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Karl D. Lewis, MD


Could ctDNA Prove to Be a Biomarker in Merkel Cell Carcinoma?

By: Joshua Swore
Posted: Thursday, July 7, 2022

A proof-of-concept study, published as a research letter in the Journal of the American Academy of Dermatology, has shown that circulating tumor DNA (ctDNA) may be useful in detecting Merkel cell carcinoma along with monitoring response and resistance to treatments. The study capitalizes on whole-exome sequencing of tumorous and matched tissue to measure levels of ctDNA. This technique may fill a void in the ability to detect Merckel cell carcinoma.

“Despite the recent approval of immune checkpoint inhibitors (ICIs), Merkel cell carcinoma remains highly lethal for most patients failing out of ICIs. Existing biomarkers (tumor mutation burden, programmed death ligand-1 expression, Merkel cell polyomavirus status) have not been particularly useful in Merkel cell carcinoma management,” said Ling Gao, MD, PhD, of the University of California, San Diego.

A total of 195 blood samples from 30 patients diagnosed with Merkel cell carcinoma were the focus of the study. The authors used these whole-blood samples for whole-exome sequencing and were able to identify 16 tumor-specific single-nucleotide variants. The variants were then compared with plasma ctDNA with ultradeep sequencing.

A total of 15 patients had successful responses to treatment, and their ctDNA levels were undetectable. The authors highlighted one patient with low levels of ctDNA following radiation treatment who experienced disease progression within 3 months. This disease progression resulted in an increase in ctDNA levels by greater than 18,000-fold. Furthermore, all patients with a high tumor burden and increased metastatic disease also had high ctDNA levels. These results led the authors to suggest that ctDNA could be a sufficient indicator of relapse and disease progression and may serve to guide treatment decisions for patients with Merkel cell carcinoma.

Disclosure: For full disclosures of the study authors, visit

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