Reversible late onset neutropenia associated with rituximab has been reported with incidence rates varying from 15 to 70% in B cell lymphoma patients receiving autologous stem cell transplantation. We conducted a retrospective descriptive study at one tertiary care center in adult B cell lymphoma patients treated with rituximab and autologous stem cell transplantation between 1 January 2004 and 30 June 2014. Late onset neutropenia was defined as an absolute neutrophil count <1.0 × 10 cells/L after neutrophil engraftment and less than six months post autologous stem cell transplantation. The primary objective was to determine the incidence of late onset neutropenia. The secondary objectives were to examine whether the use of rituximab with re-induction therapy, mobilization or high dose chemotherapy regimens increased the risk for late onset neutropenia, and to evaluate infectious complications. Of 315 subjects, 92 (29.2%) developed late onset neutropenia. Mobilization regimens containing rituximab (OR 2.90 95% CI: 1.31-6.40), high dose chemotherapy containing rituximab (OR 1.87 95% CI: 1.14-3.05), and exposure to rituximab in either or both regimens (OR 3.05 95% CI: 1.36-6.88) significantly increased the risk of late onset neutropenia. While neutropenic, 17.4% experienced an infection, 7.6% experienced febrile neutropenia, and 5.4% were hospitalized. In conclusion, rituximab with mobilization or high dose chemotherapy may increase the risk of late onset neutropenia post autologous stem cell transplantation.

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