There's no good evidence tying screening to reduced mortality

By Matt Kuhrt

It seems like basic common sense: Encourage cancer screenings, diagnose and treat the disease early, save lives. It turns out the "save lives" part of that equation is a lot harder to support, according to an article in BMJ.

The basis for the study's judgment lies in flaws inherent in the current data available around the efficacy of cancer screening. Vinay Prasad, M.D., assistant professor of medicine at the Oregon Health Sciences University, argues that the numbers show cancer screening might reduce disease-specific mortality, but pulling back to view overall mortality reveals no conclusive improvement.

Potential unnecessary harm done to otherwise healthy patients complicates matters further, as a false-positive on a screening test can lead to unwarranted interventions or overdiagnosis. Seeing a combination of these effects and statistically flawed studies that are inadequate to detect overall mortality rates at the small levels at which they occur, Prasad insists that the notion of screening saving lives has no basis in evidence.

To produce better numbers, he suggests larger trials, powered appropriately to detect overall mortality rates.

There's argument over whether the high cost of this type of trial would be warranted, especially because the question at hand, while provocative, may be splitting hairs more finely than necessary. In particular, the focus on overall mortality may set the bar artificially high, Robert Smith, Ph.D., senior director of cancer screening for the American Cancer Society, told Medscape. In his view, cancer-related morbidity presents a better framework for thinking about screening.

As the industry takes a harder look at costs associated with unnecessary testing and shifts its focus toward value-based care, questions of this sort are likely to increase, and the noise around them will inevitably filter down to patients. According to Prasad, the bottom line for practicing physicians is to strive for shared decision-making and honesty about uncertainty when helping patients assess their options.

"The harms of screening are certain, but the benefits in overall mortality are not," he says. "Declining screening may be a reasonable and prudent choice for many people."

To learn more:
- read the article in the BMJ
- read the Medscape story

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