Continuing declines in some but not all HIV-associated cancers in Australia after widespread use of antiretroviral therapy

Abstract

Objective: To describe changes in cancer incidence in people with HIV in Australia since the introduction of highly active antiretroviral therapy (HAART).

Design: Population-based, retrospective cohort study of people with HIV (n = 20 232) using data linkage between national registers of HIV/AIDS and cancer in 1982-2004.

Methods: Age-adjusted and sex-adjusted incidence rate ratios with 95% confidence intervals were calculated to compare site-specific cancer incidence during the early (1996-1999) and late (2000-2004) HAART periods with that prior to HAART (1982-1995). Five-year age-specific, sex-specific, calendar year-specific, and state-specific standardized incidence ratios with 95% confidence interval were also calculated for each period.

Results: Incidence of Kaposi sarcoma and non-Hodgkin lymphoma declined significantly (Ptrend < 0.001). Incidence of Hodgkin lymphoma was significantly higher during the early-HAART period (incidence rate ratio 2.34, 95% confidence interval 1.19-4.63) but declined thereafter (Pdiff = 0.014). Incidence of anal cancer was unchanged (Ptrend = 0.451) and remained raised more than 30-fold. Incidence declined significantly for melanoma (Ptrend = 0.041) and prostate cancer (Ptrend = 0.026), and, during the late-HAART period, was lower than in the general population for both cancers. Incidence of colorectal cancer was consistently lower than in the general population.

Conclusion: Incidence of Kaposi sarcoma and non-Hodgkin lymphoma has continued to decline among people with HIV in Australia, though it remains very substantially elevated. Incidence of Hodgkin lymphoma may now also be declining. Incidence of anal cancer has remained stable, and it is now the third most common cancer in HIV-infected Australians. Reasons for the reduced incidence of colorectal and prostate cancer, and more recently of melanoma, are unclear.