AIDS-Related Cancers Health Article

Definition

The AIDS-related cancers are a group of cancers that occur more frequently in persons with human immunodeficiency virus (HIV) infection than in the general population. The most common form of AIDS-related cancer, Kaposi's sarcoma (KS), was one of the first indications of the AIDS epidemic in the early 1980s. While the number of new cases of KS has been declining in recent years, the number of AIDS-related lymphomas has been increasing at a rate of 2% to 3% each year.

Description

In order to understand the causes and treatment of AIDS-related cancers, it is useful to begin with a basic description of HIV infection. AIDS, or acquired immunodeficiency syndrome, is a disease of the immune system that is caused by HIV. HIV is a retrovirus, a single-stranded virus containing ribonucleic acid (RNA) and an enzyme called reverse transcriptase. This enzyme enables the retrovirus to make its genetic material part of the DNA in the cells that it invades. HIV selectively infects and destroys certain subtypes of white blood cells called CD4 cells, which are an important part of the body's immune system. As an infected person's number of CD4 cells drops, he or she is at risk of developing opportunistic infections, disorders of the nervous system, or an AIDS-related cancer. HIV is transmitted through blood or blood products that enter the bloodstream— most commonly through sexual contact or contaminated hypodermic needles.

Kaposi's sarcoma

Kaposi's sarcoma is the most common type of cancer related to HIV infection. About 20% of patients diagnosed with AIDS will eventually develop KS. There are two other major subtypes of KS—so-called classic KS and African KS—with different causes that are not yet well understood. AIDS-related KS (also called epidemic KS) is characterized by purplish or brownish lesions (areas of diseased or injured tissue) on the skin, in the mouth, or in the internal organs. The lesions may take the form of small patches or lumps (nodular lesions), large patches that grow downward under the skin (infiltrating lesions), or lumpy swellings in the lymph nodes. Unlike other cancers that typically develop in one organ or area of the body, KS often appears simultaneously in many different parts of the body. It may be the first indication that the patient has AIDS.

Non-Hodgkin's lymphoma

Lymphomas are cancers of the immune system that develop when white blood cells called lymphocytes begin to grow and multiply abnormally. The increased numbers of lymphocytes cause the lymph nodes, the organs that produce these white blood cells, to swell and form large lumps that can be felt. Lymphomas are divided into two large categories: those that are related to Hodgkin's disease (HD), and non-Hodgkin's lymphoma (NHL). HD can be differentiated from NHL by the presence of Reed-Sternberg cells in the lymphatic tissue; these cells are not found in any other type of cancer.

Non-Hodgkin's lymphoma, or NHL, occurs more often than Hodgkin's disease; about 50, 000 new cases are diagnosed annually in the United States. They may involve the spleen, liver, bone marrow, or digestive tract as well as the lymph nodes. Three important types of NHL are related to AIDS:

• Primary central nervous system lymphomas (PCNSL). This type accounts for about 20% of NHL cancers found in AIDS patients, but only 1% to 2% of NHL cancers in patients not infected by HIV. Lymphomas of this type start in the brain or the spinal cord. Their symptoms include headaches, paralysis, seizures, and changes in the patient's mental condition. Patients diagnosed with PCNSL are more likely to suffer from advanced HIV infection than patients with other types of NHL.
• Systemic lymphomas. These are also called peripheral lymphomas. They begin in the lymph nodes or other parts of the lymphatic system and may spread throughout the body. Burkitt's lymphoma (BL) is a type of systemic lymphoma that is one thousand times more common in AIDS patients than in the general population.
• Primary effusion lymphomas, also called body cavity-based lymphomas (BCBL). This type of NHL is relatively rare, but seems to be related to infection by human herpesvirus 8 (HHV-8) in addition to HIV.

HIV-associated Hodgkin's disease

The symptoms of Hodgkin's disease include painless swelling of the lymph nodes of the neck, groin, and armpits; itching; night sweats; weight loss; and fever. While one study has indicated that HIV-positive gay men have a higher risk of developing Hodgkin's disease as well as non-Hodgkins lymphomas, the Centers for Disease Control and Prevention (CDC) has not defined Hodgkin's disease as an AIDS-related cancer as of early 2001. Hodgkin's disease appears to occur more frequently in HIV-positive intravenous drug users, however, than in other persons with HIV infection.

Cervical and anal cancers

In women, cancer of the cervix (the lower end of the uterus or womb) is more likely to occur in HIV-infected individuals than in the general female population. About 60% of women with HIV infection are found to have some kind of abnormal tissue growth or cell formation in the cervix when a Pap test is performed. The human papilloma virus (HPV) is thought to be a co-factor in the development of cervical cancers. Papilloma viruses are a group of tumor-causing viruses that also cause genital warts. Cervical cancers develop more rapidly in HIV-positive than in HIV-negative women, are harder to cure, and are more likely to recur.

Cancers of the anus represent less than 1% to 2% of cancers of the large bowel. There are about 10, 000 cases of anal cancer annually in the United States. The high rates of occurrence of this type of cancer in gay men may be related more closely to the presence of HPV and to the practice of anal intercourse than to HIV infection by itself.

Other AIDS-associated cancers

Other cancers linked to HIV infection include testicular cancer, cancers of the mouth, and a type of cancer of the bone marrow called multiple myeloma. Some other cancers, including breast cancer, lung cancer, andmelanoma (a type of skin cancer), are thought to occur more frequently among people with AIDS even though they are not identified as AIDS-associated cancers in the strict sense.