Bin Sing Teh MD, Presenter: Nothing to Disclose

Wei-Yuan Mai MD, Abstract Co-Author: Nothing to Disclose

Thomas M. Schroeder MD, Abstract Co-Author: Nothing to Disclose

John E. McGary PhD, Abstract Co-Author: Nothing to Disclose

Walter H. Grant PhD, Abstract Co-Author: Nothing to Disclose

E. Brian Butler MD, Abstract Co-Author: Nothing to Disclose

E.B.B.: Homos Corp: Provides data mgt. support.

Purpose/Objective: Radiation dose response has been suggested for patients receiving post-prostatectomy radiation therapy. IMRT allows dose escalation in intact prostate cancer patient without significant increase in treatment-related toxicity. Previously, we have reported a favorable toxicity profile related to post-prostatectomy IMRT (Int J Radiat Oncol Biol Phys 2001;49(2):465-472). The purpose of this study is to report the biochemical outcome and the associated predictors of response to post-prostatectomy IMRT (PPI). Materials/Methods: Between 1998 and 2002, there were 123 patients treated with IMRT to the prostate bed after radical prostatectomy. None of these patients had positive pelvic lymph node. 25 patients had an undetectable PSA and were treated with adjuvant IMRT for adverse pathologic features. Salvage IMRT was given for either a persistently detectable PSA after radical prostatectomy (n=14) or for a delayed rise in PSA (n=84). Androgen ablation was administered to 36 patients, ranging from 4 to 12 months. All patients were treated in the prone position in a customized immobilization system. A rectal balloon was used to provide a more consistent and reproducible target volume each day. Sequential tomotherapy (NOMOS Peacock IMRT treatment planning and delivery system Cranberry Township, PA) was utilized to deliver IMRT in all patients. Mean dose to the prostate bed was 70 Gy, with a prescribed dose of 64 Gy over 32 fractions. The primary endpoint was freedom from biochemical failure (bNED). Numerous clinicopathological factors (pathological stage, pathologic radical prostatectomy) Gleason score, androgen ablation, seminal vesicles invasion, surgical margin, perineural invasion, pre-IMRT PSA, pre-radical prostatectomy PSA, extracapsular extension) were analyzed for their impact on bNED. Kaplan-Meier survival curves were plotted from the date of IMRT completion, and the log-rank test was used to determine differences between the curves. The chi-square test was used to test for differences in proportions. Multiple co-variate analysis was performed using Cox proportional hazards regression analysis. The median follow-up was 27 months with a range of 10 to 67 months. Results: Two patients (8%) in the adjuvant IMRT group subsequently developed a rising PSA level. The 3-year bNED rate was 82.3%. For the salvage IMRT group, 4 patients (28.6%) (in the persistently detectable PSA group) and 18 patients (21.4%) (in the delayed rise in PSA group) subsequently developed a rising PSA level. The 3-year bNED rates were 71.4% and 74.6% respectively. Pathologic Gleason score (>7) was the significant predictor of biochemical recurrence in the salvage IMRT group. When all patients were considered in multivariate analysis, the pathologic Gleason score was also significant in predicting biochemical outcome (p7) predicts increased risk for biochemical recurrence. Similar to the data with post-prostatectomy radiotherapy using the conventional approach, adjuvant IMRT is shown to be more efficacious than salvage IMRT. In the absence of prostate and seminal vesicles, target delineation in the post-prostatectomy IMRT (PPI) setting is difficult and hence (PPI) is not commonly performed. However, this study showed that, despite smaller treatment volume, post-prostatectomy IMRT offered no inferior bNED outcome compared to conventional radiotherapy. Smaller treatment volume with PPI allows radiation dose escalation to be explored in future.

Teh, B, Mai, W, Schroeder, T, McGary, J, Grant, W, Butler, E, Intensity-Modulated Radiation Therapy (IMRT) Following Radical Prostatectomy: Biochemical Outcome and Predictors of Response.  Radiological Society of North America 2004 Scientific Assembly and Annual Meeting, November 28 - December 3, 2004 ,Chicago IL. http://archive.rsna.org/2004/4418000.html