Breast cancer following multiple chest fluoroscopies among tuberculosis patients. A case-control study in Denmark.

A case-control study of breast cancer among tuberculosis (TB) patients in Denmark (1937-1954) was conducted to provide additional information on the radiation risk associated with low-dose chest fluoroscopy exposures. Records of 46013 TB patients were linked to the Danish Cancer Registry and 125 subsequent female breast cancers identified. Medical records were located for 89 (71%) of these women who developed breast cancer and on 390 controls, who were individually matched to cases on age and calendar year of TB diagnosis, and survival. Common risk factors for breast cancer such as nulliparity (relative risk (RR) = 2.5) and high relative weight (RR = 2.6) were also identified in this population of TB patients. However no risk was evident with exposure to any type of fluoroscopy (RR = 0.6; 95% CI = 0.2-1.4), or to fluoroscopies performed to monitor lung collapse therapy (RR = 0.8; 95% CI = 0.5-1.4). Although based on only 7 breast cancers, there was a suggestion of an increased risk among women who received greater than 1 Gy to their breasts (RR = 1.6; 95% CI = 0.4-6.3). Because of the infrequent use of fluoroscopy in our study, the breast doses were too low, 0.27 Gy on average, to expect to detect a significant elevation in breast cancer risk overall. The findings do suggest, however, that current estimates of breast cancer risk following radiation are not greater than presently accepted, and that a relative excess of 40 per cent can be excluded with reasonable confidence following breast doses on the order of 0.3 Gy.