Study Discounts Premature Aging for Those With HIV

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By Michael Smith, North American Correspondent, MedPage Today
Published: October 04, 2010
Reviewed by Barry S. Zingman, MD; Professor of Clinical Medicine, Albert Einstein College of Medicine, Bronx, NY and
Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner    
Action Points 

    * Note that this study, which attempted to control for age when comparing cancer rates in those with AIDS versus the general population, found that most cancers did not occur earlier in people with AIDS.


    * Note that this study had significant limitations that effect the reliability and generalizability of the results, including lack of HIV positive/non-AIDS patients, and absence of Latinos with AIDS in the analysis.

The age at diagnosis of most types of cancer is some 20 years earlier for people with AIDS than in the general population, researchers said.

But after adjusting for the fact that there are fewer people 65 and older who have AIDS, the median ages of diagnosis for most non-AIDS defining cancers are much the same, according to Meredith Shiels, PhD, and colleagues at the National Cancer Institute.

The finding, from analysis of HIV/AIDS and cancer registries, is a count against the notion that people with HIV are vulnerable to what has been called premature aging, Shiels and colleagues argued in the Oct. 5 issue of Annals of Internal Medicine.

"Our results do not support including cancer as part of a general syndrome of premature aging in HIV-infected persons," they concluded.

The study is "an important stepping stone" in clarifying the debate, according to Jeffrey Martin, MD, and Paul Volberding, MD, both of the University of California San Francisco.

But, in an accompanying editorial, Martin and Volberding argued that premature aging might take several forms, while Shiels and colleagues tested only one -- that premature aging preferentially increases cancer risk at a younger age in those with AIDS.

Their analysis "cannot account for all elements of the premature aging debate," Martin and Volberding argued.

The reason that cancer is diagnosed earlier in people with HIV is that very few have been followed during older age, when most cases of cancer occur, Shiels and colleagues noted. In fact, the proportion of people with AIDS who are 65 and older is 1.5%, compared with 12.5% in the general population.

To see how that difference affected the observation of earlier non-AIDS defining cancers, the researchers looked at 212,055 people with AIDS enrolled in the U.S. HIV/AIDS Cancer Match Study from 1996 to 2007.

That study linked 15 HIV/AIDS and cancer registries in areas with a large HIV-infected population, such as San Francisco and New York City.

To compare rates, they estimated what the age at diagnosis among the general population would be if the general population were demographically similar to the AIDS population and calculated standardized incidence ratios in the two groups for a range of malignancies.

They found that, with few exceptions, standardized incidence ratios were not significantly different. For instance, the researchers reported, the median age at diagnosis for colon cancer was 52 in both groups.

The exceptions included:

    * Anal cancer, for which the median age of diagnosis among people with AIDS was 42, compared with 45 for the general population, a difference that was significant at P<0.001.
    * Lung cancer, median age of diagnosis among people with AIDS, 50; 54 for the general population (P<0.001)
    * Testicular cancer, median age of diagnosis 35 among people with AIDS, 38 for the general population (P<0.018)
    * Hodgkin lymphoma, for which, on the other hand, median age of diagnosis was older among people with AIDS, at 42 versus 40 in the general population, a difference that was significant at P<0.001.

The study did not have information on many cancer risk factors, including cigarette smoking, which might have affected the results, Shiels and colleagues noted.

Also, they reported, the analysis was restricted to non-Hispanic white and black people with AIDS, which could affect the applicability of the findings to other groups or to people with HIV but not AIDS.

The lack of data on risk factors is a central limitation to all studies of this type, Martin and Volberding argued in the editorial, and to account for such confounding factors requires very well-characterized patients.

"Unfortunately, because of the relative rarity of cancer and the need for large sample sizes, it is very uncommon to have study populations that are both sufficiently large and well characterized," they noted. In particular, the study population Shield and colleagues analyzed -- although large -- doesn't have the necessary level of detail, they argued.