Fludeoxyglucose F 18 Positron Emission Tomography in Predicting Risk of Relapse in Patients With Non-Hodgkin's Lymphoma Who Are Undergoing Combination Chemotherapy With or Without Autologous Stem Cell or Bone Marrow Transplant

DISEASE CHARACTERISTICS: * Histologically confirmed aggressive non-Hodgkin's lymphoma of 1 of the following subtypes: * Diffuse large B-cell lymphoma * Mediastinal (thymic) B-cell lymphoma * Grade 3 follicular lymphoma * Anaplastic large cell lymphoma * Peripheral T-cell lymphoma * Must have adequate staging of disease by the following techniques: * CT scan or MRI of affected sites * Bone marrow biopsy (in cases where results influence the duration of chemotherapy only) * Lumbar puncture (if clinically indicated) * Stage I-IV disease * Any International Prognostic Index risk category * Radiographically measurable disease * None of the following aggressive non-Hodgkin's subtypes are allowed: * Mantle cell lymphoma * Lymphoblastic lymphoma * Burkitt's lymphoma * Mycosis fungoides/Sezary's syndrome * HTLV-1-associated T-cell leukemia/lymphoma * Primary CNS lymphoma * HIV-associated lymphoma * Transformed lymphomas * No prior diagnosis of another hematologic malignancy * No known progressive disease during prior first-line chemotherapy * No active CNS involvement by lymphoma, except CNS involvement at diagnosis that is previously treated and in remission PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-4 (0-2 for peripheral blood stem cell \[PBSC\] or bone marrow transplantation \[BMT\] patients) Life expectancy * Not specified Hematopoietic * Absolute neutrophil count \> 1,000/mm\^3\* * Platelet count ≥ 75,000/mm…