Experimental blood test detects early-stage cancers using circulating tumour DNA: study

Findings from a proof-of-concept study published Wednesday in Science Translational Medicine demonstrated the feasibility of using targeted error correction sequencing (TEC-Seq) to detect circulating cell-free DNA from many early-stage tumours. "There is a lot of excitement about liquid biopsies, but most of that has been in late-stage cancer or in individuals where you already know what to look for," explained study leader Victor Velculescu, but "the surprising result [from the new technique] is that we can find a high fraction of early-stage patients having alterations in their blood." 

In the study, researchers used TEC-Seq to examine 58 cancer-related genes encompassing 81 kb. The authors said analysis of plasma from 44 healthy individuals showed genomic changes related to clonal haematopoiesis in 16 percent of asymptomatic individuals, versus no alterations in solid tumour-related driver genes. The investigators then analysed plasma samples from 200 patients with colorectal, breast, lung, or ovarian cancer, uncovering somatic mutations in 71 percent, 59 percent, 59 percent and 68 percent, respectively, of patients with stage I or II disease. 

Further analyses revealed "high concordance" between mutations in plasma and alterations in the patients' tumours, the authors reported. Meanwhile, among patients with resectable colorectal cancer, the study found that higher pre-operative circulating tumour DNA levels were linked to disease recurrence and diminished overall survival. 

Commenting on the news, American Cancer Society deputy chief medical officer Len Lichtenfeld described the study as "important research [that] moves us one step further down the path to developing a blood test that might find cancer earlier." Lichtenfeld added "we still need to improve the sensitivity, but this is a step forward." 

Earlier this month, results from a study published in the NEJM indicated that analysis of circulating cell-free Epstein-Barr virus DNA may help screen for early nasopharyngeal carcinoma in asymptomatic people. In addition, findings from another recent study showed that Grail's experimental high-intensity 508-gene circulating-tumour DNA assay could be used to detect a broad range of tumour signals in blood.

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