Bortezomib washout duration prior to stem cell mobilization in patients with newly diagnosed multiple myeloma

Objectives: We aimed to determine the impact of washout period in patients with multiple myeloma between bortezomib-based induction regimens and the collection of stem cells. Methods: This was a single-center historical prospective study, including all sequential newly diagnosed patients with myeloma between 2012 and 2017 that were given a first-line bortezomib-based induction therapy (≤6 cycles) followed by stem cell collection (n = 75). Results: We found a statistically significant correlation between the days from last dose of bortezomib and both CD34⁺ cells/kg yield on the first collection day and the overall collected CD34⁺ cells/kg (r =.466, P <.001, and r =.341, P =.03, respectively). The optimal receiver operating curve's cutoff point was 8.5 days (79% sensitivity and 71% specificity, P =.001). On multivariate analysis, timing of last dose of bortezomib remained statistically significant (P =.01). Based on this, we developed a model to predict the total collected CD34⁺ cells/kg = 11.76 + 0.13 (timing in days of last dose of bortezomib) −0.1 (age) −1.39 (if female) −0.01 (≥PR) −1.35 (if prior radiation). Conclusions: Timing of last dose of bortezomib may predict a successful collection. A washout period of 9 days is associated with a better collection yield. A prospective validation of this novel finding is required.