HIV Infection Not Associated With Lung Cancer

Sandra Yin

November 17, 2011

November 17, 2011 (Bethesda, Maryland) — Higher lung cancer rates have been reported in people with HIV/AIDS than in the general population, but it has not been clear why.

To find an answer, researchers at the University of California at San Francisco sought to determine the incidence and risk factors for lung cancer among women and men in 2 longitudinal studies of HIV infection in the United States. Results were announced here at the 13th International Conference on Malignancies in AIDS and Other Acquired Immunodeficiencies (ICMAOI) at the National Institutes of Health.

The researchers hypothesized that the increased incidence of lung cancer among HIV-infected people was primarily due to cigarette smoking and secondarily to preexisting lung disease.

HIV infection was not associated with lung cancer in a sample of women and was no longer significant in a sample of men after adjustment for prior AIDS diagnosis, according to Nancy Hessol, MSPH, professor in the departments of clinical pharmacy and medicine at the University of California at San Francisco, who reported findings from the Women's Interagency HIV Study (WIHS) and Men in the Multicenter AIDS Cohort Study (MACS).

"Other factors, such as HIV-related diseases, especially lung disease, may have a greater influence on the development of lung cancer," she said during her presentation.

Case studies have found that most lung cancers in HIV-infected people have occurred in people already diagnosed with AIDS. Earlier studies had linked a higher incidence of lung cancer to preexisting pulmonary infections and pneumonia.

The study population included 3763 women and 6972 men. Most of the women (74%) were HIV positive, while only 42% of the men were. Participants were seen twice a year. Lung cancers were ascertained via searches of state-wide cancer registries, medical record review, and death certificates.

Incidence rates were calculated as the number of incident cancers divided by the number of person-years of follow-up among those at risk for lung cancer.

Those who reported a history of smoking were more likely to be in the female sample than in the male sample, and to be HIV positive, older, and African American or have a history of recreational or injection drug use.

Among HIV-positive participants, current or former smokers were more likely to have higher HIV viral loads and were more likely never to have received highly active antiretroviral therapy (HAART).

Among the women, the number of lung cancer cases per 100,000 person-years was 75.5, compared with 21.9 for the men.

All lung cancer cases were among people who smoked only.

Subsequent analyses focused on the 6816 people who had ever smoked. An unadjusted Poisson regression found no statistical association between HIV status and risk for lung cancer in either the men or the women.

Among other findings:

  • Women aged 60 years or older had a 9 times greater risk of getting lung cancer than women younger than 50 years of age after taking into account their cigarette smoking history;

  • Women with more than 30 pack-years of smoking had a 22 times greater risk of getting lung cancer than women with less than 10 pack-years (a pack-year is the average number of packs smoked per day times the number of years smoked);

  • Men with more than 30 pack-years of smoking faced a 10 times greater risk for lung cancer than those with less than 10 pack-years of smoking;

  • African-American women faced a more than 4 times higher risk for lung cancer than all other women;

  • CD4 count, HIV viral load, and HAART use were not significant; and

  • Prior diagnosis of AIDS pneumonia had a significant effect for women.

Ms. Hessol noted that the study had limitations. Among them, the number of incident lung cancers was relatively small. In addition, the results may not apply to all people living with or at risk for HIV infection, especially those living in developing countries, where tobacco use, environmental factors, and lung cancer diagnosis may differ from those in the United States.

Smoking was by far the most important risk factor, Joel Palefsky, MD, FRCP(C), professor in the Department of Medicine at University of California at San Francisco, told Medscape Medical News.

"While one cannot exclude a role for it," Dr. Palefsky said of HIV, "the most important takeaway is that the most important risk factor is modifiable, and that's reducing smoking."

Ms. Hessol and Dr. Palefsky have disclosed no relevant financial relationships.

13th International Conference on Malignancies in AIDS and Other Acquired Immunodeficiencies (ICMAOI); Abstract #025. Presented November 8, 2011.

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