Evaluating growth hormone deficiency (GHD) when it occurs as a late effect of radiotherapy in childhood cancer survivors is an opportunity to provide these patients with appropriate therapy, and the controversy about the benefit-to-risk ratio of these treatments “highlights the importance of appropriate patient selection and accuracy of testing for GHD,” according to a study published in the Journal of Clinical Endocrinology & Metabolism.
There is limited data and guidance available for selecting laboratory testing modalities for diagnosing GHD that occurs as a late effect of radiotherapy in childhood cancer survivors. An Endocrine Society taskforce was charged with developing guidance on the management of hypothalamic/pituitary (HP) and growth disorders in childhood cancer survivors and conducted a literature review to evaluate screening for GHD. Specifically, the evaluation was of studies using insulin-like growth factor (IGF)-I and/or IGFBP-3 measurements compared with GH dynamic testing and GHD diagnoses using various GH dynamic tests.
A total of 15 studies (IGF-I [n=8] and IGFBP-3 [n=7]) was included, with a total cohort of 477 patients. Researchers found that overall, both IGF-I and IGFBP-3 had suboptimal diagnostic accuracy but had a strong correlation, although using both tests simultaneously did not add to the diagnostic accuracy of either test used alone. Even though there was high variability in the testing protocols, dynamic tests were the most accurate for appropriately identifying patients with GHD. The insulin tolerance test (ITT) was the most accepted reference test when used alone or in combination with arginine but the performance of growth hormone-releasing hormone and/or arginine stimulation were similar to ITT. GHRH with arginine stimulation had 88% specificity and 66% sensitivity when compared with ITT. The data was insufficient to determine the accuracy of serial GH testing.
“The diagnostic accuracy of various dynamic tests for growth hormone deficiency in childhood cancer survivors appears to follow the same patterns as in other patients,” wrote the investigators.
Sfeir JG, Kittah NE, Tamhane SU, et al. Diagnosis of growth hormone deficiency as a late effect of radiotherapy in survivors of childhood cancers [published online June 29, 2018]. J Clin Endocrinol Metab. doi:10.1210/jc.2018-01204