Dual immune checkpoint inhibition with nivolumab and ipilimumab (N+I) in patients with advanced anaplastic thyroid carcinoma (ATC).

e18075 Background: There are no standard of care therapies in advanced incurable setting for BRAF wild type (WT) ATC, 4/5 (80%) in 2 nd line after either mixed response or progressive disease (PD) on D+T. Best overall response (BOR) in N+I+D+T group was partial response (PR, 1/5, 20%) ORR 20%. 14/19 (74%) pts received N+I, 12/14 (86%) as 1 st line palliative therapy. 5 pts in N+I group (all with DM) received local therapies concurrently (1: debulking thyroid surgery, 3: radiation therapy (RT) to thyroid, PR (3, 21.4%); SD (4, 28.6%); ORR 50%. Excluding 5 pts with concurrent local therapies, ORR was 33.3% (1/9 CR, 2/9 PR).PD-L1 TPS was available for 12/19 pts (4: N+I+D+T, 8: N+I) and ≥1 in all tumors (range, 1-100). In 8 pts in N+I group, ORR stratified by PD-L1 TPS: TPS <50 (range, 1-30): 0% (0/2: 1 SD, 1 PD), & TPS ≥50 (range, 80-100): 83.3% (5/6: 3 CR, 2 PR, 1 PD). Any grade irAEs were observed in 16/19 (84.2%) pts. ≥Grade 3 irAEs occurred in 11/19 (57.9%) pts, most frequent were colitis (5, 26.3%), dermatitis/pruritus (3, 15.8%), myocarditis (2, 10.5%), & adrenal insufficiency (2, 10.5%). There were no treatment-related deaths. Conclusions: In this largest real-world cohort study of pts with advanced ATC, N+I therapy showed high ORR of 50% (congruent with DFCI trial), albeit with high rates of iRAEs. High ORR was seen with PD-L1 TPS ≥50. Survival outcomes and genomic biomarkers, currently under investigation, will be presented at the meeting. N+I merit further investigation in an ATC focused clinical trial.