Prognostic Value of the Modified Endothelial Activation and Stress Index (m-EASIX) for 90-Day Mortality in Patients with Moderate-to-Severe Hypercalcemia of Malignancy

Background: Hypercalcemia of malignancy (HCM) is associated with poor short-term prognosis, particularly when it represents the initial manifestation of an underlying, as yet uncharacterized malignancy. Serum calcium concentration alone may not adequately capture the systemic biological burden associated with advanced disease. Methods: In this retrospective, single-center cohort study, 71 patients with moderate-to-severe hypercalcemia (corrected calcium ≥12 mg/dL) in whom a hematologic or solid malignancy was subsequently diagnosed were evaluated. The modified Endothelial Activation and Stress Index (m-EASIX = LDH × CRP/platelet count) was calculated at presentation. Univariate and multivariable logistic regression, receiver operating characteristic (ROC) analysis and Kaplan–Meier survival analysis were used to evaluate the association between Log2 m-EASIX and 90-day mortality. Results: Log2 m-EASIX remained independently associated with 90-day mortality in multivariable analysis (adjusted OR = 1.96, 95% CI 1.37–2.82, p < 0.001), whereas white blood cell count and albumin did not reach statistical significance in the same model. Corrected serum calcium was not associated with mortality (p = 0.702). Log2 m-EASIX showed good discriminative performance (AUC = 0.857, 95% CI 0.768–0.946) and stratified 90-day survival in both hematologic (p < 0.001) and solid malignancies (p = 0.002), with no significant interaction between m-EASIX and malignancy subgroup (p = 0.499). Conclusions: m-EASIX, calculated from routinely available laboratory parameters, may provide clinically useful prognostic information for early risk stratification in patients presenting with hypercalcemia of malignancy.