How is Kaposi sarcoma staged?
For many types of cancer, the stage is a description of how far the cancer has spread, based on the results of physical exams, biopsies, and imaging or other tests (see “How is Kaposi sarcoma diagnosed?”). The stage of a cancer is often one of the most important factors in selecting treatment options and predicting a patient’s survival outlook.
The results of the staging process are usually described in a standard way, using a staging system. Staging systems for most other types of cancer are based on the size of the primary tumor (the first one to develop) and how far the cancer has spread from there. But for people with AIDS-related Kaposi sarcoma (KS), the most common type in the United States, the outlook is influenced at least as much by the presence of other AIDS-related problems as it is by the spread of KS. For this reason, staging of KS also considers factors such as how much the immune system is damaged and the presence of AIDS-related infections.
There is no officially accepted system for staging KS like there is for most other forms of cancer. But for AIDS-related KS, most doctors use the AIDS Clinical Trials Group system.
The AIDS Clinical Trial Group system
The AIDS Clinical Trials Group (ACTG) system for AIDS-related KS considers 3 factors:
- The extent of the tumor (T)
- The status of the immune system (I), as measured by the number of certain immune cells (CD4 cells) present in the blood
- The extent of involvement within the body or systemic illness (S)
Under each major heading, there are 2 subgroups: either a 0 (good risk) or a 1 (poor risk). The following are the possible staging groups under this system:
T (tumor) status
T0 (good risk): Localized tumor
KS is only in the skin and/or the lymph nodes (bean-sized collections of immune cells throughout the body), and/or there is only a small amount of disease on the palate (roof of the mouth). The KS lesions in the mouth are flat rather than raised.
T1 (poor risk): The KS lesions are widespread. One or more of the following is present:
- Edema (swelling) or ulceration (breaks in the skin) due to the tumor
- Extensive oral KS: lesions that are nodular (raised) and/or lesions in areas of the mouth besides the palate (roof of the mouth)
- Lesions of KS are in organs other than lymph nodes (such as the lungs, the intestine, the liver, etc.). Kaposi sarcoma in the lungs is a particularly bad sign.
I (immune system) status
The immune status is assessed using a blood test known as the CD4 count, which measures the number of white blood cells called helper T cells.
I0 (good risk): CD4 cell count is 150 or more cells per cubic mm (mm3).
I1 (poor risk): CD4 cell count is lower than 150 cells per mm3.
S (systemic illness) status
S0 (good risk): No systemic illness present; all of the following are true:
No history of opportunistic infections (infections that rarely cause problems in healthy people but affect people with suppressed immune systems) or thrush (a fungal infection in the mouth).
No B symptoms lasting more than 2 weeks. B symptoms include:
- Unexplained fever
- Night sweats (severe enough to soak the bed clothes)
- Weight loss of more than 10% without dieting
And this is true:
- Karnofsky performance status (KPS) score of 70 or higher. This means you are up and about most of the time and able to take care of yourself.
S1 (poor risk): Systemic illness present; one or more of the following is true:
- History of opportunistic infections or thrush
- One or more B symptoms is present
- KPS score is under 70
- Other HIV-related illness is present, such as neurological (nervous system) disease or lymphoma
Overall risk group
Once these features have been assessed, patients are assigned an overall risk group (either good risk or poor risk). In fact, since highly active antiretroviral therapy (HAART) became available to treat HIV, the immune status (I) has become less important and is often not counted in determining the risk group:
- Good risk: T0 S0, T1 S0, or T0 S1
- Poor risk: T1 S1
Last Medical Review: 08/08/2014
Last Revised: 02/09/2016