Since the appearance of AIDS in the early 1980s, the United States military has been collecting health-related information on affected personnel and their family members. So far, data on nearly 4,500 HIV positive people has been collected. Analyses of this data set can be a powerful tool to better understand changes in HIV-related conditions over several decades.
Recently, military medical personnel used this data set to investigate trends in cancers and found a significant shift in the type of cancers over time. The implications of their findings are discussed later in this report.
Researchers focused their analysis on the period spanning 1984 and 2007. Here is the average profile of participants at the time they were diagnosed with HIV infection:
- 9% female, 91% male
- age -- 28 years
- ethno-racial background: 45% Black, 44% White, 11% from other groups
- CD4+ count -- 510 cells
- 24% developed an AIDS-related infection during the study
- most participants were part of the study for seven years
Over a 20-year span, about 10% of the group, or 446 people, developed cancer. Most of the cancers (68%) occurred before 1996 and were related to AIDS (Kaposi's sarcoma and so on). In general, AIDS-related cancers became less common after 2001. Indeed, rates of cancers unrelated to AIDS have significantly increased in the present era compared to the time before HAART, as outlined below:
- Before 1996, 20% of cancers were unrelated to AIDS.
- Between 1996 and 2000, 30% of cancers were unrelated to AIDS.
- After 2001, 71% of cancers were unrelated to AIDS.
Cancers that were unrelated to AIDS and that occurred during the study were as follows:
- skin cancer -- 63 cases
- anal cancer -- 16 cases
- Hodgkin's disease (a cancer of the immune system) -- 14 cases
- prostate cancer -- 8 cases
- kidney cancer -- 7 cases
Of these cancers, only anal cancer rates increased in a statistically significant manner between 1984 and 2007.
Overall, the study team calculated that the risk of cancers unrelated to AIDS was twice as high in HIV positive people compared to healthy HIV negative people. Anal cancer was 13 times more common in HIV positive men than in HIV negative men of a similar age.
The military researchers noted that the older a person was in this study, the greater his or her risk for developing cancer. This makes sense because people's immune systems slowly degrade with age. Another finding was that Black people were less likely to develop skin cancer than White people.
There did not seem to be any relation between CD4+ counts and the risk of developing cancers unrelated to AIDS.
During the study about 34% of participants died. Among people who experienced non-AIDS-related cancer, 40% died. For people with these cancers, the following proportions died a certain time after their cancer was diagnosed:
- one year after diagnosis -- 15% were dead
- three years after diagnosis -- 29% were dead
- five years after diagnosis -- 41% were dead
Survival was generally better in participants who developed AIDS-related cancers.
Why the Increase in Certain Cancers?
There may be many reasons for the increase in cancers unrelated to AIDS, as follows:
- Now that life-threatening infections are not killing large numbers of HIV positive people, their survival has been extended. This provides more time for slow-growing tumours to flourish.
- In general, as people age, their immune systems become weaker. So perhaps ageing places HIV positive people at increased risk for more commonplace cancers.
- The microbes that are linked to tumour formation (human papillomavirus, viruses of the herpes family, and perhaps other emerging viruses) are sexually transmitted and commonly found in HIV positive people. Perhaps a certain minimal level of immunity is needed to suppress the tumour-promoting effects of these viruses. And because HAART does not fully restore the immune system's competence, cancers can form more easily.
- Some HIV positive people may have a higher-than-usual exposure to cancer-causing substances, such as tobacco smoke. Other researchers have unexpectedly found that many carcinogenic compounds from tobacco smoke accumulate in the wet tissues of the mucosa in the genitals. This latter finding might explain the persistent link between tobacco use and cervical cancer. It is also possible that smoking tobacco might increase the risk of other cancers such as anal cancer.
Steps to Safety
It is noteworthy that many of the cancers (nearly 80%) unrelated to AIDS in this study occurred when CD4+ counts were above the 350-cell level. This finding suggests that in addition to HAART other steps are needed to help protect HIV positive people from these cancers. Such steps might include the following:
- getting help and support for quitting tobacco
- practising safer sex to reduce exposure to more sexually transmitted cancer-causing viruses
- getting tested and vaccinated against hepatitis B virus
- getting tested for exposure to hepatitis C virus
- considering treatment options for hepatitis B or C viruses if co-infected
- requesting a referral for anal cancer screening (where available)
- having a dermatologist check for any unusual skin growths
Some Good News
Although long-term HIV infection is increasingly associated with a heightened risk for certain cancers, the actual number of people developing such cancers is relatively small. And, as more research is done on cancers unrelated to AIDS, perhaps more ways of preventing these cancers will become available.
Next up in CATIE News: a British study on cancer uncovers a surprising and potentially disturbing trend.
- Crum-Cianflone N, Hullsiek KH, Marconi V, et al. Trends in the incidence of cancers among HIV-infected persons and the impact of antiretroviral therapy: a 20-year cohort study. AIDS. 2009 Jan 2;23(1):41-50.
- Bonnet F and Chêne G. Evolving emidemiology of malignancies in HIV. Current Opinion in Oncology. 2008 Sep;20(5):534-40.