Bilateral Wilms tumors treated according to the Japan Wilms Tumor Study Group protocol

The introduction of multimodal therapy has improved the survival rate of bilateral Wilms tumors (BWT); however, the results are still not satisfactory in terms of the renal preservation. To establish a new treatment strategy for BWT, we reviewed the results of the cases registered in the Japan Wilms Tumor Study Group (JWiTS).

This analysis concerned patients with synchronous BWT registered in the JWiTS between 1996 and 2011. In these patients, the management of BWT included initial tumor resection or biopsy followed by chemotherapy. The details of the treatments and outcomes were analyzed.

Among the 355 cases registered in the JWiTS database, 31 (8.7%) had BWT. They were 16 males and 15 females with a mean age of 15.5 months. Preoperative chemotherapy was performed in 24 cases. Bilateral nephron-sparing surgery (NSS) was achieved in 10 of 28 cases (36%). All of the cases were of favorable nephroblastoma without anaplasia, and a WT1 mutation was detected in 21 of the 27 cases (78%) examined. The 5-year overall survival was 92.6%; however, 10 children (40%) developed impaired renal function and three of them developed renal failure.

The long-term survival rates for patients with synchronous BWT have improved. However, more than half of patients receive nephrectomy. The protocol should be changed to improve the rate of preservation of the renal parenchyma. Preoperative chemotherapy should be performed to shrink the tumors in every case, and subsequent NSS should be carried out after a central imaging evaluation.