 6.1 Rituximab is an acceptable maintenance agent if the last dose was given at least one month prior to enrollment and no additional doses are planned for the duration of the study through the month 6 visit or early termination. If a patient received rituximab and was then prescribed another maintenance agent, the patient is eligible if there are no plans by the treating physician to change the dose of the maintenance other than for safety purposestoxicity for the duration of the study through the month 6 visit or early termination. 