RATIONALE: Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage cancer cells. Peripheral stem cell transplantation may allow the doctor to give higher doses of chemotherapy and radiation and kill more cancer cells. It is not yet known whether chemoradiotherapy plus peripheral stem cell transplantation is more effective than combination chemotherapy alone in treating non-Hodgkin's lymphoma.