Monitoring B-cell repopulation after depletion therapy in neurologic patients.

Objective: To determine the factors that influence B-cell repopulation after B-cell depletion therapy in neurologic patients and derive recommendations for monitoring and dosing of patients.

Methods: In this study, we determined the association of body surface area (BSA; calculated by body weight and height with the Dubois formula), sex, pretreatment therapy, age, CSF data, and white blood cell counts with the risk and timing of B-cell repopulation, defined as 1% CD19+ cells (of total lymphocytes), following 87 B cell-depleting anti-CD20 treatment cycles of 45 neurologic patients (28 women; mean age ± SD, 44.5 ± 15.0 years).

Results: Patients with a larger BSA had a higher probability to reach 1% CD19+ cells than those with a smaller BSA ( p < 0.05) following B-cell depletion therapy, although those patients had received BSA-adapted doses of rituximab (375 mg/m2 ). Sex, pretreatment, age, CSF data, or absolute lymphocyte and leukocyte counts during treatment did not significantly influence CD19+ B-cell recovery in the fully adjusted models. Intraindividual B-cell recovery in patients with several treatment cycles did not consistently change over time.

Conclusions: B-cell repopulation after depletion therapy displays both high inter- and intra-individual variance. Our data indicate that a larger BSA is associated with faster repopulation of B cells, even when treatment is adapted to the BSA. A reason is the routinely used Dubois formula, underestimating a large BSA. In these patients, there is a need for a higher therapy dose. Because B-cell count-dependent therapy regimes are considered to reduce adverse events, B-cell monitoring will stay highly relevant. Patients' BSA should thus be determined using the Mosteller formula, and close monitoring should be done to avoid resurgent B cells and disease activity.