Tumour deposit count is an independent prognostic factor in colorectal cancer-a population-based cohort study.

Background: Tumour deposits are a prognostic factor for overall survival and distant metastasis in lymph node-negative colorectal cancer. However, the current TNM staging system does not account for the presence of tumour deposits in lymph node-positive colorectal cancer, or for the presence of multiple deposits. This study aimed to investigate the prognostic effect of tumour deposit count in patients with colorectal cancer.

Methods: Patients who underwent curative surgery for colorectal cancer between 2016 and 2019 were identified nationwide from the Swedish Colorectal Cancer Registry. Patients with undisclosed tumour deposit status/count and stage IV disease were excluded. Univariable and multivariable Cox regression analyses were used to assess the prognostic effect of tumour deposit count on overall survival and distant metastasis adjusted for age, sex, neoadjuvant treatment, and number of positive lymph nodes.

Results: Of 18 913 patients assessed, 14 154 patients were analysed with tumour deposits (TDs) present in 1702 (12%) patients. Patients were stratified by tumour deposit count (0, 1, 2, 3, 4, and ≥5 TDs). Increased tumour deposit count was associated with decreased 5-year overall survival (79%, 70%, 61%, 66%, 50%, 49%) and increased 5-year risk for distant metastasis (14%, 26%, 35%, 41%, 48%, 54%) respectively. Tumour deposit count remained an independent negative prognostic factor after multivariable Cox regression analysis.

Conclusion: Tumour deposit count is a negative prognostic predictor of both overall survival and distant metastasis in colorectal cancer, independent of positive lymph nodes or neoadjuvant treatment. These findings suggest that tumour deposit count should be integrated into the TNM staging regardless of lymph nodes status to improve prognostic accuracy.