Epidemiology of nonkeratinocytic skin cancers among persons with AIDS in the United States

Abstract

Objective: Immunosuppression may increase risk for some skin cancers. We evaluated skin cancer epidemiology among persons with AIDS.

Design: We linked data from population-based US AIDS and cancer registries to evaluate risk of nonkeratinocytic skin cancers (melanoma, Merkel cell carcinoma, and appendageal carcinomas, including sebaceous carcinoma) in 497 142 persons with AIDS.

Methods: Standardized incidence ratios (SIRs) were calculated to relate skin cancer risk to that in the general population. We used logistic regression to compare risk according to demographic factors, CD4 cell count, and a geographic index of ultraviolet radiation exposure.

Results: From 60 months before to 60 months after AIDS onset, persons with AIDS had elevated risks of melanoma (SIR = 1.3, 95% confidence interval 1.1-1.4, n = 292 cases) and, more strongly, of Merkel cell carcinoma (SIR = 11, 95% confidence interval 6.3-17, n = 17) and sebaceous carcinoma (SIR = 8.1, 95% confidence interval 3.2-17, n = 7). Risk for appendageal carcinomas increased with progressive time relative to AIDS onset (P trend = 0.03). Risk of these skin cancers was higher in non-Hispanic whites than other racial/ethnic groups, and melanoma risk was highest among men who have sex with men. Melanoma risk was unrelated to CD4 cell count at AIDS onset (P = 0.32). Risks for melanoma and appendageal carcinomas rose with increasing ultraviolet radiation exposure (P trend <10 and P trend = 10, respectively).

Conclusion: Among persons with AIDS, there is a modest excess risk of melanoma, which is not strongly related to immunosuppression and may relate to ultraviolet radiation exposure. In contrast, the greatly increased risks for Merkel cell and sebaceous carcinoma suggest an etiologic role for immunosuppression.

Figure 1

Risk of skin cancers among persons with AIDS, as a function of time relative to AIDS onset. Results are shown for melanoma (panel A), Merkel cell carcinoma (panel B), and all appendageal skin carcinomas (panel C). The standardized incidence ratios are shown as squares, with surrounding 95% confidence intervals as vertical lines. The curved line corresponds to the trend estimated in Poisson regression. The p-value for the trend test is also indicated. Note that the vertical axis differs across the panels. The time periods used in the trend test are shown with a solid square, while the time periods excluded from the trend test are shown with an open square. The two excluded periods are from 6 months before to 3 months after AIDS onset, because of possible over-ascertainment of cancers due to clinical evaluations associated with diagnosis of AIDS, and from 61 months to 120 months after AIDS onset, because potential losses to follow-up may lead to under-ascertainment of cancer outcomes.

Figure 2

Melanoma risk among persons with AIDS, according to ultraviolet radiation exposure. Results are shown for melanomas of the face, head, and upper limb (Panel A) and melanomas of the trunk, lower limb, and other/unspecified sites (Panel B). Results are restricted to non-Hispanic white adults (age 15 years or older at AIDS onset) and are expressed as the number of melanoma cases per 100,000 subjects during the overall cancer risk period (60 months before to 60 months after AIDS onset). The analysis includes 88 melanoma cases of the face, head, and upper limb, and 176 cases of the trunk, lower limb, and other/unspecified sites. The trend line and associated p-value were derived using logistic regression. Note that the vertical axis differs across the panels.