Cancer emerges as a major public health problem not only in developed countries, but also in many developing countries. It may be regarded as a group of diseases characterized y (I) an abnormal growth of cells, (II) an ability to invade adjacent tissues and even distant organs and (III) may end by death of patient if it was not successfully dealt with.
Cancer can occur at any site or tissue of the body and may involve any type of cells. The term primary tumor is used to denote cancer in the primary organ of origin. Secondary tumor denotes cancer that has spread to regional lymph nodes and distant organs.
Cancers in all forms are causing 12% of deaths throughout the world.at the beginning of this century, cancer was the sixth cause of death in developed countries. However, today, it is the second leading cause of death next to cardiovascular diseases accounting for 21% of all deaths in these countries. In developing world, it ranks third as a cause of death and accounts for 9.5% of all deaths.
Mortality from cancer is low during infancy and preschool years, and drops to its minimum level during subsequent childhood period. At older ages the rates rises consistently to a peak. More than half the cancer deaths today are persons aged 65 and over.
In general, cancer occurs more frequently in females than in males. Yet for certain types of cancer, sex differences are observed. Apart from sex differences due to anatomic differences between the two sexes, the following is observed:
- Incidence of cancer lip, larynx, lung, bronchus, tongue, pharynx and esophagus is higher among males than females.
- Cancer of thyroid and biliary passages is more among females.
- Gastro-intestinal tract cancer is equally distributed among males and females.
Cancer is more among non-whites; this can be attributed to the increase of cancer of digestive and genital system especially for males. On the other hand, skin cancer is more among whites.
Both Jewish and Muslem women have very low rates of cervical cancer due to hygienic practices associated with sexual habits and male circumcision.
Cancer cervix occurs more in married women as it is related to sexual activity. This explains the low incidence in nuns and the very high incidence in prostitutes.
Cancer breast is more common among the unmarried, so nuns appeared to have an excess risk of cancer breast than other women.
There was an inverse association between cervical cancer and socio-economic status and that higher risks have been observed among those of lower socio-economic groups. On the contrary, breast cancer was found to occur more commonly among women of high socio-economic status. These differences may be due to differences in the lifestyle, dietary pattern, marital practices, fertility pattern and personal hygiene.
There are wide variations in the distribution of cancer throughout the world. For example, stomach cancer is common in Jaban, and has a low incidence in United states. on the other hand, breast cancer is common in United states and has a low incidence in Jaban. Also it was observed that cancer mortality is highest in urban and industrial communities, and lowest in mountain areas. In Egypt, due to the prevalence of bilharziasis, cancer bladder is more common than areas where there is no bilharziasis.
The international variations in the pattern of cancer are attributed to multiple factors, food habits, lifestyle, genetic factors or even inadequacy in detection and reporting of cancers. Also it may be attributed to differences in population structure.
The secular trend of cancer shows a steady increase not only of its incidence but also of its mortality. This steady increase could be explained by the followings:
- The development of better techniques for case-finding and detection.
- In the developed countries, communicable diseases have been largely controlled. Thus a marked decline in the incidence and deaths from these diseases occurred.
- Populations are showing now a marked increase in life expectancy with a greater risk of developing cancer, which is especially prevalent among older people.
- Changes in the lifestyle and changes in the environment that lead to exposure to risk factors that lead to the development of cancer.
Etiology of cancer:
Cancer has a multi-factorial etiology.
- genetic factor:
It is now believed that cancer have a tendency for familial aggregation.
- Lifestyle and habits:
Tobacco in various form of its usage is the major environmental cause of cancers of lung, mouth, pharynx, esophagus, bladder, pancreas, and probably kidney. It has been reported that cigarette smoking is responsible for more than one million premature deaths per year.
Excessive intake of alcohol is associated with esophageal and liver cancer. Recently it was suggested that beer consumption may be associated with cancer colon.
