Can counting cancer positive lymph nodes predict survival time for colorectal cancer patients?

This study examined whether analyzing cancer spread to the lymph nodes in patients with stage III (the cancer has spread to the lymph nodes) right-sided colon cancer can predict patient outcome.

Colorectal cancer is one of the most common cancers diagnosed worldwide. Unfortunately, it is also one of the major causes of cancer related deaths worldwide. In order to provide patients with the best care possible it is valuable to accurately predict disease outcome. The most commonly used staging system for colorectal cancer is the tumor-node-metastasis (TNM) staging system which estimates how large the tumor is (T), how many lymph nodes are involved (N) and to what extent the cancer has spread (M). However, the best way to measure lymph node involvement is still debated among experts.

187 patients with stage III right-sided colon cancer were included in this study. Their lymph nodes were examined for evidence of cancer. Patients were separated based on the number of cancer positive lymph nodes: patients with 1-3 nodes involved (N1; 73% of patients), patients with 4-6 nodes involved (N2; 15.5% of patients) and patients with more than 6 nodes involved (N3; 21% of patients).

A second method was also used to separate patients based on the extent of the lymph node spread (LDN1-LDN3). For group LDN1 (59.4% of patients) the lymph nodes closest to the colon were involved, for LDN2 (29.4% of patients) some major vessels were involved and for LDN3 (11.2% of patients) the cancer had spread to main arteries.

After 5 years 68% of patients had no signs of the cancer returning and 79.3% of patients had survived. Both the number of lymph nodes with cancer cells and the extent of the lymph node spread were useful predictors of patient outcome. However, the number of cancer positive nodes was a more precise predictor of patient outcome. 76.6% of patients in group N1 were disease-free after 5 years compared to 56.9% in group N2 and 28.6% in group N3. 87.1% of patients in group N1 had survived 5 years compared to 67.8% in group N2 and 42.4% in group N3. 

The authors concluded that colorectal cancer staging does benefit from including the number of cancer positive lymph nodes to better predict patient outcome.