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The possible benefits and harms of prostate cancer screening have been hotly debated in recent years, but for the first time a new study tries to put a number on the balance of pluses and minuses for the average man.
Using data from past cancer studies and a mathematical model, researchers from the Netherlands calculated that on average, annual screening using prostate-specific antigen (PSA) testing would add three healthy weeks to a man's life.
But whether screening has a net benefit or harm for a particular man depends on how he feels about the possibility of suffering screening- and treatment-related side effects - and how much erectile dysfunction or incontinence, for example, would influence his quality of life, researchers said.
"We're even more sure than ever that it's important for doctors and their patients to talk about the prostate cancer screening decision and its potential downstream consequences," said Dr Harold Sox, a professor of medicine at the Dartmouth Institute in Hanover, New Hampshire, who wrote a commentary published with the new study.
"Now we have some real scientific evidence that a person's choice probably should reflect what the net benefit is for them."
Loss and gain
For the new study, Dr Harry de Koning of the Erasmus Medical Center in Rotterdam and his colleagues built a model based on data from the European Randomized Study of Screening for Prostate Cancer, which included over 160 000 men.
They considered the benefits of catching some cancers early as well as the harms of over diagnosis.
The researchers determined that for every 1000 men getting annual screening in their late fifties and sixties, there would be nine fewer prostate cancer deaths, 247 extra negative biopsies performed and 41 additional men getting prostate surgery or radiation. Forty-five cancers would be over diagnosed due to screening.
Based on the effects of screening and treatment on each man's quality and length of life, those 1000 men would ultimately gain 73 extra years of life, or 56 quality-adjusted life years.
But the change in quality years due to screening could range anywhere from a loss of 21 QALYs over the 1000 men to a gain of 97 QALYs, Dr de Koning's team reported in the New England Journal of Medicine.
"Some people - we don't know how many - would actually come out negative, they would lose (quality years)," Dr Sox said. "And other people would gain. Therefore it's hard to make one rule that would apply to everybody."
A step in the right direction
Dr de Koning said that at the very least, his study argues against the notion that PSA screening is typically a bad idea for healthy men.
He and some of his colleagues have received consulting fees from pharmaceutical and medical device companies, including a company that designs PSA tests.
While the European study showed a 29% reduction in the chance of dying from prostate cancer in men who were screened, another large trial from the U.S. failed to show any survival benefit.
Dr Sox said it's possible some of the figures used in the new model don't accurately reflect men's feelings about having a radical prostatectomy and ending up with erectile dysfunction and urinary incontinence, or getting radiation and developing chronic diarrhoea, for example. Still, he said the study is a step in the right direction, toward appropriately weighing the long-term harms and benefits of screening.
"It's the first research article about screening that tried to incorporate the feelings of patients toward what they might experience if they underwent screening," Dr Sox said.
"The problem (in other studies) is that the benefits are measured in one way and harms are measured another way. You end up making that judgement about whether the benefits exceed the harms, or vice versa, purely subjectively," he added.
The researchers agreed that individual men should think about how they weigh both the possible benefits and harms of getting screened for prostate cancer and discuss the decision with their doctor.
"One man might say, 'I won't take my chances,'" Dr de Koning said - while another will accept the risk of over diagnosis and related side effects and still choose to get screened.
(Reuters Health, August 2012)
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