Predictive value of the pretreatment extent of disease system in hepatoblastoma: results from the International Society of Pediatric Oncology Liver Tumor Study Group SIOPEL-1 study.

PURPOSE: Preoperative staging (pretreatment extent of disease [PRETEXT]) was developed for the first prospective liver tumor study by the International Society of Pediatric Oncology (SIOPEL-1 study; preoperative chemotherapy and delayed surgery). Study aims were to analyze the accuracy and interobserver agreement of PRETEXT and to compare the predictive impact of three currently used staging systems.

PATIENTS AND METHODS: Hepatoblastoma (HB) patients younger than 16 years who underwent surgical resection (128 of 154 patients) were analyzed. The centrally reviewed preoperative staging was compared with postoperative pathology (accuracy) in 91 patients (81%), and the local center staging was compared with the central review (interobserver agreement) in 97 patients (86%), using the agreement beyond change method (weighted kappa). The predictive values of the three staging systems were compared in 110 patients (97%) using survival curves and Cox proportional hazard ratio estimates.

RESULTS: Preoperative PRETEXT staging compared with pathology was correct in 51%, overstaged in 37%, and understaged in 12% of patients (weighted kappa = 0.44; 95% CI, 0.26 to 0.62). The weighted kappa value of the interobserver agreement was 0.76 (95% CI, 0.64 to 0.88). The Children's Cancer Study Group/Pediatric Oncology Group-based staging system showed no predictive value for survival (P = .516), but the tumor-node-metastasis-based system and PRETEXT system showed good predictive values (P = .0021 and P = .0006, respectively). PRETEXT seemed to be superior in the statistical fit.

CONCLUSION: PRETEXT has moderate accuracy with a tendency to overstage patients, shows good interobserver agreement (reproducibility), shows superior predictive value for survival, offers the opportunity to monitor the effect of preoperative therapy, and can also be applied in patients who have not had operations. For comparability reasons, we recommend that all HB patients included in trials also be staged according to PRETEXT.