POZ - Treatment News : High HIV Lung Cancer Risk (Not Just From Smoking)

The risk of lung cancer is "substantially elevated" among people living with HIV, according to new data published by researchers at the National Cancer Institute. While the report in the January 11 issue of AIDS indicates that a large percentage of HIV-positive people are smokers, tobacco use could not entirely account for the increased risk, especially among younger adults.

Previous research has established that lung cancer is the third most frequently seen cancer among HIV-positive people in the United States, with Kaposi's sarcoma (KS) and non-Hodgkin's lymphoma (NHL) being the most common. The risk of lung cancer has been estimated to be two to seven times higher among HIV-positive people, compared to those in the general population. What's more, especially among HIV-positive people, survival following a diagnosis of lung cancer is especially poor.

Because cigarette smoking is very common among HIV-positive people in the U.S. – one analysis indicated that 60% to 80% of those living with the virus are smokers (compared to smoking rates of 20% to 30% in the general population) – higher-than-average lung cancer rates in this population do not come as a surprise. However, researchers have also questioned whether or not HIV infection itself further increases the risk of lung cancer.

To better understand lung cancer risk in HIV-positive people, Anil Chaturvedi, PhD, and his colleagues at the NCI reviewed records on 397,927 people living with AIDS linked to cancer registries in six U.S. states and five metropolitan areas.

The analysis published in AIDS included adolescents and adults with AIDS – aged 15 years or older at AIDS onset – diagnosed between 1980 and 2002. Data from the cancer registries were used to identify lung cancer cases in the period spanning five years before to five years after AIDS onset. However, the analysis mostly focused on lung cancer diagnoses within four to 27 months after an AIDS diagnosis.

In the ten-year period spanning five years before to five years after AIDS onset, 1,489 lung cancer cases were documented. Compared to the general population, people with AIDS had a significantly increased risk of lung cancer, expressed statistically in the study using what is known as a "standardized incidence ratio."

Although the incidence increased appreciably with age, it was found that the risk was remarkably high in young people with AIDS. Among adolescents and adults between 15 and 29 years of age and diagnosed with AIDS relative to the age-matched general population.

As for sex, the incidence was higher in men than in women and increased with age. However, standardized incidence ratios indicated that the risk relative to the general population was higher for women.

Lung cancer risk was also elevated for all HIV risk groups, particularly injection drug users, and in all CD4 (T4 cell) count categories.

According to Dr. Chaturvedi's group, the alarming incidence of lung cancer in young people with AIDS suggests that the risk cannot be tied exclusively to the prevalence of cigarette smoking. However, it is possible that the effects of smoking – not just the duration of tobacco use – could be more severe in HIV-positive individuals.

The authors point to studies indicating an accelerated form of smoking-related emphysema – a risk factor for lung cancer – in HIV-positive people. Other types of lung damage, including significant inflammation, have also been documented in those living with the virus (including non-smokers).

Dr. Chaturvedi's group also indicate that HIV-positive people are more susceptible to lung infections and pneumonia caused by a wide range of organisms, such as Streptococcus pneumoniae, Chlamydia pneumoniae, Pneumocystis jiroveci, and Mycobacteria species (such as Mycobacterium tuberculosis). Repeated or chronic lung infections, they suggest, could increase the risk of lung cancer through chronic inflammation.