Supplementary Material for: Durable Response to PD-1 Directed Antibodies in Hypermutated Triple Negative Breast Cancer, A Case Report

Recent clinical trials have demonstrated the success of Pembrolizumab (Keytruda ™) in combination with chemotherapy against triple-negative breast cancer. Here, we report the case of a 65-year-old Native American and African American woman with incomplete lines of pretreatment diagnosed with recurrent triple-negative breast cancer (TNBC) and pulmonary metastases. Next-generation sequencing of the metastatic nodules demonstrated a significantly hypermutated tumor with rare polyploidy. The patient had a durable (14 months) and ongoing remission of the metastatic lesions after administering Programmed cell death1 (PD-1) inhibitor Pembrolizumab. No serious immune checkpoint inhibitor-related toxicities or worsening of the infection were observed during the treatment. Our report describes recurrent TNBC with a rare amount of hypermutation and the successful use of an immune-oncologic agent as a treatment.