COMORBIDITIES AND PERCEIVED CANCER RISK

Purpose: Patients with comorbidities face a lower lifetime cancer risk for the simple reason that, compared to patients without comorbidities, they are more likely to die before developing cancer. Understanding the relationship between comorbidities and cancer risk is essential for determining the potential benefits of cancer screening and early detection. Yet, evidence suggests that many elderly people with significant comorbidities, for whom the expected gains from early detection are small, are still being screened for cancer. Patients may not understand how comorbidities are related to their risk of developing cancer. We investigated the impact of comorbidities on self-perceived cancer risk.

Method: We identified a sample of 9,513 persons age 50+ who answered questions about perceived cancer risk in the 2005 National Health Interview Survey. Respondents are asked about their risk of developing cancer compared to men/women in their age group. To facilitate analysis, we dichotomized the risk measure into two categories “less likely” versus “about as likely” and “more likely”. We used logistic regression to estimate the impact of self-reported comorbidities (diabetes, heart attack, emphysema, stroke, and hypertension) on perceived cancer risk, controlling for age, sex, race, education, family history of cancer, and smoking.

Result: Only the odds ratio for diabetes was significantly different from one: 1.16 (1.01 to 1.34). Apparently, persons with diabetes believe they face an elevated risk of cancer. Only the odds ratio for stroke was less than one, 0.93 [0.74 to 1.16], but it was not significantly different from one. Odds ratios for heart attack, emphysema, and hypertension were greater and insignificantly different from one.

Conclusion: Our results point to a discord between actual and perceived cancer risk. People with comorbidities fail to appreciate that, because they face a higher risk of death from competing causes (i.e. diseases other than cancer), they actually have a lower risk of developing cancer during their lifetimes compared to people without comorbidities, all else being equal. Inaccurate perceptions of cancer risk in this population may lead to over-screening and over-detection.