Rituximab Maintenance Treatment for a Maximum of 5 Years In Follicular Lymphoma: Safety Analysis of the Randomized Phase III Trial SAKK 35/03

Rituximab maintenance has been shown to be effective in patients with follicular lymphoma. The optimal duration of maintenance remains unknown.

We prospectively registered 270 patients with untreated, chemotherapy resistant or relapsed follicular lymphoma. All patients received rituximab induction consisting of 4 weekly doses (375 mg/m²). Responding patients (PR and CR) were randomized to a short maintenance consisting of four doses of rituximab (375 mg/m²) every two months (arm A) or prolonged maintenance consisting of rituximab every two months for a maximum of five years or until disease progression or unacceptable toxicity (arm B). Primary endpoint is event-free survival. Here we present the safety analysis results after a median long-term maintenance period of 3.3 years.

From October 2004 to November 2007 165 patients were randomized, 82 in arm A and 83 in arm B. The median follow-up time is 3.2 years for arms A and B combined. While receiving maintenance therapy a total of 899 hematological and non-hematological adverse events were observed, 28 of grade 3 and 6 of grade 4. After randomization five patients experienced subsequent cancers. Seven grade 3 and 4 infections were reported. Two grade 3 infections occurred after 2 years of maintenance. Grade 3 and 4 neutropenia occurred in 6 (3.6 %) patients, decreased levels of IgG were observed in 24 (14.6 %) patients. In arm B, maintenance was stopped due to unacceptable toxicity in 2 patients after 16 and 42 months respectively and due to subsequent breast cancer in 1 patient after 20 months. One patient died 4 months after randomization because of ileus and consecutive peritonitis, considered to be unrelated to therapy. Sixty-three patients are on maintenance for two or more years of which 48 patients are on for three or more years. Two patients have completed the 5 years of maintenance.

Rituximab maintenance beyond two years is feasible without evidence for increased toxicity. However, close follow up of patients under prolonged rituximab maintenance is still necessary. The trial has been closed for accrual but there are still patients on treatment.

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