Objective:To explore the prognostic factors of patients with advanced epithelial ovarian cancer (EOC) who received neoadjuvant chemotherapy (NACT) followed by interval debulking surgery (IDS).Methods:The clinical and pathological data of patients with stage Ⅲc-Ⅳ EOC underwent surgical treatment in Sichuan Cancer Center from January 1st, 2014 to December 31th, 2018 were retrospectively analyzed, and the prognosis was followed up.Results:(1) A total of 216 EOC patients were included in the study, whose age was (52.1±8.7) years old, the median follow-up time was 44.6 months (17.2-80.1 months), the median progression free survival (PFS) was 11.1 months (8.5-13.8 months), and the median overall survival (OS) was 40.0 months (32.7-47.3 months). (2) Among 216 patients with advanced EOC, there were 75 cases in the primary debulking surgery (PDS) group and 141 cases in the NACT+IDS group. Compared with the PDS group, the serum CA 125 level before treatment (median: 859.4 vs 1 371.0 kU/L), proportion of stage Ⅳ patients [5.3% (4/75) vs 23.4% (33/144)] and no visible residual disease (R0) cytoreduction rate in the NACT+IDS group were significantly higher [(41.3% (31/75) vs 61.7% (87/144); all P<0.05]. The median PFS in the NACT+IDS group was significantly shorter than that of the PDS group (9.1 vs 15.2 months; χ2=7.014, P=0.008), but there was no significant difference in the median OS between the two groups (42.6 vs 38.0 months; χ2=1.325, P=0.250). (3) Univariate analysis showed that body mass index (BMI), preoperative serum CA 125 level, surgical-pathological stage, NACT effect, postoperative residual tumor size, time to initiation of postoperative chemotherapy and chemotherapy regimen were significantly correlated with PFS in the NACT+IDS group (all P<0.05); preoperative serum CA 125 level, surgical-pathological stage, NACT effect, postoperative residual tumor size, postoperative chemotherapy regimen were significantly related with OS in the NACT+IDS group (all P<0.05). Multivariate analysis showed that BMI, postoperative residual tumor size, time to initiation of postoperative chemotherapy were independent factors of PFS in the NACT+IDS group (all P<0.05); preoperative serum CA 125 level, surgical-pathological stage, postoperative residual tumor size were independent factors of OS in the NACT+IDS group (all P<0.05). The results showed that the PFS of patients with normal preoperative serum CA 125 level and (or) chemotherapy ≤7 days after IDS was longer, while no significant difference comparable with those in the PDS group ( P>0.05), and OS was also showing an prolonged trend, but the difference was also not statistically significant ( P>0.05). Conclusions:Normal CA 125 before IDS and time received chemotherapy no longer than 7 days after IDS are two related factors of prognosis benefit in advance EOC patients treated with NACT+IDS. Therefore, timely adjustment of the dose and regimen of NACT to reduce CA 125 level to normal range in about three cycles before IDS, and strengthen IDS perioperative management to promote postoperative recovery and perform chemotherapy as soon as possible might help to improve the prognosis of patients.