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Most Non-AIDS Cancers Not Diagnosed at Earlier Age in People With AIDS
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17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
Most non-AIDS cancers do not arise at a significantly younger age in people with AIDS than in the general population, according to results of a National Cancer Institute (NCI) study [1]. Two non-AIDS malignancies--anal cancer and lung cancer--did arise at a slightly but significantly earlier ages in people AIDS than in the general population, as did two AIDS cancers. The NCI investigators suggest that several factors may account for the age difference with these four cancers--including HIV-induced immune dysfunction, and smoking or having sex at a younger age by people with HIV.
To gauge the impact of HIV and AIDS on cancer risk, the NCI team analyzed data from the HIV/AIDS Cancer Match Study, which links 15 US HIV and cancer registries including over 338,000 people who received care from 1980 through 2008. This analysis focused on people with an AIDS diagnosis and follow-up data from 4 to 60 months after that diagnosis.
Four in 5 people in the AIDS group were male, 51% were black, and median age at AIDS diagnosis was 37 years. The registries cataloged 21,477 cancers during 916,343 person-years of follow-up after the AIDS diagnosis. The most common diagnoses were two AIDS cancers, Kaposi sarcoma in 10,281 people and non-Hodgkin lymphoma in 6668. The next three most common diagnoses were non-AIDS cancers--913 lung cancers, 346 anal cancers, and 318 Hodgkin lymphomas. There were 168 diagnoses of cervical cancer, another AIDS cancer.
Understanding different rates of AIDS and non-AIDS cancers in people with HIV and the general population depends on understanding the sharply different age distribution of these two populations in the database analyzed. The general population had a even age distribution--with similar proportions of people at each age--to about age 40. At that point, the proportion of people at each age fell slowly and evenly in the general population. In contrast, the AIDS population included very few people under 20. From that age to the late 30s, the proportion at each age rose sharply. After a peak in the late 30s, there was a mirror-image drop in the proportion of AIDS patients in each age group to about age 65. The AIDS group included few people over 65. People 65 or older contributed 13% of person-years in the general population versus 1% in the AIDS group.
For most cancers analyzed, people with AIDS were about 15 to 30 years younger at cancer diagnosis than the general population. For anal cancer, median age at diagnosis was 42 in the AIDS group versus 64 in the general population (P < 0.001). For lung cancer median age at diagnosis was 49 with AIDS versus 68 in the general population (P < 0.001). For Hodgkin lymphoma, age at diagnosis was significantly older in the AIDS population (41 versus 35, P < 0.001).
But after statisticians accounted for the dramatically different age distribution in the two populations, differences in age at diagnosis became very small or disappeared. After that age-distribution adjustment, the NCI researchers confirmed slightly but significantly earlier age at diagnosis for Kaposi sarcoma, non-Hodgkin lymphoma, anal cancer, and lung cancer. Age at diagnosis of Hodgkin lymphoma was significantly older for people with AIDS.
The investigators suggest that earlier age at diagnosis of certain cancers in people with AIDS "may represent an effect of HIV on these cancers possibly by inducing loss of immune control of infection with oncogenic viruses." But behavioral factors could also be at play. For example, people with HIV may start smoking earlier than people in the general population, or they may start having sex at a younger age and thus heighten their risk of exposure to cancer-causing viruses. The study is limited in not being able to assess the impact of these and other cancer risk factors.
Older age at diagnosis of Hodgkin lymphoma in people with AIDS, the researchers say, "represents a strong increase in the risk of Epstein-Barr virus (EBV)-positive cases that occur at older ages, rather than a shift of EBV-negative cases to older ages.
"For most cancers," the NCI researchers conclude, "there is no difference in age at cancer diagnosis among persons with AIDS compared to the general population." Apparent age differences between those populations "arise largely due to differences in the underlying populations at risk of cancer."
References
1. Shiels M, Pfeiffer R, Engels E. Do people with AIDS develop cancer at younger ages than the general population? 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 757.
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