No data are currently available concerning the ability of anti-CD20 antibody treatment in reducing the proportion of Bcl-2 positive residual cells after radiotherapy in localized FL. The objective of this study is to take advantage of the therapeutic potential of anti-CD20 monoclonal antibody to reduce or eliminate minimal residual disease in patients with FL in localized stage (I/II) after conventional treatment with local radiotherapy of the involved site(s). The effectiveness of anti-CD20 monoclonal antibody treatment will be determined by the proportion of negativization of residual Bcl-2 positive cells after radiotherapy, evaluated by qualitative and quantitative PCR detection of viable Bcl-2/IgH rearranged cells in PB and/or BM.