Estimation of Breast Doses and Breast Cancer Risk Associated with Repeated Fluoroscopic Chest Examinations of Women with Tuberculosis

Abstract

Methodology is presented to estimate cumulative breast dose and breast cancer risk for women exposed to repeated fluoroscopic chest examinations during air collapse therapy for pulmonary tuberculosis. Medical record abstraction, physician interview, patient contact, machine exposure measurements and absorbed dose computations were combined to estimate average breast doses for 1047 Massachusetts [USA] women who were treated from 1930-1954. The methodology presented considers breast size and composition, patient orientation, X-ray field size and location, beam quality, type of examination, machine exposure rate and exposure time during fluoroscopic examinations. The best estimate for the risk of radiation-induced cancer for women living longer than 10 yr after initial fluoroscopic exposure is 6.2 excess breast cancers/106 women-yr[WY]-rad with 90% confidence limits and 2.8 and 10.7 cancers/106 WY-rad. When breast cancer risk is considered as a function of absorbed dose in the breast, instead of as a function of the number of fluoroscopic examinations, a linear dose-response relationship over the range of estimated doses is consistent with the data. Because of the uncertainty due to small sample variability and because of the wide range of assumptions regarding certain fluoroscopy conditions, other dose-response relationships are compatible with the data.