# Relationship between ABO blood group and lymph node metastasis in colon cancer: a retrospective cohort study

## TL;DR

This study found that people with AB blood type may be less likely to have lymph node metastasis in colon cancer, but more research is needed to confirm this.

## Contribution

The study is the first to show a potential protective effect of AB blood group against lymph node metastasis in colorectal cancer.

## Key findings

- AB blood group was associated with a lower likelihood of lymph node metastasis (OR: 0.12).
- Factors like rectal tumor location and T4 invasion were strongly linked to lymph node metastasis.
- No significant association was found between ABO blood group and microsatellite instability.

## Abstract

Colorectal cancer is the third most common cancer and the second leading cause of cancer-related deaths worldwide, according to GLOBOCAN 2022. Lymph node metastasis is a well-recognized prognostic factor in colorectal cancer. While the relationship between ABO blood group, Rhesus (Rh) type, and lymphatic spread has been studied in other gastrointestinal tumors, limited research exists on colorectal cancer. This study primarily aimed to investigate the association between lymph node metastasis and ABO blood group, as well as the relationship between microsatellite instability (MSI) and ABO blood group.

. A retrospective observational cohort study was conducted, including all patients who underwent elective colorectal resections with curative intent for malignant colorectal tumors between March 2017 and March 2023. Eligible patients had documented ABO blood group and Rh type, along with pathology reports from surgical specimens.

. The study included 270 patients, with a median age of 74.5 years-old. The cohort was predominantly female (50.4%). Lymph node metastasis was observed in 156 patients (57.7%). A binary logistic regression model identified factors associated with lymphatic spread: rectal tumor location (OR: 3.85, 95% CI: 1.14–15.60), poorly differentiated tumors (OR: 6.84, 95% CI: 1.37–53.80), invasion depth T3 (OR: 4.88, 95% CI: 1.72–16.90) and T4 (OR: 16.20, 95% CI: 4.78–65.60), and extramural vein invasion (OR: 7.17, 95% CI: 1.37–53.80). Notably, the AB blood group (OR: 0.12, 95% CI: 0.01–0.65) was associated with a lower likelihood of lymph node metastasis, suggesting a potential protective effect. A separate binary logistic regression analysis evaluating factors related to MSI found no statistically significant associations, including for ABO blood group and Rh antigen.

Our findings suggest that the AB blood group is associated with a reduced likelihood of lymph node metastasis compared to other blood groups. However, the existing literature on the relationship between blood group and lymph node metastasis is inconsistent. Further research is necessary to clarify the prognostic role of ABO blood group in colorectal cancer.