The management of relapsed Wilms tumor.

Relapsed Wilms tumor is often very responsive to re-treatment, and cures are possible in many cases. Recurrent Wilms tumor forms a heterogeneous group because initial therapies vary widely. Given the complexity of the problem, there is a great need for an organized clinical investigative approach. Ideally, the treatment of initial relapse should be specified by the primary treatment protocol in order to better evaluate overall survival as an end-point for new primary therapy strategies. This is especially appropriate for Wilms tumor, because the investigations of this tumor over the last 20 years have attempted to determine the minimal therapy necessary for cure. Thus, survival rather than relapse-free survival is the most appropriate criterion for the success of a primary retreatment regimen. This investigative approach would also allow evaluation of treatment strategies tailored to a specific patient population. Important questions remain for those who treat recurrent Wilms tumor. Defining the role of high-dose therapy, defining the role of total body irradiation in high-dose therapy regimens, and defining the benefit and toxicity of cyclophosphamide compared with ifosfamide are three current questions under investigation. Developing new agents and regimens effective against Wilms tumor, especially against anaplastic tumors, RTK, and CCSK, is extremely important if progress is to be made in treating these tumors after relapse. Finally, there is a strong need to develop biologic information about tumors that recur, so not only will we better understand why patients relapse but also we can develop therapy tailored specifically to the biology of the recurrent tumor.