Pierre-Victor D, et al. - In this secondary analysis of data (n=64,567) from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial, researchers assessed the link between nonadherence to cancer screening tests and mortality, excluding mortality from cancers studied in the trial. They found that higher overall mortality (excluding deaths from cancers studied in the trial) was associated with a nonadherence behavior profile marked by nonadherence to protocol screenings among participants in a screening trial for multiple cancers. The authors advised that generalizability of this finding to routine clinical practice should be assessed.

Methods

• From November 8, 1993, to July 2, 2001, randomization was carried out at 10 US screening centers.
• Original follow-up was through 13 years or December 31, 2009.
• Further follow-up was performed—which started on May 18, 2011, until December 31, 2012—upon participant re-consent.
• For the PLCO Cancer Screening trial intervention arm participants (N=77,443), screening tests included chest radiographs and flexible sigmoidoscopy for both sexes, prostate-specific antigen tests and digital rectal examinations for men, and cancer antigen 125 tests and transvaginal ultrasonography for women.
• Participants were asked to complete a self-administered questionnaire at baseline.
• The investigators classified participants into different groups: those receiving all sex-specified PLCO Cancer Screening trial screening tests at baseline (fully adherent), those receiving some but not all baseline tests (partially adherent), and those receiving no baseline tests (nonadherents).
• Researchers performed secondary analysis, which was ad hoc in the original trial protocol.
• From November 24, 2017, to August 29, 2018, they performed statistical analysis.
• They used mailed annual study update questionnaires and performed searches of the National Death Index to determine the mortality.
• They assessed the link between mortality and adherence, controlling for various covariates, by using Cox proportional hazards regression.

Results

• A total of 85.3%, 3.9%, and 10.8% of study participants were found to be adherent, partially adherent, or nonadherent, respectively, with baseline screening protocol.
• Excluding deaths from cancers studied in the PLCO Cancer Screening trial and controlling only for age, sex, and race/ethnicity (model 1), the observed hazard ratio of mortality within 10 years of follow-up was 1.73 (95% CI, 1.60-1.89) for nonadherent vs fully adherent participants and 1.36 (95% CI, 1.19-1.54) for partially vs fully adherent participants.
• For nonadherent vs fully adherent participants, the hazard ratio decreased to 1.46 (95% CI, 1.34-1.59) following adjustment for medical risk factors for mortality and behavioral-related factors (model 2).