PET-guided repeat transsphenoidal surgery for previously deemed unresectable lateral disease in acromegaly.
OBJECTIVE
The object of this study was to determine if revision transsphenoidal surgery (TSS), guided by 11C-methionine PET/CT coregistered with volumetric MRI (Met-PET/MRCR), can lead to remission in patients with persistent acromegaly due to a postoperative lateral disease remnant.


METHODS
The authors identified 9 patients with persistent acromegaly following primary intervention (TSS ± medical therapy ± radiotherapy) in whom further surgery had initially been discounted because of equivocal MRI findings with suspected lateral sellar and/or parasellar disease (cases with clear Knosp grade 4 disease were excluded). All patients underwent Met-PET/MRCR. Scan findings were used by the pituitary multidisciplinary team to inform decision-making regarding repeat surgery. Revision TSS was performed with wide lateral exploration as guided by the PET findings. Endocrine reassessment was performed at 6-10 weeks after surgery, with longitudinal follow-up thereafter.


RESULTS
Met-PET/MRCR revealed focal tracer uptake in the lateral sellar and/or parasellar region(s) in all 9 patients, which correlated with sites of suspected residual tumor on volumetric MRI. At surgery, tumor was identified and resected in 5 patients, although histological analysis confirmed somatotroph tumor in only 4 cases. In the other 4 patients, no definite tumor was seen, but equivocal tissue was removed. Despite the uncertainty at surgery, all patients showed immediate significant improvements in clinical and biochemical parameters. In the 8 patients for whom long-term follow-up data were available, insulin-like growth factor 1 (IGF-1) was ≤ 1.2 times the upper limit of normal (ULN) in all subjects and ≤ 1 times the ULN in 6 subjects, and these findings have been maintained for up to 28 months (median 8 months, mean 13 months) with no requirement for adjunctive medical therapy or radiotherapy. No patient suffered any additional pituitary deficit or other complication of surgery.


CONCLUSIONS
This study provides proof of concept that Met-PET/MRCR can be helpful in the evaluation of residual lateral sellar/parasellar disease in persistent acromegaly and facilitate targeted revision TSS in a subgroup of patients.
['Bashari|Waiel A|WA|', 'Senanayake|Russell|R|', 'Koulouri|Olympia|O|', 'Gillett|Daniel|D|', 'MacFarlane|James|J|', 'Powlson|Andrew S|AS|', 'Fernandez-Pombo|Antia|A|', 'Bano|Gul|G|', 'Martin|Andrew J|AJ|', 'Scoffings|Daniel|D|', 'Cheow|Heok|H|', 'Mendichovszky|Iosif|I|', 'Tysome|James|J|', 'Donnelly|Neil|N|', 'Santarius|Thomas|T|', 'Kolias|Angelos|A|', 'Mannion|Richard|R|', 'Gurnell|Mark|M|']
D000172:Acromegaly D000328:Adult D000368:Aged D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D000072078:Positron Emission Tomography Computed Tomography D000075082:Proof of Concept Study D012086:Reoperation D013100:Sphenoid Bone
acromegaly Met-PET/MRCR DA = dopamine agonist FSPGR = fast spoiled gradient-recalled echo GH = growth hormone IGF-1 = insulin-like growth factor 1 MDT = multidisciplinary team Met-PET = PET using 11C-methionine Met-PET/MRCR = Met-PET coregistered with volumetric MRI PA = pituitary adenoma RT = radiotherapy SSA = somatostatin analog TSS = transsphenoidal surgery ULN = upper limit of normal extended TSS lateral parasellar