Prognostic value of a modified lymph node ratio for combined colorectal cancer tumour deposits: a population-based study.

BACKGROUND: Tumour deposits (TDs) without metastatic lymph nodes are classified as N1c in the 8th edition of the AJCC staging manual. However, the prognostic value of TDs and lymph node ratio (LNR) in stage III colorectal cancer (CRC) remains unclear. This study aimed to compare the prognostic significance of TD count and LNR with the newly developed modified lymph node ratio (mLNR), and to create a prognostic nomogram integrating mLNR for stage III CRC patients. METHODS: Using the SEER database, a training cohort of 25,689 stage III CRC patients was identified, alongside an external validation cohort of 563 patients from a hospital in China. Modified lymph node ratio (mLNR) was defined by combining TD count and LNR. The effects of TDs, LNR, and mLNR on cancer-specific survival (CSS) and overall survival (OS) were evaluated using Kaplan-Meier curves and Cox regression models. A nomogram incorporating mLNR was developed for prognosis prediction. RESULTS: In both cohorts, TDs positivity was associated with poorer CSS (all P < 0.001). Multiple TDs correlated with worse CSS than a single TD (training: HR, 1.978; validation: HR, 1.805). High mLNR indicated a significantly higher risk of CRC-specific death (training: HR, 2.421; validation: HR, 4.60). The nomogram incorporating mLNR demonstrated good discrimination and calibration in both cohorts. CONCLUSIONS: mLNR is an independent prognostic factor for stage III CRC. The nomogram combining mLNR can effectively identify high-risk patients, aiding treatment decisions.