CHICAGO—According to the results of a multi-institutional clinical trial, patients with colorectal cancer who undergo sentinel lymph node mapping are less likely to have a recurrence of their disease within five years of treatment.  Findings from the study were presented at the 2006 Clinical Congress of the American College of Surgeons.

After a median follow up of 63 months, the overall rate of recurrence of colorectal cancer was 7.8 percent in 165 patients who had sentinel lymph node mapping (a procedure that identifies the principal lymph nodes that drain fluid from a cancerous area and therefore may be the primary sites of minute metastases).  The recurrence rate for 157 patients who did not undergo mapping was 24.8 percent.  The difference was highly statistically significant (P=0.0001).  The rate of local and regional recurrences of colorectal cancer was more than two times higher in patients who did not have sentinel lymph node mapping (24.3 percent) than in patients who underwent mapping (11 percent). 

The researchers also found that sentinel lymph node mapping was a highly accurate method of staging colorectal cancer.  The presence of disease was detected in more patients who had sentinel lymph node mapping (48 percent) than in patients who did not (34.7 percent).  Sentinel lymph nodes were the exclusive site of metastasis in 41 percent of patients and harbored micrometastases in 26 percent of patients. 

“By doing lymph node mapping, we can find minute [evidence of] cancer that we otherwise would not find.  By finding minute cancer in the lymph nodes, we can decide which patients need chemotherapy.  We can also show that patients who have no cancer in the lymph nodes by lymphatic mapping will rarely develop a recurrence,” according to Sukamal Saha, MD, FACS, FRCS (C), a surgical oncologist at McLaren Regional Medical Center, Flint, MI.

The study included 500 consecutive patients with colorectal cancer who underwent sentinel lymph node mapping at one of three institutions: McLaren Regional Medical Center; Carson Cancer Center, Norfolk, NE; and John Wayne Cancer Institute, Santa Monica, CA. 

The analysis of disease staging included all 500 patients who had sentinel lymph node mapping and 368 patients who did not.  The analysis of disease recurrence included a subgroup of 322 patients who had been followed for a minimum of 18 months.

Sentinel lymph node mapping is common in the treatment of patients with breast cancer or melanoma.  “Sentinel lymph node mapping was first used in melanoma in 1992 and for the first time in the breast in 1994.  Now it is being done all over the world for these groups of patients,” Dr. Saha explained.  “I thought there was no reason why the same principle could not apply to patients with colon cancer,” he said.  Dr. Saha was the first surgeon to perform sentinel lymph node mapping for patients with colorectal cancer in 1996. 

During sentinel lymph node mapping, surgeons inject a radioactive tracer and a blue dye around the site of the tumor.  The tracer and the dye enter the lymphatic system and travel to the main lymph node that drains fluids from the tumor site, serving as markers of the most important lymph node to test for the presence of metastasis.

While the basic procedure remains the same whether sentinel lymph node mapping is performed for patients with breast cancer, melanoma, or colon cancer, its objective differs.  For patients with breast cancer or melanoma, sentinel lymph node mapping determines the precise location of metastatic disease so only the affected lymph nodes are removed during a surgical procedure.  This approach spares patients from complications, such as lymphedema (chronic and often debilitating swelling and inflammation), that may occur as a result of removing wide areas of lymphatic tissue.  For patients with colorectal cancer, sentinel lymph node mapping is performed to find metastases that would not be recognized by conventional disease-staging methods and to identify patients who require postoperative chemotherapy.  Patients with colon cancer still undergo wide resection of lymph nodes, Dr. Saha said.      

“Detailed pathologic analysis cannot be done on all the lymph nodes.  That would be too cumbersome and too expensive.  No department of pathology would be able to afford to do that.

In our study, we confirmed that it is in the sentinel nodes where most of the metastatic cancer will be found.  So pathologists don’t have to do expensive tests on all of the lymph nodes,” Dr. Saha said.

Dr. Saha is currently collaborating with researchers from Japan, Italy, Switzerland, Germany, the Netherlands, and Canada as well as investigators in the United States to track the long-term effects of the procedure in patients with colorectal cancer.     

Also participating in the study of sentinel lymph node mapping for colorectal cancer patients were Maher Ghanem, MD; Rajesh Sehgal, MD; Mehul Patel, MD; Thomas Beutler, MD, FACS; Anton Bilchik, MB, BCH, PhD, FACS; and David Wiese, MD, PhD.

A comparative results analysis from 10 centers around the world of more than 1,000 patients undergoing lymphatic mapping in colorectal cancers will be presented by Dr. Saha in the upcoming 5th International Congress of Sentinel Lymph Node Mapping to be held in Rome, Italy, November 1-4, 2006.