Stem-cell transplantation in chronic lymphocytic leukemia: the time for designing randomized studies has arrived

Stem-cell transplantation in conjunction with myeloablative therapy has evolved as a standard treatment option for patients with several hematologic malignancies, including chemosensitive, relapsed non-Hodgkin's lymphoma and untreated multiple myeloma. The pharmacologic basis for this treatment includes a favorable tumor dose-response curve that abrogates intrinsic drug resistance associated with these diseases and facilitates cure or prolongation of survival even in the absence of a cure. The belief that chronic lymphocytic leukemia (CLL) is a palliative disease of the elderly has been perpetuated, limiting the application of more aggressive therapies. The introduction of fludarabine and its use in combination with other agents has increased the morphologic complete response rate observed in the initial treatment of CLL, providing the rationale to explore further disease-consolidative therapies. Concomitant with this, several phase II studies have demonstrated the feasibility of performing both allogeneic and autologous stem-cell transplantation in patients with CLL. In this regard, allogeneic transplantation has produced prolonged remissions in young patients with relapsed and refractory CLL, but at the cost of high treatment-related morbidity and mortality. Application of "minitransplantation" regimens may temper the frequency of these complications and warrants further study. Autologous stem-cell transplantation has also been explored with promising disease-free survival outcomes in less heavily pretreated patients. However, relapses continue to be the most frequent source of late mortality, as has been observed previously with multiple myeloma. With scientific justification established in similar diseases and demonstrated feasibility with low morbidity, we believe the time for a randomized comparison of standard chemotherapy versus autologous stem-cell transplantation in CLL has arrived. Despite promising results observed with allogeneic transplantation, further refinements that broaden the patient eligibility and lower treatment mortality will be required before similar investigations can occur with this modality.