Lymph node testing in rectal cancer patients: is 12 still the magic number?

This study examined whether removing 12 lymph nodes is still valid for correctly staging rectal cancer patients.

Assessing whether cancer has spread to the local lymph nodes is important for correctly staging rectal cancer and correctly treating the cancer after surgery. Current guidelines for staging rectal cancer suggest that 12 lymph nodes should be tested to guarantee that patients’ nodes are cancer free (node-negative disease). However, these guidelines are based on evidence that is over 20 years old and are largely based on results from patients with colon cancer. As treatment strategies have changed in the last 20 years, whether or not 12 is really the best number of nodes to remove in rectal cancer patients has been questioned. 

This study investigated whether it is necessary to test 12 lymph nodes in rectal cancer patients undergoing curative rectal surgery. The medical records of 6793 patients were assessed. 2123 patients had received neoadjuvant treatment (usually chemotherapy and radiation therapy before surgery), and 4670 had not received treatment before surgery. Patients were separated into 4 groups depending on how many lymph nodes were removed during surgery (0-5; 6-11; 12-17; more than 18).

An average of 10 lymph nodes were removed from patients who received neoadjuvant treatment and 15 nodes from patients who did not. Significantly less patients who received neoadjuvant treatment (31.6%) were diagnosed with cancer in their lymph nodes than patients who did not (36.7%).

Patients who had 0-5 lymph nodes removed were less likely to be diagnosed with cancer in their lymph nodes (16.8% of patients who received neoadjuvant therapy and 19.4% who did not), compared to patients who had 12-17 nodes removed (38.5% of patients who received neoadjuvant therapy and 38.1% who did not).

The authors concluded that a minimum of 12 lymph nodes were needed to ensure that the cancer had not spread to the nodes. This was irrespective of whether patients had received neoadjuvant therapy.