Rituximab, Methotrexate, Vincristine Sulfate, Procarbazine Hydrochloride, and Cytarabine With or Without Radiation Therapy in Treating Patients With Primary Central Nervous System Lymphoma

1. B-cell non-Hodgkin's lymphoma(NHL) involving the brain, as demonstrated by contrast-enhanced Magnetic resonance imaging (MRI) and histologic confirmation by one of the following within 6 weeks prior to registration:

* A positive cerebral spinal fluid (CSF) cytology for lymphoma or a monoclonal lymphocyte population as defined by cell surface markers

* A biopsy of the vitreous or uvea demonstrating non-Hodgkin's lymphoma

* Brain biopsy

Note: Patients in whom the type of lymphoma could not be determined or is unknown (eg, not enough tissue for further analysis) are assumed to have a B cell lymphoma and are eligible.

2. The patient must agree to submit tissue (i.e., the original H/E stained slides and immunohistochemistry studies) for central pathology review post-registration.

3. No evidence of systemic non-Hodgkin lymphoma as demonstrated by a computed tomography (CT) scan of the chest, abdomen and pelvis within 6 weeks prior to registration (Note: Bone marrow biopsy is not required for registration but must be obtained prior to start of treatment.)

4. Age ≥ 18

5. History and physical examination within 6 weeks of registration

6. Karnofsky performance status (KPS) equal to 50 or higher, with the following exception

7. Patient must have documentation of negative HIV-1 testing within 6 weeks prior to study registration (Separate counseling and consent as per institutional guidelines)

8. Complete blood count (CBC)/differential obtained within 2 weeks prior to study registration, with adequate bone marrow function defined as follows:

* Absolute neutrophil count (ANC) ≥ 1,500 cells/mm3;

* Platelets ≥ 100,000 cells/mm3;

* Hemoglobin (Hgb) ≥ 8.0 g/dl (Note: The use of transfusion or other intervention to achieve Hgb ≥ 8.0 g/dl is acceptable.);

9. Adequate liver function within 2 weeks prior to study registration, defined as follows:

* Bilirubin \< 2.0 mg/dl

* Aspartate aminotransferase (AST) \<2.5 times upper limit of normal

10. Adequate renal function within 2 weeks prior to study registration, defined as follows

* Serum creatinine \< 1.5 mg/dl

* Calculated creatinine clearance (CrCl) \> 50cc/min/1.73m2, using the Cockcroft-Gault equation, as follows:

Male: CrCl (ml/min) = (140-age) X (Actual weight in kg) / 72 x serum Creatinine (mg/dl).

Female: CrCl (ml/min) = (140-age) X (Actual weight in kg) X 0.85 / 72 x serum Creatinine (mg/dl).

Note: A measured CrCl from a 24 hour urine collection may also be used.

11. Women of childbearing potential and male participants must agree to practice adequate contraception during therapy

12. Patient must provide study-specific informed consent prior to study registration

13. Patient must be able to swallow pills.

What this study is about