Kaposi's sarcoma occurring at higher CD4 counts

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Over a third of cases of Kaposi’s sarcoma now occur in patients with a CD4 cell count above 350 cells/mm3, investigators from the US military report in the online edition of AIDS.

The study found that although rates of the AIDS-defining cancer have fallen since effective antiretroviral therapy became available, the proportion of cases that occur at higher CD4 cell counts has increased.

“Clinicians should be aware of these trends and watchful for the occurrence of Kaposi’s sarcoma despite robust CD4 cell counts”, comment the investigators.

Glossary

Kaposi's sarcoma (KS)

Lesions on the skin and/or internal organs caused by abnormal growth of blood vessels.  In people living with HIV, Kaposi’s sarcoma is an AIDS-defining cancer.

hazard

Expresses the risk that, during one very short moment in time, a person will experience an event, given that they have not already done so.

hazard ratio

Comparing one group with another, expresses differences in the risk of something happening. A hazard ratio above 1 means the risk is higher in the group of interest; a hazard ratio below 1 means the risk is lower. Similar to ‘relative risk’.

relative risk

Comparing one group with another, expresses differences in the risk of something happening. For example, in comparison with group A, people in group B have a relative risk of 3 of being ill (they are three times as likely to get ill). A relative risk above 1 means the risk is higher in the group of interest; a relative risk below 1 means the risk is lower. 

AIDS defining condition

Any HIV-related illness included in the list of diagnostic criteria for AIDS, which in the presence of HIV infection result in an AIDS diagnosis. They include opportunistic infections and cancers that are life-threatening in a person with HIV.

Most cases of HIV-related Kaposi’s sarcoma occur when patients have a CD4 cell count below 200 cells/mm3. Although there is a large amount of evidence showing that rates of the cancer have decreased since effective antiretroviral therapy was introduced in the mid-1990s, it is not known whether Kaposi’s sarcoma will be seen at higher CD4 cell counts.

Therefore researchers from the US Military HIV Natural History Study reviewed the medical records of 5067 patients between 1985 and 2008.

Rates of the cancer were monitored in four time periods (1985-90; 1991-95; 1996-2001; 2002-2008). In addition, patients were divided according to whether their CD4 cell count was above or below 350 cells/mm3.

A total of 247 cases of Kaposi’s sarcoma were diagnosed. Compared with those seen between 1985-90, patients in the 2002-2008 time period had a 72% lower rate of the cancer (relative risk, 0.28; 95% CI, 0.16-0.47, p < 0.001).

In addition for each calendar period the investigators found that the rates of Kaposi’s sarcoma increased according to the amount of time patients spent with a CD4 cell count below 350 cells/mm3.

The investigators then looked at the CD4 cell counts of patients at the time their Kaposi’s sarcoma was diagnosed.

In 1985-90 a total of 18% of patients had a CD4 cell count above 350 cells/mm3 when their cancer was diagnosed. In 2002-2008 this had increased to 35%.

Analysis was then restricted to the 3422 patients who had received care after effective HIV therapy became available in 1996.

A total of 45 of these individuals developed Kaposi’s sarcoma.

Each 50 cell/mm3 increase in CD4 cell count reduced the risk of the cancer by 30%.

A CD4 cell count of less than 350 cells/mm3 (regardless of the use of HIV therapy) was associated with a significantly increased risk of Kaposi’s sarcoma (hazard ratio, 8.3; 95% CI, 3.4-20.2, p < 0.001).

“Our study demonstrates that although Kaposi’s sarcoma rates have declined during the HAART era and lower CD4 cell counts remain an important risk factor, a greater proportion of Kaposi’s sarcoma cases are now occurring at higher CD4 cell counts”, write the researchers.

Given these findings the investigators believe that it is important to see if starting HIV treatment at higher CD4 cell counts will reduce the risk of the cancer. “We found a suggestion of increased risk of Kaposi’s sarcoma among those not on HAART compared to those on HAART with CD4 cell counts of at least 350 cells/mm3”, they note.

References

Crum-Cianflone NF et al. Is Kaposi’s sarcoma occurring at higher CD4 cell counts over the course of the HIV epidemic? AIDS, advance online publication, September 4, 2010. DOI: 10. 1097/QAD.0b013e32833f9fb8. (Link to abstract and full-text article).