Cancer risk from Hodgkin's radiotherapy reduced
By Martha Kerr
NEW YORK (Reuters Health) - The radiation therapy that is currently used to treat Hodgkin's lymphoma is expected to reduce the rate of second cancers substantially, although the risk will vary considerably among individual patients, according to a new report in the medical journal Cancer.
"The issue of second cancer risk is probably of greatest concern for adolescent girls, where historically the excess risk of breast cancer after radiation therapy to the chest has been high," Dr. David C. Hodgson commented in an interview with Reuters Health. "We expect that this risk will be decreased by changes in radiation therapy practice that have occurred over the last decade."
Hodgson, of the University of Toronto, and colleagues devised three different radiation therapy plans for 37 consecutive patients with Hodgkin's lymphoma located in the chest. One plan consisted of 35 Gy radiation to the chest, neck and lymph nodes under the arm (mantle radiation therapy). The other two plans used 35 Gy or 20 Gy administered only to the affected area (involved field radiation therapy).
Compared with 35 Gy mantle radiation therapy, the researchers predicted the 35 Gy involved field radiation therapy would reduce the 20-year excess risk estimates for breast cancer by 63 percent and for lung cancer by 21 percent.
Low-dose 20 Gy involved field radiation therapy was associated with a 77 percent reduction in excess risk for breast cancer and 57 percent for lung cancer.
After involved field radiation therapy, there were patient-specific differences in the risk of breast cancer and lung cancer of 11-fold and 3.5-fold, respectively, Hodgson and colleagues report.
"Two potential advances in clinical practice are being tested in ongoing clinical trials," Hodgson added. "The first is that patients who have a rapid complete response to the first two or three cycles of chemotherapy may not need radiation therapy."
"The second is the further reduction in radiation field sizes to treat only areas of highest risk for relapse. For many women receiving chest radiation as part of their treatment, this would reduce the dose to the breast tissue by over 80 percent compared to treatment given in the 1980's."
The results of these trials "will help us identify which patients can safely avoid radiation therapy, and reduce the late effects among those who need it," Hodgson concluded.
SOURCE: Cancer, December 1, 2007.