Prevalence and Incidence of Cancer

Prevalence/Incidence of Cancer: Online Medical Books

16 MEDICAL BOOKS ONLINE! Review excerpts from medical books online, free, without registration, for more information about the prevalence and/or incidence of Cancer.

Breast cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The cause of breast cancer isn't known, but its high incidence in women implicates estrogen.

Certain predisposing factors are clear; women at high risk include those who have a family history of breast cancer, particularly first-degree relatives (mother, sister, and maternal aunt).

Other women at high risk include those who:

❑have long menstrual cycles or began menses early (before age 12) or menopause late (after age 55)

❑have taken hormonal contraceptives

❑used hormone replacement therapy for more than 5 years

❑who took diethylstilbestrol to prevent miscarriage

❑have never been pregnant

❑were first pregnant after age 30

❑have had unilateral breast cancer

❑have had ovarian cancer — particularly at a young age

❑were exposed to low-level ionizing radiation.

Recently, scientists have discovered the BRCA1 and BRCA2 genes. Mutations in these genes are thought to be responsible for less than 10% of breast cancers. However, these discoveries have made genetic predisposition testing an option for women at high risk for breast cancer.

Women at lower risk include those who:

❑were pregnant before age 20

❑have had multiple pregnancies

❑are Native American or Asian.

Most breast cancer deaths occur in women age 50 and older (84% of cases), and 77% of new breast cancer cases occur in this age-group. However, it may develop any time after puberty. It occurs in men, but rarely; male cases of breast cancer account for less than 1% of all cases.

The 5-year survival rate for localized breast cancer has improved because of earlier diagnosis and the variety of treatments now available. According to the most recent data, mortality rates continue to decline in White women and, for the first time, are also declining in younger Black women. Lymph node involvement is the most valuable prognostic predictor. With adjuvant therapy, 70% to 75% of women with negative nodes will survive 10 years or more compared with 20% to 25% of women with positive nodes.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Malignant spinal neoplasms: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Primary tumors of the spinal cord may be extramedullary (occurring outside the spinal cord) or intramedullary (occurring within the cord itself). Extramedullary tumors may be intradural (meningiomas and schwannomas), which account for 60% of all primary malignant spinal cord neoplasms, or extradural (metastatic tumors from breasts, lungs, prostate, leukemia, or lymphomas), which account for 25% of these malignant neoplasms.

Intramedullary tumors, or gliomas (astrocytomas or ependymomas), are comparatively rare, accounting for only about 10%. In children, they're low-grade astrocytomas.

Spinal cord tumors are rare compared with intracranial tumors (ratio of 1:4). They occur equally in men and women, with the exception of meningiomas, which occur mostly in women. Spinal cord tumors can occur anywhere along the length of the cord or its roots.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Bladder cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Certain environmental carcinogens, such as 2-naphthylamine, benzidine, tobacco, and nitrates, predispose people to transitional cell tumors. Thus, workers in certain industries (rubber workers, weavers and leather finishers, aniline dye workers, hair-dressers, petroleum workers, and spray painters) are at high risk for such tumors. The period between exposure to the carcinogen and development of symptoms is about 18 years.

Squamous cell cancer of the bladder is most common in geographic areas where schistosomiasis is endemic. It's also associated with chronic bladder irritation and infection (for example, from renal calculi, indwelling urinary catheters, and cystitis caused by cyclophosphamide).

Bladder tumors are most prevalent in men older than age 50 and are more common in densely populated industrial areas.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Cancer of the vulva: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Although the cause of cancer of the vulva is unknown, several factors seem to predispose women to this disease:

❑chronic pruritus of the vulva, with friction, swelling, and dryness

❑ chronic vulvar granulomatous disease

❑ diabetes

❑ hypertension

❑ irradiation of the skin such as nonspecific treatment for pelvic cancer

❑ leukoplakia (white epithelial hyperplasia) — in about 25% of patients

❑ obesity

❑ pigmented moles that are constantly irritated by clothing or perineal pads

❑ sexually transmitted diseases (herpes simplex, condyloma acuminatum caused by human papilloma virus).

