4CPS-059 Predictive markers of response to adjuvant treatment in locally advanced ovarian cancer

<h3>Background and Importance</h3> Along with mutations in the BRCA genes and homologous recombination deficiency, the rate of CA-125 biomarker clearance during the first cycles of chemotherapy is emerging as an indicator of chemosensitivity in ovarian cancer. The validated indicator for this clearance rate, KELIM (CA-125 ELIMination Rate Constant K), has demonstrated its prognostic value for the benefit obtained after treatment in several clinical trials. <h3>Aim and Objectives</h3> Our objective was to validate the KELIM score in clinical practice in patients with ovarian cancer treated with adjuvant chemotherapy and to determine whether the KELIM score is predictive of progression-free (PFS) and overall survival (OS). <h3>Material and Methods</h3> Patients with stage III ovarian cancer who had received adjuvant chemotherapy following cytoreductive primary surgery at our centre from January 2014 to January 2024 were included. Patients treated in the recurrent setting were excluded. Demographic and clinical parameters were collected and a multiple logistic regression analysis was conducted to identify the most significant predictor variables. KELIM was calculated, using a validated formula (https://www.biomarker-kinetics.org/CA-125), based on CA-125 values during each treatment cycle within the first 100 days of chemotherapy. At least three values were required, and the obtained score was considered favourable (KELIM ≥1) or unfavourable (KELIM &lt;1), indicating high or low chemosensitivity, respectively. Kaplan-Meier survival analyses was performed for PFS and OS. <h3>Results</h3> 43 patients were included in the analysis. Mean age was 60 years. 56.1% had a favourable KELIM score. In those patients where BRCA status was available, there was a mutation in 20.7%. 88.5% of patients had an optimal surgical cytoreduction. Bevacizumab was added to chemotherapy in 25% of patients. Median follow-up was 4.98 years. Age, BRCA mutation status and antiangiogenic treatment did not show a statistically significant effect on survival. An unfavourable KELIM score was associated with a non-statistically significant lower estimated median PFS (6.00 vs 7.66 years, p=0.167) and OS (6.37 vs 8.06 years, p=0.126) as compared to a favourable KELIM. <h3>Conclusion and Relevance</h3> Patients with ovarian cancer treated with adjuvant chemotherapy with a calculated KELIM score &lt;1 were more likely to have a lower PFS and lower OS when compared to patients with a KELIM score ≥1. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest