Patients with HIV infection and successful long-term antiretroviral therapy may have lower rates of cancer, especially types considered AIDS-defining, a new study suggests.
Researchers from the Department of Veterans Affairs performed a retrospective cohort study of HIV-positive veterans and demographically matched veterans from 1999 to 2015 to examine the potential association between viral suppression and decreased cancer risk. The study's primary outcome measures were standardized cancer incidence rates and Poisson regression rate ratios (RRs) according to viral suppression status.
Viral suppression was defined as an HIV RNA level below 500 copies/mL. Patients were considered to have unsuppressed viral loads if they had person-time with HIV RNA levels at 500 copies/mL or greater, early suppression if they spent the initial two years of antiretroviral treatment with HIV RNA levels below 500 copies/mL, and long-term suppression if suppression continued beyond two years. AIDS-defining cancer included Kaposi sarcoma, non-Hodgkin lymphoma, and invasive cervical cancer. The study results were published June 12 by Annals of Internal Medicine.
Overall, 42,441 HIV-positive veterans and 104,712 demographically matched veterans without HIV infection were included in the study. In the HIV-positive group, 3,821 people developed 4,169 cases of cancer, and of these, 616 were AIDS-defining, 817 were non-AIDS-defining cancer caused by viruses, 2,683 were nonvirus, non-AIDS-defining cancer, and 53 were poorly specified. In the group without HIV infection, 7,163 people developed 7,879 cases of cancer, with 223 considered AIDS-defining, 715 considered non-AIDS-defining cancer caused by viruses, 6,850 considered nonvirus, non-AIDS-defining, and 91 considered poorly specified.
Compared to those without HIV infection, patients with HIV infection and unsuppressed viral loads had the greatest increase in cancer incidence (RR, 2.35; 95% CI, 2.19 to 2.51). In patients with early suppression and long-term suppression, the RRs were 1.99 (95% CI, 1.87 to 2.12) and 1.52 (95% CI, 1.44 to 1.61). The trend toward decreased incidence with increased suppression was strongest for AIDS-defining cancer, weaker for non-AIDS-defining cancer caused by viruses, and not present for non-AIDS-defining cancer not caused by viruses.
The researchers noted that their study estimated time-updated HIV RNA levels, did not take each patient's entire history of viral suppression into account, and did not include many women, among other limitations. However, they concluded that antiretroviral therapy leading to long-term viral suppression may help prevent cancer, especially types considered AIDS-defining.
“Our findings suggest that early, sustained ART, which results in long-term viral suppression, may contribute to cancer prevention, with a marked risk in reduction for [AIDS-defining cancer], a much more modest reduction for virus [non-AIDS-defining cancer], and possible reductions for certain types of nonvirus [non-AIDS-defining cancer],” the authors wrote. “However, excess cancer risk remained among patients with long-term suppression.”
The authors called for future research to more closely examine lower viral suppression thresholds, as well as whether cancer risk decreases with longer-term viral suppression and the potential role of CD4+ cell count and CD4+-CD8+ cell count ratio.