treatment, patients often experience a range of side-effects including reduced libido, hot flashes and weight gain.
"One of the nice things about the intermittent therapy is you're going to go through this, but it's not forever," said Juanita Crook, a co-principal investigator of the study who works as a radiation oncologist for the B.C. Cancer Agency.
It's news that gives patients a sense that there's "a light at the end of the tunnel," she said.
The study divided 1,386 participants into two groups – half were given continuous therapy and half were given intermittent therapy. In both groups, the median survival was about nine years. The intermittent therapy group, however, had fewer of the unpleasant side-effects of hormone therapy.
In that sense, continous therapy is over-treatment for patients. While they may live many years after their diagnoses, they must deal with the impact of taking those drugs, said Martin Gleave, the director of the Vancouver Prostate Centre.
When patients go the drug-holiday route, they spend far less time in treatment, but Dr. Crook notes that their PSA levels must still be closely monitored. PSA stands for prostate specific antigen, an indicator of prostate cancer in a patient's blood.
"Intermittent therapy will be recommended as the most appropriate course in this group of patients," said Dr. Gleave, who was not involved in the study.
Intermittent therapy was pioneered in Canada. Studies in 1995 and 1999 showed the feasibility of taking drug holidays and laid the groundwork for this large clinical trial, he said.
The study's authors note that intermittent therapy may not be as effective for patients with metastatic cancer – cancer that has spread to other parts of their body. A study presented at American Society of Clinical Oncology in June found metastatic prostate cancer patients who took drug holidays did not live as long as those who receive uninterrupted treatment.
The widespread adoption of intermittent therapy could offer relief to strained provincial health care systems that foot the monthly $600-per-patient bill for hormone therapy. Dr. Crook said intermittent therapy patients only used one-third the amount of drugs as those receiving continous therapy. "It's a huge cost saving because these drugs are incredibly expensive," she said.
Albert Batten, now 77, was diagnosed with prostate cancer 16 years ago. After undergoing radiation therapy, his PSA levels rose and he was recruited for this clinical trial.
He was concerned about some of the side-effects – "They told me I might even grow breasts," he said. But he was eager to try something that would keep his cancer at bay.
After three doses of the androgen-suppressing drug, he took a break from treatment and doctors measured his PSA levels to see if they would rise. They've never climbed high enough to warrant more treatment.
The only side-effect was reduced sexual desire. To Mr. Batten and his wife, it was a worthwhile tradeoff for otherwise good health. "She said, 'I'd rather have you living than dead,'" he said.