Effect Of Cumulative Adverse Clinical Risk Factors On Patients With Multiple Myeloma Undergoing First GCSF Apheresis

With the new treatments for multiple myeloma (MM), increasing numbers of patients fail to mobilize sufficient peripheral blood stem cells (PBSC) for autologous stem cell transplant (ASCT). Multiple studies have identified clinical and laboratory factors, such as age, number of lines of chemotherapy, radiation exposure, bone marrow involvement, and low PLT count as risks for poor mobilization. However, there are fewer studies that analyze only the effect of multiple clinical risk factors on mobilization outcomes. We retrospectively analyzed 259 MM patients who underwent first apheresis after GCSF mobilization between December 2000 and December 2012. Clinical risk factors analyzed include age, number of lines of chemotherapy, number of cycles of chemotherapy, number of doses of cyclophosphamide, number of doses of lenalidomide, and prior external beam radiation. The standard dose of GCSF was 10 mcg/kg/day, however the exact dose for a significant number of patients was not known. Patients were assessed as to whether optimal (≥8x10⁶ CD34+ cells/kg) or minimal (≥4x10⁶ CD34+ cells/kg) number of stem cells for two ASCTs were collected. The median age of the entire cohort was 59.7 years (27.9-76.0). Overall 10.8% and 32.6% failed to collect the minimal and optimal number of stem cells after one round of apheresis. Of the twenty patients who underwent a second round of apheresis, 9 (45%) collected minimal and 7 (35%) collected optimal total number of stem cells, with an overall failure rate of 4.6% and 29.8%, respectively. The effect of the number of clinical risk factors on the mobilization failure during first apheresis is summarized in Table 1. For each additional clinical risk factor, the likelihood of collecting the minimal and optimal number of CD34+ cells is reduced by 34% (CI=0.484-0.893, p=0.0072) and 32% (CI=0.538–0.860, p=0.0013) respectively. On univariate analysis, all risk factors were analyzed as continuous variables, except for prior radiation which was analyzed as a categorical variable. Prior lenalidomide exposure (odds ratio=0.502, CI=0.297–0.845, p=0.0096), and prior radiation therapy (odds ratio=0.502, CI=0.293–0.861, p=0.0123) had the greatest negative predictive value. Of the 38 patients who were exposed to lenalomide (median 4 cycles; range 1-24 cycles), 13% and 42% failed to collect minimal and optimal number of stem cells in the first apheresis cycle, respectively. An association was seen between number of days required to collect target number of stem cells and number of risk factors (p≤0.001). Median number of days required to collect target number of stem cells for 0, 1 or 2+ clinical risk factors was 2, 2, and 4 days, respectively. When the effect of clinical risk factors were analyzed according to number of CD34+ cells/kg collected on each day of apheresis, statistically significant differences in collection efficiency were seen on the first 3 days of apheresis (Figure 1). In summary, clinical characteristics of patients with MM can potentially be used to predict mobilization failure. The presence of 2 or greater clinical risk factors adversely affect the ability to successfully collect the target stem cell dose. These risk factors may help in identifying high-risk MM patients who may benefit from alternative mobilization regimens that can be tested in prospective clinical trials.