Allogeneic stem cell transplantation for patients with metastatic renal cell carcinoma.

Allogeneic stem cell transplantation and donor lymphocyte infusions are currently under clinical investigation as an innovative therapeutic option for patients with metastatic renal cell carcinoma. A variety of trials have proven the clinical efficacy of allogeneic stem cell transplantation using reduced-intensity conditioning protocols and donor lymphocyte infusions, as demonstrated by the induction of objective remissions in metastatic renal cell carcinoma patients. However, despite clinical remissions, reduced-intensity conditioning protocols and donor lymphocyte infusions were associated with a high treatment-related mortality rate of approximately 17%. The disproportion between clinical efficacy and treatment-related mortality may mainly be caused by the selection of patients that had often been heavily pretreated, with a large tumor burden and rapidly progressing tumors. The improvement of efficacy with the preservation of a powerful graft-versus-tumor effect while reducing the toxicity, is the major experimental and clinical challenge of allogeneic stem cell transplantation in the treatment of metastatic renal cancer and other solid tumors. Recently, there has been a revolutionary development of molecular-targeted agents in metastatic renal cancer. These inhibitors of angiogenesis and signal-transduction pathways have demonstrated clinical efficacy and significant survival prolongation in the first- and second-line settings, while causing moderate toxicity. Some of these agents have already been approved by the US FDA and will probably replace standard cytokines, such as interferon-alpha2 and interleukin-2, in metastatic renal cancer. In the context of these innovative clinical developments, allogeneic stem cell transplantation clearly has to be regarded an investigational clinical treatment approach. Therefore, patients should only be treated at centers that are experienced in clinical trials, and patient selection remains a critical factor for a successful transplant procedure.