A healthy diet that includes low levels of animal fat and high levels of fresh fruits, vegetables, and fiber from grains will also markedly reduce the risk of cancer. Avoiding as much as possible ultraviolet (UV) radiation in sunshine is essential to prevent skin cancer later in life. Finally, knowing what chemicals in the environment are cancer-causing can help you avoid dangerous substances. Overall, if everything known about cancer prevention were practiced by everyone, up to two-thirds of all cancers could be prevented (American Cancer Society, 1997).

Another positive note is that about half of all cancer patients can be cured if their cancer is detected at an early stage before cancer cells have spread. Being “cured” of cancer means that a person’s life expectancy is the same as for a person who never had cancer. It is important to have cancer screening tests as indicated for your age and risk group; tests for the early detection of breast, colon, prostate, and cervical cancers are recommended by the American Cancer Society. You should also watch for early warning signs in functions of the body that may indicate that a cancer is developing.

 Incidence of Various Cancers

Cancers of the stomach, uterus, cervix, and testis and Hodgkin’s disease have declined significantly in recent years. However, cancers of the lung, skin, liver, prostate, and kidney and non-Hodgkin’s lymphoma have all increased in frequency. Overall, the mortality from cancer has remained virtually unchanged over the last generation, despite research and medical efforts.


The most serious increase has been the continuing rise in lung cancer in both men and women. Increases in lung cancer in men began to be noticed in the 1940s; in women, the increase did not become apparent until the 1960s. As everyone knows, the reason for the increase in lung cancer among both men and women is cigarette smoking. Women now die from lung cancer about half as often as men, and their rate of death is still increasing.


Addiction to nicotine and to cigarette smoking begins for both sexes as soon as smoking begins, during teenage years or even earlier. For this reason, government agencies and health organizations are now making a concerted effort to stop teenagers from smoking and thereby reverse the upward trend in cancer mortality.


What Is Cancer?

The term cancer comes from the Latin word meaning crab. Cancer was characterized as a crablike disease by the Greek physician Hippocrates, who observed that cancers spread throughout the body, eventually cutting off life. Now cancer generally is defined as the unregulated growth of specific cells in the body. The word cancer actually refers to over 100 different diseases, but in all cases, certain body cells multiply in an abnormal, unregulated manner.


Normally, the growth and reproduction of every cell in the body are regulated; this regulation, in turn, determines the size and functions of tissues and organs. If a normal body cell begins to grow abnormally and reproduces too rapidly, a mass of abnormal cells eventually develops that is called a tumor. A tumor generally contains millions of genetically identical abnormal cells before it can be detected or felt.


If the cells of the tumor remain localized at the site of origin in the body and if they multiply relatively slowly, the tumor is said to be benign. Benign tumors, such as cysts, warts, moles, and polyps, do not spread to other parts of the body. Benign tumors usually can be removed surgically and generally are not a threat to life. In fact, benign tumors weighing several hundred pounds have been surgically removed from persons who then recovered fully. Benign tumors cannot regrow if all of the abnormal cells are removed by surgical excision of the tumor.


Malignant tumors are composed of cells that grow rapidly, have other abnormal properties that distinguish them from normal cells, and invade other normal tissues. In particular, malignant cells may have altered shapes and cell-surface characteristics that contribute to their rapid proliferation. Many malignant cells also have abnormal chromosomes or altered genes, and they manufacture abnormal proteins. The numerous altered properties of malignant cells enable a pathologist, who is a physician who specializes in the causes of diseases, to determine whether the cells removed from a tumor are abnormal and to what degree.


The cells of most malignant tumors also undergo metastasis, a process in which cells detach from the original tumor, enter the lymphatic system and bloodstream, and are carried to other organs. Once the malignant cells spread to other organs, they develop into new tumors that often grow more rapidly than cells in the original tumor. Metastases and the growth of new tumors in many organs of the body eventually disrupt a vital body function, which is the cause of death.

Cancers are medically classified according to the organ or kind of tissue in which the tumor originates. The four major categories of cancers are carcinomas, sarcomas, leukemias, and lymphomas. Within these major categories are numerous subgroups that generally describe the organ in which the cancer originates, such as adenocarcinoma of the stomach or oat cell carcinoma of the lung. About half of all human cancers originate in one of four organs: the lung, breast, prostate, or colon, which is why so much research is devoted to these particular forms.


Cancer does not develop all at once in a cell. Several changes must occur in the genetic information (i.e., DNA) carried in a single cell before it can become a cancer cell and multiply into a tumor. Cells change their abnormal growth properties one step at a time; each genetic change pushes the cell further along the spectrum of abnormal growth. Not all cells acquire the same genetic changes nor can anyone predict when the changes will occur. That explains to some extent why some cancers develop and grow rapidly and cause death in months; other cancers may grow so slowly that the person eventually dies from a cause other than cancer.


Once a tumor has been detected, cells can be removed from it in a procedure called a biopsy; the cells are then examined under the microscope by a pathologist. In stage I, cancer cells can be distinguished from normal cells. The cancer cells are still localized (usually referred to as cancer in situ) and surgical removal of the tumor usually results in a cure. In stage II, the cancer cells have begun to metastasize and may have migrated to nearby lymph nodes. That is why lymph nodes near the tumor are removed and examined during surgery to determine if cancer cells have spread.


By stage III, the cancer cells have continued to grow and extend into the area around the tumor. In stage IV, tumors have spread to other parts of the body.


In 1997, prostate cancer was exceeded only by lung cancer as a cause of death in men. And among women, lung cancer now exceeds even breast cancer as the leading cause of death. Cancer of the colon and rectum, the third leading cause of death for both men and women, is believed to be strongly associated with fat-rich diets that are low in fiber.