PTH and vitamin D deficiency: This study is the first to investigate an effect of higher PTH on EFS/OS in childhood malignancies, independent of vitamin D. While it is often postulated that vitamin D deficiency increases the risk of cancer development and for inferior outcome (1), studies on effects of PTH are sparse despite its stimulatory effect via PTH1R not only on excessive bone resorption but also other cell types (via PTH1R and PTH2R).