Expansion and shrinkage of central nervous system tumor coinciding with human growth hormone therapy: case report

The influence of human growth hormone (hGH) therapy on the recurrence rates of childhood central nervous system tumors is controversial. Because growth hormone has the ability to increase cell proliferation, it is recommended that hGH therapy wait until central nervous system lesions are inactive and antitumor therapy complete, usually 1 to 2 years.

We report the enlargement and decrease in size of a hypothalamic pilocytic astrocytoma in a 12-year-old boy after two trials of hGH. Partial resection and radiation of the tumor were performed at 3 years of age, with no change noted over the next 9 years. His height was less than the 5th centile with midparental height at the 90th to 95th centiles. Growth velocity was 3.3 cm/yr. Bone age was normal and there were no signs of puberty. There was no GH response to clonidine and L-dopa testing.

Volume measurements were performed on gadolinium enhanced tumor images. Growth rate increased to 11.7 cm and the tumor volume increased 230% over the 12 months of hGH therapy. Significant tumor shrinkage (42%) and growth deceleration occurred within the 3 month interval of stopping hGH. Tumor volume again increased (134%) and decreased (22%) after restarting and then stopping hGH. No evidence of tumor necrosis or alteration in ventricular size was found. The patient was asymptomatic.

These observations indicate that tumor size change is associated with the metabolic response to hGH therapy. It is unclear whether the volume increase represents altered blood-brain or selective blood-tumor barrier permeability, growth factor receptors, and/or tumor cell growth.