Bone Mineral Density in Childhood Survivors of Acute Lymphoblastic Leukaemia Treated without Cranial Irradiation

Adult survivors of childhood Acute Lymphoblastic Leukemia (ALL) whose treatment included cranial irradiation (XRT) have reduced bone mineral density (BMD). Fifty three survivors of ALL (aged 6-17 yr, 22 male), who had completed their treatment without XRT, at least one year previously, and 187 (5-19 yr, 86 male) healthy controls were examined with dual energy x-ray absorptiometry of the total body (TB) and L1 to L4 vertebrae (LS) and peripheral quantitative computer tomography (pQCT) at the distal and mid-radial site. The TB and LS BMD did not differ between the ALL survivors and controls. Distal radial trabecular BMD (difference -0.080 mg/cm(3); 95% confidence interval (CI) -0.139 to -0.020; P = 0.009) but not total BMD (difference -0.006 mg/cm(3); CI -0.051 to 0.039; P = 0.80) was lower in ALL survivors compared with controls. At the mid-radial site both endosteal (11% larger; P = 0.0001) and periosteal (4% larger; P = 0.001) circumferences were greater and cortical thickness thinner by 6% (P = 0.006) in the ALL subjects leading to an increase in the axial moment of inertia in the ALL subjects (difference 13%; P = 0.008). In conclusion BMD except at the radius is normal in childhood survivors of ALL treated without XRT. At the mid-radial site, we speculate that ALL or its treatment resulted in endosteal bone loss, cortical bone thinning but the axial moment of inertia and hence strength was maintained, as a result of bone gain at the periosteal surface.