Understanding Cancer

By Marva Bohen, M.S., R.N.

Everybody is familiar with the word cancer. But, if any of us were asked, "What is cancer?" most of us would have a difficult time. Part of the difficulty stems from the fact that cancer refers to more than a hundred different diseases. All of these diseases have one thing in common: cells that divide and grow abnormally.

Normal cells keep a balance between new cell growth and the death of old cells. In cancer, cells multiply in an uninhibited fashion or they don't die off when they become old and damaged. This uninhibited growth and failure to die results in the formation of tumors.

Tumors are growths that develop within the body where the cells are abnormally dividing. Tumors tend to take nutrients away from normal cells and they also compress the normal cells and affect the ability of those cells to function. This will eventually result in a failure of the organ where the tumor is growing. In lung cancer, for example, the tumor may block airways and cause difficulty with breathing. Even if an airway is not directly blocked, the lung will not expand as easily and normal exchange of oxygen and carbon dioxide will be hampered.

It would be bad enough if cancers just destroyed the organ in which they began, but tumor cells can spread to other parts of the body. They do this in two ways. The first occurs when the tumor grows through the walls of the organ in which it begins. The tumor cells then begin to grow in the nearby structures and organs. A second way that tumors spread is by entering the lymph and blood systems. When tumor cells enter either of these systems, it can spread the cancer to very distant areas of the body. Thus, a person with lung or breast cancer can develop tumors in many other areas such as bone, liver, or brain.

The idea behind screening is to detect cancers before they have had an opportunity to spread beyond the original site. Early cancers often do not cause symptoms, so you could have a cancer and not know about it. By doing recommended screening the potential for finding a cancer in an early stage is greatly enhanced. Most cancers are more easily treated and cured if they are found at this early stage.

Many of the treatments we use for cancer are based on our knowledge about how the cancer cells behave. Most of the current standard therapies like radiation and chemotherapy treatments are designed to kill rapidly dividing cells. Unfortunately, they also affect some normal cells that tend to replicate quickly like hair and the mucous membranes of the mouth and digestive tract.

Newer treatments do things like prevent the tumor from developing its own supply of blood vessels, or they inhibit the proteins that trigger cell division for particular types of cells. The newer treatments tend to be more likely to affect only cancer cells and to have fewer side effects, but they also tend to be developed with particular types of cancers in mind. An example of this is a drug called Gleevec, which was recently approved by the FDA for a particular type of leukemia. It has proved to be useful for a couple of other types of cancer, but because of its specific action it will not be a cure-all for most cancers.

Marva Bohen is a member of the University's Cancer Center. To learn more about breast cancer, visit www.cancer.umn.edu/page/research/breast.html or call the toll-free information line at 1-888 CANCER MN (1-888-226-2376) or 612-624-2620 in the metro area. This column is an educational service of the University of Minnesota. Advice presented should not take the place of an examination by a health-care professional. For more health-related information, go to http://www.healthtalk.umn.edu/