Introduction/Background Maintenance therapy with PARP inhibitor (olaparib) is standard of care for patients with BRCA-mutated high grade epithelial ovarian cancer (HGEOC) who have a response to first-line platinum-based chemotherapy. Although the SOLO-1 trial has demonstrated a major benefit of olaparib therapy in first-line treatment, some patients experience progression during it. The modulated CA-125 elimination rate constant K (KELIM) is marker of chemosensitivity and has predictive role for response to first-line treatment. Our aim was to investigate the relationship between the KELIM score and progression to olaparib therapy in BRCA-mutated HGEOC.

Methodology Retrospectively, we have analysed the medical data of patients with BRCA-mutated HGEOC stage III-IV who started first-line olaparib maintenance therapy at the Department of Gynaecologic Oncology, the University Hospital Zagreb from July 2021 to May 2023. The KELIM score was calculated based on at least 3 CA-125 values within the first 100 days of chemotherapy.

Results Our analysis included 21 patients. The median age was 56 years. The ECOG performance status 0–1 had 86% of patients. Most patients (71%) were stage IIIC at presentation. The median duration of olaparib therapy was 10 months (range 6–25 months). At the time of analysis, the disease progression had 7 patients (34%). KELIM score was calculated in all patients. In the group of patients who experienced disease progression during olaparib therapy, 43% had KELIM <1, and the four patients (57%) had KELIM ≥1. In the patients who were still receiving olaparib or stopped therapy after two years and remained disease free, the results were the same: 43% of them had KELIM <1 and the rest of them (57%) had KELIM ≥1.

Conclusion We did not show that KELIM score is a useful tool to predict patients who will progress during olaparib therapy in BRCA-mutated patients but further researching with the larger number of patients are needed.

Disclosures The authors have declared no conflicts of interest.