背景：盆骨功能不全性骨折（PIF）是盆腔恶性肿瘤放疗的晚期并发症。我们评估了行新辅助（化疗）放疗（C）RT治疗直肠癌患者的PIF的发生率，放射学表现，临床进展和预后。 材料和方法：从荷兰癌症登记处提取自2002年至2012年期间治疗的一所大型教学医院诊断出的直肠癌患者的数据。回顾所有医院记录以确定PIF或盆骨转移的诊断。专业放射科医师重新评估了所有下背部、腹部和盆腔的成像检查。 结果：共有513名直肠癌患者，其中300名患者（58.5%）接受新辅助（C）RT治疗（长疗程放疗组：91名患者[17.7%]，短疗程放疗组：209名患者[40.7%]）。根据所有513名患者的医院记录和成像报告，最初诊断出12例PIF。这12名患者接受了新辅助（C）RT治疗。在重新评估该患者组的所有盆腔成像检查（432名患者[84.2%]）后，发现在接受新辅助（C）RT治疗的患者中额外发现了20例PIF，导致接受放射治疗的患者中PIF的发生率为10.7%。在没有接受新辅助（C）RT治疗的患者组中，发现了1例PIF。该患者因前列腺癌接受姑息性放疗，因此不纳入分析。32例PIF患者的中位随访时间为49个月。新辅助（C）RT开始和PIF诊断之间的中位时间为17个月（IQR 9-28）。PIF患者的总体中位生存期为63.5个月（IQR 44-120）。 结论：PIF是新辅助（C）RT治疗直肠癌的相对常见的晚期并发症，但通常会被漏诊为盆腔骨转移。PIF与盆腔骨转移的区分对于不同的治疗和疾病预后是重要的。

Background: Pelvic insufficiency fractures (PIFs) are a late complication of radiotherapy for pelvic malignancies. We evaluated the incidence, radiologic findings, clinical course, and outcome of PIFs in patients treated with neoadjuvant (chemo)radiotherapy ((C)RT) for rectal cancer.Material and methods: Data of patients diagnosed with rectal cancer from a large teaching hospital treated from 2002 to 2012 were extracted from the Dutch Cancer Registry. All hospital records were reviewed for the diagnosis of PIFs or pelvic bone metastases. An expert radiologist reassessed all imaging procedures of the lower back, abdomen, and pelvis.Results: A total of 513 rectal cancer patients were identified of whom 300 patients (58.5%) were treated with neoadjuvant (C)RT (long- vs. short-course radiotherapy: 91 patients [17.7%] vs. 209 [40.7%], respectively). Twelve PIFs were diagnosed initially according to hospital records and imaging reports of all 513 patients. These 12 patients were treated with neoadjuvant (C)RT. After reassessment of all pelvic imaging procedures done in this patient group (432 patients (84.2%)), 20 additional PIFs were detected in patients treated with neoadjuvant (C)RT, resulting in a 10.7% PIF rate in irradiated patients. One PIF was detected in the group of patients not treated with neoadjuvant (C)RT for rectal cancer. This patient had palliative radiotherapy for prostate cancer and is left out of the analysis. Median follow-up time of 32 PIF patients was 49 months. Median time between start of neoadjuvant (C)RT and diagnosis of PIF was 17 months (IQR 9-28). Overall median survival for patients with PIF was 63.5 months (IQR 44-120).Conclusion: PIFs are a relatively common late complication of neoadjuvant (C)RT for rectal cancer but are often missed or misdiagnosed as pelvic bone metastases. The differentiation of PIFs from pelvic bone metastases is important because of a different treatment and disease outcome.