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Editor,—The paper by Arikoski and colleagues1 provides useful information on bone mineral density (BMD) in survivors of childhood acute lymphoblastic leukaemia (ALL), and the results are consistent with other reports.2 3 However, we are disappointed in the heterogeneity of the cohort of other malignancies and the major differences in each patient’s treatment, as potentially the disease type and the nature of the cancer therapy may have an effect on BMD.
A significant proportion of the other malignancy cohort had radiation directly to or near the spine; the latter may have affected spinal BMD directly, giving a false impression of reduced BMD for the whole cohort. If these patients are removed from the total cohort studied, what impact does this have on the mean BMD?
In the five patients who had received cranial/auricular radiotherapy, what was their growth hormone status? It is not clear from the methods if this was formally assessed.
It is likely that the reduction in BMD in survivors of ALL and even other malignancies is multifactorial, and hence it is only by studying groups of patients treated in a homogenous fashion that it will be possible to tease out the causative factors and hence try to prevent this happening in the future.
Dr Arikoski and colleagues comment:
Long term studies have shown reduced bone mineral density (BMD) and bone mass in survivors of childhood acute lymphoblastic leukaemia (ALL),1-1 1-2 which might predispose these patients to osteoporosis and diminished resistance to fractures later in life. In our study, we measured BMD at completion of chemotherapy for a childhood malignancy. Because of the heterogeneity of the diagnoses, we analysed the patients in two groups, those with ALL and those with other malignancies. Our finding was that lumbar BMD was reduced only in patients with ALL whereas femoral BMD was reduced in both groups (fig 3).
We understand the concern of Dr Brennan and Professor Shalet that the effect of spinal radiation might give a false impression of reduced spinal BMD for the whole cohort of other malignancies. However, our study showed that lumbar BMD was not reduced in the group of other malignancies, part of whom had received spinal radiation (fig 3). Lumbar BMD was reduced in only those with ALL, and none of the patients with ALL had received radiation in or close to the spinal region (table 1).
The growth hormone status was not analysed formally in our study. We agree entirely with the opinion that the causes of reduced BMD in children with malignancies are multifactorial including treatments with glucocorticosteroids and methotrexate, decreased physical activity, malnutrition, radiotherapy, and growth hormone deficiency.