INSUFFICIENCY BONE FRACTURE AFTER PELVIC RADIOTHERAPY: RETROSPECTIVE EVALUATION OF RISK FACTORS AND DOSE-VOLUME RELATIONSHIP ANALYSIS.

Andrea Ruggieri, Claudia Airaldi, Barbara Baiotto, Eva Gino, Lavinia Bianco*, Michele Stasi, Chiara De Colle and Maria Grazia Ruo Redda

ABSTRACT

Introduction: Pelvic insufficiency fracture (PIF) is a possible but still underestimated complication of pelvic radiotherapy, defined as a non-physiological bone fracture related to demineralization and decreased elastic resistance. The aim of this retrospective study is to identify patients’ characteristics and possible risk factors in order to prevent, correctly diagnose and treat future PIFs. Methods: Between 2008 and 2012, 264 patients with pelvic malignancies were treated with RT. Nine had symptoms suggestive for PIF. Median age was 66 years. All symptomatic patients were studied with Magnetic Resonance Imaging, 5 underwent Positron Emission Tomography and 2 patients had a bone scan. In 6 patients we retrospectively contoured the fracture site and we analyzed Dose-Volume Histograms data. Two different treatment plans were created for each patient, 3DCRT and IMRT, and compared in order to define possible differences in target and Organs at Risk coverage and dose. Results: PIFs were diagnosed after a median of 15 months after RT, with the sacrum as the most frequently involved site. Three out of nine patients had osteoporosis and eight out of nine received neoadjuvant/concomitant chemotherapy. The mean maximum dose and the mean dose on bone which developed PIF were 53,7 Gy and 34,1 Gy, respectively. IMRT plans, even without pelvic bones optimization, were superior to 3DCRT in reducing the dose to pelvic bones (p<0,001). Conclusions: As pelvic RT has become a curative treatment for many oncological patients, late toxicity effects such as PIF need more attention and accuracy in diagnosis and treatment. Possible risk factors could be osteoporosis and neoadjuvant/ concomitant chemotherapy. The use of IMRT and the study of bone status before beginning treatment could help to prevent PIFs, especially in high risk patients.

Keywords: Insufficiency bone fractures, Pelvic Radiotherapy, Complication.