PURPOSE

To evaluate the clinicopathological features that indicate relapse and suggest a new risk based therapeutic strategy for unilateral Favorable Histology Wilms Tumor (FH-WT).

MATERIALS & METHODS: Thirty-three patients with unilateral WT were treated in two institutions between 1986 and 2010. Twenty-eight patients with FH-WT received primary nephrectomy according to the National Wilms' Tumor Study (NWTS) or the Japanese Wilms' Tumor Study (JWiTS) protocol. Retrospective analyses of the non-relapsed group (n=23) and the relapsed group (n=5) compared age, gender, tumor laterality, tumor weight, initial tumor stage, known histological subtype, chemotherapy (2 or 3 drugs), and any irradiation delivered. Stages and histological subtypes of the tumors were re-evaluated according to the Japanese staging system.

RESULTS

Five of the twenty-eight tumors relapsed, and one patient died. The initial staging (P=0.029) and the histological subtype (P=0.003) were the only factors indicating relapse. Nine of the twenty-three tumors were histologically classified as blastemal predominant subtype (BPT-WT). Five relapsed.

CONCLUSION

According to the basic Japanese therapeutic strategy, all patients underwent a primary nephrectomy before chemotherapy. This study suggests that the histological subtype pre-treatment "BPT-WT" should be included as a strong indicator of poor prognosis. Such patients should be treated as a high-risk group.