Predictors of CD34(+) Cell Mobilization and Collection in Adult Men With Germ Cell Tumors: Implications for the Salvage Treatment Strategy

Tandem or triple high-dose chemotherapy (HDCT) cycles with CD34(+) cell support is an increasingly used option in the salvage therapy of male germ cell tumors (GCT). We analyzed the combined series of 2 institutions with the aim to optimize the salvage strategy by identifying potential limitations in administering HDCT. The negative effect of previous chemotherapy load on the CD34(+) cell mobilization and harvest was observed. This might have implications in salvage treatment strategy. Background: High-dose chemotherapy with tandem or triple carboplatin and etoposide course is currently the first curative choice for relapsing GCT. The collection of an adequate amount of hematopoietic (CD34(+)) stem cells is a priority. Patients and Methods: We analyzed data of patients who underwent HDCT at 2 referral institutions. Chemotherapy followed by myeloid growth factors was applied in all cases. Uni-and multivariable models were used to evaluate the association between 2 prespecified variables and mobilization parameters. Analyses included only the first mobilizing course of chemotherapy and mobilization failures. Results: A total of 116 consecutive patients underwent a mobilization attempt from December 1995 to November 2012. Mobilizing regimens included cyclophosphamide (CTX) 7 gr/m(2) (n = 39), cisplatin, etoposide, and ifosfamide (PEI) (n = 42), paclitaxel, cisplatin, and gemcitabine (TPG) (n = 11), and mixed regimens (n = 24). Thirty-seven percent were treated in first-line, 50% (n = 58) in second-line, 9.5% (n = 11) and 3.4% (n = 4) in third-and fourth-line settings, respectively. Six patients did not undergo HDCT because they were poor mobilizers, 2 in first-and second-line (1.9%), and 4 beyond the second-line (26.7%). In the multivariable model, third-line or later setting was associated with a lower CD34(+) cell peak/mu L (P = .028) and a lower total CD34(+)/kg collected (P = .008). The latter was also influenced by the type of mobilizing regimen (P < .001). Conclusion: A decline in significant mobilization parameters was found, primarily depending on the pretreatment load. Results lend support to the role of CD34(+) cell mobilization in the therapeutic algorithm of relapsing GCT, for whom multiple HDCT courses are still an option, and potentially a cure.