regimen and 2) the combination of rituximab with lenalidomide (no chemotherapy agent) versus various chemotherapy plus immunotherapy (principally rituximab) to achieve similar complete remission and 3 year progression-free survival rates but with rituximab plus lenalidomide causing less toxicity (i.e. severe neutropenia). Many of these studies did use rituximab maintenance therapy after induction therapy. Prevention Several studies, while not conclusive, suggest that the early treatment of low risk FL reduces the incidence of the disease progressing to t-FL. The treatments used in these studies include chemotherapy, radiation therapy, and immunotherapy combinations plus rituximab maintenance therapy. Relapsed follicular lymphoma Patients who relapse after initial therapy for FL may be followed closely without therapy if asymptomatic. When treatment is required, patients may be treated with the initial treatment regimen when such treatment led to a remission that lasted for at least one year; otherwise an alternative regimen is used. The regimens commonly used in relapsed lymphoma include R-CHOP, R-CVP, RFM (i.e. rituximab, fludarabine, and mitoxantrone), and RB (Bendamustine plus rituximab). Patients who have early treatment failure (e.g. within 1–2 years of initial treatment) or multiple relapses have also been treated with either autologous (i.e. stem cells taken from patient) or allogeneic (i.e. stem cells taken from a donor) stem cell bone marrow transplantation. While studies are inconclusive, autologous stem cell bone marrow transplantation appears to prolong survival in early treatment failure patients who are healthy enough to withstand this therapy. Unfit patients may benefit from initial treatment with obinutuzumab plus bendamustine followed by maintenance treatment with obinutuzumab (if they have not been treated previously with obinutuzumab). Other mostly experimental treatments currently under study in patients with multiple treatment failures include: 1) Phosphoinositide 3-kinase inhibitors such as copanlisib, duvelisib, and idelalisib which block the phosphoinositide 3-kinase signaling pathway that promotes the survival, proliferation, and other potentially malignant behaviors of cells; 2) infusion of tisagenlecleucel chimeric antigen receptor T cells (i.e. CAR T cells) (i.e. T cells that have been isolated from patients, engineered to express a receptor for the CD19 protein on, and thereby kill, T cells, and then infused back into the donor patient); 3) Bruon's tyrosine kinase inhibitor, ibrutinib, to block the B-cell maturating actions of this kianase; 4) BCL inhibitor venetoclax to block Bcl2's action in promoting B-cell survival and proliferation; 5) histone deacetylase inhibitors abexinostat and tazemetostat to modify the expression of various genes; and 6) Checkpoint inhibitors nivolumab, pidilizumab,