ORLANDOSentinel lymph node biopsy, which is widely used to
detect micrometastases in melanoma and in breast cancer, can also
identify colorectal cancer patients who have metastatic disease and
should have adjuvant chemotherapy, Sukamal Saha, MD, reported in a
plenary presentation at the Society of Surgical Oncologys 52nd
Annual Cancer Symposium (see Figure).
Dr. Saha, of Michigan State University, suggested that routine use of
sentinel lymph node mapping in colorectal cancer patients might
prevent false-negative lymph node examinations and improve survival
prospects for the 55% of patients who do not have obvious nodal
metastases but will nonetheless die of systemic disease within 5
years of diagnosis.
If you look only at sentinel lymph nodes, the chance of missing
microme-tastases is less than 0.4% in colorectal cancer, Dr.
This conclusion was based on a prospective study of 86 consecutive
patients with colorectal cancer. In each patient, 1 mL of isosulphan
blue dye was injected subserosally around the tumor. (Dr. Saha
emphasized the importance of not injecting into the lumen.) The first
one to three blue nodes identified within the first 5 minutes after
injection of the dye were marked with sutures as sentinel lymph nodes.
An en bloc resection with regional lymphadenectomy was done, and 10
sections of each sentinel node were taken at 40-micron intervals at
three levels. The entire specimen underwent standard pathologic
evaluation. The sentinel node sections were stained with hematoxylin
and eosin (H&E) for histologic examination and were also analyzed
using immunohistochemistry for cytokeratin (Figure) and for
carcinoembryonic antigen (CEA).
The study results were as follows:
At least one sentinel lymph node was identified in 85 of the 86
patients, the only failure being in a patient with low rectal cancer
who had preoperative chemotherapy and radiation therapy. One or two
sentinel lymph nodes were found in 90% of patients.
Sentinel lymph nodes were negative in 56 patients (66%); in 53 of
these patients, all other nodes sampled were also negative. Thus,
positive subsequent nodes (skip mets) were found in only 3 of the 56
patients with negative sentinel nodes.
Sentinel lymph nodes were positive in 29 patients (39%), and in 15 of
these patients (18%), the positive sentinel node was the only sign of
metastatic disease. In 7 of these 15 patients (9%), microme-tastases
were found in only 1 or 2 sections of a single sentinel lymph node
(see Figure). Identification of
micrometastases in a sentinel node should have allowed these 15
patients to be upstaged to those most likely to benefit from adjuvant chemotherapy.
Dr. Saha said that sentinel lymph node mapping is successful in more
than 98% of colorectal cancer patients and has a 96% accuracy for
predicting the presence or absence of micrometastasis in the lymph
nodes. The method used in this study is also cost-effective, since
the dye costs only $31 per vial.
This is a quick process. It requires only 5 to 10 minutes,
needs no radioactive dyes, and allows the pathologist to focus
attention on the one to three sentinel nodes, Dr. Saha concluded.
The study was done in collaboration with investigators at Michigan
State University; McLaren Regional Medical Center, Flint, Michigan;
and Easton Hospital, Easton, Pennsylvania.
The researchers also presented their findings at the 35th annual
meeting of the American Society of Clinical Oncology (ASCO), held in
Atlanta, at an oral session on colorectal cancer (abstract number 905).