Age at cancer diagnosis among persons with AIDS in the United States

Abstract

Background: Studies have reported young ages at cancer diagnosis in HIV-infected persons and have suggested that HIV accelerates carcinogenesis. However, these comparisons did not account for differences in population age structures.

Objective: To compare ages at diagnosis for non-AIDS-defining types of cancer that occur in both the AIDS and general populations, after adjustment for differences in age and other demographic characteristics between these populations.

Design: Registry linkage study.

Setting: 15 HIV/AIDS and cancer registry databases in the United States.

Participants: 212 055 persons with AIDS enrolled in the U.S. HIV/AIDS Cancer Match Study from 1996 to 2007.

Measurements: Comparison of age-at-diagnosis distributions for various types of cancer in both the AIDS and general populations, after adjustment for age and other demographic characteristics.

Results: The proportion of person-time contributed by older persons (age ≥65 years) was far smaller in the AIDS population (1.5%) than in the general population (12.5%). Reflecting this difference, the ages at diagnosis for most types of cancer were approximately 20 years younger among persons with AIDS. However, after adjustment for differences in the populations at risk, the median ages at diagnosis in the AIDS and general populations did not differ for most types of cancer (for example, colon, prostate, or breast cancer; all P > 0.100). In contrast, ages at diagnosis of lung (median, 50 vs. 54 years) and anal cancer (median, 42 vs. 45 years) were significantly younger in persons with AIDS than expected in the general population (P < 0.001), and the age at diagnosis of Hodgkin lymphoma was significantly older (median, 42 vs. 40 years; P < 0.001).

Limitations: Information on other cancer risk factors, including cigarette smoking, was not available. Analysis was restricted to non-Hispanic white and black persons who had AIDS, which could limit the generalizability of the findings to other racial and ethnic groups or to persons with HIV but not AIDS.

Conclusion: For most types of cancer, the age at diagnosis is similar in the AIDS and general populations, after adjustment for the ages of the populations at risk. Modest age differences remained for a few types of cancer, which may indicate either acceleration of carcinogenesis by HIV or earlier exposure to cancer risk factors.

Primary funding source: National Cancer Institute.

Figure 1. Hypothetical examples of age distributions of cancers in the AIDS and general populations

The panels show hypothetical age-at-diagnosis distributions of cancers in the AIDS and general population if A) the risk of cancer is increased in the AIDS population, but the age distribution is the same; and B) the risk of cancer is increased in the AIDS population, and the age distribution is younger. The solid line represents the cases observed in the AIDS population. The dashed line represents cases expected in the general population, which are derived using indirect standardization, i.e., by applying general population rates to the accumulated person-time among people with AIDS, stratified by single years of attained age, sex, race, calendar year and registry. These expected cancers represent cases that would be seen in the general population if the general population had the same underlying demographic structure as the AIDS population. In addition to illustrating differences in age at onset, the curves provide information on relative risk for cancer in people with AIDS, because the ratio of the areas that they enclose is the standardized incidence ratio (observed cancers / expected cancers).

Figure 2. Age distribution of the AIDS and general populations (HIV/AIDS Cancer Match Study, 1996–2007)

The figure shows follow-up time at risk of cancer by age in the AIDS and general populations, for cancer regions covered by the HIV/AIDS Cancer Match Study (1996–2007). Black bars indicate the distribution for people with AIDS, and light bars indicate the distribution for the general population.

Figure 3. Age at cancer diagnosis among people with AIDS and the general population, U.S. (1996–2007)

Panels depict the age-at-diagnosis distributions for select non-AIDS-defining cancers. Points represent cancers observed among persons with AIDS. Smoothed curves show cancers observed in persons with AIDS (left axis), expected cancers in the general population (left axis) and observed cancers in the general population (right axis).