Diagnosis of GH deficiency as a late effect of radiotherapy in survivors of childhood cancers

Background: Limited guidance exists for selecting a laboratory method for diagnosing GH deficiency (GHD) when it occurs as a late effect of radiotherapy in childhood cancer survivors (CCSs). Methods: We searched Medline, Embase, Cochrane Central Register of Controlled Trials and Database of Systematic Reviews, and Scopus for studies evaluating GHD that used IGF-1 or IGF-binding protein 3 (IGFBP-3) measurements compared with GH dynamic testing. Results: We included 15 studies [IGF-1 (8 studies) and IGFBP-3 (7 studies)] enrolling 477 patients. Comparator tests varied widely. Overall, both IGF-1 and IGFBP-3 had suboptimal diagnostic accuracy but were strongly correlated. The use of both tests simultaneously in the same cohort did not improve the diagnostic accuracy. Despite high variability in the testing protocols, dynamic tests remained the most accurate for appropriately identifying patients with GHD. The insulin tolerance test (ITT) appears to be the most accepted reference test when used alone or in combination with arginine; however, standardized testing strategies among practice groups are absent. GHRH and arginine stimulation performed almost similarly to the ITT; however, in one study GHRH with arginine stimulation had 66% sensitivity and 88% specificity compared with the ITT. Insufficient data were available to assess the accuracy of serial GH testing (nocturnal or over 24 hours). Conclusion: The diagnostic accuracy of various dynamic tests for GHD in CCSs appears to follow the same patterns as those in non-CCSs. Interpreting GHRH stimulation is a challenge given the primarily hypothalamic dysfunction in CCSs. IGF-1 and IGFBP-3 perform poorly in this population.