Join or Renew and Choose Your Gift
- Offer ends Dec. 17
- Discounts on travel and everyday savings
- Subscription to AARP The Magazine
- Free membership for your spouse or partner
Cancer is the end product of a multistep process (carcinogenesis) that occurs over many years. The term "cancer" actually refers to numerous distinct diseases characterized by abnormal cell growth and differentiation. Cancers are categorized by the organ and/or cell of origin. For example, squamous cell carcinoma of the lung arises from pulmonary epithelial tissue, whereas adenocarcinoma of the breast arises from mammary duct epithelium. The natural history of a cancer is highly dependent on the organ and cell type from which it is derived. In addition, prognosis is influenced by the stage and histologic grade of the cancer. Staging is generally designated by the TNM (tumor, nodes, metastasis) staging system, which takes into account the size of the primary tumor(T), the extent to which local lymph nodes (glands) are involved (N), and whether or not distant metastases are present (M). The histologic grade, determined by microscopic examination of the biopsy specimen, provides an objective assessment of the degree of cellular differentiation.
The worldwide burden of cancer is a major health problem, with more than 8 million new cases and 5 million deaths per year. The burden from cancer may be described in terms of incidence (number of new cases per 100,000 each year), prevalence (number of people at a given point in time with a cancer diagnosis), and mortality (number of cancer deaths). With few exceptions, cancer incidence, prevalence, and mortality rates are higher in industrialized countries (e.g., United States, European nations) than in developing countries (e.g., African nations, China). Incidence rates for specific cancers can be dramatically affected by the use of screening procedures to identify asymptomatic disease. This is illustrated by the dramatic increase in the incidence of prostate cancer that accompanied the introduction of prostate-specific antigen (PSA) screening in the late 1980s. Similarly, prevalence rates may be a poor index for comparing cancers, because they are dependent upon incidence, natural history, and treatment efficacy. For example, due to the relatively short life expectancy of individuals with pulmonary neoplasms, the prevalence of lung cancer is much lower than that of prostate cancer, despite the higher mortality rates associated with lung cancer. In addition to the impact of screening and natural history, prevalence rates increase as treatment improves, because therapeutic advances enable individuals to live longer following a cancer diagnosis.
Worldwide, lung cancer is the leading cause of cancer mortality, followed by stomach cancer. Smoking remains the leading preventable cause of cancer, and mortality and incidence rates of lung cancer rise and fall with smoking rates. The current trend shows a leveling off of smoking-related cancers in developed countries, possibly because of health-promotion and disease-prevention efforts. Geographical variations occur in cancer incidence and mortality, with Africa and Asia generally having lower rates than North America and Europe. However, it has been noted that differences in data collection and diagnostic practices make worldwide cancer comparisons somewhat difficult. Overall, worldwide incidence rates of breast, colon and rectum, and prostate cancers are highest in developed countries, while cancers of the cervix, mouth and pharynx, esophagus, and liver are higher in developing countries. Migration studies generally report that migrants from developing countries to developed countries adopt cancer incidence rates equivalent to those of their new country. For example, studies of Japanese and Chinese immigrants living in the United States show that their risks for prostate and breast cancers increase dramatically the longer they reside in the United States. Similar trends for increased risk are seen among African immigrants in European countries. Geographical variations in cancer incidence and mortality also exist in the United States. Each cancer site shows some variation, such as
In the United States, cancer is the second leading cause of death; although there has been a slight decline in the number of people dying from cancer since 1990, with more than one-half of those who develop cancer being cured or surviving for over five years. Because cancer is many diseases, some cancers are more common and/or more curable than others. For example, although nonmelanoma skin cancer, mainly caused by overexposure to ultraviolet (UV) radiation from the sun, is responsible for the largest number of new cancer cases each year, mortality rates associated with it are low.
Incidence, prevalence, and mortality in the United States vary by cancer site, between whites and blacks, and between men and women. By order of incidence, the three most common cancers in men are prostate, lung, and colorectal; in women the three most common cancers are breast, lung, and colorectal. These cancer sites represent more than one-half of both new cases of cancer and deaths from cancer each year. Lung cancer is the leading cause of death from cancer for men and women, accounting for almost one-third of cancer deaths.
Although cancer risk increases with age, malignant diseases are an important cause of morbidity and mortality in the pediatric population. The most frequent cancers in children are leukemias, tumors of the nervous systems, lymphomas, soft-tissue sarcomas, and kidney tumors. Other than lung cancer, which increases dramatically after age forty, three out of every four deaths from cancer occur in individuals older than sixty years of age.
Author Info: HOWARD L. PARNES, DARRELL ANDERSON, The Gale Group Inc., Macmillan Reference USA, New York, Gale Encyclopedia of Public Health, 2002
Enter your symptoms in our Symptom Checker to find out possible causes of your symptoms. Go.
Enter any list of prescription drugs and see how they interact with each other and with other substances. Go.
Enter its color and shape information, and this tool helps you identify it. Go.
Find information on drug interactions, side effects, and more. Go.
From companies that meet the high standards of service and quality set by AARP.
Members save on purchases from The Popcorn Factory®.
Members save from top retailers online at Everyday Savings Center powered by NextJump.
Members save 10% on all Amazon Kindle e-readers and the Kindle Fire HD tablet.
Get the most out of your AARP membership – opt-in to receive AARP emails today!
Register at a location near you to keep your driving skills sharp.
Find opportunities to volunteer in your neighborhood.
NASCAR champ Jeff Gordon teams up with AARP's Foundation.
AARP Foundation Prepaid MasterCard brought to you by Green Dot.
Nothing has been viewed