BACKGROUND

Metastatic colorectal cancer (mCRC) is a global health challenge with a poor prognosis. Prognostic markers are critical for survival prediction.

AIM

To evaluate a novel tumor marker index (TMI) combining carcinoembryonic antigen and carbohydrate antigen 19-9.

METHODS

This multicenter, retrospective study measured baseline carcinoembryonic antigen and carbohydrate antigen 19-9 levels to calculate a TMI as the geometric mean of values normalized to their upper limits of normal. Receiver operating characteristic curve analysis assessed TMI's prognostic accuracy, and patients were stratified into high-TMI (≥ 1.39) and low-TMI (< 1.39) groups. The primary endpoint was overall survival (OS), with progression-free survival and treatment response as secondary endpoints.

RESULTS

The study included 305 mCRC patients with a median follow-up of 22.9 months. The median OS for high-TMI patients was 29.5 months, significantly lower than the 45.6 months observed in the low-TMI group ( = 0.02). The 2-year OS rates for the high- and low-TMI groups were 59.4% and 72.9%, respectively. Median progression-free survival was also shorter for the high-TMI group (14.0 16.0 months, = 0.84). High TMI is an independent prognostic factor for worse OS.

CONCLUSION

TMI is a simple, cost-effective prognostic tool for mCRC, with high TMI associated with poorer survival outcomes.