Gemcitabine in Treating Patients With Recurrent or Refractory Bladder Cancer

DISEASE CHARACTERISTICS: Histologically confirmed stage Tis, Ta, or T1 bladder carcinoma No stage B1 disease or greater No locally invasive or metastatic disease by CT or MRI No upper urinary tract disease Measurable persistent or recurrent superficial disease after standard treatment with intravesical BCG Stage Tis disease must fail second course of BCG if complete response achieved with first course of BCG Prior maximal transurethral resection High-grade T1 or Tis disease must be ineligible for cystectomy PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-1 Life expectancy: Not specified Hematopoietic: WBC at least 3,000/mm3 Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hepatic: Bilirubin no greater than 1.5 mg/dL AST no greater than 2 times upper limit of normal Renal: Creatinine no greater than 1.5 mg/dL Other: Not pregnant Negative pregnancy test Fertile patients must use effective contraception for 1 week prior to, during, and for at least 2 weeks after study No active bacterial infection requiring treatment with antibiotics PRIOR CONCURRENT THERAPY: Biologic therapy: See Disease Characteristics At least 4 weeks since prior immunotherapy Chemotherapy: Prior intravesical chemotherapy allowed At least 4 weeks since prior chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy No prior radiotherapy to bladder Surgery: See Disease Characteristics At least 2 weeks since prior transurethral resection of the bladder/bladder biopsy