508. OUTCOME OF NEOADJUVANT CHEMORADIOTHERAPY PLUS SURGERY FOR ESOPHAGEAL SQUAMOUS CELL CARCINOMA IN EAST ASIA VERSUS WESTERN EUROPE

Patients with different ethnic and genetic backgrounds may respond differently to specific anticancer therapies. The present study aimed to assess whether patients with esophageal squamous cell carcinoma (ESCC) who are treated with neoadjuvant chemoradiotherapy (nCRT) according to the CROSS regimen in East Asia have an inferior response compared to patients treated in Western Europe. Patients with ESCC who completed ≥80% of nCRT according to CROSS (five weekly cycles of carboplatin [AUC of 2 mg/mL/min] and paclitaxel [50 mg/m2] with concurrent 41.4 Gy radiotherapy in 23 daily fractions of 1.8 Gy) followed by esophagectomy between June 2012 and April 2020 were identified from Asian and Dutch databases. Primary endpoint was pathologically complete response (pCR), defined as ypT0N0. Asian and Dutch patients were compared with nearest-neighbor propensity score matching, adjusting for confounding factors: gender, Charlson comorbidity index, tumor location, cT and cN stage, interval from start of nCRT to surgery, and number of resected lymph nodes. In total, 839 patients were included (Asian: 175, Dutch: 664). After matching, 154 remained in each group. Confounding factors were all significantly different before matching and 26% in the Asian versus 42% in the Dutch cohort had a pCR (p