Our results suggest that, contrary to our initial hypothesis, baseline health history characteristics had minimal effects on PLCO Cancer Screening Trial adherence among the older African American men who comprised the study sample. The exceptions were current smoking, which negatively affected adherence, and family history of cancer, which positively affected adherence.
Thus, in our study, not only were current smokers less likely to receive lung cancer screening, they were also less likely to receive prostate cancer screening and colorectal cancer screening. In the future, it will be important to discover ways to motivate smokers to engage in cancer screening because their smoking status puts them at risk for developing many types of cancer.
Participants with a family history of cancer were more likely than other participants to be adherent to prostate cancer screening and lung cancer screening. This finding is corroborated by the work of other investigators who examined the association between family history of cancer and adherence to screening for other types of cancer. For example, Halbert et al. (27
) assessed self-reported screening adherence in a sample of 65 African American women in Pennsylvania at risk for hereditary breast cancer and found fairly high levels of adherence to mammography (75% adherent), clinical breast examination (93% adherent), and breast self-examination (41%).
Positive family history of cancer appears to be related to perceived risk of getting the disease (28
) and subsequent increased vigilance in self-monitoring via participation in cancer screening activities. In future studies promoting adherence to evidence-based cancer screening guidelines, it will be important to understand participants’ risk perceptions so that effective interventions to improve risk communication can be developed (29
In summary, our data show that, in a longitudinal cancer screening trial conducted with adults ages 55 to 74 years at enrollment, baseline comorbidities had little or no effect on likelihood of adherence to trial screenings. Overall, older African American men with comorbidities appear to be very good candidates for participation in longitudinal cancer screening trials, as they are generally as likely as other people to adhere to cancer clinical trial screenings.
The study findings highlight the importance of including people with comorbidities in cancer clinical trials rather than excluding them a priori. Based on our data, there appears to be no reason to exclude older African American men with comorbidities unless the comorbid condition(s) will confound the study outcome.
Study participants were older African American men living in a metropolitan area who were asked to participate in a clinical trial to evaluate the effectiveness of cancer screening tests. The findings need to be replicated before they can be generalized to clinical trials of other cancer-related outcomes such as treatment. Because the study population was restricted to older African American men, we do not know whether similar findings would be seen in a sample of women, men of other racial/ethnic groups, or among younger African American men. Another limitation is the fact that the baseline questionnaire from which baseline comorbidity data were drawn did not include information pertaining to psychiatric comorbidities (such as anxiety and alcohol/drug abuse).
Despite these limitations, this study had several strengths. First, it focused on older African American men who as a group are more likely than others to be affected by prostate, lung, and colorectal cancers. Second, it took advantage of a large national clinical trial, the PLCO Cancer Screening Trial, to address an important behavioral science research question related to adherence to trial protocols. Because the Detroit metropolitan area is sociodemographically representative of other large, urban areas, it is likely that our study results are generalizable to older African American male cancer clinical trial participants in these other, similar areas.