Attacking Cancer With Radiation

By Kathryn Dusenbery, M.D.

Scientists are continually striving to improve the way cancer is treated, including developing more effective treatment methods and reducing the side effects of current therapies. Some of the most exciting changes are happening with radiation therapy.

Radiation therapy is the use of penetrating beams of high-energy waves, called radiation, to destroy the ability of cancer cells to grow and divide. It is also used to help control the symptoms from a tumor that has spread, such as relieving pain by shrinking a tumor pressing on nerves. More than half of all cancer patients will have radiation therapy at some point during their treatment.

Most cancer patients who receive radiation therapy have external radiation in which a machine directs radiation at the tumor, but it can also affect a small margin of tissue surrounding it. Because external radiation therapy affects both normal and cancer cells, my colleagues at the University's Cancer Center are working to deliver radiation directly to a tumor by combining the cancer-killing ability of radiation with the targeting power of an antibody. These are special monoclonal antibodies, protein substances made in the laboratory, that identify and bind to cancer cells. Radiation can be attached to the antibodies, making the antibody capable of both finding cancer cells and destroying them.

Researchers also are using radioactive "seeds" to deliver radiation directly to a tumor. The seeds can be implanted into certain organs, such as the prostate, to kill the tumor from within yet without affecting surrounding normal tissue. This is a minor procedure and most patients go home the same day it is performed. We have found that these radioactive seeds are especially successful as an alternative to surgery for patients with prostate cancer.

A new tool to make radiation therapy even more effective against some kinds of cancer is a computerized technology called intensity modulated radiation therapy (IMRT). IMRT uses 3-D imagery and computer-controlled planning: the computer optimizes the distribution of radiation. This allows doctors to exactly match the dose of radiation to the shape of the tumor, allowing a higher dose at a thicker part of the tumor and a lesser dose at a thinner area. This also minimizes the risk of possible damage caused by radiation to surrounding normal tissue. IMRT is used to treat head and neck tumors, base of skull tumors, and some lung and prostate cancers.

Other research is being conducted in an effort to reduce the side effects caused by radiation. A promising study is determining if drugs called radiation protectors can prevent radiation damage to surrounding normal tissues. The drugs, given to patients before receiving radiation therapy, also may help prevent some of the side effects of chemotherapy such as fatigue and hair loss.

Kathryn Dusenbery is an associate professor and head of the University of Minnesota's therapeutic radiology-radiation oncology department and a member of the University's Cancer Center. To learn more about cancer, visit www.cancer.umn.edu 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 and advice presented should not take the place of an examination by a health-care professional. For more health-related information, go to  http://www.healthtalkandyou.com/.