Combination Chemotherapy With or Without Total-Body Irradiation Followed By Stem Cell Transplant in Treating Patients With Non-Hodgkin Lymphoma

OBJECTIVES: * To evaluate the outcome of patients with poor-risk, age-adjusted International Prognostic Index high- and high-intermediate-risk, intermediate- and high-grade non-Hodgkin lymphoma undergoing high-dose therapy comprising etoposide and cyclophosphamide, either carmustine or total-body irradiation, and autologous stem cell transplantation (ASCT) given as a consolidation therapy. * To evaluate the role of high-dose therapy and ASCT during first partial or complete remission (1PR/CR) in patients with poor-risk primary mediastinal large cell lymphoma. * To evaluate the role of high-dose therapy and ASCT during first 1PR/CR in patients with advanced-stage mantle cell lymphoma. * To evaluate the short-term and long-term toxicities of high-dose therapy and ASCT when performed during 1PR/CR in patients with poor-risk aggressive lymphomas. OUTLINE: Patients are stratified according to disease (diffuse mixed, diffuse large cell, and immunoblastic lymphoma vs primary mediastinal large cell lymphoma vs small noncleaved cell lymphoma vs stage IV mantle cell lymphoma). Patients' peripheral blood stem cells (PBSC) are collected after mobilization. A minimum of 2.0 x 10\^6 CD34+ cells/kg must be collected. Patients experiencing disease progression during stem cell collection will be removed from study. Patients are assigned to undergo 1 of 2 therapeutic regimens. * Regimen 1: Patients undergo total-body irradiation (TBI) on days -8 to -5 and receive etoposide IV over 4 hours on day -4 and cyclophosphamide IV over 2 hours on day -2. Patients undergo autologous PBSC transplantation on day 0. * Regimen 2 (for patients who have received any prior thoracic irradiation or patients who underwent previous irradiation that precludes the use of TBI): Patients receive carmustine IV over 2 hours on days -7 to -5. Patients then receive etoposide and cyclophosphamide and undergo autologous PBSC transplantation as in regimen 1. Patients with residual bulky disease greater than 5 cm may undergo involved-field radiotherapy before or after transplantation. Patients are followed at days 7, 14, 21, 100 and 180 after PBSC transplantation, every 6 months for 3 years, and then annually thereafter.