Is it better not to know you have a cancer lurking inside your body if the tumour will never pose a serious threat to your life? That question has been raised by a new study that suggests a pill can keep some relatively harmless cases of prostate cancer out of sight and out of mind.
The trial involved more than 8,000 men, aged 50 to 75, who were randomly assigned to receive either a placebo or a daily dose of the drug dutasteride, known by the brand name Avodart.
The men were considered to be at a heightened risk of developing prostate cancer because previous blood tests showed they had elevated levels of PSA, a protein linked to the disease.
The researchers performed biopsies on a group of the volunteers at two years and four years into the study to look for evidence of cancer. Over all, 659 men (19.9 per cent) taking dutasteride were diagnosed with prostate cancer compared with 858 men (25.1 per cent) taking the placebo, according to the findings published this week in the New England Journal of Medicine.
In terms of relative risks, that means those on the drug faced 23 per cent lower odds of getting a prostate cancer diagnosis.
"This is good news for a lot of men," said study's lead author, Gerald Andriole of Washington University's school of medicine in St. Louis, Mo.
Dr. Andriole doesn't think the drug actually prevents cancer. Instead, he thinks it shrinks fairly harmless tumours or inhibits their growth so they essentially evade biopsy detection.
He noted that a lot of prostate tumours grow at a very slow rate. In fact, most men are more likely to die of another cause before the cancer gets them.
Even so, many men are so worried by their cancer diagnosis that they rush into surgery or other treatments that can cause serious side effects including incontinence and impotence.
Dr. Andriole believes some men are better off not knowing they have one of these slow-growing cancers. He argues that dutasteride may help keep some unthreatening tumours below the radar screen.
But not everyone is convinced that ignorance is bliss. Patrick Walsh of Johns Hopkins Medical Institutions in Baltimore, Md. warns this strategy could be extremely risky because potentially deadly tumours may evade detection too.
In an editorial accompanying the study, Dr. Walsh points out that dutasteride is currently used to treat men with enlarged prostates, a condition associated with difficulty urinating.
The drug shrinks the prostate, easing urination. But it also artificially depresses PSA levels – which are used as the basis of the screening test for detecting possible cancer activity.
"Because PSA levels are suppressed, men may have a false sense of security, and if prostate cancer develops, the diagnosis may be delayed until they have high-grade disease that may be difficult to cure," Dr. Walsh writes.
Dr. Andriole acknowledges that the editorial raises a valid point. But he believes knowledgeable doctors can stay on top of potentially deadly tumours by reacting quickly to the slightest increase in PSA levels. He thinks it's just the bad tumours that will nudge up PSA levels, the harmless ones won't.
Dr. Walsh remains skeptical. "I don't think this drug has any meaningful benefit to [prostate cancer] patients."
What's more, there is a slight chance the drug could lower the libido or raise the risk of heart failure in a small percentage of men.
The study was financed by the drug's manufacturer, GlaxoSmithKline. Dr. Andriole was paid by the company for the work he did organizing the trial.