MONTREAL — Although the rates of AIDS-defining cancers have declined significantly among people with HIV infection since the advent of antiretroviral therapy, the rates of non-AIDS-defining cancers—particularly those associated with an underlying infectious pathogen—continue to be significantly higher than those observed in the HIV-negative population.
At the 16th Conference on Retroviruses and Opportunistic Infections, Michael J. Silverberg, Ph.D., of Kaiser Permanente in Oakland, Calif., presented findings from a retrospective cohort study comparing the incidence of non-AIDS-defining cancers (cancers other than Kaposi's sarcoma, non-Hodgkin's lymphoma, and cervical cancer) in HIV-positive and HIV-negative persons during 1996–2006. With the use of data from the managed health program, Dr. Silverberg and colleagues identified 18,890 HIV-positive patients and 189,804 age-, sex-, and year-matched HIV-negative patients and followed the cohort members from first enrollment after Jan. 1, 1996.
From Surveillance, Epidemiology, and End Results program-based Kaiser Permanent cancer registries, the investigators identified incident, non-AIDS-defining cancers in the study population and grouped the cancers as infection related (anal, head and neck, liver, Hodgkins lymphoma, and others) or infection unrelated. In the HIV-positive population, there were 482 reports of non-AIDS-defining cancers, including 220 that were infection related and 269 that were not related to infection; seven patients had both. In comparison, 3,065 non-AIDS-defining cancers were identified in the HIV-negative population, including 398 infection related and 2,698 infection unrelated (31 had both), Dr. Silverberg said.
Calculated per 10,000 person-years, the rate of infection-related, non-AIDS-defining cancers was nearly seven times greater among the HIV-positive group, at 29.7, compared with 4.4 in the HIV-negative group, Dr. Silverberg stated, noting also that the age- and sex-adjusted relative risks “did not change over time.” Specifically, the relative risks for the periods of 1996–1999, 2000–2003, and 2004–2006, were 6.4, 7.6, and 6.2, respectively. In terms of specific infection-related cancers, the significant relative risks for anal cancer, Hodgkin's lymphoma, head and neck cancer, and gynecologic cancer were 81.4, 17.4, 2.1, and 2.9, respectively, he said.
Despite the increased risk, compared with HIV-negative individuals, “the risk of developing an infection-related non-AIDS-defining cancer did drop by approximately 4% [between 1996 and 2006],” Dr. Silverberg said. The risk of anal cancer in particular decreased in the HIV-positive population by about 6% per year, he said. During the same period, the risk of infection-related cancer remained constant among HIV-negative individuals.
With respect to infection-unrelated non-AIDS-defining cancers, the incidence rates per 10,000 person-years were 36.4 and 30.6 for the HIV-positive and HIV-negative groups, respectively, Dr. Silverberg noted. The only significant rate ratio was that observed for the 2004–2006 period, at 1.3, he said. Significant cancer-specific rate ratios were observed for kidney cancer, lung cancer, melanoma, and prostate cancer at 1.8, 1.7, 1.7, and 0.7, respectively.
The study findings may not be generalizable to women because nearly three-quarters of the cancer cases identified through the registry were men who have sex with men, Dr. Silverberg noted. Additionally, because the study data came from a managed care database, the findings may not be generalizable to uninsured persons, he said.
The conference was sponsored by the Foundation for Retrovirology and Human Health and the Centers for Disease Control and Prevention.
Dr. Silverberg reported no potential conflicts of interest.
The cancers were nearly seven times more likely among the HIV-positive group compared with the HIV-negative group. DR. SILVERBERG