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

BACKGROUND: More 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: A total of 246 of 565 participants who were followed for > 6 months from a MM cohort at our institution were eligible for the retrospective study. A generalized additive model and smooth curve fitting were performed to investigate the cross-sectional relationship between the serum calcium level and RI at baseline. Multivariate-adjusted Cox regression models were fitted to assess the associations between baseline serum calcium levels and the onset of end-stage renal disease (ESRD) or death in patients with MM. RESULTS: A total of 172 of 565 patients (30.4%) 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. In patients with a serum calcium level > 2.30 mmol/L, the serum calcium level was independently associated with the occurrence of MM-related RI. Cox regression analysis showed that baseline serum calcium levels were consistently associated with a higher risk of all-cause death in the fully adjusted model, but were not associated with the occurrence of ESRD. When patients were categorized into two groups according to baseline mean serum calcium level, deaths occurred in 13 patients (15.1%) with a mean serum calcium level > 2.44 mmol/L compared to eight patients (5.0%) with a 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 nonlinear relationship between the serum calcium level and the presence of RI in patients with MM. An elevated baseline calcium level predicted all-cause death, but did not predict the occurrence of ESRD in patients with MM followed for > 6 months.