Blood Test Promising as Colorectal Cancer Screen
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Testing blood for three distinct colorectal cancer (CRC) markers showed perfect sensitivity and 90% specificity for detecting malignancy in a preliminary study, researchers said.
The test involves detection of circulating gastrointestinal epithelial cells as well as cell-free DNA analysis for certain cancer-associated genetic mutations and methylation status, and is combined with gender and age to generate an overall risk score, explained Shai Friedland, MD, of Stanford University Medical Center, in an online presentation from the Digestive Disease Week meeting canceled because of COVID-19.
In a prospective study involving 354 patients at the VA Palo Alto medical center presenting for elective colonoscopy - which served as the "gold standard" reference for presence of CRC and advanced adenomas - 11 were found to have CRC and 53 to have advanced adenomas .
All of those with CRC and 40 of the patients with advanced adenomas scored as positive on the multimodal assay, Friedland reported - thus showing sensitivity of 100% for CRC and 75.5% for advanced adenomas.
And among the 79 patients whose colonoscopies were negative for both cancer and adenomas, eight scored as positive on the assay, for sensitivity of 89.9%.
Findings with the multimodal test - developed by a company called CellMax Life, which sponsored the study - compared favorably to published data for currently available stool-based tests, according to Friedland. For example, while the Cologuard DNA test showed specificity virtually identical to the CellMax assay, its sensitivity was 92% for CRC and 42% for advanced adenomas. Specificity for a standard fecal immunochemical test is 96%, but its sensitivities are just 74% and 24% for CRC and advanced adenomas, respectively.
One important caveat is that patients in the study were not necessarily representative of the typical screening population - as a VA sample, participants were overwhelmingly male. Their age distribution and other factors affecting CRC risk were not reported. Enrollment in the Stanford / VA study is continuing, Friedland said.
Still, Friedland suggested that the CellMax test could improve on existing alternatives to colonoscopy to improve screening rates. In his presentation, I noted that colonoscopy and CT colonography, while effective, are "inconvenient and expensive." Both involve awkward and unpleasant bowel cleansing as well. Stool-based tests, meanwhile, have not been as popular with patients as their developers had hoped, as the collection methods are somewhat particular and many people simply don't want to handle fecal matter.
Two years ago, when earlier data on the CellMax Life assay were reported at a meeting, one oncologist interviewed by MedPage Today agreed that "a simple, accurate blood test could help increase screening rates" and thus improve outcomes for what is sometimes described as the most preventable of all cancers.
The CDC has estimated that about one-third of individuals recommended to undergo colonoscopy screening have not done so.
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