Outcomes for patients with metastatic solid malignancies who achieve a complete response on an immune checkpoint inhibitor.

Abstract

82 Background: Use of immune checkpoint inhibitors (ICI) in metastatic solid malignancies can occasionally result in a complete response (CR). There is limited long-term data regarding outcomes for patients who achieve a CR on ICIs. Methods: We screened the Mayo Clinic electronic medical record using an institutional database query program to identify patients whose records contained keywords such as “pembrolizumab” and “complete response” or “no evidence of disease.” Patients were included if they had measurable metastatic solid tumor disease prior to initiation of ICI and if they had a CR defined by two consecutive imaging studies at least twelve weeks apart. Exclusion criteria included oligometastatic disease treated with locoregional therapy or presence of a second confounding malignancy. Results: One-hundred four patients with a CR on pembrolizumab met criteria. Most (71.1%) patients had melanoma and 63/103 (61.2%) received had received the ICI during the first line of metastatic systemic therapy. Additional characteristics are in Table. At a median follow-up of 35.8 months (6.1-87.7), patients had received ICI for a median of 12.1 months (1.5-46.7). The vast majority of patients who stopped ICI did so electively (for reasons other than disease progression). Of 88 elective discontinuations, only 7 patients had disease recurrence after a median follow-up from start of ICI of 40.5 months. Conclusions: Patients with a metastatic solid malignancy who achieve a CR to pembrolizumab appear to maintain remissions off therapy, with low rates of relapse. Further outcomes will be explored, including analyzing and characterizing a sub-group of “hyper-responders” and patients receiving other ICI agents. [Table: see text]