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Weighing risks, benefits of mammography.

A Swedish study hints at possible dangers of exposing the breast to doses of ionizing radiation, a finding that raises added questions about the risks of mammography, an X-ray examination that can reveal tumours in their very early stages.

A separate review of eight trials finds no benefit from mammography screening from women in their forties. Both reports appear in the Oct. 20 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

Lars Erik Rutqvist and his colleagues at the Karolinska Hospital in Stockholm studied women who had undergone radiation therapy, which delivers, ionizing radiation in doses 100 to 10,000 times higher than that used in a routine mammogram.

This team analyzed data collected from 1,216 women who received radiation therapy from the 1920s through the 1950s to treat benign breast disease.

Some women in benign breast disease face an increased threat of developing breast cancer; therefore, the researchers also studied a control group of 1,874 women who had this condition but had not received radiation therapy.

Previous studies have suggested that exposure in ionizing radiation at young ages may boost the risk of breast cancer later in life (SN: 11/11/89, p.311). However, some researchers have questioned whether that risk applies to women who are exposed to radiation after age 40.

The new Sweish analysis shows a statistically significant increase in the incidence of breast cancer following radiation therapy for benign breast disease, even among women who received their treatment after age 40.

This study didn't lock at the radiation risks for healthy women who get screening mammography. However, it is prudent to assume that there may be a risk -- albeit a small one -- of developing radiation-induced tumors from mammography, comments Charles Land of the National Cancer Institute (NCI) in Bethesda, Md.

Is that small risk enough to forego screening mammography, which can also identify malignant tumors and thus save lives? For women age 50 and older, as well as women at high risk of breast cancer, scientists say mammography's benefits far outweigh any risk. For women in their forties, however, this study's findings, as well as other evidence, may argue against routine mammography, Land and other scientists believe.

They point to a second report in the NCI journal, thisone prepared by Suzanne W. Fletcher of the American College of Physicians in Philadelphia and other participants in a February 1993 NCI workshop on screening for breast cancer.

The authors reviewed the current evidence and confirmed earlier findings that for women age 40 to 49 there appears to be no survival benefit in obtaining regular mammograms.

For women age 50 to 69, however, the review noted that routine mammography reduces the risk of dying from breast cancer. For women in their 70s and older, the panel found too little data to draw any conclusions.

The report's findings regarding women in their forties have drawn the most fire: "It is scientifically unjustified to claim that screening women aged 40-49 is ineffective," according to Edward A. Sickles of the University of California School of Medicine, San Francisco and Daniel B. Kopans of the Harvard Medical School in Boston. Sickles and Kopans wrote an editorial in the same issue of the journal. They contend that the Fletcher report drew on flawed studies.

Nonetheless, NCI has proposed changing its mammography guidelines for healthy fortysomething women. The proposal would have women age 40 to 49 consult with their doctor about the advisability of a mammogram. In the past, NCI recommended a mammogram at one-to two-year intervals for women in that age group.
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Author:Fackelmann, Kathy A.
Publication:Science News
Date:Oct 23, 1993
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