Cancer of the vulva accounts for approximately 4% of all gynecologic malignancies. It can occur at any age, even in infants, but its peak incidence is in the mid-60s. The most common vulval cancer is squamous cell cancer. Early diagnosis increases the chance of effective treatment and survival. Lymph node dissection allows 5-year survival in 85% of patients if it reveals no positive nodes; otherwise, the survival rate falls to less than 75%.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Cervical cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Although the cause is unknown, several predisposing factors have been related to the development of cervical cancer: frequent intercourse at a young age (younger than age 16), multiple sexual partners, multiple pregnancies, exposure to sexually transmitted diseases (particularly genital human papillomavirus), and smoking.

In almost all cases of cervical cancer (95%), the histologic type is squamous cell cancer, which varies from well-differentiated cells to highly anaplastic spindle cells. Only 5% are adenocarcinomas. Usually, invasive cancer occurs between ages 30 and 50; rarely, in patients younger than age 20.

In 2000, 12,800 women were diagnosed with cervical cancer and there were 4,600 deaths from this disease.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Colorectal cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The exact cause of colorectal cancer is unknown, but studies showing concentration in areas of higher economic development suggest a relationship to diet (excess saturated animal fat). Other factors that magnify the risk of developing colorectal cancer include:

❑other diseases of the digestive tract

❑age (older than age 40)

❑history of ulcerative colitis (average interval before onset of cancer is 11 to 17 years)

❑familial polyposis (cancer almost always develops by age 50).

There are more than 130,000 cases of colorectal cancer diagnosed in the United States each year. It's the second-leading cause of cancer-related death, accounting for more than 50,000 per year. However, in almost all cases, it's treatable if caught early by colonoscopy.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Esophageal cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The cause of esophageal cancer is unknown, but among predisposing factors are chronic irritation caused by heavy smoking and excessive use of alcohol, stasis-induced inflammation, nutritional deficiency, and diets high in nitrosamines. A genetic link has been proposed concerning an overexpression and mutation of the p53 tumor suppressor gene. Esophageal tumors are usually fungating and infiltrating. Most arise in squamous cell epithelium. However, the number of adenocarcinomas is greatly rising in the United States. Melanomas and sarcomas are few.

Regardless of type, esophageal cancer is usually fatal, with a 5-year survival rate of approximately 10% and regional metastasis occurring early via submucosal lymphatics. Metastasis produces such serious complications as tracheoesophageal fistulas, mediastinitis, and aortic perforation. Common sites of distant metastasis include the liver and lungs. (See Staging esophageal cancer.)

Esophageal cancer most commonly develops in men older than age 60 and is nearly always fatal. This disease occurs worldwide, but incidence varies geographically. It's most common in Japan, China, the Middle East, and parts of South Africa.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Fallopian tube cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The causes of fallopian tube cancer aren't clear, but this disease appears to be linked with nulliparity. In fact, over one-half of the women with this disease have never had children.

Fallopian tube cancer usually occurs in postmenopausal women in their 50s and 60s but occasionally is found in younger women.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Gallbladder and bile duct cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Gallbladder cancer may result from a complication of gallstones. However, this inference rests on circumstantial evidence from postmortem examinations: 60% to 90% of gallbladder cancer patients also have gallstones, but postmortem data from patients with gallstones show gallbladder cancer in only 0.5%.

The predominant tissue type in gallbladder cancer is adenocarcinoma, 85% to 95%; squamous cell, 5% to 15%. Mixed-tissue types are rare.

Lymph node metastasis is present in 25% to 70% of patients at diagnosis. Direct extension to the liver is common (in 46% to 89%); direct extension to both the cystic and the common bile ducts, stomach, colon, duodenum, and jejunum also occurs and produces obstructions. Metastasis also spreads by portal or hepatic veins to the peritoneum, ovaries, and lower lung lobes.

The cause of extrahepatic bile duct cancer isn't known; however, statistics report an unexplained increased incidence of this cancer in patients with ulcerative colitis. This association may be due to a common cause — perhaps an immune mechanism, or chronic use of certain drugs by the colitis patient.

Extrahepatic bile duct cancer is the cause of approximately 3% of all cancer deaths in the United States. It occurs in both males and females (incidence is slightly higher in males) between ages 60 and 70. The usual site is at the bifurcation in the common duct. Cancer at the distal end of the common duct is commonly confused with cancer of the pancreas. Characteristically, metastatic spread occurs to local lymph nodes, the liver, lungs, and the peritoneum.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Gastric cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The cause of gastric cancer is unknown. It's commonly associated with gastritis with gastric atrophy, which may result from gastric cancer and may not be a precursor state. Predisposing factors include environmental influences, such as smoking and high alcohol intake. Genetic factors have also been implicated because this disease occurs more commonly among people with type A blood than among those with type O; similarly, it's more common in people with a family history of gastric cancer. Dietary factors also seem related, including types of food preparation, physical properties of some foods, and certain methods of food preservation (especially smoking, pickling, or salting). There's a strong correlation between infection with Helicobacter pylori and distal gastric cancer.

