4. For selected higher-risk Group B participants receiving rituximab only (e.g., those with MLBLC, Stage III with LDH ≥ 2 times upper limit of normal (ULN), and/or bone marrow/CNS involvement. All participants who receive rituximab must have hepatitis screening prior to enrollment. Participants whose results indicate that they are carrier of hepatitis B can still be treated per Group B but will NOT receive rituximab. This screening must be done for eligibility BUT the results are not needed prior to enrollment: