Prospective observational study of application of multi-target fecal FIT-DNA testing in postoperative follow-up for colorectal cancer patients.

e15642 Background: Colorectal cancer (CRC) is one of the most prevalent malignancies worldwide, with the majority of patients undergoing surgical resection. Unfortunately, 30% to 50% of patients experience disease recurrence after curative surgery. Colonoscopy is a commonly used tool for postoperative surveillance; however, its invasive nature results in suboptimal patient adherence. The multi-target fecal immunochemical test-DNA (FIT-DNA) is a non-invasive method that has demonstrated promising sensitivity in CRC screening. However, limited data are available on the application of FIT-DNA testing in postoperative monitoring of CRC patients. This study aims to assess the utility of FIT-DNA in detecting early recurrence and multiple primary colorectal tumors after surgery. Methods: This prospective observational study enrolled CRC patients initially diagnosed with TNM stage I-III disease who underwent curative surgical resection. The FIT-DNA test used a combination of KRAS gene mutation detection, BMP3 and NDRG4 gene methylation, and fecal occult blood testing. Patients underwent FIT-DNA testing once prior to preoperative bowel preparation and then every 3 months postoperatively for up to 3 years. The primary objective was to evaluate the predictive accuracy of FIT-DNA in detecting postoperative colorectal neoplasia (tumors or adenomatous polyps). Results: Between October 2020 and April 2024, 201 CRC patients were enrolled.112 eligible patients were included in data analysis (48.2% male; median age, 49 years [IQR, 24–55]). 44 (39.3%) patients developed colorectal neoplasia detected by colonoscopy postoperatively.The FIT-DNA testing yielded positive rates of 15.2% at 3 months, 20.5% at 6 months, 12.5% at 9 months, and 10.7% at 12 months after the surgery. The receiver operating characteristic (ROC) curve analysis showed an area under the curve (AUC) of 0.531 (95% CI, 0.444-0.616) for the FIT-DNA test in diagnosing colorectal neoplasia postoperatively with a sensitivity of 77.3% (95% CI, 54.2-91.3) and a specificity of 28.9% (95% CI, 20.1-39.5) . The positive predictive value (PPV) was 21.0% (95% CI, 13.0-31.7), and the negative predictive value (NPV) was 83.9% (95% CI, 65.5-93.9). Longitudinally, FIT-DNA positivity was observed a median of 7.2 months (IQR, 3.1-11.3 months) earlier than the detection of colorectal neoplasia by colonoscopy. Conclusions: Our study demonstrated that the diagnostic accuracy of FIT-DNA, with an AUC below 0.7, indicates limited utility for postoperative surveillance of CRC patients. Despite this, the findings suggest that FIT-DNA may have potential as a supplementary tool for early detection in CRC follow-up, warranting further investigation.