Cancer and Oncology

The American Cancer Society projects that in the United States alone, 1,437,180 people will be diagnosed with cancer and 565,650 will die from the disease in 2008. Accordingly, understanding what cancer is, what factors may contribute to its development, what cancer screenings and treatments are available, and most importantly, how to prevent cancer, are all important topics for consideration.

What is Cancer?

Cancer is a group of more than 100 different diseases, all characterized by cellular growth and division gone awry. Normally, when the body produces cells, younger cells divide to form the new cells that will replace the old ones as they die off. However, if cells continue to divide, even when new cells are not needed, an extra mass of cells called a tumor can form.

There are two main types of tumors: benign and malignant. Benign tumors are not cancerous and generally do not spread to other body locations. Malignant tumors, on the other hand, are cancerous and may spread from the tumor to other body parts by traveling through the bloodstream or lymphatic system. Cancer that has spread to other body organs is said to have metastasized. Not all forms of cancer develop into malignant tumors, though. Some, like leukemias for example, develop in blood cells.

Malignant tumors and cancers are classified into four major types, the majority of which are carcinomas. Carcinomas are cancers that develop in epithelial cells, which line the surfaces or cover internal organs. Sarcomas develop in bone, cartilage, fat, connective tissue, and muscle; leukemias develop in the blood cells and bone marrow; and lymphomas are cancers that originate in the lymphatic system.

Cancer Incidence and Mortality

Cancer is the second leading cause of death in the United States, accounting for one in four deaths. Among men, the five most commonly diagnosed cancers, excluding skin cancers, are prostate, lung, colon, bladder, and non-Hodgkin's lymphoma. Among women, the five most commonly diagnosed cancers are breast, lung, colorectal, uterine, and non-Hodgkin's lymphoma, in descending order of frequency. The five cancers with the highest mortality rates among men are lung, prostate, colon, pancreatic, and leukemia, respectively. For women, the cancers with the highest mortality rates are lung, breast, colon, pancreatic, and ovarian. Childhood cancers, over half of which are leukemia and brain and nervous system cancers, are the second leading cause of death in children.

Cancer Risk Factors

Over the years, researchers have struggled to answer the question, “What causes cancer?” The two main categories of risk factors that have been [Page 136]identified are heredity, which is uncontrollable; and environment, or factors that people are exposed to that are often modifiable and controllable. Heredity, or inherited gene mutations, increases one's risk of developing cancer compared to the general population, but it accounts for only about 5#x0025; to 10#x0025; of cancers. Because environmental risk factors are estimated to account for 75#x0025; to 80#x0025; of cancer cases and deaths in the United States alone, many studies have focused on identifying risk factors that may increase one's chances of developing cancer.