Stool test for colorectal neoplasia validated in high-risk group

Last Updated: 2015-11-04

By Reuters Staff

NEW YORK (Reuters Health) - A new study confirms the value of a multitarget stool DNA test (Cologuard, Exact Sciences) for detecting colorectal neoplasia in Alaska Natives, a group with the world's highest rates of colorectal cancer (CRC), limited access to colonoscopy and low rates of screening.

In this prospective cross-sectional study, 661 asymptomatic age-appropriate Alaska Native adults had both Cologuard and fecal immunochemical testing (FIT) before pre-scheduled screening or surveillance colonoscopy.

Overall, Cologuard detected significantly more screening-relevant colorectal neoplasia (SRN) than FIT alone (49% vs. 28%; p<0.001), researchers report in Mayo Clinic Proceedings online October 28.

Cologuard had "especially high sensitivities" for CRC (100% vs. 80% by FIT) and large precancerous polyps at highest risk for progression, they say. Cologuard detected 62% of adenomas 2 cm or larger vs. 29% by FIT (p=0.05). Specificities for Cologuard and FIT were 93% and 96% (p=0.03), respectively.

This is the second cross-sectional study evaluating the screening performance of Cologuard, the authors note, and neoplasm detection rates mirror those from the first study, which was a multicenter study representative of the general U.S. population. (Imperiale et al. N Engl J Med 2014;370:1287-1297.)

These "remarkably similar" Cologuard findings suggest that there are no meaningful differences in the molecular biology of colorectal neoplasia between the two ethnically different populations, report Dr. David Ahlquist and colleagues. Dr. Ahlquist is a Mayo Clinic gastroenterologist and co-inventor of the test, which has been approved by the U.S. Food and Drug Administration.

Consistent with earlier studies, the "important subset" of sessile serrated adenomas/polyps was largely undetected by FIT, but Cologuard was positive in 67% of these lesions larger than 1 cm, the researchers note in their paper.

Based on performance of Cologuard in this study, applying it to a screening program has "potential to effectively detect SRN and thereby reduce both the incidence and mortality of CRC" in the Alaska Native population. Given its test characteristics, Cologuard represents an "attractive CRC screening strategy, particularly where colonoscopy access is limited," they conclude.

"This research is further evidence that Cologuard is highly sensitive in detecting both early stage colorectal cancer and the most advanced precancerous polyps that are most likely to develop into cancer," Dr. Ahlquist added in a news release from Exact Sciences.

"A sensitive screening test like Cologuard that is delivered to a patient's home provides an opportunity to reverse that trend not only in Alaska but also in other rural and remote areas where patients have limited access to screening," Dr. Ahlquist said.

The study was supported by a grant from the Richard M. Schulze Family Foundation. Exact Sciences Corporation, which manufactures Cologuard, provided stool collection materials and performed the assays at no cost. The company had no role in the study design, data analysis, or preparation of the manuscript. Mayo Clinic has licensed technology from Exact Sciences related to Cologuard. Several authors have relationships with the company.

SOURCE: http://bit.ly/1Q4kIu0

Mayo Clin Proc 2015.