Introduction/Background Most ovarian, fallopian tube or primary peritoneal cancer patients (OC) are diagnosed with advanced stage (III-IV). EORTC 55971 published in 2009, showed neoadjuvant chemotherapy followed by interval debulking surgery (IDS) was not inferior to primary debulking surgery (PDS). Subsequent trials demonstrated both approaches had similar overall survival (OS) and progression free survival (PFS). Hereby we analyse the outcomes of survival of both strategies in advanced OC (AOC) at Hospital Clinico San Carlos (HCSC).

Methodology Retrospective analysis of 219 patients with AOC treated at HCSC from 2009 to 2022.

Results Median age at diagnosis: 67 (range 25–92), 90% symptomatic. ECOG: 0 (48.9%) and 1 (37.9%). FIGO stage: IIIA 3.6%, IIIB 10%, IIIC 63%, IVA 10%, IVB 13.2%. Serous histology 76.3%. High-grade 91.3%. BRCA mutation: 10% germinal, 3.2% somatic. Median baseline CA125 1044 U/mL (range 8–45602). Favourable KELIM score (≥1) 41.1%. PDS 66/219 of which: R0 56%, R1 20%, R2 24%; IDS 119/219 of which: R0 75% R1 8%, R2 17%. Relapse in 44/66 PDS vs 89/119 IDS: platinum-refractory (13 vs 15%), platinum-resistant (23 vs 29%), partially platinum-sensitive (23 vs 18%) and platinum-sensitive (41 vs 38%).

After a median follow-up of 33.8 months, median PFS (mPFS) and median OS (mOS): 20.167 and 30.1 months, respectively. No differences in mPFS: PDS vs IDS (24.8 vs 20.633 months, p 0.285) nor in mOS (59.467 vs 40.433 months, p 0.082). Better mPFS in R0 vs R1 (25.767 vs 16.6 months, p 0.004) and R2 (25.767 vs 12.333 months, p <0.001). No mPFS and mOS differences of CA125 ≥ or < 1000 U/mL. KELIM ≥1 demonstrated improved mPFS (25.9 vs 14 months, p <0.001) and mOS (59.7 vs 32.7 months, p<0.001).

Conclusion PDS and IDS In AOS at HCSC showed similar PFS and OS, consistent with literature. KELIM score better predicted patient ‘s outcome than CA125 at diagnosis.

Disclosures Aranzazu Manzano: Receipt of grants/research supports: ASTRA ZENECA (AZ) Receipt of honoraria or consultation fees: AZ, GSK Participation in a company sponsored speaker’s bureau: AZ, MSD, PHARMAMAR, GSK, ROVI, SANOFI.