S0271 Multi-Target Stool DNA: Rates and Reasons for Screening Failures in an Urban Health System

Abstract

INTRODUCTION: Multitarget stool DNA (MT-sDNA) is a screening test for colorectal cancer (CRC) with a reported sensitivity of 92% for detecting cancer, however it is a two-stage approach that requires patients with a positive MT-sDNA to undergo subsequent colonoscopy. The rates and reasons why patients who opt for this screening modality do not successfully complete the process have not previously been described. METHODS: We performed an analysis of all MT-sDNA orders over a 3-year period at a Chicago-area health system that incorporates 3 Illinois hospitals. MT-sDNA results were divided into 3 categories: positive, negative, and uninterpretable. Screening failures were defined as those patients that had a positive stool test and failed to complete subsequent colonoscopy, and those patients whose samples were uninterpretable specimens. If colonoscopy was not performed, the reasons for lack of completion were analyzed by chart review. These reasons were divided into three categories: 1) medical reasons that preclude colonoscopy, 2) patient refused, and 3) lack of follow up, or failure to schedule colonoscopy within 6 months after referral. Differences between groups were calculated by two sided Fishers Exact test with P = 0.05 as significant. RESULTS: A total of 2,918 MT-sDNA results from kits were received, of which 385 (13.2%) were positive, 2161 (74.1%) were negative, and 372 (12.7%) of the specimens were uninterpretable. The rate of screening failures was 472/2918 = 16.1%. Of the total screening failures (n = 472), 78.8% (n = 372) were due to an inadequate sample received by the company, and the remaining 21.2% (n = 100) of screening failures were from those who had a positive MT-sDNA but failed to complete colonoscopy. Of the patients with positive MT-sDNA, failure to complete colonoscopy occurred in 100/385 (25.9%) of the cohort. Demographics of the adherent and non-adherent to colonoscopy groups are shown in Table 1. Of the 100 remaining patients that did not complete colonoscopy, 7 (7%) were due to medical reasons, 23 (23%) refused colonoscopy and 70 (70%) had lack of follow up. CONCLUSION: A relatively high rate of the patients undergoing CRC screening by MT-sDNA in our cohort were considered screening failures. The most common reason for screening failures was inadequate sample, occurring in 12.7%, with additional 25% of positive MT-sDNA failing to complete colonoscopy. Efforts to reduce these reasons for screening failures should be implemented to improve screening compliance.Table 1.: Demographics of Patients with Positive MT-sDNA