By reducing levels of HIV in the blood (viral load) and thus strengthening the immune system, highly active antiretroviral therapy (HAART) has greatly reduced deaths from AIDS-related infections. Since the introduction of HAART in high-income countries, some cancers associated with HIV, such as Kaposi's sarcoma (KS) and lymphoma inside the brain, appear to be decreasing. Unfortunately, though, HAART does not cure HIV infection and some degree of immune deficiency remains, despite continued treatment. As a result, the risk of developing some cancers, such as lymphoma outside the brain, remains higher in people with HIV/AIDS (PHAs) than in HIV negative people.

One cancer in PHAs that has been the focus of attention is lung cancer. This cancer can arise from exposure to tobacco smoke. Some studies have found higher-than-normal levels of cigarette usage in HIV positive people. Since HAART has had an impact on some HIV-related complications, researchers are interested in understanding the impact of HAART on lung cancer. To do this, researchers in London, England, reviewed information in their database of 8,400 PHAs.

Results

In analysing data between 1986 and 2001, the researchers found the following:

• Eleven HIV positive people (one female, 10 males) were diagnosed with lung cancer, all of whom were tobacco smokers.
• Nine of the 11 developed lung cancer in the time HAART was available (1996-2001). Six of the nine were taking HAART at the time cancer was diagnosed. The other three had sufficiently high CD4+ cell counts and did not require HAART at the time their cancers developed.
• The response of the tumours to anti-cancer therapy (radiation or chemotherapy) was not good, and half of the subjects did not survive beyond five months after their cancer diagnosis.
• Overall, once diagnosed with lung cancer, survival of PHAs in the time of HAART was not different from survival of PHAs with the same cancer when HAART was not available.

Risks of Developing Lung Cancer

The researchers found that in the time before HAART, the risk of developing lung cancer was about the same in HIV negative and HIV positive people. However, in the years since HAART has become available, the risk of developing lung cancer in HIV positive people has become about eight times greater than that in HIV negative people.

In examining the data in this study and in five other studies, the researchers found that the following factors, which could have had an impact on survival, were similar before and after HAART became available:

• age at the time lung cancer was diagnosed
• number of cigarettes smoked
• level of CD4+ cells at the time lung cancer was diagnosed

The researchers aren't sure why cigarette smokers who use HAART appear to be at increased risk of developing lung cancer as compared to HIV negative smokers. Their speculation is as follows:

HAART helps to partially repair the immune system of PHAs. This partial improvement is enough to protect them from many AIDS-related infections, and therefore prolongs their survival. However, over time, because the immune system has only been partially restored, it cannot always detect the presence of abnormal growths. As PHAs live longer with weakened immunity, abnormal growths can develop into tumours.

Not mentioned by the researchers is the need for smoking cessation programs for PHAs who smoke tobacco.

References

1. Gérard L, Galicier L, Maillard A, et la. Systemic non-Hodgkin lymphoma in HIV-infected patients with effective suppression of HIV replication: persistent occurrence but improved survival. Journal of Acquired Immune Deficiency Syndromes 2002;30(5):478-484.
2. Gérard L, Galicier L, Boulanger E, et al. Improved survival in HIV-related Hodgkin's lymphoma since the introduction of highly active antiretroviral therapy. AIDS 2003;17(1):81- 87.
3. Bower M, Powles T, Nelson M, et al. HIV-related lung cancer in the era of highly active antiretroviral therapy. AIDS 2003;17(3):371-375.