Causes & symptoms
Kaposi's sarcoma (KS) is caused by herpesvirus 8. Malignant cells are found in the tissues under the skin or mucous membranes that line the mouth, nose, and anus. KS causes red or purple patches on the skin and/or mucous membranes and spread to other organs, such as the lungs, liver, or intestinal tract. KS is seen in three forms:
The primary distinction between the three forms of KS is the rate of growth and the location of the lesions. In the past, the indolent form of Kaposi's sarcoma was the most common, and was most often seen in men over the age of 60 years of Jewish or Italian ancestry; in African men; and in patients who had organ transplants or had their immune systems impaired for other reasons. KS was frequently left untreated. Because of its slow growth, the cancer was not a threat to the patient. Since the 1980s, a far higher percentage of cases with rapid growth have been observed, usually accompanied by AIDS (HIV disease).
The aggressive form of KS is seen in about one-third of patients with AIDS, and has become endemic in equatorial African. In African nations, aggressive KS is seen most often among young men and children.
Lymphadenophic KS affects the lymph nodes as well as the skin structures.
KS is traditionally diagnosed based on the red or purple patches on the skin or mucous membranes. A biopsy is usually performed in order to verify the diagnosis. Since other cancers may have a similar appearance to KS, it is often useful to test for the presence of human herpesvirus 8 in order to confirm the diagnosis.
In indolent KS, localized treatment is often adequate. Superficial lesions may be removed surgically. Alternatives are radiation therapy, electrical curettage, in which the lesion is burned with an electrical current, or cryotherapy, in which a source of extreme cold, such as liquid nitrogen, is applied to the cancer in order to kill the cells.
Among patients who develop KS after an organ transplant, reduction in the dose of drugs used to control the immune response may be enough to control or eliminate the cancer, although this treatment increases the risk of transplant rejection. One report from the University of Barcelona in Spain states that a change of medication may resolve the problem of KS after transplantation.
In KS associated with AIDS, systemic chemotherapy is usually required.
The Gay Men's Health Crisis (GMHC) has reviewed a number of alternative therapies which have been tried in KS, but none have shown consistently favorable results. Among the treatments mentioned were shark cartilage, herbal and purifying massage therapies to enhance immune function, and transcendental meditation. Homeopathy has been tried, but here too the results have not been reliable.
There are no current best-practice treatments for KS. For rapidly growing KS, a standard treatment is systemic chemotherapy with a combination of adriamycin, bleomycin, and vincristine (ABV); however, several studies have reported that single-agent treatments may be as effective as combinations. Single-agent treatments that have shown evidence of effectiveness are a liposomal form of adriamycin used alone; methotrexate, and trimetrexate. Interferon-alpha has also been reported to be effective in AIDS-related KS.
The expected results depend primarily on the underlying condition of the patient. Those patients who have classic slow-growing KS may live many years, even in the absence of treatment. For patients with AIDS, a proposed staging system has divided patients into low- and high-risk groups, depending both on the extent of the sarcoma and their underlying immune function. Patients with well-functioning immune systems, no AIDS associated opportunistic infections, and KS confined to the skin have an estimated survival of about three years. Those with impaired immune systems, other infections, and more widespread KS have an estimated survival of about one year. Overall length of survival will depend on the patient's response to treatment.
The United States Public Health Service (USPHS) guidelines for prevention of KS call for prophylactic administration of drugs that are effective against human herpesvirus-8. The primary drugs for this purpose are foscarnet and ganciclovir. In each case, the dose must be adjusted based on the patient's condition. While the USPHS recognizes that KS may affect children as well as adults, no formal recommendations for prevention have been published.
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Samuel Uretsky, Pharm.D.