The issue si that Rituximab as single agent. Rituximab (Rituxan®) is a monoclonal antibody that has been used to treat various cancers of the blood (leukemia) and the lymphatic system (lymphoma). Rituximab (given with cyclophosphamide, vincristine and prednisolone) is recommended as a possible treatment for people with symptomatic stage III or IV follicular lymphoma who haven' t been treated before. It has been used successfully, both alone and in combination with standard chemotherapy, in patients whose follicular lymphoma has recurred or proven resistant to other treatment. The addition of rituximab to first-line chemotherapy has been found to improve survival of patients with previously untreated follicular lymphoma.
Regarding maintenance: data from five clinical trials in patients with follicular lymphoma whose disease had relapsed or was resistant to treatment, those who received maintenance therapy with rituximab survived longer than those who did not receive maintenance therapy. However, this finding leaves unanswered the question of whether maintenance rituximab is superior to treatment with rituximab on relapse. However, it is being recommended by the Cochrane Database. NCCN is a bit unclear in that it lists single agent Rituxan but with a note, "initial management of patients with follicular lymphoma should INCLUDE rituximab". They list maintenance but state: "It is strongly recommended that this treatment be offered in a prospective clinical trial".
Vidal L, Gafter-Gvili A, Leibovici L, Dreyling M, Ghielmini M, Hsu Schmitz SF, Cohen A, Shpilberg O. Rituximab maintenance for the treatment of patients with follicular lymphoma: systematic review and meta-analysis of randomized trials.J Natl Cancer Inst. 2009 Feb 18;101(4):248-55.
Vidal L, Gafter-Gvili A, Leibovici L, Shpilberg O.Rituximab as maintenance therapy for patients with follicular lymphoma.Cochrane Database Syst Rev. 2009 Apr 15;(2)