Módulo 2 – Curso pós-graduado – VIH e Envelhecimento

Non-AIDS Defining Cancers Among HIV Infected People

The epidemiology of non-AIDS defining cancers among HIV infected patients

Autor: Prof. Doutor Julian Falutz, MD, FRCP (McGill University Hospital Center, Montreal, Canada)

Changing epidemiology of cancer in effectively treated HIV patients

The incidence of the typical AIDS defining cancers (Kaposi Sarcoma, non-Hodgkin’s lymphoma) preceded the introduction of highly active antiretroviral therapy (HAART), although the relationship with older mono/bi antiretroviral regimes is uncertain13. Nevertheless, the overall standardized incidence ratio for AIDS-defining cancers (Kaposi sarcoma, primary central nervous system lymphoma, large cell B-cell lymphoma, non-Hodgkin’s lymphoma, cervical cancer) had a three-fold decrease after HAART compared to pre-HAART era. Conversely, the overall incidence ratio of NADCs, such as Hodgkin’s lymphoma (HL), anal cancer, lung cancer, head and neck tumors, prostate cancer and hepatocellular carcinoma, increased by three times.

The number and incidence of Kaposi sarcoma, the typical AIDS defining cancer, had decreased in the United States of America (USA) from 1991 until 200514. The same trend was found for non-Hodgkin’s lymphoma regardless of the histology (although there are some important differences among the histological subtypes). However, the incidence of cervical cancer remained stable after a decrease in the early 90’s, although the number of cases gradually increased14. This is actually reflective of a concern, because HIV population is increasing and cervical cancer is still occurring, i.e., it hasn’t decreased as much as the other AIDS-defining cancers.

When considering the NADCs, anal carcinoma has increased both in the number of new cases and in terms of incidence. The incidence of lung cancer had been slightly decreasing, although the number of cases has increased. Of notice, the prevalence of tobacco users is almost two times higher in HIV population than in the general population, and tobacco use is a risk factor for several NADCs15. The number of primary hepatoma cases has increased, although incidence remained relatively stable. The same features were observed for HL and colorectal cancer. However, the incidence and number of cases of prostate cancer in HIV patients has increased14.

Several factors may have contributed to the increase in the incidence of NADCs over the last 15 years. Two major ones are the increase in size of the HIV population and the increase in number of patients getting older. As people get older, there is an increase in cancer incidence. Tobacco is a strong risk factor, as well. Some risk of cancer may be increased in the setting of immunodeficiency and some suggest that HIV may increase the risk of cancer occurring at a younger age, though this is far from being settled. A higher exposure of HIV patients to oncogenic virus may also increase the risk of developing cancers, and some in vitro studies suggest that HIV itself may also be oncogenic.

However, comparison of cancer incidence ratios must account for differences in age distribution between the HIV/AIDS patients and general population, since the age distribution in HIV population is much narrower than in the usual comparative populations. In fact, there are two hypothetical scenarios. A given disease may occur more often in HIV patients vs. controls but at the same median age of presentation, or a given disease occurs more often in HIV patients vs. controls and at an earlier age16. Hence, the comparison of the incidence of a specific tumour in the HIV population to the general population must be performed for the same age distribution.

For instance, regarding anal cancer, it has been observed that there are more cases at an earlier age among HIV patients in the USA, 1996-2007, compared to the general population for the same age distribution16. The same findings were observed for lung cancer, with more cases among HIV patients than general population at the same age distribution. Regarding liver cancer, there are more cases occurring in HIV patients but at the same age as in the similarly age distributed general population. HL, however, occurs much more often in HIV patients than in the general population with the same age distribution, but it occurs later than in the general population. Prostate cancer, colon cancer and breast cancer are NADCs with fewer cases occurring in the HIV population than in the general population, but at the same age, when you control for age distribution.

In summary, when comparing the age at presentation of a particular tumour among HIV patients vs. the general population, it may seem that all NADCs are occurring at a younger age for HIV patients. However, after matching the expected number of cases for the same age distribution, anal and lung cancers seem to occur earlier, there is no difference in breast cancer and in melanoma, among others, but Hodgkin’s occurs at an older age in HIV patients compared to age matched population16. The increased rate of development of comorbidities, in regards to NADCs, suggests a state of accentuated rather than accelerated aging.

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