Higher Rate of Metastasis to Main Nodes in Transverse Colon Cancer

Routine prophylactic extended lymphadenectomy for the superior mesenteric artery (SMA) may not be necessary for caecum and ascending colon cancer, due to slower rates of metastasis. Dissecting around the SMA may be more necessary in cases of transverse colon cancer due to higher rates of metastasis in main nodes, according to a study published in Annals of Gastroenterological Surgery.

Complete mesocolic excision (CME) has been found to reduce the risk of the recurrence of colon cancer and can help with prognosis. CME consists of central vascular litigation (CVL), as well as resection of mesentery and resection to remove pericolic lymph nodes. Lymph node metastasis information is important for CVL, but the level of detail is scarce. The SMA and superior mesenteric vein (SMV) are the 2 main areas of dissection of lymph nodes. However, the SMA is hard to dissect lymph nodes around for right-sided colon cancer.

This study aimed to assess the frequency and location of lymph node metastasis as well as the short-term results of surgery with lymph node dissection.

Healthy large intestine anatomy on doctor hands | Image credit: Orawan - stock.adobe.com

The study was conducted in 5 hospitals in Japan where lymph node dissection takes place. Patients were eligible if they had a tumor located in the caecum, ascending colon, or right side of their transverse colon. They were also considered if they had stage II or III disease, had mainly lymph nodes around the SMA and SMV for dissection, and had a bowel resection of more than 10 cm beyond the tumor planned. History of chemotherapy or multiple cancers were criteria that were excluded.

All patients had a D3 lymph node dissection for right-sided colon cancer. This was defined as the dissection of at least the main lymph node around the root of the main artery in the tumor. The main lymph nodes were divided between those that were around the SMA and those that were around the SMV to assess frequency of metastasis.

The primary end point was metastasis rate for each lymph node station based on tumor location and the main feeding artery. Postoperative complications acted as the secondary end point.

There were 208 patients enrolled from April 2018 to August 2021, with 25.0% having the tumor in the caecum, 54.8% in the ascending colon, and 20.2% in the transverse colon. The ileocolic artery (ICA) was the main artery in 62.5%, the right colic artery (RCA) in 13.0%, and the middle colic artery (MCA) in 24.5%. RCA was recognized in 37.5% of patients during the operation and 60.6% did not have pathologic lymph node metastasis.

A total of 22.6% had open surgery and 77.4% had laparoscopic surgery, with right hemicolectomy (82.7%) being the most frequently performed surgical procedure. The median (range) operation time was 213 (102-447) mins and the median number of harvested lymph nodes was 38 (12-107).

There were 6 (2.9%) patients who had metastasis in main lymph nodes with the frequency of metastasis to the main lymph nodes being 3.8% in patients with caecal cancer. The 6 patients who had metastasis in. main nodes had a mean (range) number of metastatic lymph nodes of 12 (5-32), with all coming from the pericolic or intermediate lymph nodes.

The main lymph node was around the SMV in 4 of the patients, with the remaining 2 having metastases around the SMA in 1 and around both the SMA and SMV in the other. There was 1 case each of metastasis in the pericolic and intermediate lymph nodes after 189 patients had right hemicolectomy but no metastases in main nodes.

Metastases in lymph nodes that involved 2 of ICA, RCA, and MCA was only found in 4.8% of patients with caecal cancer. However, metastasis was found in 39.6% of patients with cancer of the ascending colon and 30.8% of those with transverse colon cancer. A total of 17% of tumors with the ICA as the main feeding artery had lymph node metastasis compared with 66.7% when the RCA was the main artery and 41.2% when the MCA was the main artery.

There were some limitations to this study. The number of lymph node metastases that were involved with the SMA or SMV, as well as the subgroups of colon cancer type, were small. Lymph nodes were not dissected in areas other than the mesentery. Preoperative imaging and intraoperative findings were not collected.

The researchers concluded that the rate of metastasis was higher in transverse colon cancer compared with caecal and ascending colon cancer when dealing with main nodes around the SMV and SMA. Patients with transverse colon cancer or with a main artery of MCA may need to dissect around the SMA.

Reference

Tsukamoto S, Ouchi A, Komori K, et al. A multicenter prospective observational study of lymph node metastasis patterns and short-term outcomes of extended lymphadenectomy in right-sided colon cancer. Ann Gastroenterol Surg. 2023;7:940-948. doi:10.1002/ags3.12703