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Colon Cancer Survival Linked to Lymph Nodes 

CancerWise - June 2007

An analysis of 17 studies from nine countries has found that the more lymph nodes are removed and examined during surgical treatment of colon cancer, the better the outcome appears to be for patients.

Significance of results

The findings, reported in the March 21 issue of the Journal of the National Cancer Institute, should help support ongoing efforts by medical professionals to recommend a minimum number of lymph nodes that are extracted and examined during surgery, says the study’s lead author, George Chang, M.D., an assistant professor in M. D. Anderson’s Department of Surgical Oncology and a specialist in its Gastrointestinal Center.

“Currently, just over one-third of colon cancer patients in the United States are getting an adequate lymph node evaluation,” he says.

Research methods

Researchers analyzed 17 study results and reports from nine countries involving patients with Stage II to III advanced colorectal cancer.

Primary results

In one of the studies examined, a national clinical trial enrolled more than 3,200 patients to study the effects of chemotherapy on colon cancer recurrence after surgical resection.

The findings involved patients who had:

More than 20 lymph nodes removed – This group of patients with Stage II colorectal cancer experienced a 14% increase in five-year survival over Stage II patients who had less than 11 lymph nodes removed.

More than 40 lymph nodes removed – The survival advantage for patients with Stage IIIA and Stage IIIB cancer was 23% greater than patients who had fewer than 11 lymph nodes removed.

Secondary results

All but one of the 17 studies of Stage II cancer showed the same association between the number of lymph nodes evaluated and improved outcome, as did four of six studies of more advanced cancer, Chang says.

“This tells us that surgeons and pathologists involved in the care of colon cancer patients should make every effort to improve their collection and evaluation of lymph nodes.”

However, because all of the studies examined were observational, he stresses that researchers cannot definitively say increasing the number of lymph nodes examined leads to improved survival. Such a statement only could be supported by a randomized, controlled clinical trial, which would not be feasible.

Background

Removing colon tissue during surgery in a way that captures all of the tumor-associated lymph nodes requires attentiveness, Chang acknowledges. A surgeon needs to trace the origins of blood vessels closest to the tumor because the lymphatic system works closely with the blood system.

Sometimes the lymph nodes can be difficult for pathologists to find, especially when they are small or when the patient is obese.

“Everyone is different,” he says. “Some people have more nodes; some people have fewer; nodes can be large and easy to identify or small and the number may differ depending on which part of the colon contains the tumor. The factors that determine the total number of lymph nodes are not altogether known.”

What’s next?

Chang hopes that the findings encourage physicians to remove and examine the lymph nodes as completely as possible during colon cancer surgery.

In the meantime, these findings can serve as an empowerment tool for patients in need of colon cancer surgery, he says.

Studies have found that the number of lymph nodes examined can be improved with increased awareness and education and that surgeons and pathologists with greater interest and expertise in colon cancer identify more lymph nodes

“Health care consumers are told all the time to ask general surgeons how many operations they have done, but perhaps they should ask how often they do colon and rectal cancer surgery,” Chang says. “We are not suggesting surgeons cut out more colon than necessary, but that they abide by the standards for cancer surgery, and that pathologists follow up in kind.”

– From staff reports

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© 2014 The University of Texas MD Anderson Cancer Center