Dietary factors are also related to cancer. Smoked fish is related to cancer. Dietary fibers intake was found to be protective against cancer colon while food additives are related to intestinal cancer. A high fat diet is associated with breast cancer.
- Environmental factors:
The major environmental factors include:
- Occupational exposures:
Occupational exposures are usually reported to account for 1-5% of human cancer. The risk of occupational exposure is considerably increased if the individuals also smoke cigarettes. Examples of exposures leading to cancer are: exposure to asbestos and arsenic can lead to lung cancer; exposure to aromatic amines can lead to cancer bladder and benzene can lead to leukemia.
Several studies indicated that specific viral and parasitic infestation may be related to specific cancer. Examples of viruses associated with cancer are:
- Hepatitis B virus is causally related to hepato-cellular carcinoma.
- Epstein-Barr virus (EBV) is associated with Burkett`s lymphoma and nasopharyngeal carcinoma.
- Human papilloma virus (HPV) is a suspect in cancer cervix.
- Hodgkin`s disease is also believed to be of viral origin.
- Parasitic infection may also increase the risk of cancer, as example schistosomiasis and urinary bladder cancer.
- Physical agents:
Accumulated exposure to strong sun rays is known to increase risk of skin cancer and repeated sunburn also enhance the risk of melanomas.
In general, the most radio-sensitive organs that may develop cancer on repeated exposure to radiation are breast, thyroid and bone marrow.
Air pollution is an important cause of cancer. The incidence of lung cancer tended to be higher in urban than in rural areas.
Among the most frequently used drugs with carcinogenic potential are the estrogens which proved to be responsible for vaginal and cervical cancer in young women. However, contraceptive pills are not risk factors to cancer.
Advancing knowledge has increased the understanding of causative factors of some cancer and it is now possible to control these factors in the general one third of all cancers are preventable.
This is done through:
There is a need for legislation to control known environmental pollution, occupational exposures; each pollutant should not be permitted to exceed its standard level.
Legislation should also cover tobacco sales and alcohol as well as food, drugs and cosmetics. Testing these items for carcinogens should be enforced by law.
- Control of tobacco and alcohol consumption
- Health education:
Cancer education is an important preventive service. It should be directed towards behaviors related to:
- Avoiding smoking.
- Avoiding alcohol consumption.
- Improving personal female hygiene (cancer cervix).
- Attending for immunization (hepatitis B vaccine to prevent primary hepatocellular carcinoma and human papilloma virus vaccine to prevent cervical cancer).
- Attending for early detection and treatment of precancerous lesions ( as chronic cervicitis, intestinal polyposis and warts).
Efforts should be done to remind the public of the early warning signs of cancer jointly with cancer organizations. These are:
- A lump or hard area in the breast.
- A change in a wart or mole.
- A persistent change in digestive or bowel movement.
- A persistent cough or hoarseness.
- Excessive loss of blood at the monthly period pr loss of blood outside the usual dates.
- Blood loss from any natural orifice.
- A swelling or sore that does not get better.
- Unexplained loss of weight.
- Protection of workers
Measures to protect workers from exposure to industrial carcinogens should be enforced in industries.
It comprises the following measures:
- Early detection of cases:
Cancer screening is the main weapon for early detection of cancer at a pre-invasive state (in situ). This is because: (a) in many instances malignant disease is preceded for a period of months or years by a premalignant lesion which can be removed, (b) most cancers begin as localized lesions and if found at this stage a high rate of cure is obtainable and (c) as much as 75% of all cancer in body sites are accessible.
Effective screening programs by focusing on high risk groups have been developed for certain cancers as cervical cancer, breast cancer and oral cancer. Also, self-examination should be emphasized especially in cancer breast.
Treatment facilities should be available to all cancer patients as surgical removal, while some other cancers respond to radiation or chemotherapy or both. Treatment should include pain relief. Rehabilitation and psychological support must be done.
- Health education
All cancer patients should be motivated to attend for checkups and to comply with treatment given. They should be motivated to formulated cancer club associations and make use of cancer organizations.
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