Background
Previously, no international consensus on reporting complications after gastric cancer surgery existed, making comparisons between studies difficult. In 2015 the Esophagectomy Complications Consensus Group (ECCG) published a standardized list for classification of postoperative complications after esophagectomy for esophageal cancer, which also was applied for gastric cancer. In 2019 the Gastrectomy Complications Consensus Group (GCCG) reported outcomes after gastrectomy for gastric cancer with a list of different complication types. This study aimed to compare the two classifications in reporting postoperative outcomes after gastrectomy for gastric cancer.

Methods
This population-based study, based on the Finnish National Esophago-Gastric Cancer Cohort, included all patients age 18 years or older undergoing gastrectomy for gastric cancer in Finland during 2010–2016. For classifying and describing different postoperative outcomes, both the ECCG and GCCG lists of complications were used separately.

Results
The study analyzed 1115 patients. The occurrence of complications 90 days postoperatively was 23.0% according to the GCCG classification (504 individual complications) and 43.0% according to the ECCG classification (1084 individual complications). Most of the notable differences between the classifications in reporting complications were in cardiac dysrhythmia, infections, and myocardial infarction, with the GCCG classification reporting a lower incidence. Additionally, 131 complications occurring in 13 individual types of complications defined only in the ECCG and not in the GCCG were recorded.

Conclusions
This study suggests that the ECCG classification is more comprehensive and sensitive in evaluating complications of gastrectomy than the GCCG classification. Use of the ECCG classification may be preferable in the context of gastrectomy.