The evaluation of bone health in childhood solid tumor and lymphoma survivors

Introduction: Long-term survival in childhood cancer survivors is gradually increasing as the treatments' success improves. Bone health is one of the areas that need long term follow-up. There are many studies on vitamin D insufficiency, low bone mineral density (BMD), and increased fracture rates in childhood cancer survivors. However, research on solely solid tumor and lymphoma cases involving both vitamin D status and BMD are relatively few. Aim: This study aims to investigate bone health status in solid tumor and lymphoma cases. To investigate bone health of solid tumor and lymphoma survivors involved in Istanbul Medical Faculty, Pediatric Hematology and Oncology, mainly vitamin D levels and BMD measurements were evaluated. Material and Methods: A total of 70 cases that were diagnosed with solid tumors and lymphoma before the age of 18 and whose treatment was completed in Istanbul University, Istanbul Medical Faculty, Pediatric Hematology and Oncology Clinic, also who accepted to participate in the study and didn't have an additional disease that would affect bone health were included in the study. Patient information forms about the duration of sun exposure, sun protection measures, bone fracture history, and physical activity habits were filled with patients and families. Information about the disease course and the details of treatments were obtained from the medical files. The anthropometric measurements, calcium, phosphorus, magnesium, alkaline phosphatase, parathormone, 25(OH)D levels and BMD values obtained by the dual energy X-ray absorptiometry (DXA) were evaluated. Also, the anthropometric measurements, biochemical data, and 25(OH)D values of 70 control cases under the age of 18, without a known disease or medication use, were recorded retrospectively. Results: Cases involved in the study consisted of 40% lymphoma and 60% of solid tumors. The average age of diagnosis was 6,6, age at study time was 11,4, and time from diagnosis was 4,9 years. Vitamin D insufficiency (25(OH)D ≤20) was seen in 45,7% of the cases and similarly in 47,1% of the control group (p=0,927). The Z-scores were corrected volumetrically. Low Z-score (≤ -1) was seen in 30% and very low Z-score (≤ -2) was seen in 2,9% of the cases. The average volumetric Z-score was normal with a value of -0,3. Girls' vitamin D levels were lower (p=0,060) and the prevalence of girls in the vitamin D deficient group was 2 times higher (p=0,011). In contrast to the common belief, the reason for these findings was unrelated to girls going out less or preferring conservative clothing due to sociocultural influences (p=0,378). It was found that the Z-scores improved as the time from diagnosis increased, especially from the third year on (p=0,020). In addition, as an observation, the average age at diagnosis was 8,5 years and higher in the low Z-score case group (p=0,081). The prevalence of low Z-score was higher in the lymphoma group compared to the solid tumor group (p=0,055) but the vitamin D insufficiency frequencies were similar (p=0,557). Conclusion: Vitamin D insufficiency was found to be similar in childhood lymphoma and solid tumor survivors and healthy population, but the fact that 70% of the cases had a history of vitamin D use is remarkable. There was no significant defect in BMD values, however in patients diagnosed after the age of 8, a BMD measurement might be valuable in the first 3 to 5 years after diagnosis.