Introduction/Background The Chemotherapy Response Score (CRS) has been validated to assess the response and prognosis of high-grade ovarian cancer (HGOC) to neoadjuvant chemotherapy (NACT). Similarly, the peritoneal cancer index (PCI) before and after NACT could quantitatively assess the variation of tumor burden in the peritoneal cavity. The aim of the study was to evaluate the ability of PCI to predict histopathologic response to NACT and achieve complete cytoreduction at interval debulking surgery (IDS).

Methodology Thirty-two patients with advanced HGOC who underwent IDS at the Padua University Gynecological and Obstetric Clinic between August 2021 and September 2023 were included. Data were prospectively collected. Histopathologic response to NACT was assessed using CRS. The variation of PCI calculated at the exploratory laparoscopy and at IDS was used to assess the clinical response. PCI variation was related to CRS and to complete cytoreduction (R=0).

Results The median age was 63,5 years (range 42–81). CRS 1 was found in 13 patients (40,6%), CRS 2 in 14 patients (43,8%), CRS 3 in 5 patients (15,6%). Complete cytoreduction was achieved in 28 patients (87,5%). The median variation of PCI at the exploratory laparoscopy and at IDS in all 32 patients was 9,5 (range 0–34). The median variation of PCI in CRS 1 was 8 (range 0–14), in CRS 2 was 10,5 (range 0–20), in CRS 3 was 18 (range 13–34). The median variation of PCI in patients with R=0 was 10 (range 0–34), in patients with incomplete cytoreduction was 1,5 (range 0–9) (p<0.01).

Conclusion The variation of PCI represents a reliable predictor of the histologic response to NACT and complete cytoreduction at IDS. Incorporating PCI evaluation into routine surgical practice before and after NACT could influence the choice of surgical treatment.

Disclosures None.