Inclusion Criteria:

1. Histologically confirmed, Ann Arbor stage II, III, or IV DLBCL according to the
REAL/WHO classification (from initial diagnosis made prior to starting CHOP21-R
therapy);

2. Central pathology review confirming the DLBCL diagnosis and CD20 positivity, and no
evidence/evidence with an infiltration <25% of DLBCL in bone marrow;

3. The first part of the treatment of DLBCL must have been 4 cycles of standard CHOP21
chemotherapy (cyclophosphamide 750 mg/m2, doxorubicin 50 mg/m2, vincristine 1.4 mg/m2
up to a maximum of 2 mg on day 1, and at least 40 mg/m2/day prednisone on Days 1 to 5
every three weeks) in combination with rituximab (375 mg/m2);

4. Complete remission (CR), unconfirmed complete remission (CRu), partial response, and
non-responder according to the International Workshop Response Criteria for NHL
described by Cheson et al (18) after four cycles of CHOP21-R. CT scans of the neck,
thorax, abdomen, and pelvis and PET total body must have been performed within 3
weeks after the last dose of the last course of CHOP21-R;

5. Patients 60-years-of-age or older at time of accrual;

6. WHO performance status (PS) of 0 to 2 within 1 week of accrual;

7. Absolute neutrophil count (ANC) more than 1.5 x 109/L within 1 week of accrual;

8. Hemoglobin (Hgb) more than 10 g/dL within 1 week of accrual;

9. Platelets more or equal than 150 x 109/L within 1 week of accrual.

10. Life expectancy of 3 months or longer

11. Written informed consent obtained according to local guidelines

Exclusion Criteria:

1. Presence of any other malignancy or history of prior malignancy except non-melanoma
skin tumors or stage 0 (in situ) cervical carcinoma;

2. Prior radioimmunotherapy, radiation therapy, or any other NHL therapy;

3. Presence of gastric, central nervous system (CNS), or testicular lymphoma at first
diagnosis;

4. Histological transformation of low-grade NHL;

5. Known seropositivity for hepatitis C virus (HCV) or hepatitis B surface antigen
(HbsAg);

6. Known history of HIV infection;

7. Abnormal liver function: total bilirubin > 1.5 x ULN or ALT > 2.5 x ULN within 1 week
of accrual;

8. Abnormal renal function: serum creatinine > 2.0 x ULN within 1 week of accrual;

9. Nonrecovery from the toxic effects of CHOP21-R therapy;

10. Known hypersensitivity to murine or chimeric antibodies or proteins;

11. G-CSF or GM-CSF therapy within two weeks (or four weeks if pegylated) prior to
screening laboratory sampling;

12. Concurrent severe and/or uncontrolled medical disease (e.g., uncontrolled diabetes,
congestive heart failure, myocardial infarction within 6 months of study, unstable
and uncontrolled hypertension, chronic renal disease, or active uncontrolled
infection) which could compromise participation in the study;

13. Treatment with investigational drugs less than 4 weeks before the planned Day 1 or
nonrecovery from the toxic effects of such therapy;

14. Surgery less than 4 weeks before the planned Day 1 or nonrecovery from the side
effects of such surgery;

15. Concurrent corticosteroid use for any reason except as premedication in case of known
or suspected allergies to contrast media or as premedication for potential side
effects of rituximab treatment;

16. Unwillingness or inability to comply with the protocol.