Blastemal predominant type Wilms tumor in Japan: Japan Children's Cancer Group

Background Persistence of blastemal components after chemotherapy is a marker of poor outcome in Wilms tumor ( WT ). Recent reports from local Japanese areas have described pre‐chemotherapy blastemal predominant type WT to also be a risk factor for relapse. The significance, however, of blastemal predominant WT remains to be evaluated in a larger study. This study retrospectively evaluated the prognostic significance of pre‐chemotherapy blastemal predominant type WT in the Japan Wilms tumor Study ( JW i TS ) trials. Methods The JW i TS trial (1996–2013) was a prospective, single‐arm study. The outcomes of blastemal predominant type WT were retrospectively evaluated compared with non‐blastemal type WT excluding anaplasia between 1996 and 2013. Relapse‐free survival ( RFS ) and overall survival ( OS ) were estimated. Results Of 319 primary renal tumors diagnosed by the central pathology review system, advanced stage of pre‐chemotherapy blastemal predominant type WT ( n = 53; 16.1%) occurred more frequently in older children than non‐blastemal type WT ( n = 225), and was especially frequent in female patients registered in the JW i TS trials. No significant difference in 10 years RFS and OS (78.8% vs 84.5; P = 0.201) or in 10 years RFS and OS (89.3% vs 93.5; P = 0.45) was seen between pre‐chemotherapy blastemal predominant type and non‐blastemal type WT . Conclusions Relapse‐free survival and OS are not significantly different between pre‐chemotherapy blastemal predominant type and non‐blastemal type WT .