Comparison of Cyclophosphamide- Versus Etoposide-Based Chemomobilization for Autologous Stem Cell Transplant in Lymphoma

Abstract

Background Chemomobilization is a strategy commonly used for hematopoietic progenitor cell collection prior to high dose chemotherapy followed by autologous stem cell transplant (aHCT). Collection protocols and target yields for aHCT are variable and institution specific. At UNC Hospital, etoposide (VP16) was the preferred chemomobilization agent, but was switched to cyclophosphamide (Cy) due to a drug shortage beginning in February 2018. This study compares the efficacy and safety of Cy- and VP16-based chemomobilization strategies. Methods This is a single-center retrospective review comparing all lymphoma patients between January 1, 2017 and April 30, 2019 receiving chemomobilization with either a single dose of Cy 2 g/m2 or VP16 300 mg/m2 daily for two days. All patients received G-CSF at 10 mcg/kg rounded to nearest vial size starting approximately 24 hours after chemotherapy through completion of collection, while select patients used plerixifor per institutional algorithm. The primary endpoint was the rate of successful stem cell collection, defined as 2 × 106 CD34+ cells/kg in two or fewer apheresis sessions. Secondary endpoints included the rate of optimal stem cell collection of at least 4 × 106 CD34+ cells/kg in two or fewer apheresis sessions, time between chemomobilization and final apheresis session, rate of plerixafor use, incidence of febrile neutropenia, hemorrhagic cystitis, emergency department (ED) visits, and hospital admission rates between chemomobilization and final apheresis session as well as time to neutrophil and platelet engraftment. Results There were no differences in sex, race, or diagnoses between patients receiving Cy (n=28) vs. those who received VP16 (n=31). There was a trend towards older age in the Cy group, [median age 60 (range, 20-76) vs 53 (23-75) years; p=0.06]. All patients in both arms collected 2 × 106 CD34+ cells/kg in two or fewer apheresis sessions and there was no difference in stem cell collection of at least 4 × 106 CD34+ cells/kg in two or fewer apheresis sessions between the groups (Cy: 85.7%, VP16: 74.2%; p=0.27). Plerixafor was used in 23 patients (Cy: 39.3%, VP16: 38.7%; p=0.96). Rates of febrile neutropenia (Cy: 10.7%, VP16: 3.2%; p=0.34), hemorrhagic cystitis (Cy: 0%, VP16: 0%; p>0.99), ED visits (Cy: 10.7%, VP16: 12.9%; p>0.99), and hospital admission (Cy: 7.1%, VP16: 6.5%; p>0.99) were similar. The median days between chemomobilization and final apheresis were similar [Cy: 12 days (8-18), VP16: 12 days (8-15); p=0.32]. There were no differences in the median days to neutrophil [Cy: 11 (9-26), VP16: 11 (9-14); p=0.80) or platelet engraftment [Cy: 14 (10-38), VP16: 15 (11-149); p=0.16) between Cy and VP16 regimens. Conclusion There was no difference in the rates of successful stem cell collection or adverse events between Cy and VP16 chemomobilization. Both regimens are reasonable options for chemomobilization in lymphoma patients.