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

Purpose To demonstrate how a suboptimal 125I prostate implant can be salvaged by reimplantation. Methods and materials A 125I 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 V100 and D90 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 V100 and D90 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.