Successful Hydrogel Spacer Placement for Salvage Radiation Therapy After Focal High-Intensity Focused Ultrasound for Prostate Cancer: A Case Report.

After focal high-intensity focused ultrasound (HIFU) for prostate cancer, evidence on the safety of hydrogel spacer placement remains limited. A 65-year-old man who had undergone focal HIFU for low-risk localized prostate cancer two years earlier presented with local recurrence (prostate-specific antigen (PSA) 6.5 ng/mL, rT1cN0M0, Gleason scores 4+3 and 3+4) and was referred for salvage radiation therapy. Hydrogel spacer placement was planned before radiation therapy. The patient was placed in the lithotomy position under sacral block and local anesthesia, and the procedure was performed under transrectal ultrasound guidance. Using a transperineal approach, saline was injected into the dorsal aspect of Denonvilliers' fascia for hydrodissection, during which moderate tissue resistance was noted. However, no significant adhesions were identified, and adequate separation between the prostate and rectum was achieved. The hydrogel spacer was then successfully inserted without procedure-related complications. External beam radiation therapy (60 Gy in 20 fractions) was completed without early adverse events. This case demonstrates that salvage radiation therapy with hydrogel spacer placement can be safely performed in patients with prostate cancer previously treated with focal HIFU.