Ropidoxuridine in Treating Patients With Advanced Gastrointestinal Cancer Undergoing Radiation Therapy

PRIMARY OBJECTIVES: I. To conduct a phase I dose escalation trial, to determine the safety and the maximum tolerated dose (MTD), of oral (po) IPdR (ropidoxuridine) given daily for 28 consecutive days with concurrent intensity-modulated radiation therapy (IMRT) in patients with advanced gastrointestinal cancers treated with palliative radiation. SECONDARY OBJECTIVES: I. To observe and record anti-tumor activity. II. To establish the pharmacokinetics of daily po dosing of IPdR x 28 days. III. To assess, for patients treated at the MTD, for biochemical evidence of IPdR effect in normal tissue (circulating granulocytes) and tumor tissue (in patients with accessible tumor tissue) by measuring %iododeoxyuridine (IUdR)-deoxyribonucleic acid (DNA) cellular incorporation by flow cytometry and high-pressure liquid chromatography (HPLC) analyses. IV. To assess the use of %IUdR-DNA cellular incorporation (measured by the investigational laboratory assays of flow cytometry and HPLC) as an exploratory biomarker of IPdR for the following effects: the %IUdR-DNA tumor cell incorporation from day 8 tumor biopsies in gastrointestinal (GI) cancer patients receiving MTD doses of IPdR as an exploratory biomarker of tumor radiosensitization using Response Evaluation Criteria in Solid Tumors (RECIST) criteria. V. To assess the use of %IUdR-DNA cellular incorporation (measured by the investigational laboratory assays of flow cytometry and HPLC) as an exploratory biomarker of IPdR for the following effects: the %IUdR-DNA cellular incorporation in patients' circulating granulocytes taken weekly during the 28-day IPdR MTD dose, on day 29, and week 8 as an exploratory biomarker of IPdR systemic toxicities to bone marrow as measured by complete blood count (CBC)/differential values. OUTLINE: This is a dose-escalation study of ropidoxuridine. Beginning 30 minutes to 2 hours before radiation therapy, patients receive ropidoxuridine PO once daily (QD) on days 1-28 in the absence of disease progression or unacceptable toxicity. Beginning on day 8, patients undergo IMRT 5 days a week for 3 weeks in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up for 4 weeks.