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GH Replacement Safe

After Cranial Irradiation

E-Newsletter No. 75

     Hormone deficiencies caused by damage to sensitive centers in the hypothalamus and pituitary frequently occur following cranial radiotherapy for such diseases as childhood leukemia. Growth hormone (GH) deficiency is the most common post-irradiation hormone problem, affecting up to two-thirds of patients within the first few years of treatment.  

     It can impede children’s growth and interfere with their general quality of life, normal body composition maintenance, and cardiovascular health. GH replacement therapy (GHRT) may correct these problems and improve these patients’ psychological well-being, but its long-term safety is controversial. Cranial irradiation itself increases secondary tumor incidence, and the potential mitogenic activity of GH and its target hormone, insulin-like growth factor-I (IGF-I), raises fears that GHRT could compound this risk. The limited literature that exists on GHRT’s effects on tumor risk is reassuring, but a recent analysis from the Childhood Cancer Survivor Study (CCSS) found a 2-fold increase in secondary brain tumors among patients receiving GHRT.To investigate this apparent contradiction,

     Georg Brabant, M.D., Ph.D., at the Christie Manchester Academic Health Science Centre in Manchester, U.K., and his co-workers evaluated GHRT’s impact on tumor recurrence and secondary tumor incidence. They used imaging data from two groups of 110 patients—one receiving long-term GHRT and the other untreated—matched by age, sex, and radiation dose and fractionation. Median follow-up was 14.5 years. The team found no significant differences in the number of tumor recurrences (6 vs. 8, GHRT vs. control group) or secondary tumors (5 vs. 3). 

     Writing in The Journal of Clinical Endocrinology & Metabolism,* the researchers state: “Growth hormone replacement in patients with a history of cranial irradiation does not appear to be associated with increased risk of recurrent or secondary neoplasms.”

* Mackenzie S, Craven T, Gattamaneni R, Swindell R, Shalet SM, Brabant G.
Long term safety of growth hormone replacement following CNS irradiation.
J Clin Endocrinol Metab,
in press.

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