Identifying high-risk relapse in early-stage I to II ovarian cancer using the CA125 ELIMination rate constant K (KELIM) score: a Gynecologic Cancer InterGroup individual patient-data meta-analysis
Despite curative surgery and adjuvant chemotherapy, a significant number of early stage I to II ovarian cancers relapse. The CA125 ELIMination rate constant K (KELIM) is a pragmatic indicator of tumor intrinsic chemosensitivity in advanced epithelial ovarian cancer. We assessed the prognostic value of KELIM in patients with early-stage ovarian cancer, with respect to 5-year recurrence-free survival and overall survival, using the Meta-Analysis in Ovarian Cancer, which is the Gynecologic Cancer InterGroup individual patient-data meta-analysis of randomized trials evaluating different adjuvant chemotherapy regimens. Individual patient KELIM values were previously estimated in 5884 patients from the Meta-Analysis in Ovarian Cancer. The prognostic value of KELIM was assessed using univariable & multivariable analyses in patients with resected International Federation of Gynecology and Obstetrics stage I and II disease. Overall, 1143 patients were identified, including clear cell (46.7%); serous (23.7%); endometrioid (12.4%); and mucinous carcinomas (3.9%). In multivariable analyses, a favorable KELIM score (≥1.0) was associated with higher 5-year recurrence-free survival (68.3% vs 55.9%; HR 0.61, 95% CI 0.48 to 0.77) and 5-year overall survival (80.7% vs 72.8%; HR 0.50, 95% CI 0.36 to 0.68), as was the histological sub-type. In exploratory analyses, KELIM score was a prognostic factor regarding 5-year recurrence-free survival and overall survival across all sub-types (especially clear cell carcinoma and serous, with HR ranging from 0.45 to 0.63) with baseline CA125 ≥15 IU/L, except for mucinous histology. The pragmatic KELIM score is an independent prognostic factor in patients with a non-mucinous stage I to II ovarian cancer optimally resected and treated with adjuvant chemotherapy. KELIM may help identify the patients at higher risk of relapse and death requiring closer follow-up or treatment intensification.