Bone Health in Children and Adolescents Undergoing Hematopoietic Cell Transplantation in a Singapore Center

We retrospectively reviewed 103 pediatric patients transplanted between 2001-2010 to evaluate the prevalence of low bone mineral density (BMD). Areal BMD of the lumbar spine and whole body were determined by dual energy X-ray absorptiometry (DXA) imaging. Z-scores calculated were standardized by age and gender based on a reference population. BMD was defined as normal if Z-score > -1.0; borderline low if -2.0 < Z-score ≤ -1.0; low if Z-score ≤ -2.0; and osteoporosis if Z-score ≤ -2.0 with a history of fracture. Spine Z-scores were used in analysis. Only 45 of the 103 patients had any BMD records. Of these, 18 had serial BMD evaluations. The median age at time of hematopoietic cell transplant (HCT) was 10.2 (range, 0.1-16.8) years. Forty-three patients had allogeneic (4 had 2 HCT) while 2 had autologous HCT. Majority (N = 30) received non-radiation based preparative regimen; the commonest indication being a hematologic malignancy (N = 33). Majority (N = 33) had graft versus host disease; 27 of whom required systemic steroids. Of the patients who had pre HCT BMD, 45% (5 of 11) already had abnormal Z-scores. Trending of BMD was possible in 17 of the 45 patients who had more than one BMD. Recovery from a nadir Z-score was noted in 40% (7 of 17) of these patients at the time of analysis. Of the patients who had post HCT BMD, 23% (9 of 39) and 28% (11 of 39) had borderline low and low Z-scores, respectively. One of these 20 patients (5%) had clinically significant fractures fulfilling the WHO criteria for osteoporosis. Musculoskeletal pains were reported by 29% (13 of 45) of patients but an abnormal Z-score was noted in only 60% (8 of 13). Endocrinopathies including sex hormones and thyroid function deficiencies was noted in 13% (6 of 45) of patients. The 3 patients with hypogonadism also had abnormal BMD and required hormonal replacement. One of these 3 patients received an oral bisphosphonates. Majority had calcium/ vitamin D supplements and about half (19 of 45) had physiotherapy to optimize bone health. Despite the limitations known of BMD as a surrogate marker of bone health in children/ adolescents, the prevalence of compromised bone health determined by DXA correlated with symptoms in our cohort demonstrated the value of this objective measure. There is need to systematize BMD evaluations to optimize the opportunities of restoring bone mineral loss during the growing years of pediatric HCT recipients.