Why Is Nonadherence to Cancer Screening Associated With Increased Mortality?

Abstract

Victor and Pinsky 1 use data from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial 2 to demonstrate an association between lack of adherence to cancer screening and increased mortality from causes not related to the screening. Participants in the PLCO Cancer Screening trial were 55 to 74 years of age and generally healthy. At trial entry, participants of both sexes in the screening arm were asked to undergo chest radiographs for lung cancer and flexible sigmoidoscopy for colon cancer, men were asked to undergo prostate-specific antigen tests and digital rectal examinations for prostate cancer, and women were asked to undergo cancer antigen 125 tests and transvaginal ultrasonography for ovarian cancer. Those randomized to the control group received usual care.Of the participants randomized to screening, 10.8% did not complete any of the recommended screening tests at baseline and were defined as nonadherents. After 10 years of followup, the risk for mortality (excluding mortality due to lung, colon, prostate, and ovarian cancers) was increased about 50% in nonadherents compared with full adherents who underwent all of the recommended tests at baseline. Increased mortality was due to a wide range of causes, including respiratory, digestive, and cardiovascular diseases, as well as cancers unrelated to screening. The comparison of nonadherents with full adherents was not randomized; this is an observational study of mortality rates among participants in the screening arm of the PLCO Cancer Screening trial and, like all observational studies, is susceptible to confounding.There is no way that nonadherence with cancer screening could cause increased mortality from a range of diseases not associated with screening. The analyses were adjusted for age, race/ethnicity, sex, educational level, cigarette smoking, body mass index, marital status, and major comorbidities, indicating that these health-related variables are unlikely to account for the findings. So, what does account for the increased risk of death? As the authors note, it is most likely that nonadherence with recommended screening is a marker for behaviors that are associated with increased mortality. Previous studies have shown that patients who are adherent to recommended medications are more likely to seek out other pre-

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