Helical tomotherapy and intensity modulated proton therapy in the treatment of dominant intraprostatic lesion: A treament planning comparison

Abstract

PurposeTo compare helical tomotherapy (HT) and intensity modulated proton therapy (IMPT) for prostate cancer irradiation while concomitantly boosting dominant intraprostatic lesions (DILs). Methods and materialsTreatment plans of seven patients were designed for HT and IMPT (pencil beam size: 3mm sigma). The prescribed median PTV/DIL doses were 71.4/100Gy in 28 fractions, while satisfying “safe” dose constraints for organs at risks (OARs) including rectum, bladder, femoral heads, penile bulb and urethra. The planner could further reduce the dose to OARs if PTV/DIL constraints were reached. ResultsIMPT achieved better dose conformity (CI=1.11 vs 1.31, p<0.05) and coverage (V95%=97.3% vs 95.3%, p<0.05) in PTV. Concerning DIL volumes, both techniques delivered the prescribed dose (Dmedian: HT=100Gy, IMPT=102.1Gy) with similar dose conformity (CI: HT=1.49, IMPT=1.44) and same dose homogeneity, D99%, D1%, while satisfying the OARs constraints.Excepting urethra, the sparing of OARs was significantly better with IMPT; in general, the lower the dose, the greater the benefit of IMPT. Normal tissue complication probabilities for the rectum were in favor of IMPT with an absolute reduction of 3–8%, depending on the NTCP model (p<0.05). ConclusionsBoth techniques allowed delivering 100Gy to DILs, while complying with the OARs constraints. IMPT was superior in sparing OARs for doses up to approximately 70Gy, with larger benefit at lower doses.