Adrenal function testing in pediatric cancer survivors

Background Central adrenal insufficiency is observed after cranial radiation therapy for cancer. Screening at risk patients is recommended, but the best screening strategy is unknown. Methods A retrospective review of pediatric cancer survivors who underwent hypothalamic/pituitary/adrenal axis testing was conducted. Data included: cancer diagnosis, radiotherapy dose, other endocrinopathies, and adrenal function testing. Adrenal testing included sequential low‐dose corticotropin test (LDCT) and standard‐dose corticotropin test (SDCT). 8 a.m. serum cortisol levels were compared to LDCT results. LDCT results were compared by radiotheroapy dose and according to the presence of endocrine comorbidities. Results Seventy‐eight subjects (56% male, mean age at diagnosis 6.5 years) underwent testing. 67.9% had been treated with radiotherapy to the hypothalamus/pituitary. Mean time to diagnosis of adrenal insufficiency was 6.8 years after cancer diagnosis. Adequate adrenal function was found in 65% of patients by LDCT and 89% by SDCT. Only 21% of patients had basal serum cortisols collected at 8 a.m. Agreement between 8 a.m. baseline cortisol and LDCT was fair. Agreement between random baseline cortisol and LDCT was poor. Prevalence of central adrenal insufficiency diagnosed by LDCT increased with radiotherapy dose (8% for 10–19.9 Gy; 83% for ≥40 Gy) and the number of endocrine comorbidities. Conclusions In pediatric cancer survivors, central adrenal insufficiency was common even in patients receiving <40 Gy to the hypothalamus/pituitary. We recommend use of LDCT, not 8 a.m. serum cortisol to screen patients who received >30 Gy of radiotherapy and those with other central endocrinopathies. Pediatr Blood Cancer 2009; 53:1302–1307. © 2009 Wiley‐Liss, Inc.