Predictors Of Gamma Knife Radiosurgery Outcome In Acromegaly

Lap Tak Poon1, samuel cheong lun leung2, Christopher Yee Fat1, Chung Ping Yu1

1Queen Elizabeth Hospital 2neurosurgery department

Keywords: pituitary adenoma, gamma knife, acromegaly, outcome, radiosurgery

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     Gamma knife radiosurgery is gaining its popularity in treatment of patients with acromegaly after transphenoidal tumor excision. 
     The efficiency of treatment and the predictors for biochemical remission are examined.
     We retrospectively reviewed our gamma knife statistics database from 1997 to 2008.  All patients with acromegaly that had tumor size and hormonal level recorded before and after gamma knife were included.  Forty patients were included in the study. Mean age was 64 (range 19-73). 3 patients died during the study period. Twenty nine patients (72.5%) underwent one radiosurgery session and eleven patients (27.5%) required two radiosurgery sessions.
     Transphenoidal subtotal tumor excisions were performed for all included patients except three patients, whom had high surgical risk. All the gamma knife treatment plans were formulated by one single radiosurgeon. Biochemical remission defined as growth hormone (GH) level less than 5 MIU/L and normal IGF-1 level with reference to age and sex. The mean follow up after radiosurgery was 73.8 months (range 12-132 months). The data are tested by Chi-square test. P<0.05 was regarded to be statistically significant.
       Among patients that underwent one radiosurgery session, good responses in terms of 76-100% reductions in tumor size, GH and IGF-1 levels were observed in 17 patients (61.5%) (P<0.0001), 18 patients (69.2%) (P<0.0001) and 4 patients (16.67%) (P=0.2615) respectively.  Tumors with sizes less than 1 cc and with no evidence of cavernous sinus extension were statistically significantly related to good response in tumor size reduction (P=0.029, P=0.0016).  Subgroup analysis was performed in patients with biochemical remission in GH level including sex, age, target volume, isodose volume, prescribed dose and isodose, pre-radiosurgery GH level and evidence of cavernous sinus extension.  Only male sex is the statistically significant good predictor (P=0.0124) and presence of cavernous sinus extension is the statistically significant poor predictor (P=0.0011) in our study.
     This is a retrospective study.
     Subtotal tumor excision followed by gamma knife radiosurgery is an effective treatment modality for acromegaly. 
     Tumors with sizes less than 1 cc and with no evidence of cavernous sinus extension show good response in treatment. Male sex and absence of cavernous sinus involvement can be regarded to be predictors in biochemical remission.


Project Roles:

L. Poon (), s. leung (), C. Fat (), C. Yu ()