In a discussion of the study, Douglas Corley, MD, PhD, of the Division of Research at Kaiser Permanente, San Francisco Medical Center, California, said it remains unclear whether blood tests can improve the early detection of cancer, though such an approach would be welcomed.

“We are getting closer to zero deaths from colon cancer,” he said, noting screening colonoscopy has been associated with a markedly decreased risk for death from colorectal cancer. “Circulating tumor cells for screening looks promising, especially with the low false-positive rate, but must be interpreted with caution. The interpretation of new screening tests depends heavily on the population tested and requires replication.”

To accentuate this note of caution, Dr. Corley pointed to septin 9 methylated DNA, initially purported to be a sensitive and specific blood test for colorectal cancer, after studies found a sensitivity of 90% in detecting colorectal cancer of all stages.¹ A subsequent meta-analysis, however, of 1,462 patients from all septin 9 trials found the sensitivity to be 67%.²

“Circulating tumor cells are an interesting target for screening,” he concluded, “but we need confirmation in screening populations and case/control studies that balance risks, stage, and symptoms in a screening population.”

Additional Commentary

In a statement, Nancy Baxter, MD, Professor of Surgery at the University of Toronto and designated ASCO expert in gastrointestinal cancers, also commented: “Screening for colorectal cancer can be lifesaving,

Nancy Baxter, MD

but Americans still lag behind federal government screening goals because current screening options can be inconvenient and uncomfortable for patients. Though this research needs more investigation, a simple, accurate blood test could help increase screening rates, which could ultimately improve detection of colorectal cancers at earlier stages, when treatment is most likely to be curative.” ■

DISCLOSURE: Drs. Corley and Baxter reported no conflicts of interest.

REFERENCES

1. Warren JD, et al: Septin 9 methylated DNA is a sensitive and specific blood test for colorectal cancer. BMC Med 9:133, 2011.

2. Zhang M, et al: A pooled analysis of the diagnostic efficacy of plasmic methylated septin-9 as a novel biomarker for colorectal cancer. Biomed Rep 7:353-360, 2017.