Introduction/Background* Advanced epithelial ovarian cancer (EOC) is a severe disease with high mortality rate. Achieving complete cytoreduction (R=0; CCR) is crucial for the patient's prognosis. Extensive peritoneal carcinomatosis is often the limiting factor for achieving CCR in EOC and therefore is the deciding factor for therapy planning. The Peritoneal Cancer Index (PCI) after Sugarbaker has been an established tool to describe the extension of the disease. A patient presenting a PCI < 25 is considered to be operable 1 . We examined the predictive power of various markers (CA-125, CTscans, PCI) for achieving complete cytoreduction after neoadjuvant chemotherapy (NACT). Methodology The data of 23 patients treated in our hospital between 01/2015 und 12/2020 with inoperable EOC were retrospectively analyzed. Clinical and radiological data were collected and statistically analysed (univariate analysis: Chi-Square Tests, Mann-Whitney U test and multivariate analysis: Binary logistic regression, ROC-curve). Result(s)* The reduction of the PCI itself after neoadjuvant chemotherapy showed to be a powerful predictor for complete cytoreduction (CCR), but it also showed to be significant even if the different PCI baseline values were considered. The reduction of the initial PCI score by minimum 8.5 points was a better predictor for CCR than the PCI < 25.Neither the RECIST analysis 2 of the CT-scans nor the reduction of the tumor marker CA-125 proved to be a significant predictor. Conclusion* Whether CCR can be achieved during debulking surgery, is best predicted by the reduction of the PCI. A combination of the three markers might be even more powerful. Larger studies are needed to confirm this.