Consistent Data about the Predictive Factors of the Success of Interval Debulking Surgery (CC0-IDS) in Patients with Advanced Ovarian Cancers in Two Large Independent Datasets.

5560 Background: More than 50% of patients with FIGO stage III-IV epithelial ovarian cancers are treated with neoadjuvant chemotherapy (NACT) to achieve a complete interval debulking surgery (IDS), in the case of tumor response. Therefore, understanding the determinants of IDS success is crucial. The French GINECO and the Gemelli (Italy) groups analyzed 2 independent datasets to identify the predictive factors associated with low peritoneal carcinomatosis index (PCI) after 3or4 NACT cycles; complete IDS with no macroscopic residual lesion (CC0); high pathological chemotherapy response score (CRS3). Methods: The French dataset was built with the CHIVA (C) randomized phase II trial in 133 patients (NCT01583322). The Italian dataset was built with the Policlinico GEMELLI (G) real-life registry with 357 patients (ID5936–ProtN45). Univariate/multivariate logistic regression models were used to identify the clinical and biological covariates associated with: 1) low PCI after NACT (Sugarbaker PCI ≤ 10, or Fagotti score at IDS ≤ 2); 2) CC0 IDS; and 3) pathological CRS3. The tested predictors were the modeled CA-125 longitudinal kinetics parameter KELIM; the best radiological response according to RECIST 1.1; and BRCA mutation/ homologous recombination deficiency (HRD) status (C: ShallowHRD; G: Myriad&AmoyDx). The analyses were led independently in the 2 datasets. Results: Odds-ratios (OR) outcomes [95%CI] are presented in Table (*significant variables at multivariate). In both datasets, higher KELIM was the only predictor reproducibly associated with lower PCI after NACT (OR 4.08-4.44); higher probability of complete IDS (OR 4.66-7.29); and higher probability of pathology CRS3 (OR 2.97-12.43). The radiological response was inconsistently significant. The BRCA/HRD status was not predictive of IDS success elements. Conclusions: In 2 independent international datasets, the tumor primary chemosensitivity (assessed by CA-125 KELIM) was the only consistent predictor of IDS success after NACT in both datasets. Clinical trial information: NCT01583322 . [Table: see text]