Association Between Serum Magnesium Levels and Outcomes of Atezolizumab in Patients With Metastatic Urothelial Carcinoma.

Abstract

Evidence suggests that serum magnesium levels are associated with outcomes of immune checkpoint inhibitors (ICIs). However, this association remains under-explored in patients with metastatic urothelial carcinoma (UC) treated with ICIs. This prognostic study used individual participant-level data from 1,281 patients with locally advanced or metastatic UC treated with atezolizumab (N=855) or chemotherapy (N=426) who participated in the IMvigor210 and the IMvigor211 trials. Multivariable Cox proportional hazards regression and Fine-Gray subdistribution hazards regression models were used to examine the association of baseline serum magnesium levels with overall survival (OS), progression-free survival (PFS), and immune-related adverse events (irAEs). No evidence of an association was found between baseline serum magnesium levels and PFS or OS in patients treated with atezolizumab [PFS, hazard ratio (HR)=1.03, 95% confidence interval (CI)=0.78-1.35; OS, HR=1.13, 95%CI=0.84-1.51] or chemotherapy (PFS, HR=0.93, 95%CI=0.62-1.40; OS, HR=0.91, 95%CI=0.59-1.40). We also found no evidence of association with irAEs (subdistribution HR=1.29, 95%CI=0.81-2.07) in patients receiving atezolizumab. This study found no evidence of an association between baseline serum magnesium levels and treatment outcomes or irAEs in patients with metastatic UC receiving atezolizumab. Contrary to previous research suggesting a role for magnesium in cancer therapy, these results indicate that serum magnesium levels may not serve as a biomarker to predict outcomes in these patients.