Inclusion Criteria:

• Folicular Lymphoma CD20-positive, grade 1, 2 or 3a, confirmed in previous 4 months.
• Patients no treated previously.
• Ann Arbor Stage II, III o IV.

• Symptoms or signes wich indicate necesary treatment (GELF criteria):

  • Ganglionar or extraganglionar mass
  • B Symptoms
  • LDH or B2-microglobuline increased
  • 3 ganglionar territory afected (> 3 cm)
  • Esplenomegalia
  • Compresive syndrome
  • Pleural/peritoneal effusion
  • Secondary medular insufiency due to infiltration
• Age> 18 years and <75 years.
• ECOG < 2
• Adecuate hematological function: Hemoglobin > 8,0 g/dl (5,0 mmol/L); RAN >1,5 x 109/L; platelets > 100 x 109/L
• No pregnant women. Women and man should use an appropiate anticonceptive method during the study and one year after
• Informed consent

Exclusion Criteria:

• Transformation in high grade lymphoma
• FL grade 3b.
• Skin or gastro-intestinal primary lymphoma
• History of CNS diseases ( or CNS lymphoma)
• Previous treatment
• Regulary treatment with corticosteroids (permited < 20 mg/day prednisone or equivalent).
• Previous cancer diseases
• Major surgery in 28 days before inclusion in study.
• Creatinine > 2,0 mg/dl (197 mmol/L)
• Bilirubin > 2,0 mg/dl (34 mmol/L), AST (SGOT) > 3 x upper normal limit.
• HIV infection or active infection VHB o VHC < 4 weeks before inclusion.
• Other complicated diseases

Criteria investigador:

• Life expectancy < 6 months.
• Hipersensibility to Ibritumomab tiuxetan, rituximab, other murines proteins or any excipients.
• Treatment in other experimental study in previous 30 days
• Any medical o psicologycal condition that can modify the capacity to give the consent