Association of Serum Calcium Levels with Renal Impairment and All-Cause Death in Chinese Patients with Newly Diagnosed Multiple Myeloma: A Cross-Sectional, Longitudinal Study
Abstract Background: A number of studies have shown that serum calcium has a crucial role in many types of cancers. However, few studies have determined the association between serum calcium levels and renal impairment (RI) and all-cause death in Chinese patients with multiple myeloma (MM).Methods: Two hundred forty-six of 566 participants who were followed for > 6 months from a MM cohort at our institution between January 2011 and June 2017 were eligible for the retrospective study. A generalized additive model and smooth curve fitting were conducted to investigated the cross-sectional relationship between serum calcium level and RI and eGFR at baseline;Multivariate-adjusted Cox regression models were fitted to assess associations between baseline serum calcium levels and onset of end-stage renal disease(ESRD) or death in patients with MM followed for > 6 months.Results: Using the IMWG criteria,162 of 566 patients (28.6%) with newly diagnosed MM presented with RI . The mean duration of follow-up was 26.64 months. Twenty-one patients (8.54%) died and 28 patients(11.52%)had ESRD.The serum calcium level was independently associated with the occurrence of MM-related RI. There was a non-linear relationship between the serum calcium level and the presence of RI in patients with MM in the cross-sectional analysis of the baseline data. Cox regression analysis showed that baseline serum calcium levels were consistently associated with a higher risk of all-cause death after adjustment for various clinical and laboratory factors, but were not associated with the occurrence of ESRD. When patients were categorized into 2 groups according to baseline mean serum calcium level, deaths occurred in 13 patients (15.1%) with mean serum calcium level > 2.44 mmol/L compared to 8 patients (5.0%) with mean serum calcium level < 2.44 mmol/L (p < 0.05); Eighteen patients (11.46%) with a mean serum calcium level < 2.44 mmol/L progressed to ESRD compared to 13 patients (11.6%) with a serum calcium level > 2.44 mmol/L (p > 0.05).Conclusions: This observational study showed that there was a non-linear relationship between the serum calcium level and the occurrence of RI. An elevated baseline calcium level can predict all-cause death in patients with MM, but cannot predict the occurrence of ESRD, suggesting that the serum calcium level may serve as a useful clinical biomarker for the survival rate of patients with MM followed for > 6 months. Additional data from larger prospective longitudinal studies are required to validate our findings.