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Why is it that one of the most frequent questions asked by people diagnosed with cancer is "how long do I still have to live"? The answer lies in the fact that your chances of survival after cancer is diagnosed remains relatively low compared to other diseases.(1) Cancer is the general term for all tumors that can invade other tissues and spread to distant parts of the body.(2) It is a chronic disease whose common effects depend on its primary site of growth and its eventual site of spread. Bodily harm becomes apparent when cancer cells exert their deleterious effects on normal cells in its immediate vicinity and those in distant sites by causing their destruction and altering their normal functioning via release of certain hormones, compression of their nerve supply and parts, and blockage of blood vessels responsible for their nutrient supply.(3) How cancer cells are produced and how they harm the body will be discussed in more detail in the next sections.
Our body is made up of trillions of cells whose growth and division are carefully monitored and controlled. When the body's control system that promotes the growth of one type of cell malfunctions (4) because of spontaneous genetic mutations and/or exposure to infectious agents, radiation or chemicals, these cells undergo uninhibited growth and cancer cells are formed. The abnormal cells will prompt more blood vessels to grow around its vicinity to provide the massive amounts of nutrients and oxygen necessary to facilitate its fast growth and frequent replication(5). As cancer cells undergo rapid division, they pile up and form a lump or mass that most of us refer to as tumor. Several cancer cells may sometimes break away from the mass, travel all over the body in the blood stream or lymph then invade distant organs in the process known as metastasis.
This occurrence can affect all of your cell types and can occur in every part of your body. Signs and symptoms of cancer are felt when the abnormal mass of cancer cells exerts pressure and/or invade surrounding tissues and when the cancer cells metastasize and invade distant organs.
EFFECTS OF CANCER CELLS
The cancer cells at the sites of local growth and metastasis can cause numerous harmful effects on its surrounding healthy cells. First, the normal functions of the body's cells are altered by the presence of the tumor and the hormones it can release. A very large mass of cancer cells inside the body's limited space can crowd and squeeze all surrounding tissues including solid and hollow organs, nerves and blood vessels in the area.
Compression of nearby cells comprising solid organs like the brain, liver and kidneys can lead to the death of the portion of the said organ that has lost its oxygen and nutrient supply. The same thing happens when nearby blood vessels are compressed, nutrient- and oxygen-rich blood will be blocked from reaching the normal cells, causing many of them to die. In contrast, if a portion of a hollow organ like the trachea and bronchi, gastrointestinal tract, ureter, and urinary bladder is crushed, substances passing thru the organs will be blocked. For example, if the trachea or bronchi becomes completely blocked by a tumor, air cannot pass deeper into the lungs and your body will be deprived of oxygen; if a portion of the gastrointestinal tract is compressed, food and water cannot go beyond the obstruction leading to nutrient deprivation; and if the ureter and urinary bladder are squeezed, urine cannot be completely excreted out of your body.
When tumor cells compress nearby nerves to the extent that they become crushed and deprived of oxygen, nerve damage may occur.
The symptoms of nerve damage depend on the type of nerve involved, whether sensory, motor or autonomic. Damage of sensory nerves will impair sensations and lead to intense pain, numbness, tingling sensation, etc. Motor nerve damage will affect all organs responsible for movement hence symptoms will include weakness, paralysis, twitching and muscle atrophy. Autonomic nerve damage will cause malfunctions of all involuntary body functions (heart rate, breathing, blood pressure, sweating, etc.), including gland dysfunctions. (6) Glandular involvement especially that of the endocrine glands will cause decreased or excessive production of certain hormones that can also alter the usual functioning of normal cells.(7)
Invasion of adjacent tissues is another hallmark of tumor cells. Bleeding may occur when cancer cells breach an organ's natural borders. Also, if the tumor cell has replaced most of the normal cells of a particular organ, its functions will not be carried out anymore. For example, when the site of blood cell production, the bone marrow, has been infiltrated by cancer cells, the number of all blood cells will decrease including white blood cells (leucopenia), red cells (anemia), and platelets (thrombocytopenia). Hence you will be prone to infections because there are not enough white cells to fight off infections, you will feel week because there are not enough red blood cells to supply oxygen to your cells and you will bleed easily because you don't have enough platelets to produce a strong clot.
Last, cancer cells cause many normal cells to die. They tend to selfishly obtain all available nutrients to promote their rapid growth and frequent reproduction. This will leave the surrounding normal cells with very little resources to keep them healthy and functioning, hence most of them die, thereby leaving behind a larger space to accommodate the cancer cells' rapid expansion. The physical manifestation of these changes in man is sudden severe weight loss due to the continuous death of normal body cells and the appearance of a mass or "tumor" that continues to grow bigger until it becomes palpable or physically obvious.
Some cancer cells will eventually detach from the main tumor and let the blood stream or lymph carry them to distant sites. Cancer cells are also not choosy; they will invade any organ that they come into contact with. As cancer cells invade distant sites, more organs become affected, hence symptoms become more severe. If your body's cells cannot perform their proper functions, then your body as a whole will start to breakdown. Furthermore, if there are not enough normal cells to maintain your body organ's function, organ failure will occur thereby leading to death.
In summary, cancer cells are abnormal cells whose growth and reproduction cannot be controlled. Their rapid division and ability to invade and spread to distant sites cause a multitude of harm on the body by killing normal cells and/or altering their function. Many cells die and numerous organs cease to function properly with the release of certain hormones, compression of their nerve supply and parts, and blockage of blood vessels responsible for their nutrient supply. If there are not enough normal cells to maintain your body's over-all function, death follows.