2. Previous anti-CD20 radioimmunotherapy (RIT) or non-rituximab anti-CD20 therapy (such as obinutuzumab) within 6 months prior to randomization. Patients who have received previous anti-CD20 RIT or non-rituximab anti-CD20 therapy (such as obinutuzumab) must have attained a partial or complete response lasting at least 6 months, and must have recovered from any hematologic or other toxicity.