HIV infection independently heightened risk of several cancers, including non-AIDS cancers, in U.S. patients 65 or older, according to a case-cohort analysis by National Cancer Institute (NCI) researchers.
Old age and HIV infection are both associated with heightened cancer risk, but the combined impact of aging and HIV is not well described. To address that question, NCI investigators conducted a case-cohort study including all cancer patients in SEER-Medicare, which links 17 cancer registries across the United States and covered about 9.4 million Medicare enrollees in 2004-2011. Medicare is the U.S. national health insurance plan for people 65 and older. SEER-Medicare includes Medicare claims for all linked SEER patients with cancer and for a random 5% of the entire Medicare population living in SEER areas. The case-cohort analysis included this 5% subcohort and everyone with cancer in the SEER-Medicare population in 2004-2011.
The NCI researchers identified HIV patients through Medicare claims. They calculated cancer incidence among HIV-positive and HIV-negative people. In the HIV group they estimated five-year cumulative cancer incidence in an analysis accounting for the competing risk of death. To estimate the association between HIV and cancer incidence, the NCI team used weighted Cox regression adjusted for sex, age, race and calendar year.
The 5% subcohort included 469,954 people 65 or older using Medicare in 2004-2011, and 41,604 in this group (8.9%) had a cancer diagnosis. There were 361 HIV-positive people (0.08%) in the subcohort. Compared with HIV-negative people in the subcohort, those with HIV were more likely to be men (73% versus 42%), to be black (36% versus 9%), to be younger (median 66 versus 70 years) and to die during follow-up (28% versus 23%).
Among the 653 cancers diagnosed in people with HIV, 598 (92%) were non-AIDS cancers. One in 10 HIV-positive people over 65 got diagnosed with cancer every five years (five-year cumulative incidence 10.1%). For individual cancers, five-year cumulative incidence in the HIV group was 2.2% for lung cancer, 1.9% for prostate cancer, 0.9% for colorectal cancer, 0.8% for non-Hodgkin lymphoma and 0.6% for anal cancer.
Compared with HIV-negative people 65 or older, the elderly HIV group ran more than a 50% higher overall cancer risk (adjusted hazard ratio [aHR] 1.52, 95% confidence interval [CI] 1.32 to 1.75). Elderly people with HIV had a higher risk of getting diagnosed with Kaposi sarcoma (aHR 94.4, 95% CI 54.6 to 163)), anal cancer (aHR 34.2, 95% CI 23.9 to 49.0), Hodgkin lymphoma (aHR 6.30, 95% CI 2.79 to 14.3), liver cancer (aHR 3.35, 95% CI 2.21 to 5.07), non-Hodgkin lymphoma (aHR 2.55, 95% CI 1.91 to 3.39), oral cavity/pharyngeal cancer (aHR 1.79, 95% CI 1.11 to 2.90) and lung cancer (aHR 1.61, 95% CI 1.31 to 1.98). The HIV group had more than a 20% lower chance of prostate cancer (aHR 0.78, 95% CI 0.63 to 0.98). HIV was not associated with incidence of breast cancer or localized or distant colorectal cancer but was associated with a 70% higher incidence of regional-stage colorectal cancer (aHR 1.70, 95% CI 1.12 to 2.58).
The researchers conclude that overall cancer incidence is 50% higher in HIV-positive people 65 and older than in HIV-negative people the same age. Absolute cancer risk in HIV-positive elderly people, they note, "is sizeable, reflecting effects of both HIV and aging." Pointing to the high overall incidence of lung cancer, the NCI team proposes that "the elderly HIV population might particularly benefit from lung cancer screening with low-dose computed tomography."