Phase II study of avelumab in multiple relapsed/refractory testicular germ cell cancer.

Abstract

e16045 Background: Testicular germ cell tumors (TGCTs) represent a highly curable disease; however, a small proportion of patients develop disease recurrence. PD-L1 expression is significantly higher in germ cell tumors (GCTs) in comparison to normal testicular tissue and high PD-L1 expression is associated with inferior progression-free and overall survival compared to patients with low PD-L1 expression. This study aimed to determine the efficacy and toxicity of PD-L1 antagonist, Avelumab, in patients with refractory GCTs. Methods: From November 2017 to January 2018, 8 patients with refractory GCTs were enrolled in the phase II study. All patients were pretreated with at least 2 cisplatin-based therapies (median 5, range 2 – 6); 5 tumors (62.5%) were absolutely refractory to cisplatin and 5 patients (62.5%) had visceral non-pulmonary metastases. Avelumab was administered at a dose of 10mg/kg biweekly until progression or unacceptable toxicity. The primary end point was 12-weeks progression-free survival (PFS). If < 8 responses to study therapy will be observed among the first 15 patients, the study will be terminated. Results: Median age was 29 years (range: 22 – 52 years). During a median follow-up period of 2.6 months (range: 0.3 - 14.4), 7 (87.5%) patients experienced disease progression and 6 patients (80.0%) died. Twelve-week PFS was 0%, median PFS was 1.4 months, 95%CI (0.9 – 1.4) and median OS was 2.7 months, 95% CI (1.0 – 3.3). No objective response was observed. Avelumab was well tolerated, no severe adverse event was observed. Conclusions: This study failed to achieve its primary end point and our data suggest lack of Avelumab efficacy in unselected multiple relapsed/refractory TGCTs. Clinical trial information: NCT03403777.