Does lymph node size matter after chemoradiotherapy for rectal cancer?

This study evaluated whether lymph node size is useful for predicting lymph node invasion in rectal cancer patients.

Locally advanced rectal cancer indicates that the cancer has spread beyond the lining of the rectum or has spread to the nearby lymph nodes. Patients with locally advanced rectal cancer are often treated with chemotherapy and radiation (chemoradiotherapy: CRT) before undergoing rectal surgery.

The stage of rectal cancer (how advanced the cancer is) is important in determining the best treatment strategy and surgery for the patient. For some, rectal surgery includes the removal of nearby lymph nodes to determine whether the cancer has spread to the lymph nodes. Unfortunately, after receiving CRT it can be difficult to accurately stage the cancer. Therefore, new methods are needed that can more accurately predict lymph node invasion. It is not yet known whether lymph node size can be used to predict lymph node invasion after CRT.

This study examined 59 patients with rectal cancer to determine whether lymph node size can predict lymph node spread. Patients were divided into two groups. Group 1 included 29 patients who received CRT followed by curative rectal surgery. Group 2 included 30 patients who did not receive CRT before undergoing curative rectal surgery. Patient lymph nodes were removed during surgery and the size of each lymph node was measured.

A total of 422 lymph nodes were removed from the 29 patients in group 1 and 474 lymph nodes were removed from the 30 patients in group 2. 6.9% of the nodes in group 1 were positive for cancer and 8.2% of nodes in group 2 were positive for cancer.

There was no difference in the size of non-cancerous lymph nodes between group 1 and group 2. However, the average size of the cancer positive lymph nodes was significantly bigger in group 1 (6.0 mm) than group 2 (4.0 mm). Nodes larger than 4.5 mm from group 1 were useful for predicting lymph node invasion (77.9% accurate). Node size from group 2 could not accurately predict lymph node invasion (59.9% accurate).

The authors concluded that lymph node size could be useful for predicting local lymph node invasion in rectal cancer patients after CRT.