Abstract 2301: CA125 levels as a proxy for residual disease in a diverse cohort of epithelial ovarian cancer patients: results from the Kaiser Permanente Research on Ovarian Cancer Survival (KPROCS) study
Authors: Lindsay Jane Collin, Farzin Khosrow-Khavar, Valerie S. Lee, Juraj Kavecansky, Christine Garcia, Scarlett L. Gomez, Jennifer A. Doherty, Lawrence H. Kushi, Elisa V. Bandera
Journal: Cancer Research (2025)

Background: Ovarian cancer has a poor 50% five-year survival rate. The presence of residual disease at the time of surgery is a key prognostic indicator; however, it is often not available or challenging to obtain. Cancer antigen (CA)125 is a well-established biomarker for monitoring ovarian cancer progression, but its utility as a biomarker to identify women with residual disease after surgery have not been evaluated. Methods: We included 1218 epithelial ovarian cancer patients from the Kaiser Permanente Research on Ovarian Cancer Survival (KPROCS) cohort who had both information on residual disease from surgical notes (i.e., gold standard) and CA125 measurements within 6 months of surgery. Residual disease from surgical notes was determined using natural language processing to classify as optimal (&amp;lt;1cm) or suboptimal debulking (≥1cm). For each patient, we obtained the lowest CA125 value during the period starting 2 weeks after surgery and up to 6 months post-surgery (if they did not have chemotherapy) or up to the date of the first chemotherapy cycle. CA125 values were then dichotomized (&amp;gt;100 vs ≤100 ug/mL) to evaluate utility in identifying presence or absence of residual disease by estimating sensitivity and specificity, as well as positive and negative predictive values (PPV and NPV, respectively), with corresponding 95% confidence intervals (CIs). We evaluated differences by race and ethnicity and time since surgery (≥30 days vs &amp;lt;30 days). Results: In this validation study of 1218 epithelial ovarian cancer patients, 229 (19%) were Asian American/Pacific Islander, 66 (5.4%) were non-Hispanic Black, 171 (14%) were Hispanic, 738 (61%) were non-Hispanic white, and 14 (1.0%) were of other racial and ethnic groups. The average time since surgery to the lowest CA125 value was 33 days (interquartile range 25, 46 days). According to the surgical notes, 5% were classified as having suboptimal debulking status, whereas 80% were classified as having CA125 &amp;gt;100 ug/mL, which corresponded to sensitivity of 70%, specificity of 82%, PPV of 17%, and NPV of 98%. The sensitivity and specificity were 78% and 87% among Asian American/Pacific Islander individuals, 43% and 95% among non-Hispanic Black individuals, 63% and 83% among Hispanic individuals, and 77% and 79% among non-Hispanic White individuals. Finally, the sensitivity and specificity were 72% and 50% for those who had their lowest CA125 value &amp;lt;30 days after surgery and 56% and 72% for ≥30 days after surgery. Conclusions: In our initial results, we demonstrate that elevated CA125 serves as a modest proxy to identify residual disease, with some variation by race and ethnicity and time since surgery. Future work will seek to explore CA125 cut points and variation by patient characteristics to optimize performance. Citation Format: Lindsay Jane Collin, Farzin Khosrow-Khavar, Valerie S. Lee, Juraj Kavecansky, Christine Garcia, Scarlett L. Gomez, Jennifer A. Doherty, Lawrence H. Kushi, Elisa V. Bandera. CA125 levels as a proxy for residual disease in a diverse cohort of epithelial ovarian cancer patients: results from the Kaiser Permanente Research on Ovarian Cancer Survival (KPROCS) study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2301.