Examining more carefully the lymph nodes to which colorectal cancer is most likely to have spread may improve the accuracy of colon cancer staging and spare some patients the cost and toxicity of chemotherapy.

Colon cancer is the second most common cause of cancer death in the United States.

To determine the stage to which the cancer has progressed as well as assess treatment options, physicians surgically remove and examine cancer patients' lymph nodes. Patients whose cancer has spread to the lymph nodes have been shown to benefit from chemotherapy in addition to surgery, while those whose cancer has not spread to the lymph nodes may not see any benefit to combination treatments over surgery alone. " One-third of patients with tumor-free lymph nodes have recurrences, and therefore, adjuvant chemotherapy may be beneficial in these patients," the authors write. " However, if all node-negative patients are treated, 70 percent will be subjected to unnecessary chemotherapy because surgery alone is curative. A better understanding of high-risk, node-negative patients and improved methods of lymph node evaluation are therefore needed."

Anton J. Bilchik, John Wayne Cancer Institute and Saint Johns Health Center, Santa Monica, and colleagues studied 132 patients ( 63 men and 69 women, median age of 74 years ) with stage I and II colon cancer who were recruited from four referral cancer centers between March 2001 and June 2005.
In a process known as lymphatic mapping, blue dye was injected near the site of each participant's tumor. The dye stained the sentinel lymph nodes down the lymph channel, the pathway through which lymph--a fluid containing lymphocytes and the bacteria, cancer cells and other organisms they have attacked--drains from the spaces between body tissues. The tumor, sentinel nodes and other lymph nodes in the region were then removed and examined. " The sentinel node paradigm is based on the premise that lymphatic drainage from a primary organ site occurs in an orderly and progressive fashion," the authors write. "The sentinel lymph node is the first node to receive lymphatic drainage from a primary anatomical site and is therefore the most likely node to harbor a metastasis."

Of the 132 participants, 33 ( 30 percent ) had stage I cancer, 46 ( 41 percent ) had stage II and 32 ( 29 percent ) stage III. Twenty-eight patients ( 23.6 percent ) were classified at a more severe stage based on the analysis of sentinel nodes. The sensitivity of the lymphatic mapping/sentinel node procedure was 88.2 percent, meaning that 45 of 51 patients whose cancer had spread to their lymph nodes had tumors in their sentinel nodes. False negatives, when an individual's cancer had spread to lymph nodes but was not detected in the sentinel node, occurred in six of 81 ( 7.4 percent ) of patients who were determined to be node negative. Eighteen percent of the sentinel nodes had tumors, compared with 6 percent of the other lymph nodes.

The results "suggest that lymphatic mapping and sentinel lymph node techniques are feasible and accurate in colon cancer, " the authors write. " The improved risk stratification afforded by standardization of both surgical and pathological techniques may improve the selection of patients for chemotherapy, thereby avoiding the unnecessary toxic effects and expense for those cured by surgery alone."

Source: Archives of Surgery, 2006


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