Staging is the process of using physical examinations, imaging tests, and, in some cases, biopsy results to determine where and how much cancer is in the body. For many types of cancer, the stage is the most important factor considered in selecting treatment options and predicting a patient's outlook for recovery and survival. The results of the staging process are usually described in a standardized way, using a staging system.

Unlike most other forms of cancer, there is no officially accepted system for staging all types of Kaposi sarcoma.. Many doctors use the AIDS Clinical Trials Group (ACTG) system for KS in AIDS patients.

For most other types of cancer staging systems are based mostly on the size of the primary lesion (the first one to develop) and how far the cancer has spread from that lesion. KS doesn’t’ generally develop just in a single area so this staging approach isn’t used. In addition, the outlook for patients with AIDS-related KS is influenced at least as much by other AIDS-related problems as by the spread of KS. For this reason, staging KS also considers factors such as how much the immune system is damaged and the presence of AIDS-related infections.

The AIDS clinical trial group system

In 1988, a group of researchers known as the AIDS Clinical Trials Group (ACTG) proposed a staging classification system for AIDS-related Kaposi sarcoma (KS). The ACTG system considers 3 criteria:

• the extent of the tumor (abbreviated T)

• the status of the immune system (I), as measured by the number of certain cells (CD4 cells) present in the blood, and

• the extent of involvement within the body or systemic illness (S)

Under each of these major headings, there are 2 subgroups identified by either a zero (0) or a one (1). A zero (0) means good risk, while a one (1) means poor risk. The following are the possible staging categories under this system:

T (tumor) status

T0 (good risk): Localized tumor

KS is confined to the skin and/or the lymph nodes. If there are lesions in the mouth, they can only be on the palate (roof of the mouth), and those lesions are flat (not raised or rounded).

T1 (poor risk): Disseminated (widespread) tumor. One or more of the following is present:

• edema (swelling) due to the tumor
• lesions are ulcerated (open sores, oozing, or bleeding)
• extensive oral KS (nodular lesions and/or lesions not limited to the palate)
• KS is affecting the stomach or intestines
• KS is in the lungs or other internal organs.

I (immune system) status

I0 (good risk): CD4 cell count is at least 200 (in cells/ microliter). The normal range for CD4 count is 600-1,500. Some experts use a lower cut-off for good risk such as 150 or 100.

I1 (poor risk): CD4 count is lower than 200 (again some have used lower cut-offs such as 150 or 100).

S (systemic illness) status

S0 (good risk): No systemic illness present and all of the following are true:

• No history of opportunistic infections or thrush (a fungal infection in the mouth)
• No B symptoms are present. B symptoms are:
• unexplained fever
• night sweats
• weight loss of more than 10% (without trying to lose weight)
• diarrhea for more than 2 weeks
• The patient is doing well - up and about most of the time and he can take care of himself. In medical terms this is called having a good performance status. Performance status can be given a score based on something called the Karnofsky performance status scale. This score needs to be at least 70 to be in the good risk category.

S1 (poor risk): Systemic illness is present; and one or more of the following is true:

• History of opportunistic infections or thrush
• One or more B symptoms is present
• Performance status score under 70

Other HIV-related illness is present, such as neurological (nervous system) disease or lymphoma

Survival

For cancer, a standard measure of survival is the 5-year survival rate. The 5-year survival rate refers to the percentage of patients who live at least 5 years after their cancer is diagnosed. Many of these patients live much longer than 5 years after diagnosis, and 5-year rates are used to produce a standard way to discuss prognosis.

Five-year relative survival rates do not include patients dying of other diseases and are considered to be a more accurate way to describe the prognosis for patients with a particular type and stage of cancer. Of course, 5-year survival rates are based on patients diagnosed and initially treated more than 5 years ago. They may no longer be accurate. Improved treatments have meant a more favorable outlook for patients diagnosed more recently. For example, patients diagnosed with KS in the 1980s had a 5-year relative survival rate of only about 10%. Patients diagnosed with KS in the past 10 years had a 5-year relative survival of more than 50%. As treatments for AIDS improve, these rates are expected to get even better.

The ACTG stage affects survival as well as treatment. It is important to understand that this system was designed early in the AIDS epidemic - before effective treatment for HIV was available. Before highly active antiretroviral therapy (HAART) was used, people who were at good risk in any of the categories lived longer than those who were not. When this system was looked at more recently, T and S factors seemed to be the most important. Ninety percent of KS patients who are at good risk in these categories (T0S0) survive for at least 3 years after diagnosis. Only half of the KS patients who are at poor risk in both of these categories (T1S1) are still alive 3 years after diagnosis. The immune system status when the patient is first diagnosed seems to be less important if HAART is given.