Background:Patients with high-risk smoldering multiple myeloma (HR-SMM) have a 5-year risk of progression to symptomatic multiple myeloma of approximately 75% and a median time to progression of less than 2 years (Lakshman et al., Blood Cancer J 2018) (Rajkumar et al., Blood 2015). We previously reported the primary results of our phase 2 trial of carfilzomib, lenalidomide, and dexamethasone followed by lenalidomide maintenance (KRd-R) as prevention of symptomatic multiple myeloma in patients with HR-SMM (Kazandjian et al., JAMA Onc 2021). Herein, we present follow-up data after all patients have completed lenalidomide maintenance to evaluate the durability of responses off therapy.