This is a phase III, randomized, open-label, multicenter trial, conducted in Sweden, Norway, Finland, Denmark, Italy, Australia and New Zealand, in elderly patients with untreated diffuse large B-cell lymphoma. Elderly is defined as either ≥80 years of age, or ≥75 years and frail, according to a simplified Comprehensive Geriatric Assessment. Patients will be randomized 1:1 to either the standard treatment for this population, R-miniCHOP, or an experimental regimen, R-pola-miniCHP, where vincristine is substituted by an immunoconjugate, polatuzumab vedotin. The duration of the screening period is up to 4 weeks. The duration of active treatment is 18 weeks in both arms, and patients will be followed up to 36 months after end of treatment. Start of enrollment is planned in Q1 2020, and the last visit of the last patient included (end of trial) is estimated in Q1 2027.