Four-dimensional computed tomography-based treatment planning for intensity-modulated radiation therapy and proton therapy for distal esophageal cancer.
OBJECTIVE
To compare three-dimensional (3D) and four-dimensional (4D) computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing.


METHODS
The IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing.


RESULTS
Compared with IMRT, median lung volumes exposed to 5, 10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%, 5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%, 5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index [CI], 1.99) and greater irradiation of the heart (heart-V40, 41.8%) compared with the IMRT plan(CI, 1.55, heart-V40, 35.7%) or the three-beam proton plan (CI, 1.46, heart-V40, 27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas filling.


CONCLUSIONS
Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.
Zhang
Xiaodong
X
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Zhao
Kuai-le
KL
Guerrero
Thomas M
TM
McGuire
Sean E
SE
Yaremko
Brian
B
Komaki
Ritsuko
R
Cox
James D
JD
Hui
Zhouguang
Z
Li
Yupeng
Y
Newhauser
Wayne D
WD
Mohan
Radhe
R
Liao
Zhongxing
Z
D003964:Diaphragm / Q000000981:diagnostic imaging; D004938:Esophageal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005740:Gases; D006321:Heart / Q000000981:diagnostic imaging / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000528:radiation effects*; D009068:Movement; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects; D013270:Stomach / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000379:methods*
D005740:Gases