Sites Of Gastric Cancer Recurrence After Adjuvant Chemoradiotherapy.

68 Background: Since the Intergroup 0116 study in 2000, adjuvant post-operative chemoradiotherapy (CRT) has been offered routinely to similar patients with resected gastric cancer at Princess Margaret Hospital (PMH) using CT-planned and 3D conformal/intensity modulated radiotherapy (RT). The objective of this study was to analyze patterns of recurrence with respect to RT treatment volumes. Methods: Date and site (local, locoregional or distant) of first recurrence data was obtained from chart review for all patients treated at PMH with adjuvant CRT for resected gastric adenocarcinoma (Jan. 1, 2000-Nov. 30, 2009). Patients whose recurrences were limited to local (gastric remnant, duodenal margin, gastric bed recurrence) and/or regional sites (regional lymph node recurrence) were selected for analysis. When available, diagnostic imaging of recurrence site was registered to the original planning RT dataset. The center of mass for each recurrence was identified as a point and its location categorized according to the isodose encompassing it; in-field (≥ 90%), marginal (50%-89%), and out-of-field (< 50%). Results: Three-year OS, and RFS were 66% (95% CI: 58-73) and 58% (50-60), respectively. Of 203 patients treated, 75 recurrences were identified (Table). Of the 13 local/locoregional recurrences, 4 were in-field, 1 marginal, 1 could not be registered due to change in body habitus, and 7 did not have an available original dataset. Conclusions: Rates of isolated local and/or regional recurrence in this study were low. This represents a change in the pattern seen with surgery alone suggesting the addition of CRT results in decreased isolated local and/or regional recurrence. Of the small number of local and/or regional recurrences available for analysis, all were in-field or marginal. Further studies involving a larger cohort of patients might allow for more meaningful analysis of trends in recurrence site with evolving RT techniques. [Table: see text] No significant financial relationships to disclose.