The risk of several cancers increases with age for older HIV-positive people, investigators from the United States report in Clinical Infectious Diseases. HIV-positive individuals aged 50 and over had a significantly higher incidence of numerous cancers, including several not normally considered HIV-related.
Although the incidence of some of these malignancies declined with age, the absolute risk of anal, lung, liver, and oral/throat cancers increased as people with HIV got older. Cancer risk was highest within five years of HIV diagnosis, underlining the importance of prompt detection and treatment of HIV.
The investigators found that ageing in itself did not result in a greater increase in the risk of cancer for people with HIV compared to the general population, suggesting that the higher prevalence of risk factors such as smoking, alcohol consumption and cancer-causing viral infections is responsible for the increased risk of some cancers in older people with HIV.
“We observed that cancer risk was elevated in older PLWH [people living with HIV] compared to the general population, though the relative risk of most cancers declined with age,” comment the authors. “However, EARs [excess absolute risks], which measure absolute risk and thus reflect the number of excess cancers occurring among PLWH, increased with age for some NADCs [non-AIDS-defining cancers].”
The development of effective and safe antiretroviral therapy means that most people with HIV can now expect to live well into older age. The diseases of ageing – including certain cancers – are now an important cause of serious illness and death among people with HIV.
As well as the general ageing process, several factors contribute to the increased cancer risk seen in older people with HIV, including HIV-related immune suppression, co-infection with cancer-causing viruses and lifestyle factors, especially smoking.
Investigators from the United States wanted to measure cancer risk among HIV-positive people aged 50 and above. They therefore designed a study comparing cancer risk between people with HIV and individuals in the United States general population.
Both AIDS-defining (Kaposi's sarcoma, non-Hodgkin lymphoma, cervical) cancers and non-AIDS-defining (anal, lung, liver, oral/throat, breast, prostate and colon) cancers were included in the analysis.
The researchers first compared cancer incidence rates between people with HIV and the general population by calculating standardised incidence ratios (SIRs), a measure of relative risk that takes into account the relative distributions in the population of people of differing ages. They also calculated EARs, or the excess risk of developing cancer for a person with HIV.
Cancer risks in people with HIV were calculated according to age (50-59, 60-69, 70 or older), AIDS diagnosis and time since HIV diagnosis.
The study population consisted of 183,542 people enrolled in the HIV/AIDS Cancer Match study. These people received care between the introduction of effective HIV treatment in 1996 and 2012 and contributed a total of 928,194 person-years of follow-up. During this time, there were 10,371 cancer diagnoses, of which 16% were AIDS-related and 84% non-AIDS-related.
The incidence of all three AIDS-defining cancers was significantly higher among people with HIV compared to the general population (Kaposi's sarcoma, SIR = 103.34; non-Hodgkin lymphoma, SIR = 3.05; cervical cancer, SIR = 2.02). Rates of several non-HIV-related cancers were also elevated among people with HIV, including cancers of the anus (SIR = 14), liver (SIR = 2.91), lung (SIR = 1.71) and mouth/throat (SIR = 1.66). In contrast, people with HIV had a reduced relative risk of cancers of the breast (SIR = 0.61), prostate (SIR = 0.47) and colon (SIR = 0.63).
The relative risks for almost all cancers were highest for the youngest people and decreased with age. If ageing led to a higher risk of cancer in people with HIV compared to the general population, the reverse would be true.
The absolute risk for all three AIDS-defining cancers and Hodgkin lymphoma also decreased with age. However, the absolute risk increased with age for cancers of the anus, lung, liver and mouth/throat.
A previous AIDS diagnosis was associated with an increased risk of the two main AIDS-defining cancers, Kaposi's sarcoma, non-Hodgkin lymphoma, and also Hodgkin lymphoma, anal, lung and oral/throat cancers (aIRRs ranging from 1.37-2.66).
Rates of most cancers were highest within the first five years after HIV diagnosis and then gradually decreased with time. Significant decreasing trends were observed for Kaposi's sarcoma (p < 0.0001), non-Hodgkin lymphoma (p < 0.0001), lung cancer (p = 0.0002), breast cancer (p = 0.02) and Hodgkin lymphoma (p = 0.04).
In contrast, there was some indication of risk increasing with time since HIV diagnosis for anal and liver cancers, though the trends were of borderline significance.
“There is continued need for cancer prevention and early detection among older PLWH,” conclude the researchers. “Cancer risk was…highest within the first 5 years after HIV diagnosis for most cancers, underscoring the importance of early HIV diagnosis, rapid initiation of HAART after HIV diagnosis, and interventions to reduce traditional risk factors in older PLWH.”