Volumetric arc intensity-modulated therapy for spine body radiotherapy: comparison with static intensity-modulated treatment.
OBJECTIVE
This clinical study evaluates the feasibility of using volumetric arc-modulated treatment (VMAT) for spine stereotactic body radiotherapy (SBRT) to achieve highly conformal dose distributions that spare adjacent organs at risk (OAR) with reduced treatment time.


METHODS
Ten spine SBRT patients were studied retrospectively. The intensity-modulated radiotherapy (IMRT) and VMAT plans were generated using either one or two arcs. Planning target volume (PTV) dose coverage, OAR dose sparing, and normal tissue integral dose were measured and compared. Differences in treatment delivery were also analyzed.


RESULTS
The PTV DVHs were comparable between VMAT and IMRT plans in the shoulder (D(99%)-D(90%)), slope (D(90%)-D(10%)), and tail (D(10%)-D(1%)) regions. Only VMAT(2arc) had a better conformity index than IMRT (1.09 vs. 1.15, p = 0.007). For cord sparing, IMRT was the best, and VMAT(1arc) was the worst. Use of IMRT achieved greater than 10% more D(1%) sparing for six of 10 cases and 7% to 15% more D(10%) sparing over the VAMT(1arc). The differences between IMRT and VAMT(2arc) were smaller and statistically nonsignificant at all dose levels. The differences were also small and statistically nonsignificant for other OAR sparing. The mean monitor units (MUs) were 8711, 7730, and 6317 for IMRT, VMAT(1arc), and VMAT(2arc) plans, respectively, with a 26% reduction from IMRT to VMAT(2arc). The mean treatment time was 15.86, 8.56, and 7.88 min for IMRT, VMAT(1arc,) and VMAT(2arc). The difference in integral dose was statistically nonsignificant.


CONCLUSIONS
Although VMAT provided comparable PTV coverage for spine SBRT, 1arc showed significantly worse spinal cord sparing compared with IMRT, whereas 2arc was comparable to IMRT. Treatment efficiency is substantially improved with the VMAT.
Wu
Q Jackie
QJ
Department of Radiation Oncology, Duke University, Durham, NC 27710, USA. Jackie.Wu@Duke.edu
Yoo
Sua
S
Kirkpatrick
John P
JP
Thongphiew
Danthai
D
Yin
Fang-Fang
FF
D000465:Algorithms; D004947:Esophagus / Q000000981:diagnostic imaging / Q000528:radiation effects; D005240:Feasibility Studies; D006321:Heart / Q000528:radiation effects; D006801:Humans; D007422:Intestines / Q000528:radiation effects; D007668:Kidney / Q000528:radiation effects; D008099:Liver / Q000528:radiation effects; D008168:Lung / Q000528:radiation effects; D010865:Pilot Projects; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D011877:Radionuclide Imaging; D016634:Radiosurgery / Q000379:methods* / Q000592:standards; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods* / Q000592:standards; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods* / Q000592:standards; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D018709:Statistics, Nonparametric; D013679:Technology, Radiologic