A comprehensive comparison of IMRT and VMAT plan quality for prostate cancer treatment.
OBJECTIVE
We performed a comprehensive comparative study of the plan quality between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of prostate cancer.


METHODS
Eleven patients with prostate cancer treated at our institution were randomly selected for this study. For each patient, a VMAT plan and a series of IMRT plans using an increasing number of beams (8, 12, 16, 20, and 24 beams) were examined. All plans were generated using our in-house-developed automatic inverse planning (AIP) algorithm. An existing eight-beam clinical IMRT plan, which was used to treat the patient, was used as the reference plan. For each patient, all AIP-generated plans were optimized to achieve the same level of planning target volume (PTV) coverage as the reference plan. Plan quality was evaluated by measuring mean dose to and dose-volume statistics of the organs at risk, especially the rectum, from each type of plan.


RESULTS
For the same PTV coverage, the AIP-generated VMAT plans had significantly better plan quality in terms of rectum sparing than the eight-beam clinical and AIP-generated IMRT plans (p < 0.0001). However, the differences between the IMRT and VMAT plans in all the dosimetric indices decreased as the number of beams used in IMRT increased. IMRT plan quality was similar or superior to that of VMAT when the number of beams in IMRT was increased to a certain number, which ranged from 12 to 24 for the set of patients studied. The superior VMAT plan quality resulted in approximately 30% more monitor units than the eight-beam IMRT plans, but the delivery time was still less than 3 min.


CONCLUSIONS
Considering the superior plan quality as well as the delivery efficiency of VMAT compared with that of IMRT, VMAT may be the preferred modality for treating prostate cancer.
Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX, USA.
Enzhuo M
EM
Quan
Xiaoqiang
X
Li
Yupeng
Y
Li
Xiaochun
X
Wang
Rajat J
RJ
Kudchadker
Jennifer L
JL
Johnson
Deborah A
DA
Kuban
Andrew K
AK
Lee
Xiaodong
X
Zhang
D000465:Algorithms; D005270:Femur Head / Q000528:radiation effects; D006801:Humans; D008297:Male; D059351:Organ Sparing Treatments / Q000379:methods / Q000592:standards; D058958:Organs at Risk / Q000528:radiation effects; D011467:Prostate / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D058996:Quality Improvement / Q000592:standards; D011836:Radiation Tolerance; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods / Q000592:standards*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods / Q000592:standards*; D012007:Rectum / Q000528:radiation effects; D012669:Seminal Vesicles / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects