Roxanne Nelson

November 21, 2008

November 21, 2008 — The risk for non-AIDS cancer is higher for individuals infected with HIV than for the general population, according to a new meta-analysis. HIV-infected men also appear to be at higher risk than HIV-infected women. When compared with the general population, the risk for cancer is more than double for HIV-infected men, and approximately 50% greater for HIV-infected women.

The meta-analysis also found that, among individuals with HIV infection, incidence rates were similar for those with and those without AIDS.

The study was presented at the Seventh Annual American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research, held in Washington, DC.

"The increased incidence of non-AIDS-defining cancers is likely multifactorial, but is of growing importance and interest," commented Gregory Kirk, MD, PhD, an infectious disease specialist at the Bloomberg School of Public Health at Johns Hopkins University, in Baltimore, Maryland. "Clearly, until HAART was available, the competing risks for death from AIDS prevented development of some non-AIDS-defining cancers."

However, the advent of improved treatment has dramatically increased the lifespan of people with HIV. "Now, we have an aging HIV-positive population with improved survival," Dr. Kirk told Medscape Oncology. "HIV-positive populations have higher risk behavior than the general population (which puts them at risk for some cancers), such as a higher incidence of smoking, and exposure to oncogenic viruses, including hepatitis B and C and papillomavirus."

Dr. Kirk, who was not involved in this study, pointed out that cancer still remains a rare event, even inlarge HIV-cohort studies. Previous large studies of HIV and cancer have really relied on linking AIDS to cancer registries, and these studies do not incorporate the risk for non-AIDS-defining cancers.

"The meta-analysis is an important attempt to bring data together to get a more precise picture," he said. "I'm not surprised that the risk is not greatly different by history of AIDS. To further explore the gender differences, I think we'll need to break down the specific types of cancer."

HIV Linked to Higher Incidence of Lung Cancer

In a paper published last year, Dr. Kirk and colleagues studied the association between HIV infection and lung cancer (Clin Infect Dis. 2007;45:103-110). Their results showed that HIV infection increases the risk for lung cancer, and that this effect is independent of smoking status. After adjustment for individual smoking exposure, they identified a statistically significant 3.5-fold elevated risk for lung cancer associated with HIV infection.

Several studies of HIV and lung cancer have suggested an increased risk associated with HIV that is not fully accounted for by smoking status. "Our study directly controlled for smoking in a cohort of both HIV-positive and HIV-negative persons, and still found a 3- to 4-fold increased risk for lung cancer," Dr. Kirk said. The mechanisms are not fully explained, but previous immune perturbations, inflammation, pre-existing lung disease, genotoxicity of antiretrovirals, along with other factors, have been suggested."

Dr. Kirk noted that HIV-associated lung cancer appears to manifest in younger people with more minimal smoking histories. The lung cancer mortality rate was also higher among those with HIV infection, and in an analysis unadjusted for age, HIV infection was associated with a 50% increased incidence of lung cancer death.

"The mortality in this cohort seems extremely high and largely related to advanced presentation at diagnosis," he said. "Perhaps it represents both barriers to care and less clinical suspicion for lung cancer in younger HIV-positive men."

Elevated Risk for Non-AIDS Cancers

In the current study,Meredith Shiels, MHS, a doctoral candidate at the Johns Hopkins School of Public Health, and colleagues analyzed data from 11 American and international studies comparing cancer incidence in individuals with HIV and in the general population.

"We defined non-AIDS cancers as all cancers except for Kaposi's sarcoma, non-Hodgkin's lymphoma, and cervical cancer, which are considered AIDS-defining conditions," said Ms. Shiels.

Because of the heterogeneity between studies, the researchers were unable to calculate an overall pooled estimate, so they used metaregression to estimate modification of the general-population standardized incidence ratio by gender and AIDS. Compared with the general population, the standardized incidence ratio of non-AIDS cancers in HIV-infected people, after adjustment for AIDS and study design, was 2.3 in men (95% confidence interval [CI], 1.7 - 3.1) and 1.5 in women (95% CI, 0.9 - 2.3).

For HIV-infected patients with AIDS, the ratio was 1.88 and 1.98 for men and women, respectively, without AIDS.

Their study did not investigate the reasons for the higher risk for non-AIDS cancers among patients with HIV infection, Ms. Shiels explained, but clinicians should be aware of the potential for increased cancer risk in this population.

The study was supported by the National Institutes of Health.

American Association for Cancer Research's Seventh Annual International Conference on Frontiers in Cancer Prevention Research: Abstract A117. Presented November 18, 2008.


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