Jornal de Imunologia Clínica e Celular
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Impact of Non-Fixed Versus 6 Month Fixed Retreatment Schedules on Serum Immunoglobulins Following Rituximab in Patients with Rheumatoid Arthritis

Inmaculada de la Torre, Maria J Leandro, Delia Gerona, Lara Valor, Luis Carreno and Geraldine Cambridge

Objectives: To assess the incidence of secondary hypogammaglobulinemia in patients with rheumatoid arthritis (RA) following multiple cycles of rituximab (RTX) related to two different therapy regimens.

Methods: 73 patients with RA were retreated using 6 months-fixed strategy and 63 patients using a non-fixed regimen. All received ≥ 2 courses of RTX. Data on serum immunoglobulins (Ig), serious infections and DAS28 were collected, with maximum follow-up being 24 months for the 6 months fixed group and 156 months for the non-fixed group). Statistics for non-parametric analysis were applied.

Results: The percentages of patients developing low IgG or IgM did not differ between groups after the 3rd cycle, but those with non-fixed retreatment tended to be higher. After 4 cycles, median IgM levels were significantly lower in both groups compared with pretreatment (p<0.05). Only patients in the fixed retreatment group receiving 4 cycles of treatment showed a significant drop in median IgG level (p<0.05). IgA levels remained within the normal range. Withdrawals due to infections per 100 patient years (py)s in patients with low IgG were higher after 3 Cycles in patients within the fixed retreatment group (4.60/100py vs 1.36/100py, CI: 0.59, 6.23). DAS28 did not differ between cohorts after multiple cycles.

Conclusions: Although the percentage of RA patients developing low IgG tended to be higher in the nonfixed group, median IgG level was significantly lower after 4 Cycles of RTX in the fixed regimen group. The fixed retreatment group also had more patients discontinuing rituximab over a shorter period of time (24 months compared with 156 months), with no significant differences in median DAS28 after multiple Cycles. If multiple cycles of RTX are to be instituted, non-fixed regime may allow the opportunity to control the disease with a lower incidence of withdrawal due to low Igs and infections.