221. INTERVAL METASTASES AFTER NEOADJUVANT CHEMORADIOTHERAPY IN PATIENTS WITH LOCALLY ADVANCED ESOPHAGEAL CANCER: A MULTICENTER OBSERVATIONAL COHORT STUDY

Abstract

Abstract Background Despite trimodality treatment, 10–20% of patients with esophageal cancer develop metastases after surgery. Re-staging after neoadjuvant chemoradiotherapy (nCRT) may be useful to identify these patients who should not have proceeded to surgery. In this multicenter observational cohort study, we assessed the proportion of patients with interval metastases after nCRT. Secondary outcomes were overall survival (OS), location and treatment of metastases. Methods Between 2013–2021, patients with cT2-4aN0–3 M0 esophageal/junctional cancer who underwent nCRT were identified from three prospective study-databases. Re-staging with 18F-FDG-PET/CT ≤14 weeks after completion of nCRT was performed in all patients. Metastases detected on imaging or during surgery were categorized into oligometastatic (≤3 lesions located in one single organ or in one extra-regional lymph node station) or non-oligometastatic. Treatment of metastases was based on pretreatment multidisciplinary tumor board reports for patients with oligometastatic disease and consisted of systemic therapy, loco(regional) therapy or best supportive care. OS was calculated from completion of nCRT until date of death or last day of follow-up. Results Metastases were detected in 100 of 973 patients (10.3%). The majority (84%) were detected by 18F-FDG-PET/CT and in 16% during surgery of which 60% were peritoneal metastases. Oligometastatic disease was seen in 30% of patients and 12 patients (40%) were treated with potentially curative intent. Median OS of patients with oligometastatic disease who were treated with potentially curative intent was 22.8 months (95% CI 10.4-NA), compared to 13.8 months (95% CI 9.2–27.1) in patients treated with palliative intent. Oligometastases were mostly located in non-regional lymph nodes (33.3%) or bones (26.7%). Median OS non-oligometastatic disease 9.0 months (95% CI 7.4–10.9). Conclusion Interval metastases were detected in about 10% of esophageal cancer patients after nCRT and the majority had non-oligometastatic disease. This underlines the benefit of restaging to select patients who are not candidates for esophagectomy. Treatment of oligometastases might lead to favorable survival in selected patients.