CONCURRENT TREATMENT PLANNING FOR OUTPATIENT HIGH-DOSE-RATE PROSTATE TEMPLATE IMPLANTS

Purpose: Since November of 1991, we have treated locally advanced (B2- C) prostate cancer using external beam radiotherapy integrated with ou tpatient high dose rate interstitial implant boost as part of a Phase II clinical trial. This required (a) rapid, automated planning; (b) in corporation of image data and (c) dose optimization. Methods and Mater ials: A treatment planning system was designed which integrates imagin g and needle guidance with source reconstruction and dose display. All components of treatment planning (reconstruction, optimization, dose prescription, dose display) are largely automated. A rectal reference point was defined which was reproducible and easily verified. No pretr eatment planning was required. Results: As of November 1992, 83 treatm ents were delivered using this system. Intra-operative treatment decis ions were made possible due to the speed and ease of interpretation of the system. The system has proven satisfactory in the operating room. Rectal doses were calculated for all patients, and ranged from 35-79% of the prescribed dose, with a mean of 58%. The first echelon of a Ph ase II escalating dose trial has been completed, with 22 patients trea ted over a period of 1 year. Conclusion: Outpatient high dose rate bra chytherapy appears to be a practical means of boosting locally advance d prostate cancer patients. Rapid treatment planning is possible incor porating on-line ultrasound images to allow immediate dose optimizatio n to be performed during and after implant placement.