Proton therapy posterior beam approach with pencil beam scanning for esophageal cancer : Clinical outcome, dosimetry, and feasibility.
OBJECTIVE
The aim of this study is to present the dosimetry, feasibility, and preliminary clinical results of a novel pencil beam scanning (PBS) posterior beam technique of proton treatment for esophageal cancer in the setting of trimodality therapy.


METHODS
From February 2014 to June 2015, 13 patients with locally advanced esophageal cancer (T3-4N0-2M0; 11 adenocarcinoma, 2 squamous cell carcinoma) were treated with trimodality therapy (neoadjuvant chemoradiation followed by esophagectomy). Eight patients were treated with uniform scanning (US) and 5 patients were treated with a single posterior-anterior (PA) beam PBS technique with volumetric rescanning for motion mitigation. Comparison planning with PBS was performed using three plans: AP/PA beam arrangement; PA plus left posterior oblique (LPO) beams, and a single PA beam. Patient outcomes, including pathologic response and toxicity, were evaluated.


RESULTS
All 13 patients completed chemoradiation to 50.4 Gy (relative biological effectiveness, RBE) and 12 patients underwent surgery. All 12 surgical patients had an R0 resection and pathologic complete response was seen in 25 %. Compared with AP/PA plans, PA plans have a lower mean heart (14.10 vs. 24.49 Gy, P < 0.01), mean stomach (22.95 vs. 31.33 Gy, P = 0.038), and mean liver dose (3.79 vs. 5.75 Gy, P = 0.004). Compared to the PA/LPO plan, the PA plan reduced the lung dose: mean lung dose (4.96 vs. 7.15 Gy, P = 0.020) and percentage volume of lung receiving 20 Gy (V20; 10 vs. 17 %, P < 0.01).


CONCLUSIONS
Proton therapy with a single PA beam PBS technique for preoperative treatment of esophageal cancer appears safe and feasible.
Department of Medical Oncology, Cancer Center, Shengjing Hospital of China Medical University, 39 Huaxiang Road, 110022, Shenyang, China.|Department of Radiation Oncology, University of Washington Medical Center, 1959 NE Pacific Street, Campus Box 356043, 98195, Seattle, WA, USA.
Yue-Can
YC
Zeng
Department of Radiation Oncology, University of Washington Medical Center, 1959 NE Pacific Street, Campus Box 356043, 98195, Seattle, WA, USA.
Shilpa
S
Vyas
Seattle Cancer Care Alliance Proton Therapy Center, 1570 N 115th St., 98133, Seattle, WA, USA.
Quang
Q
Dang
Seattle Cancer Care Alliance Proton Therapy Center, 1570 N 115th St., 98133, Seattle, WA, USA.
Lindsay
L
Schultz
Department of Radiation Oncology, University of Washington Medical Center, 1959 NE Pacific Street, Campus Box 356043, 98195, Seattle, WA, USA.|Department of Radiology, University of Washington Medical Center, 1959 NE Pacific Street, 98195, Seattle, WA, USA.
Stephen R
SR
Bowen
Department of Medical Oncology, University of Washington Medical Center, 1959 NE Pacific Street, 98195, Seattle, WA, USA.
Veena
V
Shankaran
Department of Surgery, Division of Cardiothoracic Surgery, University of Washington Medical Center, 1959 NE Pacific Street, 98195, Seattle, WA, USA.|Department of Surgery, Surgical Outcomes Research Center, University of Washington Medical Center, 1959 NE Pacific Street, 98195, Seattle, WA, USA.
Farhood
F
Farjah
Department of Surgery, University of Washington Medical Center, 1959 NE Pacific Street, 98195, Seattle, WA, USA.
Brant K
BK
Oelschlager
Department of Radiation Oncology, University of Washington Medical Center, 1959 NE Pacific Street, Campus Box 356043, 98195, Seattle, WA, USA.
Smith
S
Apisarnthanarax
Department of Radiation Oncology, University of Washington Medical Center, 1959 NE Pacific Street, Campus Box 356043, 98195, Seattle, WA, USA. jzeng13@uw.edu.
Jing
J
Zeng
D000368:Aged; D000369:Aged, 80 and over; D059248:Chemoradiotherapy / Q000379:methods*; D004938:Esophageal Neoplasms / Q000473:pathology / Q000628:therapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy / Q000009:adverse effects / Q000379:methods*; D011832:Radiation Injuries / Q000209:etiology / Q000517:prevention & control*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
Esophageal cancer; Proton therapy; Toxicity