Abstract
BACKGROUND: Neoadjuvant chemoradiotherapy (nCRT) in patients with oesophageal squamous cell carcinoma (OSCC) may lead to clinical complete response (cCR). It is important to know the accuracy of clinical response evaluations (CREs) before advocating active surveillance instead of oesophagectomy. METHODS: This was a prospective, multicentre study of patients with locally advanced OSCC. They received the first CRE (bite-on-bite biopsies) 4-6 weeks after nCRT. Patients with residual tumour underwent surgery. Patients with a cCR at CRE-1 underwent a second CRE 10-12 weeks after nCRT using PET-CT, bite-on-bite biopsies and endoscopic ultrasound fine-needle aspiration (EUS-FNA). All patients without distant metastases underwent surgery. Primary endpoint was the accuracy of CREs for detecting Tumour Regression Grade (TRG)3-4 or TRG1-2 with ypN+ residual tumour with a prespecified false-negative rate (FNR) of 19.5%. Circulating-tumour DNA (ctDNA) at CREs was performed for exploratory analysis. RESULTS: In total 309 patients were included. Eighteen of 133 patients with TRG3-4 or TRG1-2 with ypN+ residual tumours were not detected by bite-on-bite biopsies and EUS-FNA (FNR: 13.5%). Sensitivity, specificity, negative predictive value and positive predictive value of detecting any residual tumour were 81.7%, 93.2%, 68.7% and 96.5% respectively. PET-CT detected interval distant metastases in 13 (4.9%) of 268 patients presurgically. After a minimum 12-month follow-up, systemic recurrence rates were 28.0% in patients with positive ctDNA at CREs and 5.3% in those with negative ctDNA. CONCLUSIONS: Bite-on-bite biopsies and EUS-FNA were accurate in detecting residual disease after nCRT in OSCC. Positive ctDNA at CREs may indicate an increased risk of systemic metastases.