Objectives To quantify tumor positivity and upstaging rates for all staging surgery steps in EOC patients. Differences between subgroups based on their clinical and histological characteristics are explored.

Methods A systematic search using synonyms of ‘ovarian cancer’, ‘neoplasm staging’, and ’neoplasm metastasis’ was conducted in PubMed, Embase, and the Cochrane Library. Meta-analysis was performed on 23 included studies, comprising 5194 clinical stage I or II EOC patients who underwent comprehensive surgical staging. Studies were assessed using the Newcastle-Ottawa Scale risk-of-bias tool. Pooled proportions and 95% confidence intervals were calculated using an inverse variance weighted random-effects model.

Results Overall upstaging rate of clinically early-stage EOC patients was 18.7% (95%CI: 14.1–23.4%). Serous histology or high grade EOC showed the highest upstaging rate at 35.3% (95%CI: 21.8–48.7%) and 40.9% (95%CI: 35.6–46.2%). Lymph node involvement resulted in an upstaging rate of 8.7% (95%CI: 6.2–11.3%). Tumor was identified in uterus, cytology, peritoneal biopsies, omentum and appendix in 6.2% (95%CI: 1.8–10.7%), 18.4% (95%CI: 13.8–22.9%), 9.7% (95%CI: 3.8–15.6%), 5.2% (95%CI: 1.7–8.8%) and 3.6% (95%CI: 0.0–7.5%) of EOC patients. The corresponding upstaging rates were 5.9% (95%CI: 1.4–10.4%), 8.5% (95%CI: 1.8–15.2%), 3.5% (95%CI: 1.0–6.0%), 3.9% (95%CI: 1.4–6.3%) and 1.6% (95%CI: 0.0–3.4%), respectively.

Conclusions The attributive value of comprehensive surgical staging in clinically early-stage EOC patients remains substantial, particularly in serous and high grade tumors.