Endocrine Abstracts

JOINT1615

Background: Although gonadotroph tumor regrowth is frequent after pituitary surgery, the systematic use of adjuvant radiotherapy is limited by its long-term complications. In this context, it is important to predict which tumors are most likely to regrow after surgery, and especially, which tumors are most likely to regrow rapidly, and thus which patients might benefit the most from adjuvant radiotherapy vs active surveillance. Clinicopathological characteristics associated with the prognosis of radiotherapy-naïve, recurrent pituitary tumors are currently unknown.

Methods: Here, we performed a longitudinal, observational, retrospective, monocentric cohort study, with the aim of analyzing the clinicopathological characteristics associated with the prognosis of recurrent, radiotherapy-naïve gonadotroph tumors, specifically with the progression-free survival after a second pituitary surgery.

Results: Forty-four patients with recurrent gonadotroph tumors met the inclusion criteria. Ten of these patients had received adjuvant radiotherapy after the second surgery and were excluded from the study cohort. Of note, none of these 10 patients with adjuvant radiotherapy after the second surgery has progressed during the available follow-up (P = 0.009). In addition, we found that the Ki67 index of radiotherapy-naïve, recurrent gonadotroph tumors was the only parameter statistically associated with the progression-free survival after the second surgery, P = 0.02. Specifically, radiotherapy-naïve gonadotroph tumors with a positive Ki67 index had lower progression-free survival after the second surgery (median 31 months) compared to radiotherapy-naïve gonadotroph tumors with a negative Ki67 index (median 75 months).

Conclusion: Our study confirms the good efficacy of adjuvant radiotherapy for gonadotroph tumors. In addition, our study pinpoints that the Ki67 index could be used to guide the management strategy for recurrent gonadotroph tumors that are still radiotherapy-naïve by the time of the second pituitary surgery. Specifically, a positive Ki67 index should tilt the balance towards adjuvant radiotherapy instead of active surveillance.