Mobilization of CD34+ cells in elderly patients (≥ 70 years) with multiple myeloma:: influence of age, prior therapy, platelet count and mobilization regimen

The mobilization of peripheral blood stem cells was studied in 984 multiple myeloma patients, including 106 patients aged greater than or equal to 70 years. Increasing age correlated inversely with CD34(+) yield (P < 0.0001), but also with greater than or equal to 12 months of prior standard chemotherapy (P = 0.0001), < 200 x 10(9) /l platelets (P = 0.0006) premobilization and mobilization with growth factors only (P = 0.0001). After controlling for these age covariates, multivariate analysis identified less than or equal to 12 months standard therapy and platelet count greater than or equal to 200 x 10(9) /l premobilization as favourable variables (both P < 0.0001), while increasing patient age remained an unfavourable factor (P = 0.0009). With both favourable variables, 85% of elderly patients collected greater than or equal to 4 x 10(6) /kg CD34(+) cells in a median of one collection. The effect of age was incremental with no age threshold showing acceleration in the decline of CD34(+) yield. Chemotherapy significantly increased CD34(+) yield compared with growth factors only. However, the subgroup of patients with > 12 months prior therapy and premobilization platelet count < 200 x 10(9) /l mobilized as many CD34(+) cells with granulocyte colony-stimulating factor (G-CSF) alone as with chemotherapy and haematopoietic growth factors. Increasing patient age had no effect on post-transplant neutrophil recovery, but significantly delayed platelet recovery (greater than or equal to 50 x 10(9) /l) if < 2 x 10(6) /kg CD34(+) cells were infused, but this effect was eliminated completely with infusion of greater than or equal to 4 x 10(6) /kg CD34(+) cells. Increasing age adversely affected CD34(+) yield even with limited premobilization therapy, indicating that early collection is important in elderly patients.