DISEASE CHARACTERISTICS: Histologically confirmed malignancy No more than 5 days since placement of central venous catheter for administration of chemotherapy Expected length of catheter use at least 16 weeks

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: At least 16 weeks Hematopoietic: Platelet count at least 100,000/mm3 Absolute neutrophil count at least 1,500/mm3 No known coagulopathy Hepatic: Bilirubin no greater than 2 times upper limit of normal (ULN) except in case of Gilbert's syndrome AST no greater than 3 times ULN (no greater than 5 times ULN in case of liver metastases) PT/PTT no greater than 1.5 times ULN Renal: Creatinine no greater than 2 times ULN Cardiovascular: No uncontrolled hypertension, unstable angina, or symptomatic congestive heart failure No myocardial infarction in past 6 months No uncontrolled cardiac arrhythmia Other: No known hypersensitivity (including heparin induced thrombocytopenia) to dalteparin, heparin, or other low molecular weight heparins No active uncontrolled infection, including existing catheter related infection HIV negative No CNS trauma in past 3 months No retinal detachment in past 6 months No mental incapacitation or psychiatric illness that would preclude study compliance No other serious concurrent disease that would preclude study participation No active gastrointestinal or genitourinary tract bleeding No intracranial or intraocular hemorrhage in past year Must weigh at least 90 pounds

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent high dose chemotherapy with stem cell transplantation Chemotherapy: See Disease Characteristics No concurrent induction/consolidation chemotherapy for leukemia No concurrent high dose chemotherapy with stem cell transplantation Endocrine therapy: Not specified Radiotherapy: Not specified Surgery: At least 3 months since prior eye, ear, or CNS surgery Other: At least 30 days since prior aspirin, dipyridamole, unfractionated heparin, other low molecular weight heparins, or other anticoagulation therapy (except heparin flushing)