Cancer Over View

   Cancer is doubtless the most dreaded disease afflicting the human race today. Although deaths from cancer, the second most common killer in the United States are exceeded only by those from heart disease, cancer creates far greater fear in the sufferer than do coronary heart disease, stroke, diabetes, or chronic kidney failure-diseases that also take a heavy toll on life. Every two years cancer kills more Americans than the total number killed in the four most recent wars: World War I, World War II, Korea, and Vietnam. And every year cancer kills seven times the number of Americans killed in automobile accidents!

   More than 1.3 million new cases of cancer occur every year in the United States, Of these, 400,000 are skin cancers with a relatively low mortality, but for the remaining 900,000, the annual death rate is about 50 percent! Cancer of the lung accounts for the largest number of these deaths, among both men and women. For those who receive treatment, the results are often given in terms of five-year survival rates. Unfortunately, this often causes the victims to be haunted by fear that the cancer will recur.

   In spite of these  somber facts, though, the outlook for cancer victims has been steadily improving. The five-year survival rate has doubled in the last fifty years, and of saved by early diagnosis and prompt treatment. It one adds to this the fact that almost all lung cancers could be eliminated if tobacco smoking were abolished, the outlook for anyone dying from this disease is far less discouraging than it was just a few years ago.

Read more »

What is a cancer

   Cancer is not a single disease, but takes more than 100 forms, all of which are characterized by a multiplication of cells that threaten life. In this sense, the term neoplasm, or new growth, is most fitting. In most types, a tumor, or enlarging mass, develops as a result of a steady and abnormal multiplication of cells. Cell multiplication that is restricted to a single site is called a benign tumor.  When the multiplying cells invade adjoining tissues, or when they are carried in body fluids (blood, lymph) to other parts of the body, the mass is called a malignant tumor, or carcinoma.  Thus the most common medical terms used to designate a cancer are malignant tumor, malignant growth, neoplasm, or carcinoma. 

   All but the most highly specialized cells of the body can replace themselves when worm out, injured, or aged. The superficial cells of the skin, and hose lining the intestinal tract and the uterus, are constantly being rubbed or sloughed off. New cells forming in the deeper layers replace those that are lost, thus maintaining a constant balance between loss and renewal.

    This is also true of blood cells. Red blood cells live for about 120 days. Each second some two to three million worm-out red corpuscles are taken out of circulation by the spleen. At the same time, a similar number of new red blood cells enter the circulatory system from the bone marrow, where they are manufactured. White blood cells always increase in number under the stimulus of an infection, but the body will return to a normal production level when the infection is over.

   Normally, the human body maintains a precise control over the number of cells that make up its tissues, so that it produces only the cells that it needs. When the required number is reached, cell production stops. This control over cell production resides in the genes that are found in the nucleus of each cell. The DNA molecules in the genes are "coded" to regulate how each cell grows and the work it does, thus enabling every cell in the body to work in cooperation with all other cells. As the body grows, beginning at conception and continuing to adulthood, the number of cells increases enormously, but the rate of increase is always controlled very carefully so that only the proper number of each cell is produced.

   In a cancer cell, though, the DNA molecules have been altered or rearranged in subtle ways hat change them into what we call "oncogenes," or cancer genes. The oncogene calls in a developing neoplasm or cancer multiply in spite of the body's normal checks and balances. The body loses control of its cell growth, and the cancer cells no longer obey the signal to stop growing.

Read more »

Types of cancer

   Cancers are subdivided into two large classes: benign and malignant. Benign tumors,  as already mentioned, remain isolated from the surrounding tissues and grow within their own capsule. Although benign means harmless, the increasing size of these tumors may displace adjoining structures, and by placing pressure on adjacent tissues may sometimes cause damage. A fatty tumor called lipoma, which develops under the skin, causing a bump on the body's surface, belongs to this benign class.

   Malignant tumors

   Malignant tumors are composed of cells whose multiplication is out of control, and as they continue to multiply they send out tentacle like projections called processes that invade surrounding tissues. The invading growth often destroys these structures, usually by interfering with and appropriating their supply of blood. This may lead to bleeding and ulceration.

   Often these wildly-growing cells break away in small groups and, carried in the blood or lymph, travel to distant organs. Here they set up a beach-head, and, once established, develop into secondary tumors similar to the original one. This process of migration is called metastasis.  Metastatic tumors may endanger the victim's life even more than the original tumor.

