SUMMARY: HIV infection is significantly associated with lung cancer, increasing the risk by nearly 2-fold, but this was far overshadowed by tobacco smoking, which raised the risk by almost 10-fold, according to a study presented last week at the 17th Conference on Retroviruses & Opportunistic Infections (CROI 2010) in San Francisco. Smoking-related risk declined over time after quitting, but never fell to the level of people who never smoked.

By Liz Highleyman

Recent studies have shown that people with HIV are at higher risk for non-AIDS-defining cancers overall especially those with an infectious cause such as human papillomavirus but rates for specific types of cancer have not been consistent. Some studies have found that HIV appears to be independently associated with an increased risk of lung cancer, but others have not.

To shed further light on this issue, Keith Sigel from Mt. Sinai School of Medicine and colleagues analyzed lung cancer incidence in a large cohort of HIV positive and negative individuals, adjusting for smoking and other key confounding variables. Previous work investigating this association has been limited by small sample size, lack of appropriate HIV negative controls, or lack of smoking data, they noted.

The researchers merged data from the Veterans Aging Cohort Study Virtual Cohort (a large administrative HIV cohort) and the Veterans Large Health Survey (which contains detailed self-reported data about smoking), yielding a cohort of 3707 HIV positive patients and 9890 HIV negative control subjects.

The 2 groups were similar in terms of sex (about 90% men), race/ethnicity, and age. However, the HIV positive participants were more likely that the HIV negatives to smoke (32% vs 28%) and have a history of drug use or heavy alcohol use (16% vs 10%).

Participants were followed for a median of 8 years; the HIV positive group accumulated 28,500 person-years of follow-up, while the HIV negative group amassed 76,800 person-years.

Lung cancer was defined using International Classification of Diseases (ICD-9) codes. The investigators calculated incidence rates of lung cancer, then determined adjusted incidence rate ratios (IRRs) adjusting for age, race/ethnicity, smoking, and chronic obstructive pulmonary disease (COPD).

Results

	The overall incidence of lung cancer was 0.26 per 100 person-years among the HIV positive participants, compared with 0.16 per 100 person-years among the HIV negative controls (IRR 1.50).
	The IRR of lung cancer associated with HIV infection remained significant after adjustment for smoking, age, race/ethnicity, and COPD.
	In a multivariate analysis, HIV infection was associated with an IRR of 1.80, or 80% greater risk of lung cancer.
	Smoking, however, was associated with a much greater risk:
	Current daily smoking: IRR 9.75, or nearly 10 times the risk; Current occasional smoking: IRR 3.37; Recently quit smoking: IRR 9.93; Quit smoking 1 or more years ago: IRR 5.14.

"In our cohort of demographically similar HIV-infected and HIV-uninfected subjects, incidence of lung cancer was significantly increased in HIV-infected subjects even after adjusting for smoking exposure," the investigators concluded.

Of note, even occasional smoking increased the risk of lung cancer more than HIV infection did, and ex-smokers remained at substantially elevated risk even at the end of follw-up.

This study adds to the already substantial evidence that smoking is a health hazard and quitting is beneficial. Another study presented at CROI showed that smoking cessation lowered cardiovascular risk in people with HIV, although the rate of all-cause death did not fall as consistently.

Mt Sinai Sch of Med, New York, NY; Yale Sch of Med, New Haven, CT; James J Peters VAMC, Bronx, NY; Univ of Pittsburgh Sch of Med, PA; Rutgers Univ, Brunswick, NJ; Emory Univ Sch of Med, Decatur, GA; Baylor Coll of Med, Houston, TX; George Washington Univ Sch of Med, Washington, DC.

2/26/10

Reference
K Sigel, J Wisnivesky, A Justice, and others. HIV Infection Is an Independent Risk Factor for Lung Cancer. 17th Conference on Retroviruses & Opportunistic Infections (CROI 2010). San Francisco. February 16-19, 2010. Abstract 30.