Gemcitabine With or Without Cisplatin in Treating Patients With Unresectable Locally Advanced or Metastatic Cholangiocarcinoma or Other Biliary Tract Tumors

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed biliary tract, gallbladder, or ampullary carcinoma * Intra- or extra-hepatic disease allowed * Unresectable locally advanced, recurrent, or metastatic disease * No brain metastases PATIENT CHARACTERISTICS: Performance status * ECOG 0-2 Life expectancy * At least 3 months Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 10 g/dL (transfusion allowed) * WBC ≥ 3,000/mm\^3 Hepatic * AST and ALT ≤ 3 times upper limit of normal (ULN) (5 times ULN if liver metastases are present) * Bilirubin ≤ 1.5 times ULN * Alkaline phosphatase ≤ 3 times ULN (5 times ULN if liver metastases are present) * Adequate biliary drainage * No unresolved biliary tract obstruction Renal * Creatinine \< 1.5 times ULN * Urea \< 1.5 times ULN * Glomerular filtration rate (GFR) ≥ 45 mL/min * If GFR \< 60 mL/min, isotope EDTA confirmation of adequate renal function is required Other * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception during and for 3 months after study participation * No active, uncontrolled infection * No other severe or uncontrolled systemic disease * No other malignancy within the past 5 years except nonmetastatic basal cell or squamous cell skin cancer or carcinoma in situ of the cervix treated by cone-biopsy or resection * No psychiatric disorder that would preclude giving informed consent PRIOR CONCURRENT THERAPY: Chemotherapy * At least 6 months since prior adjuvant chemotherapy * No prior gemcitabine hydrochloride * No prior cisplatin * No prior systemic chemotherapy for locally advanced or metastatic disease except low-dose radiosensitizing chemotherapy in conjunction with radiotherapy Radiotherapy * Prior radiotherapy for localized disease allowed provided there is clear evidence of disease progression afterwards Surgery * Prior curative surgery allowed provided there is evidence of nonresectable disease relapse requiring systemic chemotherapy Other * Recovered from all prior therapies * Prior photodynamic therapy (PDT) allowed provided it was given for localized disease only (with no evidence of metastatic disease) and resulted in subsequent disease progression after completion of therapy OR to relieve biliary obstruction in the presence of metastatic disease * PDT must have been completed ≥ 4 weeks ago * At least 4 weeks since prior investigational agents * No other concurrent, curative anticancer therapy