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Abstract
We aimed to evaluate the inter-clinician variability in the clinical target volume (CTV) for postoperative radiotherapy (PORT) for biliary tract cancer (BTC) including extrahepatic bile duct cancer (EBDC) and gallbladder cancer (GBC). Nine experienced radiation oncologists delineated PORT CTVs for distal EBDC (pT2N1), proximal EBDC (pT2bN1) and GBC (pT2bN1) patients. The expectation maximization algorithm for Simultaneous Truth and Performance Level Estimation (STAPLE) was used to quantify expert agreements. We generated volumes with a confidence level of 80% to compare the maximum distance to each CTV in six directions. The degree of agreement was moderate; overall kappa values were 0.573 for distal EBDC, 0.513 for proximal EBDC, and 0.511 for GBC. In the distal EBDC, a larger variation was noted in the right, post, and inferior direction. In the proximal EBDC, all borders except the right and left direction showed a larger variation. In the GBC, a larger variation was found in the anterior, posterior, and inferior direction. The posterior and inferior borders were the common area having discrepancies, associated with the insufficient coverage of the paraaortic node. A consensus guideline is needed to reduce inter-clinician variability in the CTVs and adequate coverage of regional lymph node area.

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Affiliations

Taeryool Koo 1, Kwang-Ho Cheong 1, Kyubo Kim 2, Hae Jin Park 3, Younghee Park 4, Hyeon Kang Koh 5, Byoung Hyuck Kim 6, Eunji Kim 7, Kyung Su Kim 8, Jin Hwa Choi 9
1Department of Radiation Oncology, Hallym University College of Medicine, Anyang, Republic of Korea.
2Department of Radiation Oncology, Ewha Womans University Mokdong Hospital, Ewha Womans University College of Medicine, Seoul, Republic of Korea.
3Department of Radiation Oncology, Hanyang University College of Medicine, Seoul, Republic of Korea.
4Department of Radiation Oncology, Soonchunhyang University Seoul Hospital, Soonchunhyang University College of Medicine, Seoul, Republic of Korea.
5Department of Radiation Oncology, Konkuk University School of Medicine, Seoul, Republic of Korea.
6Department of Radiation Oncology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Republic of Korea.
7Department of Radiation Oncology, Korea Institute of Radiological and Medical Sciences, Seoul, Republic of Korea.
8Department of Radiation Oncology, Ewha Womans University Seoul Hospital, Ewha Womans University College of Medicine, Seoul, Republic of Korea.
9Department of Radiology, Chung-Ang University College of Medicine, Seoul, Republic of Korea.