OUTLINE: This is a randomized, multicenter study. For salvage therapy, patients are stratified according to participating center, International Prognostic Index score at relapse/study entry (0 or 1 vs 2 vs ≥ 3), immunophenotype (B cell vs T cell), response to or response duration after initial chemotherapy (no response or progressive disease vs > 1 year vs ≤ 1 year), and prior rituximab (yes vs no). For maintenance therapy, patients are stratified according to participating center, salvage therapy treatment randomization (with or without rituximab, cisplatin, dexamethasone, and gemcitabine vs with or without rituximab, cisplatin, dexamethasone, and cytarabine), response to salvage therapy (complete response [CR] and CR unconfirmed [CRu] vs partial response [PR] vs stable disease [SD]), and prior rituximab (yes vs no).