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

Aim: The 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).

Method: Patients 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 3 years after treatment was obtained. The primary outcome was the rate of PIFs; secondary outcome was risk factors of PIFs evaluated in multivariate analysis.

Results: During 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 65 years (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.

Conclusion: Preoperative CRT in the treatment of rectal cancer was associated with a 14-fold higher risk of PIFs after 3 years, whereas female gender and age above 65 years each tripled the risk of PIFs.