Phase II Fixed Dose Rate Gemcitabine for Advanced or Metastatic Colorectal Cancer

Inclusion Criteria: * Age \>18 years * Histologically proven colorectal adenocarcinoma. * Locally advanced (inoperable) or metastatic colorectal carcinoma treated with at least one prior chemotherapy regimen. * Progressive disease documented by CT either during or within 3 months of completion of previous chemotherapy * No previous malignant disease other than non-melanotic skin cancer or carcinoma-in-situ of the uterine cervix. * Unidimensional measurable disease as assessed by CT. * Adequate bone marrow function; Hb \>10g/dl, platelets \>100 x109/l, WBC \>3x109/l, Neut \>1.5x109/l. * Adequate liver function: Serum Bilirubin \<1.5 x upper limit of normal * Adequate renal function: Serum Creatinine \< 0.11 mmol/L * No concurrent uncontrolled medical conditions * WHO performance status 0,1 or 2 * Adequate contraceptive precautions, if appropriate * Informed written consent * Negative pregnancy test in women of child bearing age * Life expectancy \> 3 months Exclusion Criteria: * Medical or psychiatric condition that comprise the patient's ability to take informed consent. * Patients within 4 weeks of chemotherapy or radiotherapy (6 weeks for nitrosureas or mitomycin C). * Previous treatment with gemcitabine. * Patients with uncontrolled cerebral metastases.