Clinical implications and predictive value of the creatinine-cystatin C ratio in patients with multiple myeloma and renal impairment

The creatinine (Cr)-cystatin C ratio (CCR) at the time of cancer diagnosis is associated with survival; however, to the best of our knowledge, the association between this ratio and mortality in patients with multiple myeloma and renal impairment (RI) is unclear. Therefore, the present study aimed to assess this association, as well as disease prognosis and the clinical significance of the CCR in patients with multiple myeloma and RI. The present retrospective study included 191 patients diagnosed with multiple myeloma and RI between 2012 and 2022. The predictive value of the CCR was evaluated using area under the receiver operating characteristic curve (AUC) values. The factors affecting overall survival (OS) were assessed using uni- and multivariate logistic regression analyses. The effect of the CCR on survival was evaluated using a Cox regression model and the Kaplan-Meier method. There was a significant association between low CCR and poor progression-free survival (PFS) and overall survival (OS). The 1-, 2- and 3-year PFS and OS rates in patients with a low CCR were significantly lower than those in patients with a high CCR. The 1-, 2- and 3-year AUC values of the CCR were 0.712, 0.764 and 0.746 respectively. Multivariate analysis revealed sex, age, Cr levels, CCR and C-reactive protein levels as independent prognostic factors affecting OS rates. The CCR is a potential prognostic indicator in patients with multiple myeloma with RI and is associated with clinical stages.