Abstract B044: Assessing the impact of ethnicity on performance of an Extracellular Vesicle and Particle based blood test and CA125 in women with no ovarian cancer from UKCTOCS – an exploratory subgroup analysis

Abstract Introduction: Non-white women with ovarian cancer (OC) are less likely to present with elevated CA125 levels at diagnosis when compared to white women potentially leading to delays in treatment and limiting the development and generalizability of screening protocols. Extracellular vesicle and particle (EVP) based blood tests incorporating multiple cancer associated biomarkers may be less susceptible to variability in race and ethnicity. The United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) was a randomized controlled trial where over 200,000 postmenopausal women were randomly assigned to three arms. Here, we report on the specificity of an EVP-based OC Test and CA125 as a function of ethnicity in serum samples from postmenopausal women who did not develop OC in UKCTOCS. Methods: We previously evaluated the EVP-based Test and CA125 in a blinded case-control study nested within the no screening (NS) and annual ultrasound screening (USS) arms of UKCTOCS. Women who developed invasive epithelial OC within 36 months following sample donation were matched 1:10 by age at collection (+/-2 years) to women who had no OC detected either before or within the trial, median 16 year follow up (controls). The EVP-based Test was run using a previously locked method and classifier algorithm utilizing three independent biomarker combinations tested in duplicate. A commercially available CA125 immunoassay was run with a previously established cutoff. At recruitment, women provided demographic information including ethnicity. In this analysis, test signals in controls were compared based on demographic annotation. Results: The sample comprised of 1167 controls, 41 with non-white (Black, Asian, other) ethnicity and 1126 white. Non-white (Black, Asian, other) ethnicity compared to white was associated with a significant decrease in CA125 signal (-1.921 U/mL, p = 0.018 Two-sample T-Test) and a non-significant increase in EVP-based test signal (+0.0139 U, p = 0.528 Two-sample T-Test). In samples from non-white control women, specificity between the EVP-based test and CA125 was similar (98% vs 98%, p = 0.3432) while in white women, a higher specificity was observed in the EVP-based test compared to CA125 (98% vs 96%, p = 0.001). Conclusion: In serum samples from non-white postmenopausal women, CA125 levels were marginally lower and test specificity was higher than samples from white women. An EVP-based blood test exhibited no difference mean test signal or specificity between white and non-white women. These preliminary results suggest the EVP-based blood test may be a more generalized modality for population screening for ovarian cancer. Citation Format: Brendan Manning, Sanchari Banerjee, Troy B. Hawkins, Michael M. Smith, Sophia Apostolidou, Aleksandra Gentry-Maharaj, Toumy M. Guettouche, Usha Menon, Dawn R. Mattoon. Assessing the impact of ethnicity on performance of an Extracellular Vesicle and Particle based blood test and CA125 in women with no ovarian cancer from UKCTOCS – an exploratory subgroup analysis [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr B044.