High Non-AIDS Cancer Risk With HIV—But Many Questions Remain Unanswered

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High Non-AIDS Cancer Risk With HIV—But Many Questions Remain Unanswered

andra M. Levine, MD

Posting Date: September 03, 2008

Chief Medical OfficerCity of Hope National Medical CenterDuarte, California

The prospective observational cohort study by Patel and colleagues[1] found that, as HIV-infected patients live longer because of effective antiretroviral therapy, they are being diagnosed with certain non-AIDS–defining cancers at a rate higher than that expected in the general US population (Capsule Summary). These non-AIDS malignancies include anal cancer, vaginal cancer, Hodgkin’s disease, lung cancer, liver cancer, melanoma, oropharyngeal cancer, leukemia, colorectal cancer, and renal cancer. Whether these cancers are associated with HIV itself, with underlying immunodeficiency, with certain lifestyle factors (such as smoking or sun exposure), or with infection with other organisms (such as human papillomavirus) remains unknown.

Results of this study underline the extreme importance of educating HIV-infected patients on how they can proactively decrease their risk of developing cancer. Essentially all studies on lung cancer and HIV found that cancer developed almost exclusively among smokers,[2,3] with a higher risk of cancer among those who have smoked the most. Whether HIV potentiates the effect of smoking on the risk of lung cancer is unknown. In addition, sun exposure is associated with an increased risk of melanoma—an extremely difficult cancer to treat once it has spread. Use of strong sun blockers or avoidance of sunlight should be advocated by physicians caring for HIV-infected persons. Finally, with the increased risk of colorectal cancer among HIV-infected persons, it will be important for physicians to encourage their patients to start routine colonoscopy screening at the age of 50.

One surprising finding in this study was the significantly decreased risk of prostate cancer identified among HIV-infected persons. Testosterone is a growth factor for prostate cancer cells, and prostate cancer is seen with increasing frequency as men age. It is possible that the majority of HIV-infected men in the United States are not yet old enough to have developed prostate cancer, and prostate cancer risk in men with HIV must be evaluated very carefully over time.

This study was conducted by comparing data from 2 large cohorts of HIV-infected patients (the Adult and Adolescent Spectrum of HIV Disease (ASD) Project and the HIV Outpatient Study [HOPS]) with data from the Surveillance, Epidemiology and End Results (SEER) program, which includes cancer incidence data from 13 geographic regions in the United States. The strengths of this analysis are the large number of HIV-infected persons studied and the ability to compare rate ratios for many different types of cancer with those derived from the SEER population-based registry. However, although case ascertainment is close to 100% in the SEER registries, approximately 75% to 85% ascertainment has been postulated in the HIV cohorts. Therefore, this analysis may underestimate rate ratios for cancer among HIV-infected persons. Furthermore, the HIV cohorts are not geographically located within the 13 SEER registry areas, making direct comparison more difficult. Detailed information is not available either from the patients in the 2 HIV cohorts or from the SEER registry regarding these cancers, nor have cases from either group undergone pathology review to confirm the diagnoses. No data are available regarding smoking history or other lifestyle factors associated with cancer risk.

Several important questions about non-AIDS cancers in HIV-infected populations remain to be answered. First, it will be very important to determine the precise role of various risk factors on the incidence of these cancers. For example, HIV-infected persons are known to have an increased incidence of smoking when compared with the US population as a whole.[2] Is the increased risk of lung cancer a result of smoking, or does HIV per se play a role in the development of lung cancer? In this regard, 2 recent studies have demonstrated that smoking alone does not entirely explain the higher risk of lung cancer among HIV-infected patients.[4,5] Second, in a similar fashion, is the increase in melanoma related to an increased risk of sun exposure among HIV-infected persons, or is HIV or immunosuppression part of the risk for melanoma, independent of sun exposure? Third, have cancer screening programs been employed among HIV-infected persons to the same extent as in other populations? More or less intense screening can affect the incidence of a given cancer in a population. For example, if screening colonoscopy is not routine among HIV-infected persons, early precancerous polyps would not be recognized and removed; failure to do so would heighten the risk of colon cancer.

References

1. Patel P, Hanson DL, Sullivan PS, et al. Incidence of types of cancer among HIV-infected persons compared with the general population in the United States, 1992-2003. Ann Intern Med. 2008;148:728-736.

2. Savès M, Chêne G, Ducimetière P, et al. Risk factors for coronary heart disease in patients treated for human immunodeficiency virus infection compared with the general population. Clin Infect Dis. 2003;37:292-298.

3. Friis-Møller N, Weber R, Reiss P, et al. Cardiovascular disease risk factors in HIV patients-association with antiretroviral therapy: results from the DAD study. AIDS. 2003;17:1179-1193.

4. Kirk GD, Merlo C, O’Driscoll P, et al. HIV infection is associated with an increased risk for lung cancer, independent of smoking. Clin Infect Dis. 2007;45:103-110.

5. Chaturvedi AK, Pfeiffer RM, Chang L, et al. Elevated risk of lung cancer among people with AIDS. AIDS. 2007;21:207-213.

Link to the original abstract.

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