title: Multicenter validation study of a prognostic index for portal vein tumor thrombosis in hepatocellular carcinoma.
abstract: OBJECTIVE
  We previously reported on a staging system and prognostic index (PITH) for portal vein tumor thrombosis (PVTT) in hepatocellular carcinoma (HCC) patients treated with radiotherapy (RT) at a single institution. The aim of this study is to validate the PITH staging system using data from patients at other institutions and to compare it with other published staging systems.
  
  
  METHODS
  A total of 994 HCC patients with PVTT who were treated with RT between 1998 and 2011 by the Korean Radiation Oncology Group were analyzed retrospectively. All patients were staged using the Cancer of the Liver Italian Program (CLIP), Japanese Integrated Staging (JIS), Okuda, and PITH staging systems, and survival data were analyzed. The likelihood ratio, Akaike information criteria (AIC), time-dependent receiver operating characteristics, and prediction error curve analysis were used to determine discriminatory ability for comparison of staging systems.
  
  
  RESULTS
  The median survival was 9.2 months. Compared with the other staging systems, the PITH score gave the highest values for likelihood ratio and lowest AIC values, demonstrating that PITH may be a better prognostic model. Although the values were not significant and differences were not exceptional, the PITH score showed slightly better performance with respect to time-dependent area under curve and integrated Brier score of prediction error curve.
  
  
  CONCLUSIONS
  The PITH staging system was validated in this multicenter retrospective study and showed better stratification ability in HCC patients with PVTT than other systems.
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jeong Il
authors.initials: JI
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Sang Min
authors.initials: SM
authors.lastname: Yoon
authors.affiliation: Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Hee Chul
authors.initials: HC
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Research Institute and Hospital, National Cancer Center, Goyang, Korea.
authors.forename: Tae Hyun
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Research Institute and Hospital, National Cancer Center, Goyang, Korea.
authors.forename: Joong-Won
authors.initials: JW
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Jinsil
authors.initials: J
authors.lastname: Seong
authors.affiliation: Department of Radiation Oncology, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Ik Jae
authors.initials: IJ
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, The Catholic University of Korea College of Medicine, Seoul, Korea.
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Jang
authors.affiliation: Department of Radiation Oncology, Incheon St. Mary Hospital, The Catholic University of Korea College of Medicine, Incheon, Korea.
authors.forename: Chul Seung
authors.initials: CS
authors.lastname: Kay
authors.affiliation: Department of Radiation Oncology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Chul Yong
authors.initials: CY
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Eui Kyu
authors.initials: EK
authors.lastname: Chie
authors.affiliation: Department of Radiation Oncology, Keimyung University Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea.
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Korea Institute of Radiological and Medical Sciences, Seoul, Korea.
authors.forename: Mi-Sook
authors.initials: MS
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Young Min
authors.initials: YM
authors.lastname: Choi
keywords: Hepatocellular carcinoma; Multicenter study; Portal vein; Radiotherapy; Validation