Purpose: We investigated the association between serum ionized calcium and prognosis of EOC and determined the optimal cutoff value of ionized calcium level to predict the prognosis of EOC.
Methods: The medical records of patients who were newly diagnosed with EOC from 2001 to 2016 were retrieved. Preoperative ionized calcium test was performed within 2 weeks before surgery, and the cutoff of high normocalcemia was defined based on the receiver operating characteristic (ROC) curve for recurrence. Cox proportional hazards regression models were used to identify independent prognostic factors for progression-free survival (PFS).
Results: From 2001 to 2016, 83 patients diagnosed with EOC were identified at a single institution. The optimal cutoff value was set to 4.7 mg/dL (high normocalcemia vs. control group) by plotting the ROC curve for recurrence. Stages III/IV were more frequent in high normocalcemia, with borderline significance (72.9% vs. 52.2%, p = 0.053). Recurrence (67.6% vs. 43.5%, p = 0.029) and death (46.0% vs. 15.2%, p < 0.01) were significantly more frequent in the high normocalcemia group. In multivariate analysis, high normocalcemia (HR 1.9, 95% CI 1.03-3.61, p = 0.04), age (HR 1.04, 95% CI 1.01-1.08, p = 0.02), stage (HR 3.67, 95% CI 1.13-11.92, p = 0.03), residual tumor > 1 cm (HR 3.79, 95% CI 1.61-8.95, p < 0.01), and lymph node metastasis (HR 2.46, 95% CI 1.27-4.78, p < 0.01) were independent risk factors for recurrence.
Conclusion: This study showed positive association between relatively high level of ionized calcium level and recurrence risk of EOC. High normocalcemia showed the potential as a biomarker for prognosis of EOC.
Keywords: Epithelial ovarian cancer; High normocalcemia; Ionized calcium; Predictive biomarker.