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DOES RADIOTHERAPY INCREASE RISK OF CANCER IN THE OPPOSITE BREAST.

Even contemporary radiotherapy techniques for breast cancer expose the contralateral breast to potentially carcinogenic levels of radiation. This case-control study compared the use of radiotherapy in two groups of women from the Connecticut Tumor Registry who were diagnosed with breast cancer between 1935 and 1982: 655 women who developed cancer in the contralateral breast 5 or more years after the initial tumor, and 1189 controls without a contralateral cancer. Cases and controls were matched for age, year of diagnosis, and race.

Among women who survived at least 10 years after diagnosis, radiation treatment was associated with a marginally elevated risk of contralateral breast cancer; this risk rose with higher doses of radiation. However, the increased risk was seen only in women who were under age 45 when they received radiotherapy (relative risk, 1.6).

Patients with cancer in one breast are three times more likely than average to develop a second breast cancer, even without radiation therapy. The investigators calculate that radiotherapy increases this risk by 2.7 percent overall, and by 11 percent in women receiving radiotherapy before age 45. They conclude that the small additional risk of cancer in the contralateral breast should not affect decisions about using radiotherapy in breast cancer.

— ALK

Published in Journal Watch General Medicine March 24, 1992

Citation(s):

Boice JD et al. Cancer in the contralateral breast after radiotherapy for breast cancer. N Engl J Med 1992 Mar 19 326 781-785.

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