Skepticism Warranted When Interpreting Risk Factors for Skin Cancer
Patients in close contact with the health care system are more likely to get diagnosed with skin cancer, suggesting the possibility of detection bias in studies.
Patients in regular contact with the health care system who undergo health care screenings are more likely to get diagnosed with skin cancer, a recent study published in JAMA Dermatology reported.1 The association is not to suggest that health care screening practices cause skin cancer, but that epidemiological studies investigating risk factors for skin cancer could be skewed by detection bias, and skepticism is warranted when interpreting the results.
“This study was focused on epidemiologic methods,” primary study author Aaron Drucker, MD, ScM, assistant professor at the University of Toronto, Canada, told Cancer Therapy Advisor. He noted that the study was not intended to have clinical takeaways. “The takeaway is whenever you're reading a study that is looking at risk factors for skin cancer, and the risk factor that's being examined is something that could be tied to people accessing the health care system, then that risk factor needs to be examined in that light,” he said.
For instance, diabetes is often mentioned as a risk factor for skin cancer, but people with diabetes tend to see their doctors more frequently, such as to get their blood sugar levels checked. “They are probably more likely to point out a spot on their skin that is maybe a slow-growing skin cancer, that would have taken a lot longer, if ever, to present to a physician in people who don't have diabetes or don't have as much access to the health care system as someone with diabetes,” Dr Drucker explained.
The association between health care screening and skin cancer diagnosis was elucidated using a large, cohort-based study design. The study included 117,492 individuals from two US cohorts: Nurses' Health Study and Health Professionals Follow-Up Study. In both cohorts, individuals were followed from 1990 to 2012 and asked about their participation in various health care screening practices, including physical examination by a physician, sigmoidoscopy or colonoscopy, eye examination, serum cholesterol test, mammography, breast examination and pelvic examination, prostate-specific antigen test, and rectal examination.
For the Nurses' Health Study, 77,736 women were followed up with for 1,388,523 person-years, and 14,319 incident basal cell carcinomas (BCCs), 1517 squamous cell carcinomas (SCC), and 506 melanomas were detected. For the Health Professionals Follow-Up Study, 39,756 men were followed for 635,319 person-years, and 8741 incident BCCs, 1191 SCCs, and 469 melanomas were detected.