REDUCED BONE-MINERAL DENSITY IN LONG-TERM SURVIVORS OF MEDULLOBLASTOMA

Bone mineral density (BMD) reaches a peak at approximately 30 years of age, and may be influenced by radiotherapy before completion of skeletal maturation. Regional BMD has been measured using dual energy X-Ray absorptiometry (DEXA) in adults following craniospinal irradiation for medulloblastoma between ages 4 and 19 years, receiving doses of 3500-4000 cGy to the brain and spinal cord. Lumbar spine (LS) and femoral neck (FN) BMD measurements were compared with normal age-sex matched control values. There was failure to achieve normal adult BMD at both LS and FN, with a mean reduction at LS of 12.1% +/- 2.4% (p < 0.01) and a mean reduction at FN of 14.3 % +/- 3.4% (p < 0.01). The mean body mass index (BMI) was also less than that of a standard population (21.8 +/- 1.5), as were mean standing and sitting heights. No relationship was found between reduction in BMD at either site and age at irradiation, time elapsed since irradiation or BMI at time of scanning. Biochemical and endocrine markers including corrected calcium, alkaline phosphatase, sex hormones and IGF-1 were normal in all seven patients. The reduction in BMD outside the irradiated area suggests that indirect factors may be important in this effect.