Abstract
BACKGROUND: A stool methylated syndecan-2 (meSDC2) test has demonstrated high sensitivity and specificity in diagnosing colorectal cancer (CRC). We aimed to evaluate the cross-reactivity of the meSDC2 test through multi-cancer analysis. METHODS: This study is a prospective, single-centre study. We recruited patients with 13 different types of cancers, including CRC, as positive control. Excluding those with CRC, participants did not undergo colonoscopy. Stool samples were collected from each patient before starting definitive therapy for each cancer and sent to the central lab for methylation analysis. We investigated the cancer incidence rates based on Korean cancer statistics to infer the predicted positivity rates for each cancer type. RESULTS: A total of 168 patients with 13 different types of cancer were included in the study. The positive rate for patients with CRC was 89.5% (17/19). The next highest positive rate was observed in biliary tract cancer at 44.4% (4/9), with the lowest rates being observed in breast cancer at 12.5% (1/8), and in ureter cancer at 12.5% (1/8). The meSDC2-positive rates for overall gastrointestinal and pancreaticobiliary cancers ranged from 15.8% to 44.4%. Based on the incidence rates, the predicted positivity rates for each cancer type were 4.86 per 10,000 persons for CRC and 0.04 to 1.13 per 10,000 persons for non-CRC malignancies. CONCLUSIONS: The stool meSDC2 test demonstrated a high positivity rate in CRC but showed low positivity rates in other cancers, except in biliary tract cancer. This indicates that the stool meSDC2 test has a high specificity for CRC, as the results are minimally influenced by other cancer types.