Dosimetric comparison between VMAT with different dose calculation algorithms and protons for soft-tissue sarcoma radiotherapy.
BACKGROUND
To appraise the potential of volumetric modulated arc therapy (VMAT, RapidArc) and proton beams to simultaneously achieve target coverage and enhanced sparing of bone tissue in the treatment of soft-tissue sarcoma with adequate target coverage.


METHODS
Ten patients presenting with soft-tissue sarcoma of the leg were collected for the study. Dose was prescribed to 66.5 Gy in 25 fractions to the planning target volume (PTV) while significant maximum dose to the bone was constrained to 50 Gy. Plans were optimised according to the RapidArc technique with 6 MV photon beams or for intensity modulated protons. RapidArc photon plans were computed with: 1) AAA; 2) Acuros XB as dose to medium; and 3) Acuros XB as dose to water.


RESULTS
All plans acceptably met the criteria of target coverage (V95% >90-95%) and bone sparing (D(1 cm3) <50 Gy). Significantly higher PTV dose homogeneity was found for proton plans. Near-to-maximum dose to bone was similar for RapidArc and protons, while volume receiving medium/low dose levels was minimised with protons. Similar results were obtained for the remaining normal tissue. Dose distributions calculated with the dose to water option resulted ~5% higher than corresponding ones computed as dose to medium.


CONCLUSIONS
High plan quality was demonstrated for both VMAT and proton techniques when applied to soft-tissue sarcoma.
Oncology Institute of Southern Switzerland, Medical Physics Unit, Bellinzona, Switzerland. afc@iosi.ch
Antonella
A
Fogliata
Marta
M
Scorsetti
Piera
P
Navarria
Maddalena
M
Catalano
Alessandro
A
Clivio
Luca
L
Cozzi
Francesca
F
Lobefalo
Giorgia
G
Nicolini
Valentina
V
Palumbo
Chiara
C
Pellegrini
Giacomo
G
Reggiori
Antonella
A
Roggio
Eugenio
E
Vanetti
Filippo
F
Alongi
Sara
S
Pentimalli
Pietro
P
Mancosu
D000465:Algorithms; D006801:Humans; D007866:Leg / Q000473:pathology; D007867:Leg Bones / Q000473:pathology; D019042:Muscle Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009929:Organ Size; D058958:Organs at Risk / Q000473:pathology; D017785:Photons / Q000009:adverse effects / Q000627:therapeutic use; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011522:Protons / Q000009:adverse effects; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012509:Sarcoma / Q000473:pathology / Q000532:radiotherapy*; D047368:Tumor Burden
D011522:Protons