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Cancer Screening: Doubts and Difficulties

November 23, 2009

It hasn’t gotten too much coverage here that I’ve seen (aside from here and here), but cancer screening is big news in the US these days. I first encountered this very tricky issue in a presentation I attended at a conference on science and technology policy more than three years ago, in which a Dartmouth professor made the controversial assertion that we are over-screening for certain types of cancer, and that this is having detrimental effects on public health. Well, it’s safe to say that the issue has grown. The New York Times reported in July:

An upshot of the decades-long war on cancer is the popular belief that healthy people should regularly examine their bodies or undergo screening because early detection saves lives. But in fact, except for a few types of cancer, routine screening has not been proven to reduce the death toll from cancer for people without specific symptoms or risk factors — like a breast lump or a family history of cancer — and could even lead to harm, many experts on health say.

There are a few reasons for this.
First, diagnosis involves a great deal of uncertainty. Is the cell abnormal? Is it malignant? How fast is it developing? These and other questions all impact an assessment of of a person’s risk.

Second, cancer treatment is often dangerous, invasive, and life-altering, if not life-threatening.

The more you screen for cancer, the more likely you are to prescribe unnecessary and dangerous treatment. For example:

[Screening for prostate cancer] increases a man’s risk of being treated for a cancer that would never have harmed him in the first place. The European study found that for every man who was helped by P.S.A. screening, at least 48 received unnecessary treatment that increased risk for impotency and incontinence.

The last year has seen announcements by expert groups that recommend less frequent screening for prostate, breast, and cervical cancer. All of them sparked confusion, outrage, denial, and political wrangling. Kevin Sack at the New York Times provides insight into the breadth and importance of this debate:

This week, the science of medicine bumped up against the foundations of American medical consumerism: that more is better, that saving a life is worth any sacrifice, that health care is a birthright.
Two new recommendations, calling for delaying the start and reducing the frequency of screening for breast and cervical cancer, have been met with anger and confusion from some corners, not to mention a measure of political posturing.
The backers of science-driven medicine, with its dual focus on risks and benefits, have cheered the elevation of data in the setting of standards. But many patients — and organizations of doctors and disease specialists — find themselves unready to accept the counterintuitive notion that more testing can be bad for your health.

One of the biggest issues related to science policy in this context is that of formulating expert recommendations. How does one come up with official advice that will result in the largest possible public good? How do translate population statistics to the level of the individual? This is an extremely difficult task, because it involves a lot more than simply assessing the latest scientific/medical research. It also requires understandings of patient and doctor behavior, negotiating the politics of health and well-being, and adoption of a value system related to what constitutes good health and a fulfilling life.

Health advocacy groups can come up with their own answers to these questions, but the government needs to address them as well.

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