OBJECTIVES: I. Confirm the greater than 20% response rate to irinotecan in patients with metastatic or recurrent colorectal cancer who have not receive prior chemotherapy for their advanced disease. II. Characterize pharmacokinetic parameters of irinotecan and its metabolite SN-38 and their relationship to response and toxic effect. III. Characterize tumor samples for topoisomerase I activity, proliferative fraction (ki67 expression), and p53 expression and determine whether clinical response is related to these tumor characteristics in patient population. IV. Determine the in vitro inhibition of topoisomerase I activity by irinotecan, SN-38, and other camptothecin analogs and evaluate whether the degree of in vitro sensitivity to irinotecan and/or SN-38 is associated with clinical response in these patients. VII. Determine the frequency of somatic mutations following irinotecan and correlate this with pharmacologic parameters.