DISEASE CHARACTERISTICS:

• Histologically confirmed Hodgkin's lymphoma or, using the WHO classification, aggressive non-Hodgkin's lymphoma including:

  • Large B- or T-cell lymphomas (including transformed lymphomas)
  • Mantle cell lymphoma
  • Immunoblastic lymphoma

• At least 1 unidimensionally measurable lesion

  • At least 2 cm by conventional techniques OR
  • At least 1 cm by spiral CT scan
  • Lymph nodes no greater than 1 cm in the short axis are considered normal
• Relapsed or refractory disease after first-line chemotherapy

• Cohort 1:

  • No more than 3 prior conventional cytotoxic chemotherapy regimens
  • Must have had at least a partial response (PR) lasting no more than 6 months or refractory disease
  • Patients with disease refractory to or relapsed less than 100 days from peripheral blood stem cell (PBSC) transplantation are not eligible

• Cohort 2:

  • No limit on prior treatment
  • Must have had at least a PR to the last therapy lasting at least 6 months
  • Patients who have received high-dose chemotherapy as part of PBSC transplantation are eligible if relapse occurred at least 100 days after transplantation
• No clinically significant pleural effusions or ascites

• No active brain or leptomeningeal metastases

  • Treated CNS disease allowed

PATIENT CHARACTERISTICS:

Age

• 18 and over

Performance status

• Karnofsky 70-100%

Life expectancy

• Not specified

Hematopoietic

• Absolute neutrophil count greater than 1,000/mm^3
• Platelet count greater than 75,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• AST/ALT no greater than 2.5 times ULN (4 times ULN if liver involvement)
• Alkaline phosphatase no greater than 5 times ULN

Renal

• Creatinine no greater than 1.5 mg/dL OR
• Creatinine clearance at least 50 mL/min

Cardiovascular

• No symptomatic congestive heart failure
• No New York Heart Association class III or IV heart disease
• No unstable angina pectoris
• No cardiac arrhythmia
• No myocardial infarction, cerebrovascular accident, or transient ischemic attack within the past 6 months
• No history of orthostatic hypotension
• No EKG evidence of acute ischemia or significant conduction abnormality (e.g., bifascicular block or 2nd or 3rd degree atrioventricular blocks)
• No uncontrolled hypertension requiring active manipulation of antihypertensive medications
• No grade III or IV edema

Other

• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

• No ongoing or active infection

  • Febrile episodes up to 38.5° Celsius without signs of active infection allowed
• No other concurrent active cancer
• No other concurrent serious medical illness
• No psychiatric illness or social situation that would preclude study compliance

PRIOR CONCURRENT THERAPY:

Biologic therapy

• See Disease Characteristics
• At least 3 months since prior monoclonal antibody therapy (e.g., rituximab)

Chemotherapy

• See Disease Characterisitics
• At least 4 weeks since prior cytotoxic chemotherapy (6 weeks for mitomycin or nitrosoureas) and recovered

Endocrine therapy

• At least 7 days since prior steroids
• No concurrent steroids

Radiotherapy

• See Disease Characteristics
• At least 4 weeks since prior radiotherapy and recovered

Surgery

• More than 4 weeks since prior major surgery

Other

• No prior antifolates
• No concurrent folic acid supplementation
• No other concurrent investigational agents
• No concurrent combination antiretroviral therapy for HIV-positive patients
• No other concurrent investigational or commercial agents or therapies with the intent to treat the malignancy