A new study examines non-melanoma skin cancers & HIV
by Chael Needle
In the pre-HAART era, an AIDS diagnosis or even an HIV-positive diagnosis illuminated a particular set of urgent health concerns. Now that treatment often affords longer life for HIV-positive individuals, HIV disease is increasingly intersecting with health concerns related to lifestyle and growing older. Non-melanoma skin cancers (NMSCs) are one of these concerns and a new Kaiser Permanente study, “HIV Infection Status, Immunodeficiency, and the Incidence of Non-Melanoma Skin Cancer,” recently published in the Journal of the National Cancer Institute, explores why and the extent to which individuals living with HIV/AIDS are at risk for two of its forms: basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs).
Basal cells are round cells located in the lower epidermis. Most often forming on the head and neck and associated with sun exposure, BCCs account for about eighty percent of skin cancers.
Squamous cells are flat, scale-like cells and comprise most of the epidermis. SCCs account for about twenty percent of skin cancers. This type is also caused by sun exposure, though it can form in burned, chemical-damaged, or X-ray-exposed skin, as well.
Individuals who are being treated for HIV/AIDS and their physicians are probably aware of the three AIDS-defining cancers: Kaposi sarcoma, non-Hodgkin lymphoma, and invasive cervical cancer. But the focus needs to expand to include the broad range of cancers, including NMSCs, for which patients with HIV and AIDS are at higher risk, says Michael J. Silverberg, PhD, MPH, of the Kaiser Permanente Division of Research, and lead author of the study. Now, in light of the study’s findings—showing a correlative link between immunodeficiency and NMSCs—HIV physicians and patients can be more vigilant about these non-AIDS-defining cancers, with routine skin cancer screenings and limiting excessive sun exposure.
Non-melanoma skin cancers are the most common cancers in the United States—more than 3.5 million new cases are diagnosed each year. Part of the impetus for this study was “to get a better handle on the full spectrum of cancers that HIV patients are particularly susceptible to,” says Dr. Silverberg. The absence of NMSCs from national cancer registries, which collect data on other reportable cancers, and the difficulty of recruiting the tens of thousands needed for clinical research means that little is known about NMSCs in this population, he notes.
In this context, the researchers took advantage of the “rich resource,” says Dr. Silverberg—HAART-era HIV-positive and HIV-negative patients’ clinical data and outcomes collected during routine medical care in Kaiser Permanente Northern California, a large integrated healthcare delivery system.
Comparing 6,560 HIV-positive and nearly 37,000 HIV-negative patients in this same healthcare system, researchers found that HIV-positive subjects had a 2.1-fold higher incidence rate of BCCs and 2.6-fold higher incidence rate of SCCs compared with HIV-negative subjects.
Researchers also found that the increased incidence rate of BCCs for HIV-positive subjects seemed to be limited to men, while the increased incidence rate of SCCs was seen in women, HIV-positive MSM, and heterosexual HIV-positive men. Additionally, lower recent CD4 counts among HIV-positive subjects translated to a higher incidence rate for SCC but not for BCC.
“It’s pretty clear that immunodeficiency greatly contributes to the risk of NMSCs, especially squamous cell carcinoma. Interestingly, previous studies have suggested a link between the cancer-causing human papillomavirus for SCCs, but not BCCs. In fact, many of the cancer types increased in HIV-positive patients are linked to human papillomavirus or other infections.”
Referring to the study, Dr. Silverberg notes: “One very encouraging finding here was if you looked at HIV patients with CD4 counts greater than 500, they had a more similar pattern of NMSCs compared with HIV-negative subjects. For example, in the general population, a dermatologist may see about four cases of basal cell carcinomas for every one case of squamous cell carcinoma. Among HIV patients with greater than 500 CD4 cells, you see the same exact ratio.
“What that means to me is that earlier treatment of HIV to manage viral load and CD4 cell counts may also be an effective preventative measure against the development of certain cancers or other non-AIDS-defining conditions.”
The research field, notes Dr. Silverberg, is now increasingly focused on consequences of aging: “With effective treatment, our patients now have lifespans quite similar to the general population. As a result, this population is experiencing more cancers, more cardiovascular disease—and our research indicates that the risk for these outcomes is greater than what you would expect based on age alone. With earlier diagnosis and treatment of HIV, there is hope that this increased risk will be mitigated to some extent.”
Chael Needle reported on the anti-diarrheal Fulyzaq in the February issue.