Endocrine Abstracts

Background: Childhood cancer survivors (CCS) are at high risk of 25-hydroxivitamin D (25(OH)D) inadequacy and the lack of a consensual definition has hampered its epidemiological study. Despite international recommendations, bone health and vitamin D inadequacy (VDI) are still quite undervalued, even in a high-risk population as CCS, due to disease treatment, physical limitations and insufficient solar exposure.

Objectives: Our aims were to determine the prevalence of plasma 25(OH)D inadequacy in CCS in a tertiary pediatric center and to identify potential risk and protective factors for VDI.

Material and Methods: A retrospective cross-sectional cohort study was performed in Portuguese survivors under the age of eighteen diagnosed, followed and treated for cancer from January 1, 2016 to April 30, 2021. 25(OH)D status was defined according to Munns et al Global Consensus: deficiency (<12 ng/mL) and insufficiency (12-20 ng/mL). Bivariate analysis was carried out to study the impact of age at diagnosis, pubertal stage, cancer type and treatment exposures.

Results: Of the 219 CCS recruited, 94 (43%) had at least one routine 25(OH)D blood screening, with median age 7.71 years, interquartile range: 10; 55% males. Of these, 25(OH)D inadequacy was highly prevalent (58.5%) among cancer survivors: 8 (14.5%) deficiency and 47 (85,5%) insufficiency; only 39 (70.9%) of them underwent supplementation. Median of 25(OH)D levels was 17.0 ng/mL (IQR: 7.0; minimum: 4.0). The most frequent oncologic diagnoses included lymphoproliferative disorders (39%), brain tumors (41%; 13% gliomas), solid non-brain tumors (15%) and Langerhans cell histiocytosis (4%). Thirty percent of survivors had at least one sequel, being hemiparesis (5%) the most prevalent one; 13% had metastatic disease. There was a positive and statistically significant correlation between plasma 25(OH)D level and age at diagnosis (P < 0,001; δ: 0.484). Concerning pubertal stage, cancer type and treatment exposures, no statistically significant associations were found.

Conclusion: The prevalence of 25(OH)D inadequacy was even higher than expected in this population, considering international literature and country latitude. This reinforces the necessity to value bone health by diagnosing VDI, ensuring therapeutic supplementation and monitoring in risky populations.