The concept of locally advanced gastric cancer. Effect of treatment on outcome. The Gastrointestinal Tumor Study Group. In previous Gastrointestinal Tumor Study Group (GITSG) reports, gastric cancer patients with locally unresectable disease, treated with combined radiation and chemotherapy had a shorter median survival (40 weeks) but more remained alive at 4 years (18%) when compared to those randomized to receive chemotherapy alone (76 weeks and 6%, respectively). To further test the concept that combined modality therapy might increase the number of long-term survivors, a second protocol was designed, but with three major modifications. A course of chemotherapy would precede the 5-fluorouracil-potentiated radiation therapy. Doxorubicin would be added to the 5-fluorouracil plus methyl-CCNU combination. Radiation therapy would be given as a single course of 4320 cGy, with 5-fluorouracil given daily for 3 days at the beginning and end of the course. Median survival of 46 patients treated with chemotherapy alone was 59 weeks, with 11% alive after 3 years. Following combined modality therapy, median survival was 62 weeks, but only 7% lived 3 years. Although the problem of early deaths in the combined modality group was resolved, long-term survival with combination therapy was not demonstrated in this study. 