Blood test shows promise for early detection of colorectal adenomas
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A noninvasive multimodal blood test demonstrated high sensitivity and specificity for the detection of colorectal advanced neoplasia, according to prospective study results presented at Gastrointestinal Cancers Symposium.
These findings suggest the blood test, FirstSight (CellMax Life), can be used to stratify individuals for screening or for post-polypectomy surveillance colonoscopy, according to the researchers.
“Colonoscopic polypectomy is the primary reason for declining colorectal cancer incidence and mortality,” Shai Friedland, MD, gastroenterologist at the Digestive Health Center of Stanford Health Care and professor of medicine (gastroenterology and hepatology) at Stanford University Medical Center, and colleagues wrote. “However, many of the approximately 50,000 annual colorectal cancer deaths can be attributed to one-third of eligible Americans not following screening guidelines or approximately one-half of the population not adherent to the follow-up post-polypectomy guidelines. Colorectal cancer is among the most preventable cancers when adenomatous polyps are detected and removed at an early stage because of its slow progression.”
Colonoscopies are the gold standard for screening but have low compliance rates due to the invasiveness of the procedure, according to the researchers. Stool-based tests have poor compliance and low sensitivity for advanced adenomas, at about 24% to 42%.
“As colorectal adenomas account for 98% of actionable colonoscopies, there is an unmet need for a more sensitive noninvasive test for colorectal adenoma detection that would be in equipoise with colonoscopy,” the researchers wrote.
Researchers developed the FirstSight blood test to detect adenoma-carcinoma pathways in blood samples based on the presence of circulating gastrointestinal epithelial cells and somatic mutations of cell-free tumor DNA.
The analysis included 458 individuals who had their blood drawn prior to undergoing colonoscopy at VA Palo Alto Health Care System and who had no prior history of colorectal cancer. Of them, 239 individuals underwent screening colonoscopy and 219 underwent surveillance colonoscopy. Most of the individuals (86%) were asymptomatic, whereas 14% had symptoms or a positive fecal immunochemical test.
Researchers included 346 of these individuals in the training set, for whom researchers calculated the probability of advanced neoplasia by ordinal/nominal logistic regression methods, SEER incidence rates and prior history of advanced adenomas. Based on this analysis, researchers established a cutpoint for the quantitative score of 90%, which conferred sensitivities of 100% (95% CI, 72.3-100) for the detection of colorectal cancer and 80% (95% CI, 68.2-88.2) for the detection of advanced neoplasia.
In the validation cohort (n = 112), the blood test demonstrated 91.4% (95% CI, 77.6-97) specificity, with 100% (95% CI, 51-100) sensitivity for detection of colorectal cancer and 75% (95% CI, 53.1-88.8) sensitivity for detection of advanced adenomas.
“This blood test has high sensitivity for colorectal advanced neoplasia while retaining high specificity,” the researchers wrote. “The quantitative nature of the score has the potential to enable prognostic stratification of patients for screening or post-polypectomy surveillance colonoscopy.”
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Friedland S, et al. Abstract 50. Presented at: Gastrointestinal Cancers Symposium (virtual meeting); Jan. 15-17, 2021.
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