Bone mineral density and nutrition in long-term survivors of childhood brain tumors

Background and aims Childhood cancer survivors are at risk of unwanted late effects. The primary aim of this study was to assess bone mineral density Z-scores (BMDz) in long-term survivors of childhood medulloblastoma (MB) or central nervous system supratentorial primitive neuroectodermal tumor (CNS-PNET). Secondary aims were to describe nutrient intake, vitamin D status, physical activity and explore potential risk factors for decreased BMDz. Methods All MB and CNS-PNET survivors treated at Oslo University Hospital from 1974 to 2013 were invited to participate in a cross-sectional study. Dual-energy x-ray absorptiometry (Lunar Prodigy) assessed BMDz lumbar spine, BMDz total body, and lean body mass. Decreased BMDz was defined as a combination of low BMDz −1 to −1.99 and very low BMDz ≤−2. Lean body mass index (LMI) was calculated by dividing lean body mass by the squared height. Nutrient intake was assessed by a 3-day food record. Serum 25(OH)D was analyzed. Physical activity was reported by a questionnaire. Descriptive statistics and multivariable Cox regression analyses were applied. Results Fifty survivors with a median age of 25.5 years (5.5–51.9) and a median follow-up time of 19.5 years (3.2–40.5) were included. Mean BMDz lumbar spine was −0.8 (SD 1.1, 95% CI: −1.1 to −0.4), and BMDz total body was −0.6 (SD 1.1, 95% CI: −0.9 to −0.3). Decreased BMDz was detected in 48% of the lumbar spine and 34% of the total body measurements. In all, 62% had low calcium, and 69% had low vitamin D intake. 26% of participants had serum 25(OH)D < 50 nmol/L, and 62% reported an inactive lifestyle. Male sex, higher age at diagnosis, and lower LMI were potential risk factors for decreased BMDz. Conclusions Long-term survivors of childhood MB and CNS-PNET had decreased BMDz, and risk factors were male sex, higher age at diagnosis, and lower LMI. Inadequate calcium and vitamin D intake, an inactive lifestyle, and a high prevalence of 25(OH)D ≤ 50 nmol/L were detected.