Utilization of <i>SDC2</i> gene in conjunction with <i>SEPTIN9</i> gene methylation analysis for the diagnosis and efficacy assessment of colorectal cancer.

240 Background: SDC2 gene encodes the transmembrane proteoglycan molecule Syndecan-2. Syndecan-2 protein affects the proliferation, migration and invasion of colorectal cancer cells by participating in the regulation of cell adhesion, tissue differentiation and angiogenesis. Plasma methylated SEPTIN9 gene has been shown to be a sensitive and specific biomarker for the detection of CRC, which is involved in apoptosis, pseudopod projection, tumor cell migration and invasion. The aim of this study is to validate the value of SDC2 and S9 gene methylation detection in the diagnosis and efficacy evaluation of CRC. Methods: A total of 102 patients were enrolled in the study. The methylation levels of fecal SDC2 gene and blood SEPTIN9 gene were detected by fluorescence PCR. The clinical diagnostic accuracy of SDC2 kit was evaluated by patients with benign gastrointestinal lesions, gastrointestinal tumors and healthy subjects. Combined detection of SDC2 and S9 to improve the detection rate of CRC. SDC2m levels were analyzed in 26 patients with partial remission or stable disease after palliative treatment and 32 patients with complete remission after radical surgery. Results: The detection rate of SDC2 in patients was 0.0% for UC and CD, 66.7% for AA and 60.0% for NA, 25.0% for HOP. For 8 healthy subjects with negative colonoscopies, the true negative rate was 100%. The detection rates of GC and EC were 50.0% and 0.0%, respectively. Data from 72 patients with CRC were evaluated, with a sensitivity of 89.1% (41/46,95%CI 0.798-0.985) for patients with untreated CRC. The sensitivity of SDC2 was 46.2% (12/26,95%CI 0.256-0.667) in patients with partial response or stable disease after palliative treatment. The difference was statistically significant (P &lt; 0.001). The sensitivity of S9 for CRC detection was 88.2% (15/17, 95%CI 0.712-1.053). By two tests, 94.1%(16/17, 95%CI 0.816-1.066) of CRC cases could be detected.The sensitivity was 89.1% (41/46 95%CI 0.798-0.985) in untreated CRC and 46.2% (12/26 95%CI 0.256-0.667) in patients with PR and SD after chemotherapy/radiotherapy/targeted/immunotherapy. The difference rate of SDC2m between two groups was statistically significant (P &lt; 0.001). Among 46 untreated patients with CRC, 32 patients with positive SDC2m underwent radical surgery, of which 30 CR patients turned SDC2m test negative after surgery. We found reduced SDC2m in stool from patients with clinical benefit (CR+PR+SD). Conclusions: Detection of SDC2m in untreated CRC patients has high sensitivity and has the potential to become a non-invasive diagnostic tool for CRC. Combination of S9 and fecal SDC2 could improve the detection rate of SDC2 in non-dominant population. The methylation level of SDC2 may be helpful for postoperative follow-up of CRC after radical surgery, prediction of recurrence, and monitoring the efficacy of a series of palliative treatments for CRC.