Helical tomotherapy vs. Intensity-modulated proton therapy for whole pelvis irradiation in high-risk prostate cancer patients: Dosimetric, normal tissue complication probability, and generalized equivalent uniform dose analysis
Widesott L.,ATreP Agenzia Provinciale per la Protonterapia |
Pierelli A.,St Raffaele Scientific Institute |
Fiorino C.,St Raffaele Scientific Institute |
Lomax A.J.,Paul Scherrer Institute |
And 8 more authors.
International Journal of Radiation Oncology Biology Physics | Year: 2011
Purpose: To compare intensity-modulated proton therapy (IMPT) and helical tomotherapy (HT) treatment plans for high-risk prostate cancer (HRPCa) patients. Methods and Materials: The plans of 8 patients with HRPCa treated with HT were compared with IMPT plans with two quasilateral fields set up (-100°; 100°) and optimized with the Hyperion treatment planning system. Both techniques were optimized to simultaneously deliver 74.2 Gy/Gy relative biologic effectiveness (RBE) in 28 fractions on planning target volumes (PTVs)3-4 (P + proximal seminal vesicles), 65.5 Gy/Gy(RBE) on PTV2 (distal seminal vesicles and rectum/prostate overlapping), and 51.8 Gy/Gy(RBE) to PTV1 (pelvic lymph nodes). Normal tissue calculation probability (NTCP) calculations were performed for the rectum, and generalized equivalent uniform dose (gEUD) was estimated for the bowel cavity, penile bulb and bladder. Results: A slightly better PTV coverage and homogeneity of target dose distribution with IMPT was found: the percentage of PTV volume receiving ≥95% of the prescribed dose (V 95%) was on average >97% in HT and >99% in IMPT. The conformity indexes were significantly lower for protons than for photons, and there was a statistically significant reduction of the IMPT dosimetric parameters, up to 50 Gy/Gy(RBE) for the rectum and bowel and 60 Gy/Gy(RBE) for the bladder. The NTCP values for the rectum were higher in HT for all the sets of parameters, but the gain was small and in only a few cases statistically significant. Conclusions: Comparable PTV coverage was observed. Based on NTCP calculation, IMPT is expected to allow a small reduction in rectal toxicity, and a significant dosimetric gain with IMPT, both in medium-dose and in low-dose range in all OARs, was observed. © 2011 Elsevier Inc.
Fava G.,AtreP Agenzia Provinciale Per la Protonterapia |
Widesott L.,AtreP Agenzia Provinciale Per la Protonterapia |
Fellin F.,AtreP Agenzia Provinciale Per la Protonterapia |
Amichetti M.,AtreP Agenzia Provinciale Per la Protonterapia |
And 8 more authors.
Radiotherapy and Oncology | Year: 2012
Purpose: We estimated the potential advantage of remote positioning (RP) vs. in-room positioning (IP) for a proton therapy facility in terms of patient throughput. Materials and methods: Monte Carlo simulations of facilities with one, two or three gantries were performed. A sensitivity analysis was applied by varying the imaging and setup correction system (ICS), the speed of transporters (for RP) and beam switching time. Possible advantages of using three couches (for RP) or of switching the beam between fields was also investigated. Results: For a single gantry facility, an average of 20% more patients could be treated using RP: ranging from +45%, if a fast transporter and slow ICS were simulated, to -14% if a slow transporter and fast ICS was simulated. For two gantries, about 10% more patients could be treated with RP, ranging from +32% (fast transporter, slow ICS) to -12% (slow transporter, fast ICS). The ability to switch beam between fields did not substantially influence the throughput. In addition, the use of three transporters showed increased delays and therefore a slight reduction of the fractions executables. For three gantries, RP and IP showed similar results. Conclusions: The advantage of RP vs. IP strongly depends on ICS and the speed of the transporters. For RP to be advantageous, reduced transport times are required. The advantage of RP decreases with increasing number of gantries. © 2011 Elsevier Ireland Ltd. All rights reserved.