Rhabdoid Tumor of the Kidney and Soft Tissues: Results from National Wilms Tumor Study-5 and Children's Oncology Group Study AREN0321

National Wilms Tumor Study-5 (NWTS-5) and AREN0321 evaluated the outcomes of children with rhabdoid tumor of the kidney (RTK) and malignant rhabdoid tumor of soft tissues (MRT). Eligible patients with RTK were enrolled prospectively on NWTS-5 (1995-2002) and treated with carboplatin and etoposide alternating with cyclophosphamide (Regimen RTK). Patients with RTK or MRT were enrolled on AREN0321 (2005-2012) and received vincristine, doxorubicin, and cyclophosphamide alternating with carboplatin, cyclophosphamide, and etoposide (Regimens UH-1 or dose-reduced Revised UH-1). We report event-free survival (EFS) and overall survival (OS) from each study. Thirty patients received Regimen RTK on NWTS-5; on AREN0321, 20 received UH-1 and 19 received Revised UH-1. Patient and disease characteristics were statistically similar between studies. Patients on AREN0321 had significantly improved EFS and OS compared to those on NWTS-5 (4-year EFS = 23.1% vs. 16.7%; p = 0.020; 4-year OS = 30.6% vs. 20.0%; p = 0.014), mostly driven by patients with Stage I/II disease (p = 0.05). Median time to an event was 3.6 months on NWTS-5 compared to 7.2 months on AREN0321. There were no differences in EFS or OS by revised versus original Regimen UH-1 on AREN0321, or by renal versus extra-renal primary disease when the studies were pooled. The more intensive treatment regimen used on AREN0321 improved EFS and OS overall, a result driven by patients with Stage I/II disease. Despite this improvement, outcomes for patients with rhabdoid tumor remain unsatisfactory and there is a need for novel therapeutic strategies.