1. From the Departments of Gastrointestinal Medical Oncology and Digestive Diseases, Radiation Oncology, Surgical Oncology, and Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, TX; Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ; and Division of Oncology Drug Products, Center for Drug Evaluation and Research, Food and Drug Administration, Rockville, MD.