Adrenal function testing in pediatric cancer survivors

Abstract

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 >or=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.