Osteopenia in survivors of Wilms tumor.

Diminished bone mass (osteopenia) is recognized increasingly as a consequence of therapy in survivors of cancer in childhood. It has been reported in two small series of survivors of Wilms tumor. The objectives of this study were to explore, in a larger sample of such subjects, the prevalence of osteopenia and a possible relationship between osteopenia of the lumbar spine and abdominal irradiation. All survivors of Wilms tumor (n=49) in a single institution were considered eligible for study. Thirty-one agreed to participate; the non-participants were not notably different in their demographic characteristics and diseases/treatment experience. Information was obtained about prior treatment, and usual diet, sun exposure and physical activity. Bone mineral content was measured by dual energy X-ray absorptiometry, and biochemical markers of bone turnover, calciotropic hormones and minerals were assessed in a single blood sample. By Z-scores of whole body bone mineral content, 8 subjects were osteopenic. This was unrelated to milk intake or sun exposure and was not more common in the lumbar spine of those who had been irradiated (15/31 subjects). Physical activity correlated positively with bone mineral density Z-scores (p<0.005). Normal bone formation was reflected in normal blood levels of osteocalcin. C-telopeptide levels, reflecting bone resorption, were high but approximately correlated inversely with maturity. Low serum magnesium and parathyroid hormone levels were detected in a minority of subjects. Osteopenia is present in a large minority (27%) of survivors of Wilms tumor, and an imbalance of bone turnover (with excessive resorption) may be common. Irradiation does not appear to play a causal role. It is possible that a subtle renal tubular defect exists in these individuals; a prospect worthy of further exploration.