title: Helical tomotherapy and intensity modulated proton therapy in the treatment of early stage prostate cancer: a treatment planning comparison.
abstract: OBJECTIVE
  To compare helical tomotherapy (HT) and intensity modulated proton therapy (IMPT) on early stage prostate cancer treatments delivered with simultaneous integrated boost (SIB) in moderate hypofractionation.
  
  
  METHODS
  Eight patients treated with HT were replanned with two-field IMPT (2fIMPT) and five-field IMPT (5fIMPT), using a small pencil beam size (3 mm sigma). The prescribed dose was 74.3 Gy in 28 fractions on PTV1 (prostate) and PTV2 (proximal seminal vesicles), 65.5 Gy on PTV3 (distal seminal vesicles) and on the overlap between rectum and PTVs.
  
  
  RESULTS
  IMPT and HT achieved similar target coverage and dose homogeneity, with 5fIMPT providing the best results. The conformity indexes of IMPT were significantly lower for PTV1+2 and PTV3. Above 65 Gy, HT and IMPT were equivalent in the rectum, while IMPT spared the bladder and the penile bulb from 0 to 70 Gy. From 0 up to 60 Gy, IMPT dosimetric values were (much) lower for all OARs except the femur heads, where HT was better than 2fIMPT in the 25-35 Gy dose range. OARs mean doses were typically reduced by 30-50% by IMPT. NTCPs for the rectum were within 1% between the two techniques, except when the endpoint was stool frequency, where IMPT showed a small (though statistically significant) benefit.
  
  
  CONCLUSIONS
  HT and IMPT produce similar dose distributions in the target volume. The current knowledge on dose-effect relations does not allow to quantify the clinical impact of the large sparing of IMPT at medium-to-low doses.
authors.affiliation: Agenzia Provinciale per la Protonterapia, Trento, Italy. schwarz@atrep.it
authors.forename: Marco
authors.initials: M
authors.lastname: Schwarz
authors.forename: Alessio
authors.initials: A
authors.lastname: Pierelli
authors.forename: Claudio
authors.initials: C
authors.lastname: Fiorino
authors.forename: Francesco
authors.initials: F
authors.lastname: Fellin
authors.forename: Giovanni Mauro
authors.initials: GM
authors.lastname: Cattaneo
authors.forename: Cesare
authors.initials: C
authors.lastname: Cozzarini
authors.forename: Nadia
authors.initials: N
authors.lastname: Di Muzio
authors.forename: Riccardo
authors.initials: R
authors.lastname: Calandrino
authors.forename: Lamberto
authors.initials: L
authors.lastname: Widesott
mesh_terms: D005270:Femur Head / Q000528:radiation effects; D006801:Humans; D008297:Male; D009367:Neoplasm Staging; D010413:Penis / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D061766:Proton Therapy; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D036542:Tomography, Spiral Computed / Q000379:methods; D001743:Urinary Bladder / Q000528:radiation effects; D011522:Protons
chemical_list: D011522:Protons