Salvage of suboptimal prostate seed implantation: Reimplantation of underdosed region of prostate base

Abstract

Purpose: To demonstrate how a suboptimal (125)I prostate implant can be salvaged by reimplantation.

Methods and materials: A (125)I implant was preplanned to deliver 150 Gy to the prostate of a patient with early stage prostate cancer. A CT scan at 35 days postimplant indicated that V(100) and D(90) were 46% and 49 Gy, respectively. The cause was a systematic source placement error that left the base significantly underdosed. A reimplantation of the underdosed region was planned by superimposing a template grid onto the 35-day postimplant CT scan images and digitizing them into the treatment planning computer as if they were TRUS images. The reimplantation was carried out under fluoroscopy guidance so that the initial implant was visible.

Results: The reimplantation increased V(100) and D(90) to 98% and 201 Gy, respectively. The misplaced seeds resulted in a high dose to the apical region and urethra, which was further increased by the reimplantation. The patient experienced increased urinary morbidity, which was relieved by medication.

Conclusion: It is feasible to salvage a suboptimal prostate seed implant by reimplanting the underdosed regions under fluoroscopy guidance based on a plan generated from the postimplant CT scan.