Yt90 Zevalin and Combination Chemotherapy (Z-CHOP)in Treating Patients With Stage II, Stage III, or Stage IV Diffuse Large B-cell Lymphoma

Inclusion Criteria: * Histologically confirmed CD20 positive diffuse large B-cell lymphoma with bulky stage II or stage III or stage IV * Bidimensionally measurable disease * Performance status Zubrod 0-2 * Less than 20,000/mcL circulating lymphoid cells on WBC differential count * No clinical evidence of CNS involvement, no prior diagnosis of indolent lymphoma, no histologic transformation * Ejection fraction more than or equal to 45% by MUGA or no significant abnormality by echocardiogram * Fertile patients with effective contraception method * No other malignancy within past 5 years except adequately treated basal cell or squamous cell skin cancer, stage I or II cancer in complete remission, or carcinoma in situ of cervix * No HIV positive, no prior solid organ transplantation * No prior antibody therapy, chemotherapy, radiotherapy for lymphoma Exclusion Criteria: * Serum creatinine ot bilirubin more than 2.5 X ULN unless due to lymphoma * Active uncontrolled infection * Concurrent severe and/or uncontrolled medical disease which could compromise participation in the study * Patients with more than 25% infiltrated bone marrow * Patients with platelet counts less than 100,000/mcL or neutrophil counts less than 1,500/mcL