10-Year Experience Using Low-Field Intraoperative MRI in Adenoma Surgery

Aims: The two significant advances in pituitary surgery during the past 20 years have been endonasal endoscopic techniques and intraoperative magnetic resonance imaging (iMRI).

At our institution, iMRI has been routinely used for transsphenoidal (tp) tumor surgery over a decade in microsurgical or endoscopically assisted approaches.

The aim of this retrospective study is to evaluate the effect of intraoperative low-field MRI in a possibly large (n > 200) group of patients with a reasonably long follow-up.

Methods: Patients' data from the Swiss Pituitary Database (SwissPit) were retrospectively screened for the following inclusion criteria: tp surgery, performed at our institution between 2006 and 2016, pituitary adenoma, complete pre- and postoperative radiological, endocrinological, and ophthalmological workup. Residual tumor, need for reoperation, drug or radiotherapy, complications, hormone dependency, biochemical and radiological remission rates, and improvement in vision were assessed. The study was conducted with approval of the local ethical committee.

Results: A total of 231 patients undergoing tp resections of pituitary adenomas at our institution during the past 10 years fulfilled criteria for inclusion. The median age was 56.5 years and 55% of the patients were male. Histological assessments showed nonfunctioning adenoma as the most common type (69%), followed by prolactinomas (12%) and growth hormone secreting adenomas (12%), and Cushing adenomas (4%). The surgeon intended a gross total resection (GTR) in 136 (59.1%) patients and debulking in the remaining 94 cases. Intended GTR was achieved in 102 (75%) patients and in 16 (17%) patients initially scheduled for debulking, resulting in an overall GTR rate of 51%. In 8/17 initially incomplete resections, GTR was achieved by additional iMRI-based resection. Median follow-up time since surgery was 51 months (interquartile range 18–79 months) and 17 (4%) showed regrowth or recurrence at follow-up. Twenty-three (10%) patients underwent adjuvant radiotherapy. Twelve (44%) acromegalic patients and 20 (69%) patients suffering from prolactinoma needed drug therapy at follow-up. Outcome was favorable with a Glasgow Outcome Scale of 5 in 211 (92%) patients.

Conclusions: Our single institution experience in a comparably large group of patients with reasonably long follow-up times confirms tp resection with iMRI to be an effective and safe treatment option for pituitary adenoma.