Preoperative diagnosis of prolactinomas is critical because dopamine agonists have been regarded as a primary treatment. However, serum prolactin level alone is suboptimal for differentiating prolactinomas from hyperprolactinemia-causing non-functioning pituitary adenomas (NFPAs). By using the tumor size, we investigated a more effective parameter for the discrimination.
223 patients with pituitary lesions of the histologic diagnosis were retrospectively reviewed. The prolactinoma group (n=48) showed higher serum prolactin (258.6㎍/L) and smaller maximal diameter (16.6mm) than those in the NFPA group (n=175) (44.4㎍/L and 23.9mm; both p-values < 0.001).
Using receiver operating curve analyses, we compared diagnostic performances of serum prolactin levels (PRL), a ratio of PRL to maximal tumor diameter (PRL/MD; PDR1), and MD squared (PRL/(MD)2; PDR2) in preoperative diagnosis of prolactinomas. PDR2 exhibited better performance with the cutoff value of 0.83[㎍/L]/ mm2 (area under the curve [AUC] = 0.945), compared to the PDR1 (8.93[㎍/L]/ mm with AUC 0.938) and PRL (99.㎍/L with AUC 0.910). In the external validation study, PDR2 still maintained superiority over PDR1 and PRL (Accuracy of 94.8%, 91.8%, and 75.8%, respectively).
In conclusion, PDR2 may be an effective parameter for preoperative discrimination of prolactinomas from NFPAs with hyperprolactinemia, and contribute to select patients who benefit from medical treatment primarily.