Phase II clinical trial assessing the efficacy of enzalutamide in advanced non-resectable granulosa cell ovarian tumors: The GREKO III study (GETHI2016-01).

Background: Granulosa cell ovarian tumors (GCT) are orphan disease with limited treatments. Hormone therapy is a potential treatment, due to the overexpression of hormone receptors in most tumors. This study explores the activity of the antiandrogen, enzalutamide, in metastatic cases.

Methods: We designed a phase II clinical trial under the Spanish Collaborative Group for Transversal Oncology and Rare and Orphan Tumors (GETTHI). Eligible participants were adult women with advanced GCT. Primary endpoint was objective response rate. Secondary endpoints included clinical benefit rate, progression-free survival, overall survival, and safety profile. Patients received enzalutamide 160 mg once daily.

Results: From April 2018 to March 2020, eighteen patients were screened, and sixteen were included across nine institutions. Median age was 56.4 years (range 45-71), and most were Caucasian (14 cases), one Arabian and one Latin. ECOG performance status was zero in 13 cases (81 %) and one in three (19 %). Six patients (38 %) had previously received hormone therapy as adjuvant treatment or for advanced disease, and 15 (94 %) chemotherapy. Median time from metastasis to study entry was 96 months (range 4.5-198). No objective response was observed, but the clinical benefit rate reached 68.8 % (95 % CI [46 %-91.5 %]). Median progression-free survival was 3.8 months (95 % CI [1.36-6.14]). Median overall survival was not reached, with a median follow-up of 6 months (range 2.2-19). At the time of database closure, 14 patients had discontinued treatment, 13 due to disease progression and one by personal choice. Two deaths attributed to disease progression were recorded. Five grade 3 adverse events were reported, with only one (asthenia) deemed related to the therapy.

Conclusions: Although enzalutamide demonstrated modest activity in GCT, durable stabilization was observed in some cases.

Trial Registration: ClinicalTrials.gov Identifier: NCT03464201.