David B. Kaminsky,
M.D., FIAC, March 19, 2018
H. Gilbert Welch, M.D., MPH, Professor of Medicine, Dartmouth Institute for Health Policy & Clinical Practice, Geisel School of Medicine at Dartmouth
The pathologic diagnosis of “cancer” encompasses a wide variety of growth dynamics. Some cancers are rapidly progressive (the birds), some progress more slowly (the rabbits) and others grow so slowly that they would otherwise never bother people during their lifetime – or don't’ grow at all (the turtles).
This heterogeneity poses tremendous challenges for early detection efforts. The birds are the most aggressive cancers – the cancers that have already spread by the time they are detectable. Screening can’t help with the birds; the birds are already gone. The rabbits are growing more slowly, they are the cancers that may be helped by earlier detection and treatment. The turtles don’t need to be found, because these cancers aren’t going anywhere. Unfortunately, screening is really good at finding turtles.
This heterogeneity also makes screening very counterintuitive. You might think screening can only lower your risk of getting cancer, but it turns out that it can be the fastest way to get cancer. You might think that all the “cancer survivors” in the news (and, perhaps, in your neighborhood) – those individuals whose cancers were found early by screening and who are now doing well – provide powerful evidence that screening helps save lives. But it turns out that these survivors are often less likely to be evidence of screenings benefit – more likely to be evidence of its harms.
Cancer screening involves trade-offs. Screening offers the potential benefit of avoiding advanced cancer and subsequent cancer death for a few. But it also produces the harms of false alarms, overdiagnosis and unnecessary treatment for many others. Because different individuals value these benefits and harms differently, there is no single “right” answer. That’s why screening is a choice, not a public health imperative.
Continuing Medical Education and Maintenance of Certification:
- Recognize the heterogeneity within the pathologic diagnosis of “cancer” and the resulting implications for the natural history of the disease
- Explain why early cancer detection efforts disproportionately detect more slowly progressive forms of the disease and can produce the problem of overdiagnosis
- Identify those cancers in which the efforts to detect the disease and the existence of a disease reservoir have combined to produce overdiagnosis (i.e., cancers of the breast, prostate, thyroid and kidney as well as melanoma)
- Anticipate the range of misleading feedback associated with screening: more cancer cases (perhaps even labeled as epidemic), more "favorable" stage distribution, higher 5 and/or 10-year survival rates, and more “survivors” who feel they owe their lives to the test
The United States and Canadian Academy of Pathology is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.
The United States and Canadian Academy of Pathology designates this enduring material for a maximum of 1
AMA PRA Category 1 CreditsTM
. Physicians should only commensurate with the extent of their participation in the activity.
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The following faculty reported no relevant financial relationships: H. Gilbert Welch, M.D., MPH
USCAP staff associated with the development of content for this activity reported no relevant financial relationships.