Hematopoietic stem cell mobilization increases the release of immature and maturing hematopoietic cells from the marrow into the blood circulation. For successful hematopoietic stem cell transplantation an adequate number of stem cells must be mobilized and collected. For autologous stem cell transplants, a product bag CD34+ count of > 5.0 x 106 CD34/kg is a target; however, patients have been successfully transplanted with doses as low as 2.0 x 106 CD34/kg.
Some patients are "poor mobilizers" and standard protocols do not result in adequate numbers of circulating CD34 cells to collect. Risk factors associated with poor stem cell mobilization include increasing age, underlying diagnosis, low premobilization platelet count, history of increasing cycles, and regimens of chemotherapy.
Teriparatide, a parathyroid hormone (PTH) analog has been used in "poor mobilizers." Two patients at our institution received the drug as part of an additional mobilization strategy.
Medical records of patients who had stem cell mobilization were reviewed. Two patients who failed routine mobilization protocol received PTH as part of an additional mobilization regimen. Clinical outcomes, collection, and engraftment data were reviewed.
Patient 1 had a diagnosis of Hodgkin Lymphoma and failed to mobilize adequately on the first attempt using filgrastim and plerixafor with peripheral blood CD34 counts of 1, 4, and 3 resulting in cancellation of stem cell collection. For the second mobilization attempt, teriparatide was added to the regimen. Peripheral blood CD34 counts improved to 8, 6, and 2 resulting in three collections with a total of 2.23 x 106 CD34/kg for reinfusion. Engraftment data showed 14 days for neutrophils and 17 days for platelets. The patient is 6 months post-transplant with no major morbidities reported, currently in maintenance therapy, and has not recurred.
Patient 2 had a diagnosis of multiple myeloma and failed to mobilize on filgrastim and plerixafor with peripheral blood CD34 counts of 2, 2, and 2 resulting in collections with a total of 0.6 x 106 CD34/kg for reinfusion. For the second mobilization attempt, peripheral blood CD34 counts of 2, 2, 2, and 0 resulting in collections with a total of 0.822 x 106 CD34/kg for reinfusion. For the third mobilization attempt, teriparatide was added to the regimen. Peripheral blood CD34 counts improved to 8 and 4 resulting in collections with a total of 1.8 x 106 CD34/kg for reinfusion. Patient expired one month after collection without reinfusion.
Two patients who failed standard mobilization for stem cell collection at our institution received teriparatide as part of an additional stem cell mobilization regimen. Adequate doses of stem cell products for transplant were collected. One patient was reinfused and subsequently engrafted appropriately. Teriparatide can be used in the setting of poor mobilization.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.