Study of plasma methylated septin 9 as a biomarker of follow-up monitoring and prognosis in colorectal cancer

Objectives The utility of plasma methylated septin 9 (mSEPT9) as a biomarker for colorectal cancer (CRC) surveillance is underexplored. The aim of this study was to evaluate its role in recurrence monitoring and prognostic assessment among Chinese CRC patients. Methods A total of 315 patients with CRC and 142 subjects with benign colorectal polyps from August 2019 to August 2023 were enrolled. Post-operative mSEPT9 testing was performed, with recurrence-free survival (RFS) measured from surgery to recurrence. Results The sensitivity and specificity of post-operative mSEPT9 in identifying recurrent CRC (n=67) versus non-recurrent (n=248) were 85 and 96 %, respectively. mSEPT9 (area under the curve, AUC: 0.91) outperformed CEA (AUC: 0.74), CA19-9 (AUC: 0.66), CA72-4 (AUC: 0.55), and combined biomarkers (AUC: 0.85) in detecting recurrence. The detection rate of mSEPT9 declined most post-surgery, indicating tumor load reduction. mSEPT9 positivity within one year post-operatively was strongly linked to poorer RFS (hazard ratio, HR: 17.20), with a stronger predictive power than CEA (HR: 4.73) and CA19-9 (HR: 3.38). After adjusting for covariates, only mSEPT9 within one year post-operatively remained significantly associated with RFS (adjusted HR: 15.20). Conclusions Plasma mSEPT9 shows superior potential for CRC recurrence surveillance over traditional markers and may serve as a reliable indicator of surgical treatment efficacy and prognostic assessment in CRC patients.