801P Neoadjuvant checkpoint inhibitor immunotherapy (IMT) for resectable mucosal melanoma (MM)

Abstract

Neoadjuvant checkpoint inhibition (CPI) has recently demonstrated impressive outcomes in patients (pts) with stage 3 cutaneous melanoma. However, the safety, efficacy, and outcome of neoadjuvant CPI in pts with mucosal melanoma (MM) are not well studied as MM is a rare melanoma subtype. CPI such as combination nivolumab and ipilimumab achieves response rates of 37-43% in unresectable or metastatic MM but there is limited data regarding the efficacy of these agents in the preoperative setting. We hypothesize that neoadjuvant CPI is a safe and feasible approach for pts with resectable MM. Under an institutionally approved research protocol, we identified adult MM pts with resectable disease who received neoadjuvant anti-PD1 +/- anti-CTLA4 between 2015 to 2019 at our institution. Clinical information include age, gender, presence of nodal involvement or satellitosis, functional status, pre-treatment LDH, tumor mutation status, and treatment data was collected. Outcomes include event free survival (EFS), overall survival (OS), objective response rate (ORR), pathologic response rate (PRR), and grade ≥3 toxicities were assessed. We identified 36 pts. Median age was 62; 58% were female. 78% of pts got anti-PD1 + anti-CTLA4. Node-positive disease or satellite lesions was present in 47% of pts. Primary sites of disease were anorectal (53%), urogenital (25%), head and neck (17%), and esophageal (6%). A minority of pts did not undergo surgery due to complete response (n=3, 8%) and disease progression (n=6, 17%), respectively. With a median follow up of 37.9 months, the median EFS was 9.2mo with 3-year EFS rate of 29%. Median OS had not been reached and 3-year OS rate was 55%. ORR was 47% and PRR was 35%. EFS was significantly higher for pts with objective response and for pts with pathologic response. OS was significantly higher for pts with pathologic response. Grade 3 toxicities were reported in 39% of pts. Neoadjuvant CPI for resectable MM is a feasible approach with signs of efficacy and an acceptable safety profile. As there is currently no standard approach for resectable MM, this study supports further investigations using neoadjuvant therapy for these pts.