Colon Cancer Survival Better When More Lymph Nodes Removed

March 26, 2007 — Among patients with colon cancer undergoing surgery, better survival is seen in those who have a larger number of lymph nodes removed and examined than in patients who have fewer lymph nodes evaluated. This finding comes from a review of 17 studies involving a total of 61,371 patients and is reported in the March 21 issue of the Journal of the National Cancer Institute. The researchers suggest that the number of lymph nodes evaluated could be used as a measure of quality of care in colon cancer.

"More appears to be better" is the main message. The more lymph nodes that are removed and evaluated, the better patient survival appears to be, first author George Chang, MD, from the MD Anderson Cancer Center at the University of Texas in Houston, told Medscape in an interview. "However, we need careful thought before we come up with a specific quantity measure, and we need to emphasize the quality and completeness of the surgery and the pathological evaluation of the lymph nodes," he commented.

There has been some controversy in the past around the use of lymph nodes numbers as a benchmark and also over the specific number of nodes that should be examined (12 has been proposed by some groups). Dr. Chang believes this latest article will stimulate further debate. "We hope that our research will recharge the ongoing discussions, as it provides evidence for the importance of lymph node evaluation," he said. "However, I don't know that we can identify a clear number yet."

An accompanying editorial comments that simple solutions to improve quality of care — such as setting benchmarks for the number of lymph nodes evaluated in colon cancer — are attractive to policy makers and payers, but they must be based on sound evidence. Otherwise, they are "likely to fail to achieve improvement in patient outcomes and worse, may divert attention from effective strategies," write Rocco Ricardo, MD, and Nancy Baxter, MD, PhD, from St. Michael's Hospital, University of Toronto in Toronto, Canada.

There are currently no guidelines on lymph node evaluation during colon cancer surgery, although a number of medical societies, including the American College of Surgeons and the American Society of Clinical Oncology, as well as healthcare insurance providers, have highlighted the importance of evaluating lymph nodes, and its potential as an important measure of the quality of care.

Despite this, in practice, many colon cancer patients have inadequate lymph node evaluation. Dr. Chang and colleagues cite one study that found adequate evaluation in only 37% of patients, and other studies from the United States, Canada, and Europe with similar low numbers.

Large Variation in Number of Nodes Removed
In the 17 studies that were reviewed, the number of lymph nodes evaluated ranged from 6 to 40. Dr. Chang and colleagues found that patients who had more nodes removed had better survival.

For example, in one of the studies (the Intergroup 0089 trial), among patients with stage II colon cancer, the 5-year overall survival was 87% in those who had more than 20 lymph nodes removed and was significantly lower at 73% in those who had fewer than 11 nodes removed (P < .001). Among the patients with stage IIIA/B colon cancer, the survival advantage was even more striking, with 5-year overall survival of 90% in patients who had more than 40 lymph nodes removed compared with 67% in those who had fewer than 11 lymph nodes removed (P < .001).

Overall, a positive association between increased survival and increased number of lymph nodes removed was reported by 16 of the 17 studies examined for patients with stage II colon cancer and in 4 of 6 of the studies that included patients with stage III colon cancer.

"Our study provides evidence that supports a positive association between an increased number of lymph nodes examined and improved survival," Dr. Chang concluded. However, as all the studies were observational, this analysis cannot prove that removing and examining more lymph nodes will increase a patient's chances of survival. "That could only be shown in a randomised clinical trial, but we don't know all the relevant factors to be able to perform such a trial now," he commented.

The positive impact on patient survival is thought to result from several different effects — removal of the lymph nodes takes away a reservoir of potentially lethal cancer cells, whereas evaluation of the lymph nodes and assessment of whether the cancer has metastasized or not can influence subsequent treatment, such as the choice of chemotherapy.

"Our research emphasizes the importance of lymph node evaluation," Dr. Chang told Medscape. "Surgeons and pathologists involved in the care of colon cancer patients should make every effort to improve their collection and evaluation of lymph nodes." The procedure requires attentiveness and careful adherence to all the surgical principles of cancer surgery, he commented: for example, care needs to be taken to ensure that removal of the colon tissue during surgery captures all of the tumor-associated lymph nodes, although finding all of the nodes can be difficult, especially if they are small or the patient is obese. There are many factors that can influence the procedure, he added, but the 2 that are mutable are the performances of the surgeon and the pathologist. "Clearly, both individuals are important," he said. "Surgeons need to adhere closely to all the principles of cancer surgery, and pathologists need to be attentive when collecting and evaluating the nodes."

J Natl Cancer Inst. 2007;99:414-415, 433-441.

Source: http://www.medscape.com/viewarticle/554091?src=mp