The Clinical Problem
One-third of all individuals in the United States will develop cancer. The 5-year relative survival rate for these patients (the probability of escaping death from cancer for 5 years following diagnosis) has risen to nearly 50 percent as a result of progress in the early diagnosis and the therapy of this disease. However, cancer remains second only to cardiac disease as a cause of death in this country. Twenty percent of Americans die from cancer; this amounted to 450,000 deaths in 1984. Half of the deaths were due to the three most common types of cancer: lung, breast, and colon-rectum. Lung cancer is more prevalent in males, while breast cancer is the commonest form of malignancy in females. Cancer of the colon and rectum is equally common in males and females.
Cancer typically presents to the physician as an abnormal growth, or tumor, which causes illness by production of biochemically active molecules, by local expansion, or by invasion into adjacent or distant tissue sites. The symptoms of the illness depend upon the specific molecular products and the location(s) of the tumor. Each type of cancer has a relatively distinctive natural history that describes the likely clinical course of the particular neoplastic process. Designing a proper treatment plan for an individual patient with malignant disease depends upon determining the extent of disease spread, together with a knowledge of the natural history and the available therapeutic alternatives for the particular type of cancer.