The human body is composed of trillions of cells, which have distinctive functions. They form the tissues that make up the organs including the muscles, heart, liver and lungs. Some organs have rapid cellular turnover, meaning the cells die and new ones take their place, while other organs have slow cellular turnover. Sometimes the cells do not die, however. Cancer occurs when cells divide and grow out of control. There are several types of therapy available to treat cancer.
Types
According to "Harrison's Principles of Internal Medicine," cancer therapy can be grouped several different ways. The three main types are surgery, radiation and medicines. Most surgeries are aimed at removing the cancer. These are performed if the cancer is in a place in the body that the surgeon can safely remove it, if the person is healthy enough to undergo surgery and if studies have shown that surgery helps the particular cancer of interest. Some cancers respond better to different types of treatments, or in a different order. Not all surgeries are used just to remove tissues. Another type of surgery, bone marrow transplant, replaces the bone marrow with new, healthy bone marrow. Radiation penetrates the tissues and is targeted against the cancer. Medical treatments include chemotherapy, hormone therapy and targeted cancer therapy such as gene therapy.
Mechanisms
Surgery is generally used to excise a cancerous mass of cells. Ideally, the surgeon is able to remove all the cancer. This is much more likely to be effective if the cancer is not metastatic, meaning it has not spread from it primary, or original site of growth, through the lymphatics or blood vessels to establish itself other parts of the body. The tissue that is removed is studied by a pathologist to determine the characteristics of the cancer and if the edges of the tissue are free from cancer. Radiation therapy damages the DNA of the cancer cells. This can cause the cells to stop dividing and die. The radiation can be directed into a cancer from outside the body or radioactive materials can be placed into or near the site of the lesion. Medical treatments have many mechanisms of action. Some activate the immune system against the cancer. Many others stop the process of cell division by targeting DNA. Every cell needs DNA in order to function.
Benefits
Surgery, radiation and chemotherapy have two broad benefits or goals. The first is curative intent. This means that the therapy is directed at curing the cancer. The second is palliative care. In this case, therapy is directed at relieving the symptoms of cancer, such as pain.
Side Effects
There are a number of side effects from the treatment of cancer. Surgeries can have a significant period of recovery. Radiation can cause local tissue dysfunction. For example, radiation to the head and neck for cancer in the throat can damage the salivary glands and tongue, making the mouth dry and decreasing the ability to appreciate taste. Chemotherapy frequently causes nausea and GI problems, hair loss, and decreased blood counts.
Complications
Complications of surgery can include bleeding, damage to the surrounding organs, allergic reactions, to medicines used during surgery, nerve damage, and a number of other complications. Radiation therapy can damage the DNA in normal cells as well as cancerous cells, potentially damaging their functions and can cause other cancers in the future. Medical therapy, such as chemotherapy, can also damage the DNA in normal cells. The lowered blood counts can cause fatigue and an increased susceptibility to infections. However, these complications do not occur in everybody, and generally the benefits outweigh the risks.
References
- "Harrison's Principles of Internal Medicine"; Anthony S Fauci; 17th Ed 2008
- "Robbins and Cotran Pathologic Basis of Disease"; Vinay Kumar; 8th Ed 2009
