An Efficacy and Tolerability Study of Bortezomib in Combination With Rituximab Standard Therapy in Participants With Relapsed or Refractory Follicular Lymphoma

This is a prospective (study following participants forward in time), open-label (all people know the identity of the intervention), multi-center (conducted in more than 1 center), non-randomized (study drug not assigned by chance), single-arm study in participants with relapsed or refractory cluster of differentiation 20 plus (CD-20+) follicular Grade 1 or 2 lymphoma Stage III or IV with at least 2 previous lines of therapy. The study will include 2 phases: a Screening phase and a Treatment phase. The Screening phase will be conducted 2 weeks before the Treatment phase. The Treatment phase will include 3 cycles. The duration of each cycle will be 5 weeks (35 days). After the second cycle, a response will be evaluated. In case of complete response (CR), participants will be followed-up for a period of 1 year. In case of progressive disease (PD), the participant will be excluded from the study, and in case of stable disease (SD) or partial response (PR), an additional cycle of 5 weeks will be applied and a follow-up of 1 year will be performed. In each cycle, participants will receive 1.6 milligram per meter square (mg per m\^2) of bortezomib as intravenous (through a vein in the body) infusion (a fluid or a medicine delivered into a vein by way of a needle) on Days 1, 8, 15, 22 of Cycle 1, Days 36, 43, 50 and 57 of Cycle 2 and on Days 71, 78, 85 and 92 of Cycle 3 (if applicable). Cycle 3 will be applicable only in case of SD or PR according to remission criteria after Cycle 2. In Cycles 2 and (if applicable) 3, injection of bortezomib followed by administration of rituximab (in a dose of 375 mg per m\^2) will be given as intravenous infusion. If neuropathy (a disturbance in the function of the brain or spinal cord that may affect the nerves and muscles of the body) grade of more than or equal to 2 will occur then a dose of bortezomib will be reduced from 1.6 mg per m\^2 to 1.3 mg per m\^2 and then to 1.0 mg per m\^2. Participants will be analyzed for time to disease progression or relapse, disease free survival, overall survival and remission (when a medical problem gets better or goes away at least for a while) status. Participants' safety will be monitored throughout the study.