Hyperenhancement of Pituitary Neuroendocrine Tumors on Preoperative MRI: Implications on Tumor Characteristics and Outcomes

Introduction: Pituitary neuroendocrine tumors (PitNETs) are typically hypoenhancing and rarely display hyperenhancement on MRI. The frequency and significance of this hyperenhancement has not been studied.

Methods: A retrospective review was performed on patients undergoing transsphenoidal surgery for PitNETs at a single high-volume pituitary center from 2012 to 2019. Tumor hyperenhancement upon contrast administration was defined by neuroradiologist impression of preoperative brain MRIs with contrast. Preoperative covariates collected included patient age, sex, number of prior pituitary surgeries, endocrine symptoms at presentation (if any), tumor size (defined as maximal tumor dimension and by micro/macroadenoma status), cavernous sinus invasion, and tumor functional versus nonfunctional status. Postoperative variables included tumor Ki-67 rating, extent of resection, incidence of postoperative diabetes insipidus (DI), and need for adjuvant radiation therapy. Correlation with hyperenhancement was assessed with Pearson’s chi-squared, Fisher’s exact test, and Wilcoxon’s rank-sum tests, where appropriate. All dichotomous and numeric variables with p < 0.1 were included in a multiple regression analysis to assess for confounding.

Results: A total of 836 patients were identified with PitNETs who underwent transsphenoidal resection in the defined timeframe. A total of 71 tumors (8.5%) demonstrated contrast hyperenhancement on preoperative MRI. Hyperenhancing tumors were smaller (maximal dimension 1.87 vs. 2.12 cm, p = 0.047) and more commonly microadenomas (28 vs. 18%, p = 0.042) than PitNETs exhibiting conventional hypoenhancement. Patients with hyperenhancing tumors more commonly presented with hypothyroidism (4.2 vs. 1.0%, p = 0.016), and less commonly with acromegaly (0 vs. 9.8%, p = 0.016). On multiple regression analysis, hyperenhancing tumors were more commonly associated with postoperative DI (odds ratio: 1.65, 95% confidence interval: 1.00–2.61, p = 0.039). On univariate and multiple regression, all other tumor characteristics and outcomes including tumor functional status, Ki-67 rating, extent of resection and need for adjuvant radiotherapy were not altered by tumor hyperenhancement ([Fig. 1]).

Conclusions: 8.5% of PitNETs exhibit hyperenhancement on preoperative contrasted imaging studies. While hyperenhancing PitNETs tend to be smaller, they carry 65% increased odds of postoperative diabetes insipidus after surgical resection. Patients with hyperenhancing tumors may be counseled on the increased odds of postoperative DI when surgical planning is discussed.

Fig. 1 Incidence of postoperative diabetes insipidus after PitNET resection, stratified by PitNET hyperenhancement.

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Artikel online veröffentlicht:
05. Februar 2024