HIV-positive patients have higher incidence of non-melanoma skin cancers

HIV-positive patients have a higher incidence of non-melanoma skin cancers, according to a Kaiser Permanente study that appears in the current online issue of the Journal of the National Cancer Institute. Specifically, basal cell and squamous cell carcinomas occur more than twice as often among HIV-positive individuals compared to those who are HIV-negative.

The study cohort of 6,560 HIV-positive and almost 37,000 HIV-negative subjects was drawn from members of Kaiser Permanente Northern California from 1996 to 2008.

Overall, HIV-positive subjects had a 2.1-fold higher risk for basal cell carcinomas and a 2.6-fold higher risk for squamous cell carcinomas, compared to HIV-negative subjects. In addition, squamous cell carcinomas were associated with lower CD4 counts, a measure of immunodeficiency. Prior antiretroviral therapy was not found to be associated with the incidence of either squamous cell carcinomas or basal cell carcinomas.

"These findings represent unique data on non-melanoma skin cancers in HIV patients. Most cancer registries, on which previous studies relied, do not record these types of cancers," said lead author Michael J. Silverberg, PhD, MPH, of the Kaiser Permanente Division of Research.

"This should be of interest to several fields, including HIV, dermatology and cancer. Given the increasing longevity for HIV-positive individuals, the burden of many age-related, non-AIDS-defining cancers, including NMSCs, will only continue to increase. Based on our studies, non-melanoma skin cancers are by far the most common cancer this population experiences."

Non-melanoma skin cancers are the most common cancers in the United States, with more than 3.5 million new cases diagnosed each year. Although most non-melanoma skin cancers are easily cured, many become locally invasive and destructive.

"In the general population, we see one case of squamous cell carcinoma for every four cases of basal cell carcinoma," said senior author Maryam M. Asgari, MD, MPH, a Kaiser Permanente dermatologist and investigator at the Division of Research. "It was notable in this study that for HIV-positive subjects with high CD4 counts, this ratio was similar to HIV-negative subjects. But for HIV-positive subjects with low CD4 counts, there was one case of squamous cell carcinoma for every two cases of basal cell carcinoma."

The increased incidence rate of non-melanoma skin cancers in HIV-positive subjects is consistent with the growing evidence about this population's increased risk for a broad range of cancers, according to the study authors. They cited a large meta-analysis in which both HIV/AIDS and organ-transplant populations exhibited increased incidence for many types of cancer. The increased cancer risk is likely due to immunodeficiency, the main risk factor these populations have in common. This conclusion was reinforced by a recent large, population-based study of U.S. transplant recipients.

Until now, however, limited data existed about the association between HIV/AIDS and the risk of non-melanoma skin cancer, specifically with regard to the risks for basal cell carcinomas and squamous cell carcinomas. Several studies that have used linked data from HIV/AIDS and cancer registries have reported standardized incidence ratios for other non-epithelial skin cancers that range from 1.8 to 6.5, whereas other studies have indicated no statistically significant associations with HIV infection. However, most cancer registries exclude basal cell carcinomas and squamous cell carcinomas, which are not reportable malignancies.

While non-melanoma skin cancers are harder to detect, Kaiser Permanente's comprehensive and integrated approach to care allows clinicians to identify these cancers sooner and get members the care they need.

"The clinical implications for these findings include increased vigilance in skin-cancer screening for HIV-positive individuals, especially for squamous cell carcinomas and particularly for those who are not on antiretroviral therapy or who were diagnosed late and have more advanced HIV/AIDS," said Dr. Asgari. "HIV-positive individuals should also be advised to reduce behaviors that may further increase non-melanoma skin cancer incidence, such as excessive sun exposure. In addition, given the observed association of immunodeficiency and squamous cell carcinomas, earlier initiation of antiretroviral therapy to maintain higher CD4 counts may also help reduce the burden of this cancer."