Gastrointestinal Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_15_2149 - Proton beam therapy without fiducial markers using 4-dimensional CT planning for large hepatocellular carcinomas

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Proton beam therapy without fiducial markers using 4-dimensional CT planning for large hepatocellular carcinomas
S. Shibata1, S. Takamatsu2, K. Yamamoto1, M. Mizuhata3, Y. Sato1, S. Bou1, M. Kawamura4, S. Asahi5, Y. Tameshige1, Y. Maeda1, M. Sasaki1, T. Kumano2, S. Kobayashi6, H. Tamamura1, and T. Gabata6; 1Fukui Prefectural Hospital Proton Therapy Center, Fukui, Japan, 2Kanazawa University Hospital, Kanazawa, Japan, 3Fukui Prefectural Hospital, Fukui, Japan, 4Nagoya University Graduate School of Medicine, Nagoya, Japan, 5University of Fukui Hospital, Fukui, Japan, 6Kanazawa University Graduate School of Medical Sciences, Kanazawa, Japan

Purpose/Objective(s): Classical photon radiation therapy has rarely been used in hepatocellular carcinomas (HCC) because the dose tolerance of normal liver tissue is considerably lower than that necessary for tumor control. The excellent dose distribution in proton beam therapy (PBT) makes it possible to treat large liver tumors without a high dose to normal liver. Recent studies have reported that PBT for HCC achieves good local control with less toxicity than photon therapy. In PBT for liver neoplasms, fiducial markers are often used to aid in positioning. Although complications are rare, implanting fiducial markers in the liver is an invasive procedure. We evaluated the efficacy and toxicity of PBT for HCC > 5 cm without fiducial markers using four-dimensional CT (4D-CT) planning.

Materials/Methods: The subjects were 29 patients who were treated with PBT for HCCs > 5 cm in diameter at our hospital between March 2011 and March 2015. The median total dose was 76 Cobalt Gray Equivalents (CGE) in 20 fractions (range; 66–80.5 CGE in 10–32 fractions). We used respiratory-synchronized 4D-CT (Aquilion LB TSX-201A: Toshiba Medical Systems Co., Tochigi, Japan) for planning. Respiratory gating was controlled by monitoring abdominal wall motion with the laser sensor of a respiratory gating system (AZ-733V: Anzai Medical Co., Tokyo, Japan) under stable breathing (period of breathing 10–15 times/min by inducing rhythm using a metronome). Targets were contoured at the end-expiratory phase using 4D-CT. Gross tumor volume (GTV) was delineated manually with contrast-enhanced CT and MRI. Clinical target volume (CTV) encompassed the GTV with a 0.5 cm margin in all directions. Internal target volume (ITV) was determined as CTV plus additional margin due to respiratory movement calculated by the 4D-CT analysis. The internal margin due to respiratory movement was customized based on the amount of tumor motion visualized in the gating window at 17–25% duty cycle around end of exhalation. Planning target volume (PTV) encompassed the ITV with a 0.5 cm margin in all directions (Radiation treatment planning system: XiO-N; Elekta, Mitsubishi Electric Corporation, algorithm: proton pencil beam algorithm).

Results: Patient age ranged from 38–87 y (median, 71 y). Twenty-four patients were Child-Pugh class A and five patients were class B. Tumor size ranged from 5.0–13.9 cm (median, 6.9 cm). The follow-up period ranged from 2–72 months (median; 27 months). All patients completed PBT according to the treatment protocol without grade 4 (CTCAE v4.0) or higher adverse effects. The 2-year local tumor control (LTC), progression-free survival (PFS), and overall survival (OS) rates were 95%, 22%, and 61%, respectively. The LTC was not inferior to that of previous reports using fiducial markers.

Conclusion: Respiratory-gated PBT with 4D-CT planning without fiducial markers is a less invasive and equally effective treatment for large HCCs as PBT with fiducial markers.

Author Disclosure: S. Shibata: None. S. Takamatsu: None. K. Yamamoto: None. Y. Sato: None. S. Bou: None. S. Asahi: None. M. Sasaki: None.

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