Lung cancer, also known as bronchogenic carcinoma ("carcinoma" means cancer), is the most fatal form of cancer, reports the Centers for Disease Control and Prevention (CDC). In 2003, lung cancer accounted for more deaths than breast cancer, prostate cancer, and colon cancer combined in the United States.
Lung cancer is not an AIDS-defining illness. However, HIV-infected patients have a greater chance of developing lung cancer than patients without HIV. Some researchers believe that low numbers of natural killer cells (white blood cells that attack and kill tumor cells or microbial cells) may lead to the growth of abnormal cells or, HIV may stimulate abnormal growth factors. As the life expectancy of HIV patients increases with the help of highly active antiretroviral therapy (HAART), lung cancer is expected to increase among the patient population. There is no evidence that HAART causes lung cancer or any other cancer.
Several studies show that lung cancer is more common in HIV-positive patients than non-HIV infected patients. For instance, researchers reviewed cancer and HIV registers in Texas between 1990 and 1995 and found that people with HIV were almost seven times more likely to develop lung cancer than non-infected people. In New York, an HIV cohort had three times the risk of developing lung cancer compared to the general American population. A review of cancer and HIV registers in New South Wales, Australia, also provides evidence that HIV-infected patients have an increased risk of developing lung cancer. These trends have also been demonstrated in American women.
Regardless of the cause of lung cancer, studies have shown that people with HIV have a worse prognosis than non-infected people, with an average survival time of five months in HIV-positive patients and ten months in HIV-negative patients. Since current treatments are often inadequate and most patients are diagnosed when they have late-stage cancer, only about 10% of non-HIV related lung cancers are cured. There is evidence that lung cancer is more aggressive among people who have weakened immune systems, including HIV patients.
The three main types of treatment are surgery, radiation therapy, and chemotherapy. Patients often receive combinations of these therapies, depending on the stage of the lung cancer. Surgery can be performed if the cancer is limited to the lungs and has not spread to other areas of the body. However, about half of people with lung cancer are not candidates for surgery because the cancer has spread too far. Also, surgical procedures can cause lymphocytopenia (low levels of white blood cells) in patients, which can further impair an HIV patient's immune system.
Radiation therapy generally does not cure lung cancer. Rather, it improves and extends a person's quality of life. Chemotherapy drugs, which destroy cancer cells by preventing them from growing and multiplying, are the primary treatment for small cell lung cancer, particularly if it is restricted to the lung.
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types of lung cancer
Lung cancers are classified into two major groups: small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). This classification is based on the microscopic appearance of the tumor cells.
Small cell lung cancers (SCLC)
Small cell lung cancers (SCLCs), also called oat cell carcinomas, make up about 20% of lung cancers, and they are the most aggressive and rapidly growing of all lung cancers. SCLCs are strongly associated with cigarette smoking. In fact, only 1% of SCLC tumors occur in non-smokers. SCLC can metastasize (spread to other areas of the body) rapidly. The cancer is usually diagnosed after it has spread extensively.
Non-small cell lung cancers (NSCLC)
Non-small cell lung cancers (NSCLCs) are the most common lung cancers, accounting for about 80% of all lung cancers. NSCLC has three main types, which are named based on the type of cells present in the tumor.
Adenocarcinomas: Adenocarcinomas, which account for about 50% of all NSCLC cases in the United States, are the most common type of NSCLC. While adenocarcinomas may be associated with smoking, they are most commonly seen in non-smokers. Most adenocarcinomas occur in the peripheral (outer) areas of the lungs. Bronchioloalveolar carcinoma is a subtype of adenocarcinoma that often develops in multiple areas in the lungs and spreads along the alveolar walls.
Squamous cell carcinomas:
Squamous cell carcinomas, also called epidermoid carcinomas, account for about 30% of NSCLC. Squamous cell cancers usually occur in the central chest area in the bronchi.
Large cell carcinomas: Large cell carcinomas, sometimes called undifferentiated carcinomas, are the least common type of NSCLC.