Gastric cancer is common throughout the world and affects all races; however, unexplained geographic and cultural differences in incidence occur — for example, a higher mortality in Japan, Iceland, Chile, and Austria. In the United States, during the past 25 years, incidence has decreased by 50% and the resulting death rate is one-third what it was 30 years ago. Incidence is higher in males older than 40. Hispanic, Native, and African Americans are twice as likely to develop gastric cancer than Whites. The prognosis depends on the stage of the disease at the time of diagnosis; however, the overall 5-year survival rate is approximately 19%.

The decrease in gastric cancer in the United States has been attributed, without proof, to the balanced American diet and to refrigeration, which reduces nitrate-producing bacteria in food.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Kidney cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The causes of kidney cancer aren't known, although smokers develop more renal cell tumors than nonsmokers. However, the incidence of this malignancy is rising, possibly as a result of exposure to environmental carcinogens as well as increased longevity. Even so, this cancer accounts for only about 2% of all adult cancers. Kidney cancer is more common in men than women and peaks in incidence between ages 50 and 70.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Laryngeal cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

In laryngeal cancer, major predisposing factors include smoking and alcoholism; minor factors include chronic inhalation of noxious fumes and familial tendency. Cancer of the larynx rarely occurs in nonsmokers.

Laryngeal cancer is classified according to its location:

❑supraglottis (false vocal cords)

❑glottis (true vocal cords)

❑subglottis (downward extension from vocal cords [rare]).

The ratio of male to female incidence is 3.8:1. Most victims are between ages 50 and 65.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Liver cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

The immediate cause of liver cancer is unknown, but it may be a congenital disease in children. Adult liver cancer may result from environmental exposure to carcinogens, such as the chemical compound aflatoxin (a mold that grows on rice and peanuts), thorium dioxide (a contrast medium formerly used in liver radiography), Senecio alkaloids, and possibly androgens and oral estrogens.

Roughly 30% to 70% of patients with hepatomas also have cirrhosis. (Hepatomas are 40 times more likely to develop in a cirrhotic liver than in a normal one.)

Whether cirrhosis is a premalignant state or alcohol and malnutrition predispose the liver to develop hepatomas is still unclear. Other risk factors are exposure to the hepatitis C virus and the hepatitis B virus.

Liver cancer accounts for roughly 1% of all cancers in the United States and for 10% to 50% in Africa and parts of Asia. Liver cancer is most prevalent in men (particularly men older than age 60), and incidence increases with age. It's rapidly fatal, usually within 6 months, from GI hemorrhage, progressive cachexia, hepatic failure, or metastasis.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

Lung cancer: Causes and incidence
(Professional Guide to Diseases (Eighth Edition))

Most experts agree that lung cancer is attributable to inhalation of carcinogenic pollutants by a susceptible host. Who's most susceptible? Any smoker older than age 40, especially if he began to smoke before age 15, has smoked a whole pack or more per day for 20 years, or works with or near asbestos.

Pollutants in tobacco smoke cause progressive lung cell degeneration. Lung cancer is 10 times more common in smokers than in nonsmokers; 80% of patients with lung cancer are smokers. Cancer risk is determined by the number of cigarettes smoked daily, the depth of inhalation, how early in life smoking began, and the nicotine content of cigarettes. Two other factors also increase susceptibility: exposure to carcinogenic industrial and air pollutants (asbestos, uranium, arsenic, nickel, iron oxides, chromium, radioactive dust, and coal dust) and familial susceptibility.

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Source: Professional Guide to Diseases (Eighth Edition), 2005

About prevalence and incidence statistics:

The term 'prevalence' of Cancer usually refers to the estimated population of people who are managing Cancer at any given time. The term 'incidence' of Cancer refers to the annual diagnosis rate, or the number of new cases of Cancer diagnosed each year. Hence, these two statistics types can differ: a short-lived disease like flu can have high annual incidence but low prevalence, but a life-long disease like diabetes has a low annual incidence but high prevalence. For more information see about prevalence and incidence statistics.