Breast cancer following multiple chest fluoroscopy: the Ontario experience.

The hypothesis, derived from experience in Nova Scotia, that artificial pneumothorax, requiring repeated fluoroscopy of the chest, is associated with an increased risk of subsequent breast cancer was tested in Ontario by means of a retrospective cancer patient/control study using record linkage. Sanatorium patients treated by artificial pneumothorax were estimated to have incurred a risk of breast cancer between two and three times as high as that of matched, contemporary sanatorium patients treated by other means. There was a tendency for the malignant disease to develop on the side of collapse, and there was evidence of a characteristic latent interval between exposure and onset.