53: SIGNIFICANCE OF NEOADJUVANT DOWNSTAGING IN ADENOCARCINOMA OF THE STOMACH

Abstract

Abstract Background and aim Neoadjuvant chemotherapy is established in the treatment of gastric adenocarcinoma. Histopathological regression as a result of neoadjuvant treatment may have important prognostic implications. There is little data comparing the prognosis of clinical versus pathological stage in patients receiving neoadjuvant treatment. Equally, comparison of outcomes of patients with comparable pathological stage that have received neoadjuvant treatment with those having surgery as their initial treatment is not known. The aim of this study is to determine the impact of neoadjuvant chemotherapy upon the prognosis of patients treated for gastric adenocarcinoma. Methods Consecutive patients with gastric cancer from a single, centre between 2007 and 2017 were evaluated. All patients with gastric adenocarcinoma were treated with either a subtotal or total gastrectomy and D2 lymphadenectomy. The impact of downstaging on outcomes and a stage-by-stage comparison of pTNM with ypTNM was performed. Results 654 patients underwent gastrectomy, 345 patients received neoadjuvant chemotherapy. Patients with downstaged disease had improved overall survival than patients with tumours that did not respond to neoadjuvant chemotherapy (P < 0.001). Downstaging by more than 3 stages was the strongest independent predictor of overall survival when compared with patients who did not respond to neoadjuvant treatment (median survival: 122 vs 66 months, P < 0.001). Survival was significantly improved for patients with advanced overall staging when a stage-wise comparison was performed between patients in like-for-like ypTNM and pTNM groups (ypT 3/4 N2/3 vs pT3/4 N2/3 median survival: 33 vs 16 months, P = 0.001). Conclusion Pathological staging following neoadjuvant chemotherapy is better for survival prognostication compared to clinical stage. Downstaging is associated with improved prognosis. There is a significant improvement in survival when comparing pathological stage post neoadjuvant treatment compared to those with a similar stage who had surgical treatment initially.