The Limited Screening Value of Insulin-Like Growth Factor-I in 610 Very Long Term Adult Survivors of Leukemia and Other Types of Childhood Cancer

Over the last decades childhood cancer survival rates have improved significantly. Currently, 70–80% of patients become long term cancer survivors. It has been estimated that 1 out of 640 young adults in the U.S. is a survivor of childhood cancer. Consequently, the incidence of late, treatment-related complications is increasing. Endocrine sequelae, such as the metabolic syndrome, osteopenia, sub fertility, thyroid dysfunction and growth hormone deficiency represent an important category of such late effects. Growth hormone deficiency (GHD) in childhood cancer survivors, mainly caused by cranial radiotherapy, is reflected by low levels of insulin like growth factor 1 (IGF-I). Whereas the value of IGF-I measurement for the diagnosis of GHD is controversial, low IGF-I levels are associated with high body mass index and high visceral fat percentage. However the clinical relevance of low IGF-I levels in long term childhood cancer survivors is not extensively studied. In this study we evaluated whether IGF-I is useful as a marker for altered body composition and growth hormone deficiency in this group.

We retrospectively analyzed data of 610 adult childhood cancer survivors, retrieved from the Rotterdam late effects clinic, which starts 5 years after cessation of therapy. Median age at diagnosis was 6 years (interquartile range (IQR) 3–11) and follow up time was 18 years (13–24). We assessed IGF-I Z-scores, anthropometrical measures, growth hormone stimulation tests in patients with clinical suspicion of GHD and measures of body composition (assessed by dual X-ray absorptiometry, Lunar Prodigy).

Cranial irradiated acute leukaemia survivors (25 Gy (24–25)) and locally irradiated brain tumour survivors (42 Gy (35–54)) had significantly lower IGF-I Z-scores (p<0.001), lower height SDS (p<0.001), higher body mass index (p=0.01), higher waist-hip ratio (p=0.001), higher visceral fat percentage (p<0.001), higher total fat percentage (p<0.001) and lower lean body mass (p<0.001), compared to non cranial irradiated survivors. IGF-I did not show a strong correlation with BMI (r=-0.12, p=0.04), waist hip ratio (r=-0.15, p=0.01), total fat percentage (r=-0.14, p=0.02) and lean body mass (r=0.15, p=0.01). In the patients with low IGF-I levels who had growth hormone stimulation, IGF-I Z-scores did not significantly differ between the patients with and without severe GHD (p = 0.39).

This study shows that there is a limited value of IGF-I as marker for alterations in body composition, and confirms the fact that low IGF-I levels are not predictive for GHD, in a large cohort of childhood cancer survivors. Therefore the use of IGF-I should not be encouraged in adult childhood cancer survivors.

No relevant conflicts of interest to declare.