Definition of oligometastatic esophagogastric cancer and impact of local oligometastasis-directed treatment: A systematic review and meta-analysis.

BACKGROUND

Local treatment (metastasectomy or stereotactic radiotherapy) for oligometastatic disease (OMD) in patients with esophagogastric cancer may improve overall survival (OS). The primary aim was to identify definitions of esophagogastric OMD. A secondary aim was to perform a meta-analysis of OS after local treatment versus systemic therapy alone for OMD.

METHODS

Studies and study protocols reporting on definitions or OS after local treatment for esophagogastric OMD were included. The primary outcome was the maximum number of organs/lesions considered OMD and the maximum number of lesions per organ (i.e. 'organ-specific' OMD burden). Agreement was considered to be either absent/poor (< 50%), fair (50%-75%), or consensus (≥ 75%). The secondary outcome was the pooled adjusted hazard ratio (aHR) for OS after local treatment versus systemic therapy alone. The ROBINS tool was used for quality assessment.

RESULTS

A total of 97 studies, including 7 study protocols, and 2 prospective studies, were included. OMD was considered in 1 organ with ≤ 3 metastases (consensus). 'Organ-specific' OMD burden could involve bilobar ≤ 3 liver metastases, unilateral ≤ 2 lung metastases, 1 extra-regional lymph node station, ≤ 2 brain metastases, or bilateral adrenal gland metastases (consensus). Local treatment for OMD was associated with improved OS compared with systemic therapy alone based on 6 non-randomized studies (pooled aHR 0.47, 95% CI: 0.30-0.74) and for liver oligometastases based on 5 non-randomized studies (pooled aHR 0.39, 95% CI: 0.22-0.59). All studies scored serious risk of bias.

CONCLUSIONS

Current literature considers esophagogastric cancer spread limited to 1 organ with ≤ 3 metastases or 1 extra-regional lymph node station to be OMD. Local treatment for OMD appeared associated with improved OS compared with systemic therapy alone. Prospective randomized trials are warranted.