Targeted next-generation sequencing of circulating free DNA enables non-invasive tumor detection in myxoid liposarcomas

PIK3CA mutations were found in 33% of MLS samples. Besides the well-known hotspot mutations in exon 9 (c.1624G > A, c.1633G > A, c.1633G > C, c1634A > G) and exon 20 (c.3140A > G) we identified less commonly annotated mutations in exon 5 (c.1035 T > A) and exon 8 (c. 1345C > A). [...]tracking of breakpoint fragments in cfDNA promises detection of the primary tumor and all its potential metastases. The two PIK3CA mutations (c.1624G > A and c.3140A > G) were additionally quantified by droplet digital PCR. ctDNA levels decreased after tumor resection and increased when metastatic disease was detected. Quantification of ctDNA on the basis of cancer genomic profiling could help to predict tumor recurrence, and monitor tumor heterogeneity and treatment response in metastatic disease with minimal invasiveness and at affordable cost.