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OBJECTIVE Endometrial cancer uncommonly presents at an advanced stage, and little prospective evidence exists to guide management. We aimed to summarize evidence on primary cytoreductive surgery (PCS) in the treatment of advanced stage endometrial cancer. DATA SOURCES MEDLINE, Embase, and Scopus databases were searched from inception to September 11, 2020, using search terms representing the themes "endometrial cancer," "advanced stage," and "primary cytoreductive surgery". STUDY ELIGIBILITY CRITERIA We selected for English full-text reports including ≥10 stage IV patients undergoing PCS for advanced stage endometrial cancer and reporting outcomes of incidence and survival by extent of residual disease after cytoreduction. STUDY APPRAISAL AND SYNTHESIS METHODS Two reviewers independently screened studies, with disagreements resolved by a third. Data were extracted using a standardized form. Percent of cases reaching maximal (no gross residual disease; NGRD) and optimal (<1 cm or <2 cm residual disease) cytoreduction were assessed by summing binomials proportions, and association with survival assessed with inverse variance-weighted meta-analysis of logarithmic hazard ratios. RESULTS From 1,219 unique records, we selected 34 studies for inclusion. Studies consisted of single or multi-institutional cohorts of patients collected over 6-24 years, including varying mixes of histologies (endometrioid/serous/clear cell/carcinosarcoma) and stages (III/IV). In meta-analysis of extent of residual disease after PCS, we found 52.1% of cases reached NGRD (n=18 studies, 1,329 patients), and 75% reached <1 cm (n=27 studies, 2,343 patients). The proportion of cytoreduction to both thresholds was lower for studies of stage IV vs. stage III-IV disease (41.4% vs. 69.8% NGRD, 63.2% vs. 82.2% <1 cm), but did not vary notably by histology. In meta-analysis of reported hazard ratios (HRs), submaximal (any gross residual disease vs. NGRD), and suboptimal (≥1 cm vs. <1 cm) cytoreduction were associated with worse progression-free survival (submaximal: HR=2.16, 95%CI 1.45-3.21; I2=68%; suboptimal: HR=2.55, 95%CI 1.93-3.37 I2=63%) and overall survival (submaximal: HR=2.57, 95%CI 2.13-3.10; I2=1%; suboptimal: HR=2.62, 95%CI 2.20-3.11; I2=15%). Sensitivity analyses limiting to high quality studies demonstrated consistent results. CONCLUSIONS Among cases of advanced stage endometrial cancer undergoing PCS, a significant proportion of patients are left with residual disease, which is associated with worse survival. Further investigation of the roles of neoadjuvant chemotherapy and PCS in prospective trials is warranted in this population.