Effect of incorporation of preoperative CT scan on bladder doses and irradiated volume in postprostatectomy radiation therapy (pPRT).

e561Background: pPRT increases local control, biochemical progression free survival, and even overall survival in patients with adverse features undergoing prostatectomy. The Radiation Therapy Oncology Group (RTOG) consensus definition of the clinical target volume (CTV) in 2010 was based on patterns of failure and anatomy without consideration of pre-operative imaging. This results in large volumes of bladder in the treatment field. Our study evaluates whether incorporation of pre-operative prostate volume can reduce the post-operative CTV and minimize dose to adjacent normal tissue. Methods: We reviewed records of all patients with available pre-operative pelvic CT scans treated at our institution with pPRT. The pre-operative CT scan was fused to the simulation CT. Post-operative CTV (CTV1) was delineated based on RTOG guidelines. A separate CTV (CTV2) was constructed, based on the intact prostate and proximal seminal vesicles. Plans were constructed for each CTV and doses to rectum, bladder, and penile...