Inclusion Criteria:

- Patient with histologically proven CD20+ diffuse large B-cell lymphoma (DLBCL) (WHO
classification 2008) including clinical subtypes (primitive mediastinal,
intravascular, etc.). Patients with De Novo Transformed DLBCL from low grade lymphoma
(Follicular, other...) may also be included; or CD20+ B-cell lymphoma with
intermediate features between DLBCL and Burkitt; or with intermediate features
between DLBCL and classical Hodgkin lymphoma; or CD20+ Follicular lymphoma grade 3B;
or CD20+ Aggressive B-cell lymphoma unclassifiable.

- Age from18 to 80 years.

- Patient not previously treated.

- Ann Arbor Stage : I or II.

- Normal level of LDH.

- ECOG performance status (PS) < 2.

- Age-adjusted international prognostic index (aaIPI) = 0.

- Baseline PET (PET0) performed before any treatment, even in absence of known lesion
(for stage I for which the lesion has been removed for diagnostic reason).

- Having previously signed a written informed consent.

- The subject must be covered by a social security system (in France).

Exclusion Criteria:

- Any other histological type of lymphoma, Burkitt included.

- Any history of treated or non-treated small B-cell lymphoma.

- Central nervous system or meningeal involvement by lymphoma.

- Contra-indication to any drug contained in the chemotherapy regimens.

- Poor renal function (creatinin level >150 mmol/L), poor hepatic function (total
bilirubin level >30 mmol/L, transaminases >2.5 ULN) unless these abnormalities are
related to the lymphoma.

- Poor bone marrow reserve as defined by Absolute Neutrophils Count (ANC) <1.5 G/L or
platelets <100 G/L, unless related to bone marrow infiltration.

- Any history of cancer during the last 5 years with the exception of non-melanoma skin
tumors or stage 0 (in situ) cervical carcinoma.

- Any serious active disease (according to the investigator's decision).

- Positive HIV, HBV and HCV serologies before inclusion (except after hepatitis B
vaccination).

- Treatment with any investigational drug within 30 days before planned first cycle of
chemotherapy.

- Pregnant or lactating women or women of childbearing potential not currently
practicing an adequate method of contraception.

- Adult patient under tutelage.

- Impossibility to perform a baseline PET scan (PET0) before randomization and
treatment start.