[Ectopic Injection of Hydrogel Spacer in IMRT for Prostate Cancer-A Case Study]

A hydrogel spacer injection between the prostate and rectum is reported to reduce the risk of rectal toxicity in radiotherapy for prostate cancer. We present a case of an ectopic injection of hydrogel spacer. The patient was a 77-year-old male with intermediate-risk prostate cancer. It was planned that he would receive intensity modulated radiation therapy(IMRT), and a hydrogel spacer was inserted. Three days after insertion, the patient had a fever of 38.6℃ and presented frequent urination and perineal pain. Swelling and heat sensation were observed in the perineum. CRP was 12.00 mg/dL and the white blood cell count was as high as 9,300/μL. T2-weighted images showed a 5.3×1.9 cm high-intensity area around the lower urethra. Ectopic injection of hydrogel spacer and concomitant infection were diagnosed. Upon administering antibiotic treatment, his symptoms and inflammation improved immediately. Four months after hydrogel spacer insertion, T2-weighted images showed a high-intensity area in the lower urethra and around the ischial bone, which was attributed to the remaining hydrogel spacer. The hydrogel spacer and his symptoms completely disappeared at 9 months after hydrogel spacer insertion.