4188 Introduction: Concurrent 5-FU-RT is the standard Rx for RES or LA Pan Ca. CAP is an attractive RT sensitizer due to tumor localization of thymidine phosphorylase (TP), oral administration, and relatively less toxicity. PURPOSE: To report our clinical experience with CAP-RT in Pan Ca from 04/02 - 09/03. METHODS: 27 pts (11M, 16F; Median age: 64y; 6 RES, 21 LA; 25 Adeno, 2 Endocrine) received CAP (600-800mg/m(2) PO BID M-F) with RT (5.4Gy) followed by 4-wk rest, then CAP 2500mg/m(2) BID x 14d q 3 wks x 6 cycles for RES and until progression in LA dse. Pts were assessed wkly during CAP-RT and q 3 wks during CAP. Follow-up evaluations include toxicity, re-staging CT, and CA 19-9. RESULTS: Median follow-up from time of completion of CAP-RT is 6.5m (1 - 12.5). By 9/30/03, 19 pts are alive and 8 dead with a median survival of 14m (4 - 16). 5 are alive with no evidence of dse (4 RES; 1 LA with resection). 6 are alive with stable dse. 5 LA pts underwent exploratory laparotomy 6 to 9m S/P CAP-RT. Operative findings showed response to Rx with extensive fibrosis, which prohibited all but 1 pt to be resected. 2 RES pts had recurrence in tumor bed. 4 LA pts had local progression within RT port, 3 had local progression with distant mets, and another 6 had distant mets only. Rx-related toxicity is summarized in Table 1. 5 pts developed GI bleeding within RT port as a late complication (3m S/P RT) while on CAP. 2 died from uncontrolled bleeding, 3rd responded to duodenal artery embolization, and 2 required occasional transfusions. CONCLUSION: There is no data comparing toxicity/efficacy of CAP-RT with 5-FU-RT. Our study shows that CAP-RT had favorable tumor response and survival in LA pts. Acute toxicities are manageable but GI bleeding could manifest as a late toxicity. We speculate that this may represent a "Radiation Recall" related to up-regulation of TP. We recommend caution during CAP therapy after CAP-RT. [Figure: see text] No significant financial relationships to disclose.