Rituximab Augmentation Following R-CHOP Induction Chemotherapy in Extremely Elderly Patients With Diffuse Large B Cell Lymphoma

1. Four cycles of R-CHOP chemotherapy for the induction treatment \[Dose intensity of CHOP chemotherapy is modulated according to Charlson Comorbidity Index (CCI)\] If patients with CCI \<1 * Rituximab: 375 mg/m2, day 1 every 3 weeks. * Conventional dose of CHOP chemotherapy repeat every 3 weeks. If patients with CCI ≥1 * Rituximab: 375 mg/m2, day 1 every 3 weeks. * 75% of conventional CHOP repeat every 3 weeks. 2. Rituximab augmentation * Rituximab: 375 mg/m2, every week x 4 times. * Trimethoprim-sulfamethoxazole 1 tablet per day during augmentation