Hyperenhancement of pituitary neuroendocrine tumors (PitNETs) on preoperative MRI: implications on tumor characteristics and outcomes.

PURPOSE: Pituitary neuroendocrine tumors (PitNETs), also known as pituitary adenomas, are typically hypoenhancing and rarely display hyperenhancement on post-contrast T1-weighted MRI. The frequency and significance of this hyperenhancement has not been studied.

METHODS

We conducted a retrospective review on PitNET transsphenoidal surgeries performed at a high-volume pituitary center from 2012 to 2019. Tumor hyperenhancement was defined by neuroradiologist impression of preoperative brain MRIs with contrast. Preoperative covariates included patient age, sex, number of prior pituitary surgeries, endocrine symptoms, tumor size, cavernous sinus invasion, and tumor functional vs nonfunctional status. Postoperative variables included tumor Ki-67 rating, extent of resection, incidence of postoperative transient and permanent diabetes insipidus (DI), and need for adjuvant radiation therapy. Correlation with hyperenhancement was assessed with Pearson's chi-squared, Fisher's exact, and Wilcoxon rank-sum tests, where appropriate. Dichotomous and numeric variables with p < 0.1 were included in a multiple regression analysis to assess confounding.

RESULTS

836 patients were identified with PitNETs who underwent transsphenoidal resection. Among these, 14 tumors (1.67 %) demonstrated contrast hyperenhancement on preoperative MRI. Hyperenhancing tumors were more commonly microadenomas (43 % vs 19 %, p = 0.034). On multiple regression analysis, hyperenhancing tumors were more commonly associated with postoperative transient DI (odds ratio 2.80, 95 % confidence interval 1.09-6.36, p = 0.019). On univariate and multiple regression, all other tumor characteristics and outcomes were unaltered by hyperenhancement.

CONCLUSION

Hyperenhancing PitNETs are a rare finding on preoperative post-contrast T1-weighted MRI imaging (1.67 % prevalence) and carry 2.8 × higher odds of postoperative transient diabetes insipidus after surgical resection (OR 2.80, 95 % CI 1.09-6.36, p = 0.019). Surgical teams may consider additional approaches to preserving the pituitary stalk and postoperative monitoring for dysnatremia to minimize postoperative risk of diabetes insipidus.