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For many years, the message was stark and simple: When it came to cancer prevention, get screened early and often.

That meant routine mammograms for women as young as 40 to detect breast cancer and Papanicolaou (Pap) tests every one or two years starting as young as 18 to spot cervical cancer. Men over 50 were told to have routine prostate-specific antigen (PSA) tests for the detection of prostate cancer.

The current message for certain types of cancer? Get screened, but perhaps not as early and maybe not as often.

It's nuanced advice that has been formed after rigorous study of routine breast, cervical and prostate-cancer screening programs found that for some people the risks far outweigh the potential benefits.

Last year, new guidelines recommended against routine mammograms for non-high-risk women in their 40s because the chance of false positives and unnecessary treatment is far greater than saving a life. For similar reasons, a blue-ribbon task force in the United States declared the PSA test useless last year. In August, Ontario joined other provinces when it declared sexually active women should undergo Pap tests starting at 21 instead of within three years of first sexual activity, and that routine screening could be done on three-year intervals instead of every one or two years.

Yet a year on, it's clear we're still grappling with the new guidelines. Last week, the Canadian Cancer Society in Ontario released a survey that found more than 40 per cent of women believe routine mammograms should start when a woman is in her 40s, even though guidelines recommend beginning screenings after age 50. As this later-may-be-better approach runs counter to everything we believe about cancer detection, these guidelines have sparked confusion, uncertainty and fear.

"After we've got a population really very well in line with the idea that finding it earlier is always better, it's a little more difficult to go back and say it's often better," said Heather Bryant, a physician and vice-president of cancer programs at the Canadian Partnership Against Cancer.

Is it any wonder the medical community is grappling with ways to translate sound scientific evidence into widespread acceptance?

"This is a tough discussion to have, but we really need to start having the discussion that more testing is not always better," said Gillian Bromfield, senior manager of cancer control policy at the Canadian Cancer Society.

The evidence that led to the changes is extensive. It shows that individuals are much more likely to receive a false-positive result, undergo unnecessary procedures such as biopsies or radiation, or experience life-altering side effects under the old screening programs than they are to have their life saved from cancer. Routine prostate screening, for instance, leads to a small reduction, or no noticeable reduction, in cancer deaths over a 10-year period, according to the U.S. Preventative Services Task Force, which crafted the new guidelines, while the risk of urinary incontinence, erectile dysfunction or other complications due to unnecessary testing and treatment are much higher. The PSA test leads many men to undergo treatment for cancer that never would have become symptomatic.

Despite this, many people cling to the belief that it's better to be screened often. We may recognize that on a population-wide level the risks are greater than the potential benefits, yet there's a tendency to squirm when we, or our loved ones, are told to "skip" once-routine screening for a few years.

"I suspect people are concerned that something might be missed," Bromfield said.

The debate can be boiled down to how much unnecessary anxiety, pain, health complications and money are we willing to spend to potentially prevent a single death. It's not an easy question to answer. It also doesn't help that, across the country, many different organizations and individuals are sending mixed messages or inconsistent guidance.

After the U.S. task force recommended against routine PSA tests last year, large numbers of doctors and prostate-cancer organizations protested, saying it saves lives. Media ran stories about men who say they owe their lives to the PSA test. But those cautionary tales don't include the thousands of men who became unnecessarily impotent or incontinent due to unnecessary treatment.

Groups such as the Canadian Association of Radiologists continue to promote the idea that women should get routine mammograms in their 40s. Just last week, the Canadian Cancer Society in Ontario released a survey that found more than 40 per cent of women believe routine mammograms should start when a woman is in her 40s, even though guidelines recommend beginning screenings after age 50.

The Canadian Cancer Society hasn't come down against PSA tests, women in their 40s getting mammograms or having annual Pap tests. The organization simply advises individuals to speak to their doctors.

"It needs to be a personal decision," Bromfield said.

Eitan Amir, a medical oncologist at Toronto's Princess Margaret Hospital, said even though the evidence may clearly lean against cancer screening for certain individuals, the medical community shouldn't be paternalistic. Instead, talk to patients about the risks and benefits of getting screened and let them make up their own minds.

"It's going to take a lot more time, from a physician's point of view, but it's probably better care," he said.