Estimating Cancer Risk from X-Rays

Using a new calculation to estimate the risk of cancer from exposure to diagnostic X-rays, Amy Berrington de González, of the University of Oxford, United Kingdom, and Sarah Darby, of Cancer Research UK, suggested in a recent article that in the UK around 700 of the 124,000 cases of cancer diagnosed annually could be attributable to exposure to diagnostic X-rays. The article appeared in the Jan. 31, 2004, issue of The Lancet.

The authors' estimate of around 700 additional cancer cases annually in the UK is equivalent to a cumulative risk of cancer to age 75 years of about 0.6 percent. That number rises to 3 percent in Japan, they calculated, the country with the highest estimated annual X-ray use in the world.

Berrington de González and Darby concluded that, "[a]lthough there are clear benefits from the use of diagnostic X-rays, that their use involves some risk of cancer is generally acknowledged. We provide detailed estimates of these risks." Because some of their calculations depended on assumptions, the results were somewhat uncertain.

Peter Herzog and Christina Rieger from Ludwig-Maximilians University Munich, Germany, stated in an accompanying commentary, "Berrington de González and Darby did not assess the indications or benefits achieved for patients in Xray examinations. Benefits include the earlier detection of cancers by radiological examinations and the possibility of early treatment, which probably allows more cure of cancers than radiological exposure is able to cause."

Radiation Epidemiology Short Course and Lecture Series

Under the direction of Dr. Peter Inskip, NCI's Radiation Epidemiology Branch (in the Division of Cancer Epidemiology and Genetics) will offer a short course from May 4 to 14 on a variety of topics in radiation epidemiology. Speakers include NCI staff and scientists from other government agencies and academic institutions. The course is intended for those who have epidemiology backgrounds and are interested in the health effects of exposure to radiation, particularly the relationship between ionizing radiation and cancer. The course is free but advance registration is required.

The program offers an overview of the radiation epidemiology field, with a focus on radiation-related cancer. It begins with basic radiation physics, dosimetry, radiation chemistry, and radiobiology and continues with presentations on epidemiologic studies of radiation-exposed populations, including atomic bomb survivors in Japan, medically irradiated populations, and persons with occupational or environmental radiation exposures. Methods for quantifying radiation risks, the use of such information in setting radiation protection standards, and risk communication also will be discussed. The course focuses on ionizing radiation but also considers nonionizing radiation. Throughout the course, instructors will stress the importance of radiation dosimetry in epidemiologic studies and highlight key methodologic issues, including challenges in the study of low-dose effects. Possible new sources of radiation exposure and their potential risks will be covered. For more information on the Radiation Epidemiology Course, please visit http://dceg.cancer.gov/epicourse.html.

NCI to Put Partial-Breast Irradiation to the Test

A clinical trial of partial-breast irradiation (PBI), slated to start in late summer 2004, will test whether this technique is equivalent to radiation treatment of the whole breast.

For early-stage breast cancer, lumpectomy followed by whole-breast irradiation (WBI) is an alternative to mastectomy. But it took 20 years of follow-up data to establish the scientific basis for lumpectomy. Now, PBI must be tested with similar scientific rigor. PBI often involves approximately one week of radiation treatment vs. six weeks of daily radiation for WBI. Since traveling to treatment may be a hardship for some women, the shorter duration of PBI is appealing.

"Many women are seeking out this treatment," said Dr. Paul Wallner of NCI's Radiation Research Program, especially since the Food and Drug Administration (FDA) approved a PBI device in 2002. The FDA, which based its decision on a study involving 25 women, declared the apparatus safe. The agency did not comment on the efficacy of PBI for treating breast cancer.

"We still don't know what types of patients are best suited to PBI, how much radiation to use, how much breast tissue to target, or if the end results will be equivalent to WBI," said Dr. Wallner.

In the Feb. 4, 2004, Journal of the National Cancer Institute, Dr. Wallner and colleagues detail issues that need to be addressed before PBI can become standard practice. A clinical trial dealing with these issues will be sponsored by NCI's Cancer Therapy Evaluation Program. Dr. Frank Vicini, of Michigan's William Beaumont Hospital, will head the multisite, 2.5-year study of 3,000 women.