Optimized intensity-modulated arc therapy for prostate cancer treatment

We recently implemented intensity-modulated arc therapy (IMAT) at our insti tution. In this study, we evaluate the dosimetric merits of the application of this technique to the treatment of prostate cancer. Each MAT treatment plan incorporated bilateral overlapping arcs. The dose from each beam segme nt was computed using the three-dimensional dose model of a clinical treatm ent planning system (Render Plan 3.5, Precision Therapy). The weights assig ned to the individual arc segments were optimized using a gradient search m ethod. For 12 patients, comparisons were made between the MAT treatment pla ns and corresponding plans using fixed cone-beam intensity-modulated radiot herapy (IMRT) from a commercial inverse planning system (CORVUS, NOMOS Corp .). We found that the optimized IMAT treatments produced similar dose distr ibutions to the IMRT deliveries. Compared with the IMRT treatments, the IMA T treatments produced slightly less target dose homogeneity with consistent ly greater sparing of the rectum in regions of lower dose. The trade-off be tween target dose conformity and rectum sparing can be adjusted in both opt imization procedures. Because the total beam-on time for MAT delivery is 1 to 2 minutes with approximately 5-6 minutes of patient setup time, the deli very efficiency of the MAT treatment was significantly better than the mult iple-beam IMRT treatment. (C) 2001 Wiley-Liss, Inc.