Gemcitabine Plus Pemetrexed Disodium in Treating Patients With Unresectable or Metastatic Biliary Tract or Gallbladder Cancer

One of the following histologically or cytologically confirmed cancers not amenable to treatment with combined chemotherapy and radiotherapy: Biliary tract (intrahepatic, extrahepatic, or ampulla of Vater) carcinoma Gallbladder carcinoma Unresectable or metastatic disease No CNS metastases Prior brain metastases treated with surgery or radiosurgery allowed provided treatment was completed at least 4 weeks ago and there is no evidence of CNS progression No clinically significant pericardial or pleural effusion or ascites unless able to be drained before study entry Performance status - ECOG 0-2 At least 3 months Absolute neutrophil count at least 1,500/mm^3 Platelet count at least 100,000/mm^3 Bilirubin no greater than 3 times upper limit of normal (ULN) AST no greater than 5 times ULN Creatinine no greater than 1.5 times ULN Creatinine clearance at least 45 mL/min Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer Able to tolerate folic acid, corticosteroids, or cyanocobalamin supplements More than 4 weeks since prior biologic or immunologic therapy No prior biologic or immunologic therapy for metastatic disease No concurrent immunotherapy No concurrent colony-stimulating factors during course 1 No prior chemotherapy for metastatic disease No prior gemcitabine Prior chemoembolization allowed provided the following are true: At least 4 weeks since prior chemoembolization Evidence of new tumor growth since therapy At least 6 months since prior chemotherapy used as a radiosensitizer (in adjuvant setting or for locally advanced disease) No other concurrent chemotherapy Prior radiofrequency ablation allowed provided the following are true: At least 4 weeks since prior radiofrequency ablation Evidence of new tumor growth since therapy No prior radiotherapy to 25% or more of the bone marrow More than 4 weeks since prior radiotherapy No concurrent radiotherapy Prior embolization allowed provided the following are true: At least 4 weeks since prior embolization Evidence of new tumor growth since therapy No prior pemetrexed disodium No aspirin or nonsteroidal anti-inflammatory drugs for at least 2 days (5 days for long-acting agents [e.g., piroxicam]) before, during, and for at least 2 days after administration of pemetrexed disodium No concurrent cyclo-oxygenase-2 inhibitors