Objective: HIV-infected people have elevated risk for some cancers. Changing incidence of these cancers over time may reflect changes in three factors: HIV population demographic structure (e.g. age distribution), general population (background) cancer rates, and HIV-associated relative risks. We assessed the contributions of these factors to time trends for 10 cancers during 1996-2010.
Design: Population-based registry linkage study.
Methods: We applied Poisson models to data from the U.S. HIV/AIDS Cancer Match Study to estimate annual percentage changes (APCs) in incidence rates of AIDS-defining cancers [ADCs: Kaposi sarcoma, non-Hodgkin lymphoma (NHL), and cervical cancer] and seven non-AIDS-defining cancers (NADCs). We evaluated HIV-infected cancer trends with and without adjustment for demographics, trends in background rates, and trends in standardized incidence ratios (SIRs, to capture relative risk).
Results: Cancer rates among HIV-infected people rose over time for anal (APC 3.8%), liver (8.5%), and prostate (9.8%) cancers, but declined for Kaposi sarcoma (1996-2000: -29.3%; 2000-2010: -7.8%), NHL (1996-2003: -15.7%; 2003-2010: -5.5%), cervical cancer (-11.1%), Hodgkin lymphoma (-4.0%), and lung cancer (-2.8%). Breast and colorectal cancer incidence did not change over time. Based on comparison to adjusted models, changing demographics contributed to trends for Kaposi sarcoma and breast, colorectal, liver, lung, and prostate cancers (all P < 0.01). Trends in background rates were notable for liver (APC 5.6%) and lung (-3.2%) cancers. SIRs declined for ADCs, Hodgkin lymphoma (APC -3.2%), and lung cancer (-4.4%).
Conclusion: Demographic shifts influenced several cancer trends among HIV-infected individuals. Falling relative risks largely explained ADC declines, while background incidence contributed to some NADC trends.