Radiation-induced sacral insufficiency fracture in endometrial cancer patient after adjuvant radiotherapy: a case report

Abstract

Sacral insufficiency fracture (SIF) is a common cause of back pain in the elderly. However, SIF is still under-diagnosis. We presented a patient with endometrial cancer who complained of low back pain after adjuvant radiotherapy. Finally, SIF was detected by magnetic resonance imaging (MRI). This 66-year-old woman was diagnosed with endometrioid adenocarcinoma, stage Ia, grade 3. She received staging surgery (total abdominal hysterectomy, bilateral salpingo-oophorectomy, bilateral pelvic lymph nodes dissection, omental biopsy and peritoneal washing cytology) followed by adjuvant radiotherapy with the dose of 50.4 Gy in 28 fractions to pelvic lymphatics and vaginal stump (from November 2014 to December 2014). After completion of radiotherapy for 6 months, she complained of diffuse low back pain, but denied any trauma history. The results of physical examination for pelvic and rectal area were normal. The abdomenpelvis computer tomography revealed no significant finding. The whole body bone scans disclosed the suspect bone metastases at left sacroiliac joint (SI joint). Considering the osteoporosis-associated fracture is common present in elderly women, we perform the MRI of SI joint to differentiate whether these lesions are benign process or malignancy. The result of MRI confirmed the diagnosis of radiation-associated SIF which is characterized by the signs of marrow edema (more obvious by STIR, Short T1 Inversion Recovery, MRI images). She received supportive care and had back pain subsided during regular follow-up. With the accurate diagnosis of SIF but not bony metastasis, this patient had subsequent favorable clinical course and outcome with resolution of symptoms by conservative treatment.