Stuck in a screening dilemma
Unsatisfactory science—Canada’s new breast cancer screening recommendations produce more questions than answers.
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New Canadian guidelines generally calling for reduced breast cancer screening have triggered a mixture of outrage, concern and downright bewilderment. Women can be forgiven for not knowing what to do after an expert task force recommended they get fewer mammograms, not more, and advised family doctors to stop routinely checking for breast tumours.
Experts on the Canadian Task Force on Preventive Health Care say the harm and costs of such screening outweigh the scant benefit for women who are at no special risk of breast cancer. But other experts, especially radiologists who provide mammograms, warn of more cancer deaths if the panel’s guidelines become widely accepted.
Who’s right? How are women to decide? Well, the experts agree on one thing — a decision on mammograms should be made in consultation with a physician who is up to date in this area of medicine and familiar with a woman’s particular concerns and health situation. There is no one-size-fits-all answer, even in such a field with so much attention and research dollars. Breast cancer is the most frequently diagnosed cancer in Canadian women, with 23,400 new cases expected this year. It will kill 5,100.
Two of the panel’s recommendations are especially controversial — that women between 40 and 49 not undergo routine mammography screening, and that doctors no longer feel for tumours by performing clinical breast exams. The guidelines were last updated in 2001 and, at that time, the task force offered no recommendation on mammography for women in their forties, noting there wasn’t enough data to support, or rule out, its use.
Now, after an extensive review of the science, the panel concluded that such early mammography delivers more harm than benefit for women of that age who aren’t at special risk. It estimated that 2,100 women in their forties would have to be screened every two to three years, for 11 years, to prevent a single breast cancer death. Of those 2,100, about 690 would have a false positive result; about 75 would undergo unnecessary needle biopsies, and some could suffer a needless lumpectomy or even loss of a breast.
Radiologists disagree with that bleak picture. They insist their diagnostic ability has improved and note that some of the studies cited by the task force date back to when older equipment was widely used. Modern digital machines may indeed produce better results but, according to the panel, there isn’t clear research on that.
Having a doctor feel for tumours was likewise found to produce no reduction in breast cancer deaths. And as far back as 2001, the panel recommended against routine teaching of breast self-exams – something that had been encouraged for 30 years – for the same reason.
All this seems counter-intuitive. In diagnosing cancer, women have long been told “the earlier the better.” But some aggressive breast cancers, especially those occurring in younger women, move so fast that they’re beyond treatment regardless of when they’re found. Other tumours develop so slowly that patients fall victim to old age first. Early detection makes little difference in either case, but screening can be a life-saver when confronting other breast cancers. It was in this context that the task force reviewed the data and made its recommendations. It also suggested that women between the ages of 50 and 74 receive a mammogram every two or three years, instead of once a year.
Now it’s up to each woman to decide her next step — weighing possible risks against hoped-for benefits — ideally in consultation with a doctor she trusts.
That may not bring much comfort. But research continues. Science never stands still. Although many women today are stuck with more questions than answers, there’s hope their daughters will be spared the same dilemma.
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