Incidence of radiation-induced insufficiency fractures of the female pelvis: Evaluation with MR imaging

OBJECTIVE. The purpose of this study was to assess the incidence, time of appearance, and evolution of radiation-induced insufficiency fractures of the female pelvis with MR imaging. SUBJECTS AND METHODS. Eighteen women (nine premenopausal and nine postmenopausal) with advanced cervical carcinoma were studied prospectively with MR imaging. The examinations totaled 216 and were scheduled before radiation therapy, three times during radiation therapy, and eight times after radiation therapy. T1-weighted and shea inversion time inversion recovery images were obtained. The images were evaluated by two radiologists in consensus. The criterion for fracture was edema, indicated by an area of high signal intensity on short inversion time inversion recovery images and corresponding low signal intensity on T1-weighted images. CT scans (n = 61) and bone scans (it = 58) were used to confirm each diagnosis of fracture. RESULTS. Sixteen (89%) of Is patients (seven premenopausal and nine postmenopausal) showed findings compatible with insufficiency fractures. Thirteen patients had more than one lesion. The first fracture was detected between 3 and 12 months after the end of radiation therapy. During the study, the fractures associated with edema subsided without treatment in 41 (79%) of 52 lesions in 15 (94%) of 16 patients. Fractures were confirmed with additional imaging in all 16 patients (CT in 14 patients and bone scanning in nine patients). CONCLUSION. Radiation-induced insufficiency fractures were frequently seen in premenopausal and postmenopausal women within 12 months after radiation therapy. Multiple fractures developed within 24 months. Twenty-one percent of the lesions healed during the observation period of 30 months.