Abstract
Bone atrophy is frequently seen following radiotherapy, occasionally resulting ininsufficiency fracture or necrosis as late sequelae, however, there have been no reportsconcerning early changes in bone mineral metabolism due to radiotherapy. In this study, temporal change of bone mineral density (BMD) in thoracic vertebrae during radiotherapy wasmeasured by Dual Energy X-ray Absorptiometry (DXA). To assess the accuracy of themeasurement of BMD in thoracic vertebrae, we studied experimentally with a phantom patient.From the results of the coefficient of variation (CV%) ranging from 0.13 to 0.59, this techniquewas considered to accurately quantify BMD. In a clinical study, the BMD of thoracic vertebraein 74 patients (lung cancer: 55, esophageal cancer: 12, malignant lymphoma: 7) who receivedradiotherapy for treatment of malignancies were measured by DXA. The patients' ages rangedfrom 52 to 79 (average=60.8±11.5), with 57 male cases, and 17 female cases. The doses ranged from 50 to 60Gy. The BMD of thoracic vertebrae located in the region ventral to the sternumwas measured. Also, the serum levels of parathyroid hormone (PTH) before and after radiotherapy were measured in 31 patients. The BMD of Th12 in the nonirradiated field did notchange appreciably. The BMD of thoracic vertebrae in the irradiated field decreased graduallyduring radiotherapy and reached 89.6±7.8% of the preradiation value after 50Gy, and 87.1±4.5% of the preradiation value after 60Gy. The value of PTH after radiotherapy increased slightly in comparison with that before radiotherapy (P<0.05).
