Eye View 

by David Charbonneau

Common sense, discretion useful in cancer tests

 

April 15, 2010

 

Early detection of cancer improves chances of survival, right? Then why is there any doubt that PSA tests for prostate cancer and mammograms for breast cancer are useful? The answer may be distinctly Canadian.

Women were surprised at the results of a study published in the British medical journal Lancet that concluded, contrary to common sense, mammograms did not save lives.

Canadian and American Cancer agencies said the opposite. They reviewed the same evidence and concluded that indeed mammograms do save lives. The B.C. Cancer Agency agrees. "Having regular screening mammograms has helped to reduce deaths from breast cancer in BC women by 25%."

Then the Journal of the American Medical Association added to the confusion with added doubts about mammograms. They found that while the test did detect early stages of cancer, it did a poor job in finding the deadly late-stage ones. Early-stage detection increased by 40 per cent but late-stage increased by only 10 per cent.

Why the confusion?

Part of the explanation is that mammograms are a simple test and just one tool used in diagnosis. The most easily found cancers are not the ones that will kill you and they should be left untreated. Sometimes it's best to leave sleeping cancers lie. The deadly ones are hard to find by any test.

Yet it's unwise to do nothing when breast cancer kills women and prostate cancer kills men, both second only to lung cancer.

Overdiagnosis is another potential problem but less so in Canada. U.S. health care is a market-system driven by demand of those who can pay for it. Patients can insist that low risk cancers be removed with no appreciable benefits. Worse still, unnecessary treatment can be dangerous. Canadian health care is not determined by market forces. Rather, it is a limited public resource to be used judiciously. While our health care system has flaws, at least it's not swamped by wealthy hypochondriacs.

Politics further complicates U.S. health care. In the recent heated debate, some American women worried that mammograms were being discredited as a cost-saving measure as part of President Obama's diabolical healthcare scheme. One doctor lamented: "Politically, it's almost unacceptable. If you question overdiagnosis in breast cancer, you are against women. If you question overdiagnosis in prostate cancer, you are against men."

 

 PSA tests are even more imprecise than mammograms. That's why men have to pay PSA tests in Canada unless specified by a doctor. Like mammograms, tests for prostate-specific antigens never were intended to be a stand-alone diagnosis.

PSA testing is also slowed by men's reluctance to talk about prostate cancer. Women have been openly talking about breast cancer for decades while men suffer in silence. That's starting to change.

Jack Layton has made his prostate cancer public. The NDP leader hopes to raise $350,000 for research. Only a few decades ago, news of the death of Former Prime Minister Pierre Trudeau by prostate cancer was restrained.

Although imprecise, I chose to pay for my PSA test and I'm glad I did. It provided a useful benchmark so that when my test results climbed rapidly, it alerted my doctor to call for more tests. That resulted in the diagnosis and successful treatment of my prostate cancer.

Like breast cancer, prostate cancers are sometime best left alone because they are slow growing. Most men die with prostate cancer, not of it. Sometimes the best treatment is nothing or "watchful waiting." Overdependence on PSA tests can lead to unnecessary anxiety, treatment and complications.

In a health care market, choice can result in treatments that are worse than the cancer. In Canada, direct advertising from pharmaceutical companies is prohibited. But Americans are convinced to take drugs for illness they may not have. When the customer is always right, overdiagnosis and treatment is likely.

Drug ads create a demand side to the health care market and an abundance of doctors can drive the supply side. A Kamloops doctor told me that that there are so many urologists in the U.S. that they tripping over each other in search of patients to treat.

Canada's publicly-funded health care system is naturally self-limiting so as to treat those with urgent need. Regrettably, this can result in as much patient anxiety as overdiagnosis. However, a scarce resource is less likely to be overused when prudent doctors act as gatekeepers. Overtreatment of innocuous cancers is one occasion where less is better.

 David Charbonneau is the owner of Trio Technical.
He can be reached at dcharbonneau13@shaw.ca





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