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Abstract

PURPOSE:

There has been increasing use of external beam radiotherapy for localized treatment of hepatocellular carcinoma (HCC) with both palliative and curative intent. Quality control of target delineation in primary HCC is essential to deliver adequate doses of radiation to the primary tumor while preserving adjacent healthy organs. We analyzed interobserver variability in gross tumor volume (GTV) delineation for HCC.

PATIENTS AND METHODS:

Twelve radiation oncologists specializing in liver malignancy participated in a multi-institutional contouring dummy-run study of nine HCC cases and independently delineated GTV on the same set of provided computed tomography images. Quantitative analysis was performed using an expectation maximization algorithm for simultaneous truth and performance level estimation (STAPLE) with kappa statistics calculating agreement between physicians. To quantify the interobserver variability of GTV delineations, the ratio of the actual delineated volume to the estimated consensus volume (STAPLE), the ratio of the common and encompassing volumes, and the coefficient of variation were calculated.

RESULTS:

The median kappa agreement level was 0.71 (range 0.28-0.86). The ratio of the actual delineated volume to the estimated consensus volume ranged from 0.19 to 1.93 (median 0.94) for all cases. The ratio of the common and encompassing volumes ranged from 0.001 to 0.56 (median 0.25). The coefficient of variation for GTV delineation ranged from 8 to 57 % (median 26 %).

​We added the following recommendations based on the results of our study. 

1. Small slice thickness (≤ 3 mm) is recommended for simulation CT, especially for small HCCs. 

2. Use of a respiratory motion-restricting method, such as abdominal compression, is recommended in addition to 4D-CT for patients with large (over 1–1.5 cm) respiratory movement.

3. Diagnostic multiphasic CT imaging is essential for contouring GTV. 

4. MRI fusion is strongly recommended for HCC with features including hypovascularity, ill-defined tumor margin, and PVT. Vascular structures can be used as reference points for image fusion. 

5. Consensus on inclusion of previous TACE site in GTV is inconclusive; however, inclusion of initial TACE site is recommended when marginal recurrence was observed. A multidisciplinary team approach is recommended for deciding the treatment volume. 

6. Consensus meeting is encouraged to discuss guidelines for contouring GTV, CTV, and PTV prior to developing multi-institutional study protocols involving radiotherapy for HCC.​ 

CONCLUSION:

The interobserver variability in target delineation of HCC GTV in this study is noteworthy. Multi-institution studies involving radiotherapy for HCC require appropriate quality assurance programs for target delineation.

Author information​

Kim YS1, Kim JW2, Yoon WS3, Kang MK4, Lee IJ2, Kim TH5, Kim JH6, Lee HS7, Park HC8, Jang HS9, Kay CS9, Yoon SM10, Kim MS11, Seong J12.

1Department of Radiation Oncology, Jeju National University Hospital, Jeju National University School of Medicine, Jeju, Korea.

2Department of Radiation Oncology, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.

3Department of Radiation Oncology, Ansan Hospital, Korea University Medical Center, Ansan, Korea.

4Department of Radiation Oncology, Kyungpook National University School of Medicine, Daegu, Korea.

5Center for Liver Cancer, National Cancer Center, Goyang, Korea.

6Department of Radiation Oncology, Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.

7Department of Radiation Oncology, Dong-A University College of Medicine, Busan, Korea.

8Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

9Department of Radiation Oncology, The Catholic University of Korea College of Medicine, Seoul, Korea.

10Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.

11Department of Radiation Oncology, Korea Institute of Radiological & Medical Sciences, Seoul, Korea.

12Department of Radiation Oncology, Severance Hospital, Yonsei University College of Medicine, 50-1 Yonsei-ro, 120-752, Seodaemun-gu, Seoul, Korea. jsseong@yuhs.ac.