Response evaluation with endoscopic ultrasound (EUS) measuring maximum tumor thickness to predict pathological response after neoadjuvant chemoradiation therapy (CRT) in patients with locally advanced esophageal cancer (EC)

15009 Background: EUS does not accurately assess T-stage after neoadjuvant CRT due to inflammation, necrosis and fibrosis. We evaluated whether maximum tumor thickness (MTT) can predict pathological response (tumor regression grade, TRG) after CRT. Methods: Patients (pts) with resectable, locally advanced EC, were treated with 2 cycles of docetaxel/cisplatin (DC) q3w followed by CRT (DC weekly x5 with concomitant 45 Gy radiation therapy) and surgery. Radial scan EUS (7.5MHz) measured MTT at baseline and 3–5 weeks after CRT completion. We prospectively hypothesized that MTT =6mm in the second EUS predicts complete and subtotal pathological response (TRG1 and 2), tested by logistic regression. The effect of >50% reduction of MTT was analysed as well. Results: 66 pts from 11 institutions were treated; median age 61y (35–70y); adenocarcinoma (AC) 53%; squamous cell carcinoma 46%; 40 pts were eligible for the EUS project (10 no surgery, 10 tumor stenosis prohibiting EUS, 5 MTT not measured, 1 intolerant to EUS...