Purpose: To evaluate the feasibility and safety of nonmyeloablative allogeneic stem-cell transplantation in patients with metastatic renal cell cancer (RCC) and to evaluate efficacy with respect to engraftment and tumor regression.
Patients and methods: Between February 1999 and June 2001, patients with refractory, metastatic RCC were screened for enrollment. A fludarabine and cyclophosphamide-based conditioning regimen was used. Patients received granulocyte-macrophage colony-stimulating factor-mobilized, unmanipulated stem cells from a 6/6 HLA-matched sibling donor. Prophylaxis against graft rejection and graft-versus-host disease (GVHD) included tacrolimus and mycophenolate mofetil.
Results: A total of 284 patients with metastatic RCC were seen during this time period. Eighty-four patients who had siblings available for HLA typing were actively screened for enrollment, and 15 patients have undergone treatment. Durable donor engraftment was achieved in one of the first four patients treated. Patients no. 5 through 15 received a more immunosuppressive conditioning regimen, and all have achieved sustained donor engraftment. In the 12 patients with at least 180 days of follow-up, acute GVHD has occurred in two patients and chronic GVHD in six patients, with four transplant-related mortalities. Four partial responses have been observed (response rate, 33% in all patients; 44% in the nine patients with sustained donor engraftment).
Conclusion: Nonmyeloablative allogeneic stem-cell transplantation is feasible for a minority of patients with metastatic RCC. Adequately immunosuppressive conditioning is required for sustained donor engraftment, which is required for an antitumor response. Acute and chronic GVHD are the major causes of substantial morbidity and mortality. Metastatic RCC is susceptible to a graft-versus-tumor effect promoted by allogeneic stem-cell transplantation.