Preventative medicine has some benefits, but the greatest benefits are in its ability to fund the physicians children's college educations . . .

Colorectal Cancer Screening: Not All It's Cracked Up to Be?

Over time we are finding preventative medicine particularly screenings have some benefits, but the physicians are deeply wedded to the idea due to the  benefit to their bottom line.

"'Unambiguous good news" — that's what the trends are in colorectal cancer incidence and mortality for adults 50 years and older in the United States, according to a pair of experts.

Since 1975, incidence has dropped by about 40% and mortality by about 50%, observe Gilbert Welch, MD, MPH, and Douglas Robertson, MD, MPH, from the Dartmouth Institute for Health Policy and Clinical Practice in Lebanon, New Hampshire.

"These trends are often attributed to screening," the pair write in an essay published in the April 28 issue of the New England Journal of Medicine.

But Drs Welch and Robertson are skeptical that screening has been that powerful.

The "magnitude of the changes alone" suggest that "other factors must be involved," they argue.

They also point out that screening is not always needed for a gastrointestinal cancer to decline dramatically in the United States. "Since 1930, without any screening effort, gastric cancer incidence and mortality have decreased by almost 90%," they report."

This makes sense, medicine has improved over time, we are more in tune with what is happening in our bodies, and when we think something amiss we are willing to see a physician.

"If gastroenterologists and other screening clinicians are taking too much "credit" for these disease trends, this could "exaggerate" the benefits of screening, Drs Welch and Robertson write.

This, in turn, could "distract from the more important activities of promoting health — for example, by encouraging a healthful diet and exercise — and caring the sick," they say.

Furthermore, although the "majority" of people who undergo colonoscopy screening have no cancer or large precancerous polyps, "they often endure repeated colonoscopy for surveillance of small polyps," the essayists explain."

The great problem in medicine today is the Cargo Cult belief that preventative medicine is an unalloyed good. While it can have benefits, it also has negatives, including the occasional death. Failing to understand the cost/benefit relationship, and falling into the fear trap is not a good. We need to take more care to understand exactly what we are doing, what the consequences are for the action, and what the potential positive outcomes are. Failing to do this leaves us open to financial, and physical peril.

"So what explains the decrease in mortality?

Three things, they say.

First, treatments have gotten better over time. Second, there is earlier detection of symptomatic cancer (which can reduce mortality even in the absence of screening) because of better awareness and better diagnostics in the clinic. Third, "there could be fewer cases of colorectal cancer in the first place," say Drs Welch and Robertson.

Dr Weber agrees with the pair that two of these phenomena have been at play, but disagrees with the third idea, as noted above.

What explains the decrease in incidence?

Again, the essayists cite three things.

An "obvious candidate" is diet, especially the reduction in the consumption of smoked and cured meats in the United States. A second factor is the increased use of antibiotics, which have reduced the prevalence of deleterious bacterial flora, such as Helicobacter pylori. Third is the increased use of nonsteroidal anti-inflammatory drugs, including aspirin.

Drs Welch and Robertson do not argue that screening has been ineffectual. They know it works to some extent. However, they want "clinicians to have some humility regarding the effect of screening on disease trends.'"

While we like to believe we are living in the period of modern medicine, this is only partially true. Be cautious of the preventative care, and screenings, and understand the downsides. 

Further reading.

Overdiagnosed: Making People Sick in the Pursuit of Health 1st Edition by H. Gilbert Welch

H. Gilbert Welch