Endocrinological evaluation of growth hormone-secreting pituitary macroadenoma invading cavernous sinus treated by aggressive transsphenoidal resection followed by Gamma Knife radiosurgery

Keywords: pituitary adenoma, gamma knife, hormone dysfunction, resection, acromegaly

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     Pituitary tumors involving the cavernous sinus pose difficult challenges, particularly for hormone-secreting tumors.
     The authors would like to determine long-term effect of Gamma Knife radiosurgery (GKS) for the treatment of remnant tumor in the cavernous sinus (CS) after operation using transsphenoidal approach (TSA) of growth hormone (GH)-secreting pituitary macroadenoma.
     There were 13 women and 4 men with a mean age of 41.8 years (range 27-62).
     Seventeen patients who failed to achieve biochemical remission after TSA were followed for a mean period of 70.2 months (range 17-180) after GKS. All patients underwent regular hormonal examination including serum GH, IGF-1, oral glucose tolerance test, and combined pituitary function test (CPFT). Magnetic resonance imaging (MRI) was performed 6 months after GKS and then subsequent one year interval. All patients had remnant tumor only in the CS and received hormone-suppressive medication, sandostatin LAR before or after GKS.
     Ten patients( 58.8%) achieved hormonal remission with a mean time of 47 month (median 40, range 18-129) after GKS and mean radiation dose to tumor margin was 27.9 Gy (range 14-35). Mean tumor volume decreased from 5.2 ml (at pre-GKS MRI) to 3.6 ml (at the last follow-up MRI) (p=0.000). Actuarial rate of hormonal remission at 2, 4, and 6 years were 12.5%, 40%, and 64%, respectively. Intergroup comparison between remission and non-remission group those who had a minimum hormonal follow-up period of 48 months, showed both ‘serum level of GH’ and ‘degree of decreased GH percentile’ at 12 months after GKS showed significant difference (p=0.023), (p=0.014), respectively. A new pituitary hormone deficiency that has significant difference was found only in gonadal axis (p=0.032) based on last follow-up CPFT. A radiation necrosis was detected in 4 patients.
     This was a retrospective series.
     GKS for the remnant tumor only in the CS after maximal resection of sellar and suprasellar portion of GH-secreting pituitary macroadenomais effective, especially for minimizing newly developed post-GKS hypopituitarism.
     However, careful dose planning and long-term follow-up should be necessary in terms of prevention and effective management of radiation-induced complications.


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