Chemotherapy is associated with toxicity in elderly patients with potentially curable malignancies, posing the dilemma of whether to intensify therapy, thereby improving the cure rate, or de-escalate therapy, thereby reducing toxicity, with consequent risks for under- or overtreatment. Adequate tools to define doses and combinations have not been identified for lymphoma patients. We conducted a prospective trial aimed to evaluate the feasibility and efficacy of chemotherapy modulated according to a modified comprehensive geriatric assessment (CGA) in elderly (aged ≥70 years) patients with diffuse large B-cell lymphoma (DLBCL). In June 2000 to March 2006, 100 patients were stratified using a CGA into three groups (fit, unfit, and frail), and they received a rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone modulated in dose and drugs according to comorbidities and activities of daily living (ADL) and instrumental ADL scores. Treatment was associated with a complete response rate of 81% and mild toxicity: grade 4 neutropenia in 14%, anemia in 1%, and neurological and cardiac toxicity in 2% of patients. At a median follow-up of 64 months, 51 patients were alive, with 5-year disease-free, overall, and cause-specific survival rates of 80%, 60%, and 74%, respectively. Chemoimmunotherapy adjustments based on a CGA are associated with manageable toxicity and excellent outcomes in elderly patients with DLBCL. Wide use of this CGA-driven treatment may result in better cure rates, especially in fit and unfit patients.