This is a multicenter, double-blind, randomized study comparing the efficacy, pharmacokinetics (PK)/pharmacodynamics (PD), safety and immunogenicity profile of RTXM83 (rituximab biosimilar) vs reference rituximab (MabThera®), both with CHOP, as first-line treatment of Diffuse-Large-B-Cell-Lymphoma (DLBCL).

Rituximab biosimilar and MabThera® were both administered intravenously on Day 1 of each 3-week cycle with CHOP chemotherapy for six cycles. Two additional cycles of treatment were permitted at the Investigator's discretion. Patients were followed up for 9 months after last study dose.

The primary endpoint of the investigation is to determine if the response rate obtained with RTXM83 combined with CHOP is non inferior to the response rate obtained with reference rituximab combined with CHOP.

The present study is a non inferiority trial and the study hypothesis is the following: H0: pc ≥ pe + δ vs. H1: pc < pe + δ where, pe: proportion of successes in the experimental group (RTXM83+CHOP) pc: proportion of successes in the control group (Reference Rituximab+CHOP) Type I error: the difference pc-pe is less than δ when in fact the difference is greater than or equal to δ ie, the investigators choose the experimental treatment when the control treatment is actually substantially better.

Type II error: the difference -pe is greater than or equal to δ when it is actually lest than δ ie, the investigators choose the control treatment when the experimental treatment is essentially just as good.

Inclusion Criteria:

1. Patients with measurable disease defined as existence of a unidimensional or bidimensional lesion greater than 2 cm in its longest diameter or malignant lymphocytosis greater than 5x109/L. Any other procedure for measurable disease in particular cases, may be allowed upon Sponsor approval
2. Newly diagnosed patients with a confirmed pathologic diagnosis of Diffuse large B cell-non-Hodgkin's lymphoma (DLBCL) with untreated CD20+ receptor (CD20+). Defined by the local Haematopathologist at the local laboratory according to World Health Organization (WHO) criteria
3. Stage II-III or IV or stage I with bulk defined by the referring physician on the basis of the Cotswolds modification of the Ann Arbor classification 2
4. Age-adjusted International Prognostic Index (IPI) score 0 or 1
5. Age ≥18 to ≤65 years of age
6. Performance status according to Eastern Cooperative Oncology Group (ECOG) of ≤2
7. Written informed consent obtained before starting any study-specific procedure
8. Females of child-bearing potential must test negative on standard serum pregnancy test and must be willing to practice appropriate contraceptive methods for the duration of the study (e.g. oral contraceptive, double barrier method, intra-uterine device, intra-muscular contraceptive)
9. All male patients must take adequate contraceptive precautions during the course of the study

Exclusion Criteria:

1. Life expectancy of less than three months
2. Any other lymphoma other than CD20+ DLBCL
3. Indolent lymphoma, Primary central nervous system (CNS) Lymphoma or gastro-intestinal Mucosa Associated Lymphoid Tissue (MALT) Lymphoma
4. Known hypersensitivity to active ingredients, excipients and murine and foreign proteins
5. Concurrent disease or general status that would exclude giving the treatment as outlined in the protocol
6. Active uncontrolled infection requiring systemic treatment with antibiotics or antiviral agents at Screening or history of documented recurrent clinically significant infection (e.g. 2 or more viral, bacterial or fungal infections requiring inpatient treatment)
7. Cardiac contra-indication to Doxorubicin therapy: non-compensated heart failure, dilated cardiomyopathy, coronary heart disease with ST segment depression on electrocardiogram (ECG), myocardial infarction in the last 6 months
8. Neurologic contra-indication to Vincristine as it is indicated in the Summary of Product Characteristics (SmPC): (e.g. peripheral neuropathy)
9. Chronic lung disease with hypoxemia measured by pulse oximetry (gasometry is not mandatory)
10. Severe uncontrolled hypertension, despite optimal medical treatment
11. Severe uncontrolled diabetes mellitus, despite optimal medical treatment
12. Renal insufficiency (Serum Creatinine >2 x Upper Normal Limit [UNL])
13. Hepatic insufficiency: aspartate aminotransferase (AST)/ alanine aminotransferase (ALT)>3 x UNL or >5 x UNL with involvement of the liver, total bilirubin >34.2 µmol/L, or both) not related to lymphoma
14. Clinical signs of cerebral dysfunction
15. Severe psychiatric disease
16. Known human immunodeficiency virus (HIV) infection or active chronic hepatitis B or C
17. Abnormal bone marrow function (platelets <100x109/L, neutrophils <1.5x109/L and Haemoglobin <9g/dL)
18. Post-transplantation lymphoproliferative disease
19. Pregnant or lactating women or women that intend to get pregnant during study or within 12 months following the last infusion
20. Treatment with any investigational product in the 30 days period before inclusion in the study
21. Prior radiotherapy to treat the DLBCL Non-Hodgkin's Lymphoma (NHL)
22. Limitation of the patient's ability to comply with the treatment or follow-up protocol