French Scientists Note Change in Rates of Some Cancers Unrelated to AIDS
September 9, 2014
From Canadian AIDS Treatment Information Exchange
The profoundly beneficial effects of modern anti-HIV combination therapy (commonly called ART or HAART) have helped to rescue the immune systems of many HIV-positive people. In Canada and other high-income countries where access to ART is generally subsidized by health authorities, rates of AIDS-related infections and cancers have declined dramatically. As HIV-positive people can now live longer because of ART, health complications unrelated to AIDS are becoming more of an issue. One of these complications is cancer.
Researchers from across France have cooperated in collecting health-related information from HIV-positive people for a project called the French Hospital Database (FHDB). This database was started in 1989. The comprehensive data collected enables researchers to draw well-balanced conclusions.
In the latest analysis of leading non-AIDS-defining cancers from the FHDB, researchers analysed data drawn from more than 84,000 HIV-positive people, collected between 1997 and 2009, and compared these findings to results from HIV-negative people in France. They found that among HIV-positive people, the overall risk of lung and anal cancers fell over the course of the study. In this same population, rates of Hodgkin's lymphoma and liver cancer remained stable. Among HIV-positive participants whose CD4+ cell counts rose and stayed above the 500 cell/mm3 mark, the risk for lung cancer was similar to that of the HIV-negative people. However, among HIV-positive people generally, the risk for cancers remained elevated compared to the risk among HIV-negative people.
The FHDB researchers focussed on cancers for which they had data from more than 200 HIV-positive people. Those cancers included the following:
- anal cancer
- lung cancer
- Hodgkin's lymphoma
- liver cancer
The researchers did not explore cancers that were less common because they would not have had the statistical power to draw meaningful conclusions.
In total, data from 58,525 HIV-positive men and 25,979 HIV-positive women, collected over the course of about seven years, were analysed. Most participants were between the ages of 30 and 50 years.
For information about cancer rates among HIV-negative people, researchers used data collected from France's network of cancer registries, called FRANCIM.
Results -- Number of Cancer Diagnoses
The cancers diagnosed during the course of the study were distributed as followed:
- anal cancer: 525 cases
- Hodgkin's lymphoma: 433 cases
- lung cancer: 763 cases
- liver cancer: 535 cases
Results -- Trends in New Cancer Diagnoses
- Lung cancer
Overall, rates of new cases of lung cancer fell significantly among men regardless of their HIV status. In contrast, rates of lung cancer rose among HIV-negative women and remained stable among HIV-positive women.
- Hodgkin's lymphoma
Rates of this cancer rose among HIV-negative people. However, it remained relatively stable among HIV-positive people.
- Liver cancer
Rates of liver cancer rose among men regardless of their HIV status. Among HIV-positive women, rates of liver cancer increased three-fold while among HIV-negative women the increase was very slight.
- Anal cancer
Rates of anal cancer did not change among HIV-positive or HIV-negative men. In contrast, rates of anal cancer rose significantly among both HIV-positive and HIV-negative women.
Although the incidence of some cancers changed over the course of the study, French scientists found that, in general the relative risk for all four cancers studied remained significantly higher in HIV-positive people compared to HIV-negative people.
For instance, the overall risk of lung cancer fell, but remained about six-fold greater in HIV-positive women and three-fold greater among HIV-positive men than among HIV-negative women and men, respectively.
The Importance of CD4+ Cell Counts
Among participants who were taking ART and whose CD4+ counts rose above and stayed above the 500 cell mark for at least two years, the rates of lung cancer were close to those seen among HIV-negative people. However, the rate of Hodgkin's lymphoma was nine times higher and the rate of liver cancer was twice as high as the rates among HIV-negative people.
HIV, Aging and Cancer -- Is There a Link?
Taking into account gender, age and HIV status, researchers found that HIV-positive people were diagnosed earlier with some cancers than HIV-negative people:
- lung cancer: HIV-positive people seemed to be diagnosed with this cancer about three years earlier
- liver cancer: HIV-positive people co-infected with hepatitis B virus (HBV) or hepatitis C virus (HCV) seemed to be diagnosed with liver cancer 11 years earlier
These differences were statistically significant. However, comparing HIV-positive to HIV-negative people there was no significant difference in the age at which the following cancers were diagnosed:
- Hodgkin's lymphoma
- anal cancer
In the case of liver cancer, it is likely that immune dysfunction caused by HIV does accelerate the course of that cancer. In the case of lung cancer, the relatively high rates of smoking tobacco among HIV-positive people may play a role in their greater risk for lung cancer. The researchers concluded that the overall earlier occurrence of these cancers was not likely the result of accelerated aging in HIV-positive people.
Why the Elevated Risks?
HIV infection is associated with a marked increase in activation and inflammation in the immune system. As cells of the immune system are distributed throughout the body and within different organ systems, HIV-related inflammation affects the whole body.
ART greatly decreases HIV-related inflammation, but cannot eliminate it. Some researchers have proposed that excess HIV-associated inflammation may increase the risk of cancer. However, it is noteworthy that so far, there has not been an overall increased risk for all forms of cancer in HIV-positive people. Most of the cancers that are relatively common in this population are caused by exposure to toxins (tobacco smoke) or specific viruses (more about these viruses later) that are transmitted by sex or by sharing equipment for substance use or, in the case of some people, through exposure to contaminated blood and blood products before measures were taken to significantly improve the safety of the blood supply.
No comments have been made.