Progression patterns and management after frontline platinum in advanced epithelial ovarian cancer (EOC).

e17581 Background: Most patients with EOC relapse after frontline platinum-based chemotherapy, even with maintenance therapy. Oligoprogression may define a distinct, locally treatable relapse pattern. Methods: We retrospectively analyzed advanced EOC patients treated at our institution (January/2014–December/2024) with surgery and platinum-based chemotherapy, or achieving radiologic complete response after frontline platinum chemotherapy without surgery. Progression was categorized as oligoprogression (1–5 lesions; group A) or multiple progression (group B). Associations were assessed using chi-square tests. Survival outcomes were estimated by Kaplan–Meier and compared by Cox regression. Baseline characteristics are summarized in the Table. Results: Among 107 patients (mean age 65±9.3 years), 75 (70%) relapsed and 29/75 (39%) had oligoprogression. Group A had a higher rate of frontline PARP inhibitor (PARPi) maintenance than group B (14/15 vs 11/35; p=0.02) and fewer metastatic sites at relapse (p=0.01). In the overall cohort, progression-free survival (PFS) >12 months from the end of frontline chemotherapy was associated with a higher likelihood of receiving local vs systemic therapy (p=0.002). In group A, median overall survival (OS) was 110.4±32.4 months and median PFS was 12.5±0.88 months. Local therapy (surgery and/or radiotherapy) versus systemic therapy was associated with longer OS (102.6 vs 34.3 months; p<0.001) and PFS (18.8 vs 9.4 months; p=0.003). Maintenance duration >12 months showed a trend toward longer PFS (25.4 vs 13.4 months; p=0.053). Excluding bevacizumab, PARPi >12 months versus ≤12/no maintenance showed a non-significant trend toward longer PFS (24.5 vs 13.1 months; p=0.10). Conclusions: In this real-world cohort, frontline PARPi maintenance was associated with a higher proportion of oligoprogressive relapse. Among oligoprogressive patients, local therapy was associated with clinically meaningful OS and PFS prolongation, supporting its consideration within multidisciplinary post-progression management. Characteristic Group A (n=29) (%) Group B (n=46) (%) Stage III / IV 51.7 / 48.3 69.6 / 30.4 Debulking surgery(S)/ Interval S/ no S 37.9 / 58.6 / 3.4 43.5/ 54.3 / 2.2 Chemotherapy (CT): neoadjuvant / adjuvant / palliative 58.6 / 31 / 10.3 50 / 39.1 / 10.9 HRD status: HRD+/ BRCA +, HRD+/ BRCA -, HRP, unknown 10.3 / 0 / 10.3 / 79.3 4.3 / 0 / 10.9 / 84.8 Germline BRCA status: BRCA1 / BRCA2 / wild-type / unknown 6.9 / 13.8 / 55.2 / 24.1 8.7 / 2.2 / 71.7 / 17.4 Maintenance therapy: bevacizumab / PARPi/ no maintenance 13.8 / 48.3/ 37.9 16.7 / 23.9/ 59.4 Relapse metastatic sites: 1 / 2 / 3 / 4 / 5 86.2 / 13.8 / 0 / 0 / 0 54.3 / 32.6 / 13 / 0 / 0 Progression sites (non-mutually exclusive): peritoneal/lymph nodes/liver/pleura/other 62.1 / 24.1 / 10.3 / 3.4 / 20.6 82.6 / 41.3 / 15.2 / 15.2 / 6.5 Treatment at relapse: S/radiotherapy/CT/S and CT/no therapy 31 / 6.9 / 34.5 / 24.1 / 3.4 0 / 0 / 93.5 / 4.3 / 2.2