Endoscopic Endonasal Approach for Prolactinoma: Outcomes in 56 Patients

Introduction: Prolactinoma is the most common type of hormonally active pituitary adenoma. Medication remains the primary treatment, but many studies on microsurgical outcomes of prolactinomas have been reported; however, reports using the endoscopic endonasal approach (EEA) are rare. We report a large series of prolactinoma patients analyzed by cavernous sinus invasiveness using the Knosp’s criteria.

Methods: We retrospectively reviewed 56 patients who underwent an EEA for prolactin-secreting adenomas from January 2002 to January 2015. Demographic information as well as remission rates and complications were recorded. Immediate remission (n = 54) was defined as prolactin level <20 ng/mL off of medication in the first 14 days following the operation. Long-term remission was defined as prolactin <20 ng/mL at least 2 months after the operation.

Results: Despite a patient population comprised mostly of macroadenomas (83.9%), and with a high prevalence of cavernous sinus invasion (Knosp 3–4, 51.8%), the majority of patients achieved initial endocrinologic remission (36/54; 66.7%). At long term follow up (mean: 3.8 ± 0.5 years), remission was achieved in 24 of 56 (42.9%) patients with EEA alone, whereas in 13 additional patients remission was achieved in combination with medical therapy (37/56, or 66.1%). At initial follow up, lower Knosp scores, and smaller tumors were associated with remissions (the rates of remission in Knosp 0–2, 3, and 4 were 83%, 67%, and 44% respectively). At long-term follow-up, smaller tumors were associated with long-term remission by EEA only. The Knosp scores were not predictive of long-term remission by EEA only in a statistically significant manner, but there was still a trend toward remission with lower scores (rates of remission for Knosp 0–2, 3, and 4 were 73%, 58%, 61% respectively). When evaluating long-term remission of patients undergoing EEA with medical therapy, neither the Knosp scores, nor the original size of the tumor were found to be predictive. The mean preoperative prolactin levels in patients in whom remission was achieved compared with those in whom it was not was significantly lower: 343.3 ± 161.3 ng/mL versus 1442.4 ± 429.9 ng/mL, respectively (p < 0.05). New hormonal deficits occurred in 7 of 56 patients (12.5%). These included panhypopituitarism (n = 4), hypogonadism and hypocortisolism (n = 1), hypocortisolism alone (n = 2). One additional patient developed diabetes insipidus (n = 1).

Conclusion: In conclusion, our results support high rates of remission with EEA, especially in smaller prolactinomas with lower Knosp scores. However, reasonably high remission rates and improved control with medication can be achieved even in large and invasive prolactinomas with relatively low complication rates.