COST-SPARING AND TIME-SPARING SIMPLIFIED CONFORMAL THERAPY FOR PROSTATE-CANCER - IS IT FEASIBLE

Purpose: It was hypothesized that using a simplified technique of volu mes profiles determination (STVPD) based on CT data sets (correlate an d projection) would increase the target dose without increasing the bl adder and rectal dose obtained by conventional simulation techniques. To test this hypothesis, patients referred for radical radiation treat ment for prostate carcinoma were prospectively evaluated by performing treatment planning using standard simulation, with (SSB) and without corner blocks (SSWB), STVPD, and 3D beam's eye view. Methods and Mater ials: Twenty-one patients with prostate carcinoma (stage B: 7; stage C : 14) underwent four treatment planning procedures where the field arr angement was defined by standard simulation (SSB and SSWB), STVPD, and 3D beam's eye view (BEV) with a four field (10 MV photons) box techni que. Dose-volume histograms (DVHs) for the planning target volume (PTV ), bladder, and rectum (relatives to the four techniques) were generat ed for all patients and compared; average percentage dose to the bladd er and rectum were also calculated. Results: STVPD and 3D BEV treated an increased percentage of PTV at 95% isodose level, in comparison to standard simulation (with and without blocks). No statistically signif icant differences were found between the two techniques. A significant reduction of irradiated bladder volume was found between 3D BEV and S TVPD versus simulation with and without blocks (mean percentage dose: 77.3%, 81.8%, 93.5%, and 92.6% respectively). No marked differences we re recorded in rectal irradiation (mean percentage dose: 53.1%, 53.7%, 51.9%, and 50.2% respectively). Time required for treatment planning (excluding CT scan and definitive simulation) was less than 15 minutes for STVPD and more than 120 minutes for 3D BEV. Conclusion: Our resul ts confirm the inadequacy of standard simulation. It is possible, with conformal therapy, to increase the dose to the PTV, decreasing the ir radiated volume of the bladder. The absence of sparing effect in the r ectum is discussed. Using a box technique, STVPD can be used routinely to define the PTV in patients with prostate cancer, reducing the time required for treatment planning, with dosimetric results similar to t hose of 3D BEV. (C) 1998 Elsevier Science Inc.