Factors influencing collection of peripheral blood progenitor cells following high‐dose cyclophosphamide and granulocyte colony‐stimulating factor in patients with multiple myeloma

Abstract

We treated 103 multiple myeloma (MM) patients with 7 g/m² cyclophosphamide (Cy) followed by 300 μg G‐CSF/d to harvest peripheral blood progenitor cells (PBPC). PBPC autografts containing > 2.0 × 10⁶ CD34⁺ cells per kg body weight were obtained at the first attempt from 90/100 evaluable patients. The most significant factor predicting impairment of PBPC collection was the duration of previous melphalan treatment (P < 0.0001). In multivariate discriminate analysis, treatment with melphalan during the most recent chemotherapy cycles prior to mobilization (P = 0.0727) and previous radiotherapy (P = 0.0628) had a marginally significant negative influence on the efficacy of PBPC collection. We found no reduced functional capacity of CD34⁺ cells to restore haemopoiesis after myeloablative treatment related to the duration of melphalan exposure. At the time of best response to conventional treatment, a median paraprotein reduction of 21% was achieved following high‐dose cyclophosphamide (HD‐Cy). Two heavily pretreated patients died and one patient developed pulmonary toxicity W.H.O. grade IV following HD‐Cy. Potential transplant candidates should undergo mobilization and harvesting of PBPC before melphalan‐containing treatment. Combinations of haemopoietic growth factors and their dose modifications should be investigated to improve PBPC collection, to allow a dosage reduction of the mobilization chemotherapy.