Association of Plasma Vitamin D with Outcomes in Patients with Germ Cell Tumour.

429 Background: Testicular cancer is the most common malignancy among young men. Vitamin D has pluripotent effects on cancer pathogenesis and plays a role in the metastatic cascade. The aim of this study is to analyze plasma vitamin D in association with clinico-pathological findings and prognosis in patients with testicular germ-cell tumours (GCTs). Methods: This study included 120 newly diagnosed and/or relapsed GCTs patients treated from April 2013 to July 2020. Blood samples were drawn at the time before 1st chemotherapy cycle as well as before the 2nd cycle. Plasma vitamin D was measured using ELISA and matched with disease characteristics and correlated with the patient outcome. For survival analysis the cohort was dichotomized to “low” and “high” based on median vitamin D. Results: Mean ± standard error of mean plasma vitamin D in GCTs patients was 15.87±0.68 mg/ml. Patients with brain metastases had significantly lower D vitamin compared to patients without brain metastases (10.9 ± 3.05 vs 15.99 ± 0.7, p=0.034). Vitamin D was not associated with other patient characteristics. Low vitamin D was associated with an unfavorable response compared to favorable responses (11.26 ± 1.84 vs 16.47± 0.74, p=0.016), with disease recurrence (16.19 vs 13.71, p=0.011) and with inferior progression-free survival but not with overall survival (HR= 3.02, 95%CI (1.36-6.71), p=0.014 for PFS and HR= 2.06, 95%CI (0.84 – 5.06), p=0.135 for OS, respectively). Conclusions: Our study suggests a prognostic value of pretreatment vitamin D concentrations in GCTs patients. Low plasma vitamin D was associated with unfavorable response to therapy and disease recurrence. However, it remains to elucidated whether the biology of the disease confirms a causative role of low vitamin D and if its supplementation affects the outcome.