We studied 12 patients with pituitary macroadenomas (9 patients with NFA and 3 with GHA) who were evaluated before transsphenoidal surgery and 4 months after. Before and shortly after neurosurgery all GHA patients had biochemical evidence of growth hormone hypersecretion, but they were not treated with somatostatin analogues, pegvisomant or dopamine-agonists. This group included 9 men and 3 women with a median age of 46 (range 25 – 68 years). As determined by MRI, tumour volume decreased by 58% (median) from 4.85 (1.4-13.9) cm3 to 2.6 (0-12.2) cm3 postoperatively (P < 0.01). Using TYR-PET, metabolic tumour volume decreased by 62% from 5.05 (1.1-8.0) to 2.05 (0-6.6) cm3 (P < 0.02). Figure 1 demonstrates TYR-PET imaging results pre- (A) and postoperatively (B) in a representative NFA patient. The tumour volume as determined by TYR-PET was not significantly different from its volume by MRI, both pre- or postoperatively (combined-data set, n = 24, P> 0.30). The relationship between MRI tumour volume and TYR-PET tumour volume also did not differ either between the pre- and postoperative situation. In the combined data-set, these measures of tumour volume were positively correlated ( r = 0.58, P < 0.01). PSR was 35.3 (28.4-63.8) mmol/ml/min pre-operatively, and remained unchanged after transsphenoidal surgery (33.4 (0-62.4) mmol/ml/min, P > 0.30; median change –3.3%).

To determine the effect of radiation therapy on pituitary TYR-PET characteristics, we studied 6 patients before and approximately 3 years after this treatment. This group comprised 4 patients with NFA and 2 patients with GHA, who also participated in the neurosurgical intervention protocol. In these patients the pituitary tumour was not completely removed by surgery or active acromegaly had persisted after this treatment. Fractionated radiation therapy was applied with 1.8 Gray daily dose to a total of 45 Gray in 5 weeks, using a three to five field technique, and was given 6 months after transsphenoidal surgery. This group included 5 men and 1 women with a median age of 48 (range 37- 60) years. In these patients, tumour volume by MRI was very similar before (1.95 (1-4.9) cm3) and after radiation therapy 1.95 (1-4.9) cm3, P = 1.0; median change 0%). In contrast, TYR-PET tumour volume decreased by 58% from 2.05 (1-3.7) to 1.0 (0-1.9) cm3 (P = 0.02) (Figure 2), whereas PSR decreased in 5 patients (total group: 67% change from 33.4 (2.6-40.8) to 13.2 (0-46.2) mmol/ml/min, P=0.12) (Figure 3).

Figure 1 (click to view)
Figure 2 (click to view)	Figure 3 (click to view)