Delayed recovery of serum immunoglobulin G is a poor prognostic marker in patients with follicular lymphoma treated with rituximab maintenance.

Clinical trials involving various treatment schedules for rituximab maintenance have been conducted for patients with follicular lymphoma (FL) and have not confirmed their impact on serum immunoglobulin (sIg) levels until the completion of maintenance. However, the long-term use of rituximab is a concern because of circulating plasma cell-depletion risk, suggesting that the mechanism of change in sIg levels after RM has not been determined. Additionally, the relationship between host humoral immunity and the prognosis of patients with B cell malignancies has not been determined. We retrospectively investigated data from 213 patients with FL from a single institute who achieved at least a partial response with rituximab, cyclophosphamide, vincristine, and prednisolone with or without doxorubicin. Of these, 166 patients underwent RM with a median period of 1.6 years. A significantly delayed recovery of sIgG levels was observed in the maintenance group until 3 years after RM in comparison to the observation group. A multivariate analysis showed that a sIgG level of < 718 mg/dl 1 year after RM was an independent predictor for poor progression-free survival (PFS) (hazard ratio, 2.3; P = 0.04). Therefore, the sIgG levels scarcely recovered and were significantly delayed after RM, leading to shorter PFS in patients with FL.