   As a cancer develops in a particular part of the body, its cells more or less partake of the nature of the normal cells of the tissue or organ in which it originates. For this reason, the various kinds of cancer roughly parallel the various kinds of normal tissue in which a malignant tumor may grow. While there are numerous classes and subclasses of cancers, we will mention only four major types:

   Carcinomas. The largest group of cancers, known as carcinomas, originate from epithelial cells. Some of these cover the body's surfaces, such as the skin, Others line its tubes and cavities, such as the mucous membranes of the air passageways, intestines, bladder, and uterus. Still others compose the functioning cells of its glands, as in the salivary glands, the liver, pancreas, and prostate.

   Leukemias develop in the tissues that produce blood cells, such as the bone marrow and lymph nodes.

   Lymphomas develop from the cells of the lymph glands, as for example, the spleen and lymph nodes.

   Sarcomas arise in the body's supporting tissues bone, blood vessels, muscle, and fibrous tissue.

  

Read more »

What causes cancer?

   The precise cause of cancer is not known. However, a vast amount of research over the past half century has helped us to make large strides in our understanding of this very complex and difficult disease. It now appears that most cancers develop because of a series of events that take place in a single cell of the body over a period of years. These  events convert this once normal cell into an abnormal cancer cell.

   Two types of factors contribute to this change: those that start the process of change, and those that continue the process once it has started. The first group of agents are called initiators, while the second group are called promoters. An initiator may be a chemical, radiation, or virus. A promoter may be a different agent in one of the same three groups.

   Research  has revealed that certain oncogenes produce a protein that establishes itself in the nucleus, or command post, of the cell. Other oncogenes produce a different protein found in the edges of the cell. It is possible that one of these proteins is produced by the initiator and the other by the promoter. Working hand in hand, these agents cause  the cell to multiply and spread without control.

   Chemicals that can produce a first or subsequent event in the transformation of a normal cell to a cancerous cell are called carcinogens. Carcinogens often require some other agent to work with them. These agents are called co-carcinogens. Over time, the action of one or several carcinogens (or co-carcinogens that are in the nucleus of a cell, especially those that control the multiplication of cells. When the genes that control cell reproduction finally change into an oncogene (or cancer gene), the body's normal control over the growth and multiplication of cells is lost, and a wild-growing cancer starts on its fateful course.

Read more »

Physical agents causes cancer

   Physical agents. Excessive exposure to sunlight is an important predisposing factor to cancers of the skin. The solar keratoses (thickening of epidermal cells) that occur on those portions of the body exposed to the sun are the intermediate stage between normal skin and skin cancer. These develop more frequently in farmers,sailors, and other workmen whose activities expose them to large amounts of ultraviolet radiation form sunlight. Sunbathing with prolonged and unnecessary exposure to the sun is unwise. Because of the high level of pigment in their skin, dark people are less susceptible to skin cancer than are those with a fair complexions.
   Exposure to radiation in X-rays or atomic radiation increases a person's susceptibility to cancer. When X-ray equipment was first introduced, the precautions required today were not used, with the result that those working in the field were needlessly exposed to radiation. For example, radiologists had ten times the incidence of leukemia as did physicians in general. Because of improved technology, the X-rays used today expose both radiologist and patient to a minimal amount of radiation, thus drastically reducing the risk of adverse effects.
   Excessive temperature appears to make tissues vulnerable. Cancer of the lip is quite common among pipe smokers. The heat from the pipe stem is thought to be an important factor (a promoter) in causing cancer of the lip. A testicle that has not descended into the scrotum is more likely to develop a malignant change because the body temperature inside the body is higher than in the scrotal sack.

Read more »

Predisposing factors causes cancer

   Heredity, environment, and life style all play important roles, either singly or in combination, in the development of cancer. Many experts believe that as many as 90 percent of human cancers result from exposure to carcinogens that could be avoided.

   Heredity.  There appears to be a strong hereditary tendency for the development of certain types of cancer. A woman whose female relatives have had breast cancer carries a three to five-times greater risk of developing breast cancer than does the woman without such a family history. Again, two individuals may smoke the same number of cigarettes a day and inhale just as deeply, yet twenty years later one will develop a lung cancer and the other continue in apparently perfect health. Heredity may be one reason for this. However, the conclusion that heredity caused the difference must be tempered by the fact that other important lifestyle difference must be tempered by the fact that other important lifestyle differences between the two individuals may have caused one to contract cancer and the other to remain free, even though their smoking habits were identical.

   Environment.  It is now recognized that modern man's environment is filled with opportunities for coming in contact with agents that, over the long-term, can initiate a malignant growth. We can mention several.

Read more »