Oligometastatic esophageal squamous cell carcinoma: a systematic review of current definitions and meta-analysis of local therapy outcomes.

Current European expert consensus definitions for esophagogastric oligometastatic disease (OMD) primarily relate to adenocarcinoma. Oligometastatic esophageal squamous cell carcinoma (OMESQ) may require a distinct definition and treatment strategy. This systematic review and meta-analysis aimed to identify applied OMESQ definitions and assess the impact of local treatment on overall survival (OS). A systematic search of PubMed, Embase, CENTRAL, and ClinicalTrials.gov was conducted (February 2026). Studies or protocols were eligible if they reported an OMESQ definition or outcomes of local treatment in patients with limited metastatic ESCC. The primary outcomes were the maximum number of involved organs and metastases defined as OMD. Agreement across studies was scored as absent/poor (< 50%), fair (50%-75%), or strong (≥ 75%). A meta-analysis of OS after local treatment (+/- systemic therapy) versus systemic therapy alone was conducted through a random-effects pooled analysis of hazard ratios (HRs). Of the 3844 screened articles, 27 studies (23 retrospective, 4 prospective [one randomized]) and 7 protocols were included. Agreement was observed for defining synchronous OMESQ as disease in one organ with ≤3 metastases and metachronous OMESQ as disease in one organ with ≤2 metastases. Across 10 studies, meta-analysis showed that local treatment (+/- systemic therapy) was associated with improved OS compared with systemic therapy alone (pooled HR 0.61, 95% confidence interval: 0.52-0.72; I2 = 50.7%). Current literature and trial protocols considers OMESQ as ≤3 synchronous or ≤ 2 metachronous metastases in 1 organ. Local treatment is associated with improved OS compared with systemic therapy alone.