Reproducibility of a multitarget stool-based DNA assay for colorectal cancer detection

Recent studies have demonstrated good sensitivity and specificity for the detection of colorectal cancer (CRC) utilizing a multitarget DNA assay panel (MTAP) on a single stool specimen. The aim of this study was to determine if analyzing three stool specimens obtained on three different days with the MTAP was superior to a single specimen for the detection of CRC. A secondary aim was to confirm the sensitivity of this MTAP reported in earlier studies.

Sixteen patients with newly diagnosed CRC underwent stool collection on three different days prior to surgical resection. Each specimen was analyzed using a MTAP that included 21 specific mutations of p53, K-ras and APC, and a microsatellite instability marker (BAT-26).

Eleven of the sixteen patients (69%) had at least one mutation detected in their first stool specimen. Identical mutations were found in 18 of 21 (86%) subsequent stool specimens from patients initially positive. No new mutations were detected in these 21 specimens or 9 subsequent specimens from 5 patients initially negative. Overall, there was a 93% concordance between initial results and subsequent stools analyzed.

There did not appear to be any additional benefit from performing the MTAP on more than one specimen per patient. This MTAP was reproducible with the same mutation detected in serial samples from each patient. The sensitivity detected in this study was comparable to earlier reports. Studies in an asymptomatic average-risk population are required to determine the role of the MTAP in CRC screening.