Dosimetric feasibility of magnetic resonance imaging-guided tri-cobalt 60 preoperative intensity modulated radiation therapy for soft tissue sarcomas of the extremity.
OBJECTIVE
The purpose of this study was to investigate the dosimetric differences of delivering preoperative intensity modulated radiation therapy (IMRT) to patients with soft tissue sarcomas of the extremity (ESTS) with a teletherapy system equipped with 3 rotating (60)Co sources and a built-in magnetic resonance imaging and with standard linear accelerator (LINAC)-based IMRT.


METHODS
The primary study population consisted of 9 patients treated with preoperative radiation for ESTS between 2008 and 2014 with LINAC-based static field IMRT. LINAC plans were designed to deliver 50 Gy in 25 fractions to 95% of the planning target volume (PTV). Tri-(60)Co system IMRT plans were designed with ViewRay system software.


RESULTS
Tri-(60)Co-based IMRT plans achieved equivalent target coverage and dosimetry for organs at risk (long bone, skin, and skin corridor) compared with LINAC-based IMRT plans. The maximum and minimum PTV doses, heterogeneity indices, and ratio of the dose to 50% of the volume were equivalent for both planning systems. One LINAC plan violated the maximum bone dose constraint, whereas none of the tri-(60)Co plans did.


CONCLUSIONS
Using a tri-(60)Co system, we were able to achieve equivalent dosimetry to the PTV and organs at risk for patients with ESTS compared with LINAC-based IMRT plans. The tri-(60)Co system may be advantageous over current treatment platforms by allowing PTV reduction and by elimination of the additional radiation dose associated with daily image guidance, but this needs to be evaluated prospectively.
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California. Electronic address: aukishan@mednet.ucla.edu.
Amar U
AU
Kishan
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Minsong
M
Cao
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Argin G
AG
Mikaeilian
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Daniel A
DA
Low
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Patrick A
PA
Kupelian
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Michael L
ML
Steinberg
Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California.
Mitchell
M
Kamrava
D005121:Extremities / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012509:Sarcoma / Q000473:pathology / Q000532:radiotherapy*