Potential role of hypovitaminosis D in renal cell carcinoma patients treated with immune-checkpoint inhibitors.

50 Background: hypovitaminosis D is frequent in renal diseases but it was never reported in metastatic renal cell carcinoma (mRCC). The interaction between vitamin D and its receptor (VDR) has a key role for T-cell activation. Naïve T-cells do not express VDR and had very low expression of phospholipase C-γ1 (PLC-γ1), with low responsiveness to T-cell receptor (TCR). Initial TCR signaling induces VDR expression and upregulates PLC-γ1 via the kinase p38 pathway. VDR interaction with high concentrations of vitamin D and PLC-γ1 increase are required to trigger classical TCR signaling, increasing T-cell responsiveness. On these basis, we hypothesized that hypovitaminosis D could contribute to lower responsiveness to immune-checkpoint inhibitors (CKI). Methods: we assessed vitamin D levels of mRCC patients undergoing therapy with CKI, with the aim to reveal hypovitaminosis D, evaluate its prevalence and hypothesize its potential role in the outcome of treatment with CKI. Results: of 10 mRCC patients pretreated with tyrosine-kinase inhibitors, vitamin D levels assessed before the first treatment with nivolumab (anti-PD1 CKI) revealed deficiency in 80% of cases (8 patients). Hypovitaminosis D was severe ( < 20 ng/ml) in 7 cases and moderate ( < 30 ng/ml) in one. The 2 patients without deficiency (20%), had vitamin D values near to the lower limit of normality. Oral supplementation with cholecalciferol was given when necessary, likely confounding the possible influence of vitamin D deficiency on the outcome of CKI treatment. Vitamin D normal values after two months of therapy were recovered in the great majority of cases. Interestingly, the only patient who achieved a good objective response to treatment had normal values of vitamin D before therapy. Conclusions: hypovitaminosis D could have a relevant prevalence in mRCC patients. Considering the role of vitamin D in T-cell activation, assessment of its levels and initiation of a supplementation before immunotherapy should be considered to enhance responsiveness. On the basis of these observations, we are planning a perspective multicenter study to investigate the role of hypovitaminosis D in mRCC patients treated with CKI (PRoviDenCe study).