Results from a recent review confirm that HIV-positive adults are at a higher risk for developing cancer than the general population. In particular, people with HIV are about four times more likely to develop cancer than people without HIV and are slightly more likely to develop cancer than people who have had an organ transplant.

The study authors suggested that a weakened immune system underlies the increased cancer rate.

“Our findings show that there is a need for prevention and early diagnosis of cancers related to infectious agents (such as cervical cancer, Kaposi’s sarcoma, lymphoma, gastric carcinoma) in the HIV-infected population, because they are of higher incidence, especially in individuals with CD4 counts below 500,” said Dr. Ana Katherine da Silveira Gonçalves of the Universidade Federal do Rio Grande do Norte in Brazil, and lead author of the study.

“In addition, these patients should see their doctor at shorter intervals than those recommended for uninfected people, in order to detect early lesions that can turn into cancer more quickly, since low immunity favors tumor growth,” she added.

Dr. Joel Palefsky, a professor of medicine at the University of California, San Francisco, who was not affiliated with the study, agreed that people with HIV will need to watch for cancer. “As people with HIV live longer, [these results] mean that they will need to be monitored for other potential causes of morbidity and mortality, such as various cancers,” said Dr. Palefsky.

Dr. Palefsky noted that HIV-positive people with a low nadir CD4 count (the lowest CD4 (white blood cell) count measured after HIV infection) before antiretroviral therapy may suffer more immune damage than transplant recipients, leading to increased cancer susceptibility.

According to the authors of the study, the results could be useful in designing strategies for cancer prevention or early detection in people with HIV. “An effective strategy would be to recommend that the patients undergo preventive exams more frequently than non-HIV/transplant populations. These exams are low-cost and highly effective at detecting cancer precursor lesions and carcinomas in this specific population,” said Dr. Gonçalves.

Dr. Palefsky also recommended several steps for people with HIV that might help with cancer prevention and detection. “I would advise all HIV-positive people to stop smoking if possible. I also believe that everyone should have an annual digital ano-rectal exam to feel for lumps that could indicate the presence of anal cancer,” he said.

Previous studies have shown that, in addition to its role in fighting infections, the immune system also identifies and kills cancer cells. People with decreased immunity therefore have an increased risk of developing cancer.

Previous studies have also shown that people with HIV are more prone to certain cancers, such as anal cancer, Hodgkin’s lymphoma, and others (see related AIDS Beacon news). In some cases researchers believe this is related to decreased immune function in people with HIV.

Several studies have compared the risk of developing cancer in HIV patients (see related AIDS Beacon news) or transplant recipients to the general population. Transplant patients also have a weak immune system, since they are treated with drugs that suppress the immune system to prevent rejection of the transplanted organ.

In this study, researchers reviewed data from several such previous studies to evaluate the rate of cancer in HIV-positive people and transplant recipients, in order to see what role decreased immunity might play in cancer development in these populations. They also investigated whether particular types of cancer occur more frequently in either group, with the goal of helping to guide strategies for decreasing any cancers specifically related to immune suppression.

Nineteen studies of cancer rates in HIV patients, and six studies in transplant recipients (primarily kidney transplant patients), were included in the analysis.

Results showed that people with HIV were four times as likely as the general population to develop cancer. Transplant recipients were over three times as likely to develop cancer.

According to the study authors, infectious agents such as the Epstein-Barr virus trigger some types of cancer. In particular, Kaposi’s sarcoma, Hodgkin’s lymphoma, and some liver, stomach, anal, and oral cancers are thought to be related to infectious agents.

Results showed that infectious agent-related cancers were particularly increased in HIV patients and transplant recipients. For instance, infection by the bacterium Helicobacter pylori is strongly associated with the development of stomach cancer. The results showed that the rates of stomach cancer were doubled in HIV-positive people and transplant recipients as compared to the general population.

The authors suggested that decreased immunity in these two groups of people may result in increased exposure to infectious agents, and therefore increased rates of such cancers.

Other cancers, such as those of the colon, rectum, breast, ovary, and prostate, were not increased in either population.

Some cancers occurred more frequently in one group, but not the other. Kidney and thyroid cancers occurred at increased rates in transplant recipients, but not people with HIV. Brain cancer occurred at increased rates in people with HIV, but not transplant patients.

The researchers noted that the reasons for the differences are currently unknown, but speculated that they were due to differences in lifestyle.

For more information, please see the study in the journal Cancer Epidemiology (abstract).