Central nervous system or meningeal involvement by lymphoma. Contra-indication to any drug contained in the chemotherapy regimens. Any serious active disease (according to the investigator's decision). Poor renal function (creatinin level>150µmol/l), poor hepatic function (total bilirubin level>30mmol/l, transaminases>2.5 maximum normal level) unless these abnormalities are related to the lymphoma.