Open AccessDetection of Microsatellite Instability via Circulating Tumor DNA and Response to Immunotherapy in Metastatic Castration-Resistant Prostate Cancer: A Case Series
Author(s) -
Ravindranathan Deepak,
Russler Greta Anne,
Yantorni Lauren,
Drusbosky Leylah M.,
Bilen Mehmet Asim
Publication year - 2021
Publication title -
case reports in oncology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.365
H-Index - 19
ISSN - 1662-6575
DOI - 10.1159/000512819
Subject(s) - case report
Pembrolizumab has been approved by the US Food and Drug Administration for the treatment of metastatic or unresectable solid tumors that are microsatellite instability-high (MSI-H) or mismatch repair deficient. Blood-based circulating tumor DNA (ctDNA) assays have been validated to identify tumors with MSI-H status without the need for tissue biopsy. We report 2 patients with metastatic castration-resistant prostate cancer (mCRPC) who had prior treatment with multiple lines of therapy and underwent ctDNA testing, which detected MSI-H status. Both patients were treated with pembrolizumab, resulting in an excellent clinical response measured with liquid biopsies before and after initiation of therapy, which demonstrated a significant reduction in somatic-variant allele frequency in addition to a decrease in prostate serum antigen levels.