Breast and Other Cancers Following X-Rays for Scoliosis

U.S. Scoliosis Cohort includes 5,573 female spinal deformity (93% scoliosis) patients diagnosed in any of 14 medical centers in the U.S. during 1912-1965. The primary objective of this study is to evaluate site-specific cancer risks associated with repeated low-dose radiation exposures from diagnostic x-rays. A secondary objective is to evaluate late mortality risks associated with patient characteristics, such as etiology, degree and type of curvature, and type of treatment. The current proposal is to extend mortality follow-up by 10 years. All patients not known to be deceased will be submitted to the National Death Index Plus to identify new deaths and obtain causes of death.

A feasibility study was conducted in four medical centers in the Minneapolis-St. Paul, Minnesota area during 1983-1987. The primary goals of the feasibility study were to ascertain if an adequate number of patients meeting the study criteria could be identified and located, medical and radiography records were available and substantially complete, organspecific radiation doses could be estimated from the available data and were large enough to warrant further study, and a reasonable percentage of patients would complete a follow-up questionnaire. The feasibility study was successful in meeting all goals. Enrolled for study were 1,030 female patients with spinal deformities diagnosed during 1922-1965. Medical records were abstracted, individual x-ray films were reviewed, patients were located, and follow-up questionnaire was administered to identify incident cancers. Eleven breast cancers were reported. Scoliosis patients had an 80% higher breast cancer risk compared to women in the general population and, based on internal cohort analyses, breast cancer risk increased with increasing number of x-rays and with estimated radiation dose to the breast.

An expanded study was conducted during 1988-1993. The main goals of the expanded study were to enlist the collaboration of suitable additional medical centers where large numbers of spinal deformity patients were treated before 1966, abstract data from medical and radiology records, trace patients for vital status and current location, obtain information on incident cancers and cancer risk factors by questionnaire, medically validate reported cancers, and determine causes of death for decedents. Another 4,543 patients diagnosed during 1912-1965 were enrolled from ten hospitals, bringing the total study population to 5,573 patients. Compared to women in the general population, spinal deformity patients had statistically significantly higher risks of dying from breast cancer, and for both incidence and mortality, breast cancer risk increased with increasing diagnostic radiation exposure to the breast. Patients also have elevated risks for mortality from all causes, circulatory, respiratory, nervous system, musculoskeletal, digestive, and infectious & parasitic diseases, primarily related to degree of spinal curvature. Additional mortality follow-up will enable more definitive assessments of cancer and other disease risks with radiation and other factors in these patients.