Inclusion Criteria:

Patients meeting all of the following criteria are to be included in the study:

1. Patients who are histopathologically confirmed to have the following CD20 positive
low-grade B cell non-Hodgkin's lymphoma or mantle cell lymphoma by lymph node biopsy
or evaluable tissue biopsy within 6 months before the registration WHO
Classification of Tumors (fourth edition):

- Small lymphocytic lymphoma

- Splenic marginal zone B-cell lymphoma

- Lymphoplasmacytic lymphoma

- Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue
(MALT lymphoma)

- Nodal marginal zone B-cell lymphoma

- Follicular lymphoma (Grade 1, 2, 3a)

- Mantle cell lymphoma

2. Patients with a measurable lesion ( > 1.5 cm in major axis on CT)

3. Patients without a medical history

4. Patients with at least 1 of the following clinical symptoms or signs (excluding
mantle cell lymphoma):

- Bulky disease measuring > 7 cm in major axis on CT (excluding spleen)

- B symptoms

1. Fever exceeding 38.0ºC of unknown cause

2. Night sweats

3. Weight decrease exceeding 10% within 6 months before patient registration

- Elevated serum LDH or beta 2 microglobulin

- Three or more regional lymph nodes of > 3 cm in major axis on CT

- Symptomatic splenomegaly

- Intracranial pressure

- Pleural effusion/ascites retention

5. Patients expected to live for at least 3 months

6. Patients aged between 20 and 79 years (at the time of registration)

7. Patients whose ECOG performance status (P.S.) is 0～2

8. Patients with adequately maintained major organ function (bone marrow, heart, lungs,
liver, kidneys)

- Neutrophil count: not less than 1,500 /mm3

- Platelet count: not less than 75,000 /mm3

- AST (GOT): not more than 3 times the standard upper limit for the site

- ALT (GPT): not more than 3 times the standard upper limit for the site

- Total bilirubin: not more than 1.5 times the standard upper limit for the site

- Serum creatinine: not more than 1.5 times the standard upper limit for the site

- Arterial partial pressure of oxygen (PaO2): not less than 65 mmHg

- Electrocardiogram shows no abnormal findings that require treatment

- Echocardiogram of left ventricular ejection fraction (LVEF): not less than 55%

9. Patients whose informed consent has been obtained in person

Exclusion Criteria:

Patients who fall under any one of the following criteria are to be excluded

1. Patients whose transformation has been confirmed histopathologically

2. Mantle cell lymphoma patients aged 65 years or younger

3. Patients who were administered or received transfusion of cytokine formulations such
as G-CSF (granulocyte colony stimulating factor) and erythropoietin within 14 days
before pre-registration test

4. Patients with severe active infectious disorders (receiving antibiotics, antifungals,
or antivirus IV injection)

5. Patients with serious complications (such as hepatic or renal failure)

6. Patients with severe complications of cardiac disease (examples: myocardial
infarction, ischemic heart disease) or its previous history within 2 years before
patient registration, and patients with arrhythmia requiring a treatment

7. Patients with serious gastrointestinal conditions (persistent or severe
nausea/vomiting or diarrhea).

8. Patients who are positive for HBs antigen, HCV antibody or HIV antibody (if HBs or
HBc positive, patients whose HBV-DNA test results indicate positive)

9. Patients with serious bleeding tendencies [such as disseminated intravascular
coagulation (DIC)]

10. Patients having or suspected of having symptoms indicative of CNS involvement

11. Patients with interstitial pneumonitis, pulmonary fibrosis, pulmonary emphysema
complications requiring treatment or its medical history.

12. Patients with active multiple primary cancer

13. Patients who received chemotherapy, radiotherapy, antibody therapy and antitumor
steroid therapy in the past

14. Patients with complications or medical history of autoimmune haemolytic anaemia

15. Patients who were administered investigative or unapproved drugs within 3 months
before patient registration.

16. Patients with addiction to drugs or narcotics, or alcoholism

17. Patients who have previously received hematopoietic stem cell transplantation

18. Patients who are or may be pregnant, lactating patients

19. Patients, whether male or female, who do not agree to use contraception

20. Patients otherwise judged by the investigator or the sub-investigator to be
unsuitable for inclusion in the study