Continuous Glucose Monitoring: A Valuable Monitoring Tool for Management of Hypoglycemia During Chemotherapy for Acute Lymphoblastic Leukemia

Background: Acute lymphoblastic leukemia (ALL) maintenance therapy (MT) has been occasionally associated with symptomatic hypoglycemia (SH), attributed to purine analog (mercaptopurine [6-MP]). This hypoglycemia has been hypothesized to affect substrate utilization of gluconeogenic precursor alanine in the liver. Case Report: An overweight 5-year-old boy with ALL was evaluated for SH (lethargy and vomiting) that occurred 8-10 h after fasting while receiving daily 6-MP. Hypoglycemic episodes (> 20 episodes per month) occurred predominantly around midmorning but not during the 5-day dexamethasone pulse. The adrenocorticotropic hormone test yielded a normal cortisol response, which ruled out pituitary adrenal suppression. A 12-h overnight fasting glucose was 49 mg/dL, with suppressed insulin response < 2 IU/mL, low C-peptide of 0.5 ng/mL, high insulin-like growth factor-binding protein > 160 ng/mL, high free fatty acid of 2.64 mmol/L, and negative glucagon stimulation test (change in blood glucose [BG] < 5 mg/dL). These results ruled out hyperinsulinism. The patient was placed on cornstarch therapy 5 h prior to dosing with 6-MP. This treatment reduced the SH events to fewer than two episodes per month. To study the efficacy of cornstarch, the patient was fitted with the iPro (TM) professional continuous glucose monitoring system (CGMS) (Medtronic MiniMed, Northridge, CA) with a preset low alarm at 70 mg/dL, which was worn for a period of 5 days while the patient was on cornstarch. With 1,000 sensor reading the BG range was 65-158 mg/dL, and the percentage mean absolute difference between sensor and finger-stick BG readings (the parent monitored his BG four times a day) was 9.4%. There were no hypoglycemic episodes detected by the CGMS while the patient was on cornstarch. After the cessation of chemotherapy, a 15-h fasting study was performed, and the CGMS was placed. Results showed resolution of hypoglycemia. Conclusions: The CGMS helped us devise an effective management plan for our patient. CGMS proved useful as an adjunct to characterize the pattern of hypoglycemia and to validate the benefit of cornstarch in hypoglycemia associated with 6-MP treatment of ALL.