Pelvic insufficiency fractures frequently occur following preoperative chemo-radiotherapy for rectal cancer - a nationwide MRI study

AimThe aim of this prospective case-control study was to evaluate the rate of pelvic insufficiency fractures (PIFs) in Denmark using MRI at the 3-year follow-up. All patients had rectal cancer and had undergone surgery with or without preoperative chemo-radiotherapy (CRT). MethodPatients registered with primary rectal cancer in the Danish Colorectal Cancer Group database, who underwent rectal cancer resection from April 2011 through August 2012, were invited to participate in a national MRI study aiming to detect local recurrence and evaluate quality of the surgical treatment. Pelvic MRI including bone-specific sequences 3years after treatment was obtained. The primary outcome was the rate of PIFs; secondary outcome was risk factors of PIFs evaluated in multivariate analysis. ResultsDuring the study period, 890 patients underwent rectal cancer surgery. Of these, 403 patients were included in the MRI study and had a 3-year follow-up MRI. PIFs were detected in 49 (12.2%; 95% CI 9.0-15.4) patients by MRI. PIFs were detected in 39 patients (33.6%; 95% CI 24.9-42.3) treated with preoperative CRT compared to 10 (3.5%; 95% CI 1.3-5.6) non-irradiated patients (P<0.001). In a multivariate analysis female gender (OR=3.52; 95% CI 1.7-7.5), age above 65years (OR=3.20; 95% CI 1.5-6.9) and preoperative CRT (OR=14.20; 95% CI 6.1-33.1) were significant risk factors for PIFs. ConclusionPreoperative CRT in the treatment of rectal cancer was associated with a 14-fold higher risk of PIFs after 3years, whereas female gender and age above 65years each tripled the risk of PIFs.