Cancer is a class of disease in which a group of cells grow uncontrollably (division beyond the normal limit), invade other tissue, and at times metastasis, or spread to other locations in the body via the lymph or vascular system. These three properties of malignant cancers differentiate them from benign tumors, which are localized, self-limited and do not invade other tissues. The medical specialty that is concerned with the study, diagnosis, treatment, and prevention of cancer is called oncology (Weinburg, 2006, intro).
The type and robustness of cancers are so varied that their causes are diverse as well. Cells replicate so many times and with such vigor that it is likely there will occasionally be errors (mutations). Unless some sort of error correct is available, the errors will survive and be passed down. Biology does have methods for dealing with these mutations, but of something else is not working in top level, in places the cancer might survive and progress. There are numerous substances, called carcinogens that increase errors in cell division, or are actually cellular poisons and weaken the cell from within. Cancer is like the well-known metaphor about a firestorm -- it starts off slowly, smolders for who knows how long, then erupts. Unless it is checked quickly, the speed and intensity of the fire and cancer overwhelm the body's ability to function, and cellular death occurs (Merlo, et.al., 2006).
For example, many cancers are caused by mutations resulting from the ingestion of a chemical carcinogen. Tobacco smoking causes 90% of lung cancers; exposure to asbestos typically results in mesothelioma; certain pesticides can result in variable cancers; other chemicals, like alcohol, do not necessarily cause cancer, but can contribute to the severity of cancers already in process. Excessive exposure to the sun, too, contributes to melanoma and skin cancer; some cancers (human papillomavirus, hepatitis B and C) can cause liver cancer; other bacteria may cause stomach, intestine, or gastric cancers (Sompayrac, 2003).
Statistics -- The vast majority of cancer risk factors are environmental or lifestyle oriented, leading to the view that cancer may be more preventable than previously thought. Most lung cancers are caused by smoking; being overweight is associated with colon, breast, and endomentrial cancers. Dietary practices shift statistics; gastric cancer is more prevalent in Japan, for instance; colon cancer in the United States. Tobacco is responsible for 30-40% of cancer deaths in the developed world, 20-25% in the underdeveloped world. Cancer death rates and types vary by gender and ethnicity (see Tables 1 & 2) (Melli, 2005).
Epidemiology -- Cancer is responsible for about 25% of all U.S. deaths, making it one of the most prevalent public health issues. Lung cancer causes about 30% of the cancer deaths; prostate 25% in men, and 25% in new cases for women. Worldwide, over 33% of cancer deaths are due to modifiable risk factors -- specifically smoking, alcohol, and diets low in fruits and vegetables. In children and adolescence, leukemia is the most common form of cancer (Jemal, 2008).
Types of Cancer -- There are several different major types of cancer: Breast (second most common cancer globally, usually begins in the inner lining of the milk ducts or lobules, more frequent in women than men, survival ratio dependent upon type and identification); Prostate (very common in older men in developed countries, 3% death in older men, usually hits after age 50, high survival rate when caught early), Colon (also called large bowel cancer, includes cancerous growths in the colon, rectum, and…