Management strategies for the hard-to-mobilize patient

Delayed hematopoietic engraftment, particularly of platelets, is seen in 5-35% of patients undergoing high-dose chemotherapy with autologous stem cell transplantation. Studies indicate that delayed engraftment is related to low CD34+ cell dose, and that risk factors for poor mobilization of CD34+ cells relate primarily to the type and extent of prior therapy. Data indicating an appropriate strategy to ensure that 'hard-to-mobilize' patients will achieve adequate CD34+ cell numbers are limited. It is clear, however, that marrow harvesting (performed frequently by a number of centers), is of limited value. Remobilization, best accomplished with a regimen of high-dose chemotherapy and cytokines, is of benefit in selected patients, but has substantial costs and morbidity. Instead of ad hoc treatment of patients who have a poor first mobilization, high-risk groups should be identified prospectively, and strategies should be developed to ensure adequate mobilization in all high-risk patients. The first randomized trial utilizing this approach has recently been reported. In this trial, stem cell mobilization with granulocyte colony-stimulating factor (G-CSF) alone was compared to mobilization with G-CSF combined with stem cell factor (SCF) in heavily pretreated patients with Hodgkin's and non-Hodgkin's lymphoma. The combination of G-CSF and SCF led to collection of a higher total CD34+ cell dose compared to G-CSF alone. Further, more patients in the combination group were able to mobilize an optimal CD34+ cell dose (ie 5 x 10(6)/kg). Additional trials are needed to determine long-term outcomes and the economic impact of achieving optimal stem cell mobilization in these patients, who would otherwise not be candidates for high-dose chemotherapy.