Rituximab, Fludarabine, Cyclophosphamide, and Yttrium Y 90 Ibritumomab Tiuxetan in Treating Patients With Relapsed B-Cell Non-Hodgkin's Lymphoma

DISEASE CHARACTERISTICS:

* Histologically confirmed CD20-positive B-cell non-Hodgkin's lymphoma (NHL), including any of the following subtypes:

  * Indolent NHL, including any of the following:

    * Follicular
    * Lymphoplasmacytoid
    * Marginal zone
  * Mantle cell NHL
  * Transformed B-cell NHL
* In at least first relapse with an indication for systemic antineoplastic treatment, as defined by the following:

  * Local or constitutional (B-) symptoms
  * Hypersplenism due to splenic involvement
  * Bulky disease (\> 7.5 cm in diameter)
  * Impending medical problems derived from rapid disease progression within the past 6 months, as defined by an observed or anticipated \> 50% increase in the sum of the areas calculated from multiplying the greatest perpendicular diameters of each lesion
* Measurable lesions of lymphoma infiltration
* Medically ineligible for high-dose treatment followed by autologous stem cell support
* Adequate bone marrow cellularity (\> 15% of marrow area covered by hematopoiesis)
* No CNS, leptomeningeal, spinal cord, or testes lymphoma involvement
* No lymphoma lesion mandating emergency radiotherapy
* No clinical, cytological, cytogenetic, or histopathologic indication of myelodysplastic syndrome
* If there is bone marrow infiltration detected prior to chemoimmunotherapy, patient must undergo a repeat bone marrow biopsy prior to planned treatment with radioimmunotherapy to verify the level of bone marrow infiltration is \< 25%

PATIENT CHARACTERISTICS:

* ECOG performance status 0-2
* Life expectancy ≥ 3 months
* Absolute neutrophil count \> 1,500/mm³
* Platelet count \> 150,000/mm³
* Hemoglobin \> 9 g/dL
* Creatinine \< 1.5 times upper limit of normal (ULN)
* Bilirubin \< 2 times ULN
* ALT and AST \< 2 times ULN
* Albumin \> 2.5 g/dL
* INR \< 1.5
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception during and for ≥ 12 months after completion of study treatment
* No concurrent severe and/or uncontrolled medical disease that would preclude study compliance, including any of the following:

  * Uncontrolled diabetes
  * Congestive heart failure
  * Chronic renal disease
  * Active uncontrolled infection
* No bleeding risks or disorders, including any of the following:

  * CNS abnormalities suggesting an increased susceptibility for hemorrhage, including recent history of stroke as demonstrated by cranial contrast-enhanced CT scan
  * Severe arrhythmia or uncontrolled hypertension
  * Myocardial infarction within the past 6 months
  * Diabetic retinopathy with history of symptomatic hemorrhage
  * Known and potentially active gastrointestinal bleeding foci
  * Concurrent anticoagulant medication that must be continued even with platelet count \< 20,000/mm³ (e.g., following mitral valve replacement, anti-phospholipid syndrome, or recurrent venous thromboembolism)
  * Other congenital or acquired hemorrhagic diatheses
* No ongoing autoimmune hemolytic anemia
* No known presence of anti-murine antibody reactivity
* No known hypersensitivity to murine or chimeric antibodies or proteins
* No known HIV infection
* No psychiatric illness that would preclude study requirements
* No other malignant disorder within the past 10 years except basal cell carcinoma of the skin or carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY:

* See Disease Characteristics
* Recovered from prior therapy
* No more than 4 prior systemic anti-lymphoma regimens (including single-agent rituximab)
* At least 2 months since prior systemic anti-lymphoma treatment (including single-agent rituximab)
* No prior radioimmunotherapy
* No prior autologous or allogeneic hematopoietic stem cell transplantation
* No prior treatment with purine analogues that has not resulted in remission for \> 1 year
* No prior anti-CD20 radioimmunoconjugate therapy
* More than 5 years since prior radiotherapy to extensive fields covering lymph node regions on both sides of the diaphragm or \> 50% of the spinal column
* More than 4 weeks since prior surgery
* No concurrent oral anticoagulant therapy