Long-Term Outcomes with Use of Intraoperative MRI for Transsphenoidal Resection of Pituitary Adenomas

The use of intraoperative MRI (iMRI) has grown rapidly over the past decade as a method for ensuring maximal resection of intracranial tumors. While iMRI is now widely accepted as a method to increase extent of resection in brain malignancies, its utility in benign conditions, and in particular in pituitary adenomas, is poorly defined, especially since the advent of neuroendoscopy for sellar lesions. Given its benefit in intracranial resection, iMRI may offer a way to enhance pituitary adenoma resection while preserving endocrine function. Here, we report long-term outcomes of all pituitary adenomas resected using iMRI by a single neurosurgeon from 2008 to 2017 with postoperative (PO) follow-up (FU). A total of 212 pituitary adenomas were resected, with 130 using the microscope, 75 using the endoscope, and seven using both. The mean patient age at surgery was 51.0 (range: 16.1–83.0). Average length of surgery was 196.3 minutes, with an average length of stay of 3.6 days. Patients typically were followed at 3, 6, and 12-month increments, with an average clinical and radiographic FU time of 33.3 months. Of the 212 adenomas treated, 34% were secretory (GH: 40%, ACTH: 28%, prolactin: 32%). A total of 31 out of 212 patients had undergone prior surgery (15%). Baseline tumor characteristics between microscopic and endoscopic cases were well matched. Of the 212 tumors treated, 128 (60%) underwent further resection based on iMRI results, increasing the gross-total resection (GTR) rate from 46 to 73% in tumors without cavernous sinus involvement, and from 32% to 69% in all tumors treated endoscopically. Approximately 15% of tumors demonstrated progression, with a mean time to progression of 40.3 months (range: 2.6–108.8 months). Hormone cure (HC) was achieved in 46/72 secretory tumors (64%), with a higher rate of cure in tumors treated with the endoscope (85%) compared with microscope (55%) (p = 0.01). Of the patients who achieved HC, 24% had recurrence of hormone secretion, with a mean time to recurrence of 36.6 months (range: 2.0–99.0 months). Of the 64 patients who had a preoperative hormone deficit (HD), 45% had improvement of one or more HD following surgery; this was significantly higher in the endoscopic group (66%) compared with the microscopic group (32%) (p = 0.01). New anterior pituitary HD was seen in 6% of cases, while permanent DI was seen in 3% of cases. Serious complications requiring further intervention were rare, seen in 3% of cases, including 3 patients with PO CSF leak. Taken together, these results suggest that use of iMRI significantly increases the rate of GTR, resulting in durable tumor control and HC with a low complication rate. Specifically, when paired with endoscopic technique, this series demonstrates a remarkably high secretory cure rate without a rise in rate of endocrinopathy, as well as improvement of preoperative HD in a majority of cases. While iMRI may not be feasible in all cases, it offers the ability to tailor more aggressive removal of tumors while preserving pituitary hormone function. Further studies are needed to understand which tumors maximally benefit from use of iMRI.

No conflict of interest has been declared by the author(s).