BACKGROUND: Pathological regression grade after chemotherapy evaluated by surgically resected specimens is closely related with prognosis. Since usefulness of measuring the area of the residual tumor (ART) has been reported, this study aimed to evaluate the utility of ART in predicting the prognosis of patients with gastric cancer (GC) who received preoperative chemotherapy. METHODS: This single-center retrospective study examined the relationship between ART and survival outcomes. We included 92 patients who underwent preoperative chemotherapy followed by radical surgery for GC. Digital images were used to measure the ART in the largest pathological slice of each patient's surgical tumor specimen. We simply subclassified the patients as either ART-0 (<
0.1 mm RESULTS: Significant differences were noted in overall survival and recurrence-free survival (RFS) between ART-0 (n = 19) and non-ART-0 (n = 73). The survival curves were similar to those of major pathological response (MPR) (n = 24) or non-MPR (n = 68), which are commonly used as surrogate endpoint presently. Multivariate analysis revealed ART and ypN independent prognostic factors for RFS. Survival curves stratified using ART and ypN to indicate risk grades (low-, moderate-, or high-) were not significantly different from those stratified using the other three existing pathological regression grade systems and ypN. CONCLUSION: ART-based pathological assessment is a simple and useful method for predicting the prognosis in patients with GC who underwent radical surgery after chemotherapy.