Nine studies were included in the review (16,995 patients) comprising two randomised controlled trials (RCTs) and seven observational studies. Study sample size ranged from 211 to 12,333 patients.
Systematic lymphadenectomy was associated with a statistically significantly reduced risk of death (HR 0.89, 95% CI 0.82 to 0.97; nine studies; Ι²=46%) compared with unsystematic lymphadenectomy.
Subgroup analysis on the basis of study type showed that the results were not significant for RCTs (HR 1.05, 95% CI 0.84 to 1.31; two RCTs; Ι²=0%), but were statistically significant in observation studies (HR 0.87, 95% CI 0.80 to 0.95; seven studies; Ι²=36%).
Subgroup analysis for high-risk versus intermediate-risk endometrial cancer indicated a statistically significant reduced risk of death with in patients with systematic lymphadenectomy (HR 0.77, 95% CI 0.70 to 0.86; four studies; Ι²=47%). Low-risk endometrial cancer did not show a significant difference (three studies).
Subgroup analysis on the basis of definition of lymphadenectomy indicated statistically significant differences in overall survival in favour of systematic lymphadenectomy defined as removal of more than 10 lymph nodes (HR 0.88, 95% CI 0.81 to 0.97; five studies; Ι²=41%) compared with systematic lymphadenectomy defined as removal of less than 10 to 11 lymph nodes. Results in studies with other definitions were not significant (results reported in review).
There was no evidence of publication bias.