Equivalent dose and effective dose from stray radiation during passively scattered proton radiotherapy for prostate cancer.
Proton therapy reduces the integral therapeutic dose required for local control in prostate patients compared to intensity-modulated radiotherapy. One proposed benefit of this reduction is an associated decrease in the incidence of radiogenic secondary cancers. However, patients are also exposed to stray radiation during the course of treatment. The purpose of this study was to quantify the stray radiation dose received by patients during proton therapy for prostate cancer. Using a Monte Carlo model of a proton therapy nozzle and a computerized anthropomorphic phantom, we determined that the effective dose from stray radiation per therapeutic dose (E/D) for a typical prostate patient was approximately 5.5 mSv Gy(-1). Sensitivity analysis revealed that E/D varied by +/-30% over the interval of treatment parameter values used for proton therapy of the prostate. Equivalent doses per therapeutic dose (HT/D) in specific organs at risk were found to decrease with distance from the isocenter, with a maximum of 12 mSv Gy(-1) in the organ closest to the treatment volume (bladder) and 1.9 mSv Gy(-1) in the furthest (esophagus). Neutrons created in the nozzle predominated effective dose, though neutrons created in the patient contributed substantially to the equivalent dose in organs near the proton field. Photons contributed less than 15% to equivalent doses.
Fontenot
Jonas
J
The University of Texas Graduate School of Biomedical Sciences at Houston, Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, TX 77030, USA.
Taddei
Phillip
P
Zheng
Yuanshui
Y
Mirkovic
Dragan
D
Jordan
Thomas
T
Newhauser
Wayne
W
D006801:Humans; D008297:Male; D009502:Neutrons; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D061766:Proton Therapy; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D011522:Protons
D011522:Protons