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Sentinel Lymph Node Biopsy Shows Promise in Eye and Colon Cancersby Katie Prout Matias
As the use of sentinel lymph node biopsy in melanoma and breast cancer continues to evolve, researchers at The University of Texas M. D. Anderson Cancer Center are finding ways to modify and adapt the procedure for other types of cancer, including conjunctival, eyelid, and colon cancers. Performing sentinel lymph node biopsy in tumors of the eye requires skill and teamwork because of the unique anatomic considerations in the periocular region. “It requires someone who is familiar with the eye to work closely with someone who is very familiar with doing sentinel lymph node biopsy in the head and neck region. Head and neck sentinel node biopsy is a little different from the rest of the body. It has a higher learning curve,” said Bita Esmaeli, M.D., an associate professor and chief of the Section of Ophthalmology in the Department of Plastic Surgery at M. D. Anderson and an ophthalmic plastic surgeon. Dr. Esmaeli and Merrick Ross, M.D., a professor in the Department of Surgical Oncology at M. D. Anderson, have adapted sentinel lymph node biopsy for conjunctival and eyelid tumors. “The problem with the head and neck region is that it is so rich in lymphatics, and the ambiguity of lymphatic drainage patterns is really high,” said Dr. Ross. “But in conjunctival melanomas, our experience has been that the lymphatic drainage patterns are actually relatively straightforward; they almost always drain to the parotid region and the upper neck.” Drs. Esmaeli and Ross have also performed sentinel lymph node biopsies for eyelid tumors, including sebaceous cell carcinomas and Merkel cell carcinomas, which can have rates of nodal involvement of 20% to 50%. Initial concerns that performing a sentinel lymph node biopsy in the eye region might permanently discolor the eye with the blue dye used to locate the sentinel node or cause cataracts or dryness from the radioactive tracer have not materialized. Another issue with the radioactive tracer was how much to inject. Dr. Esmaeli noticed that, because the conjunctiva is a mucous membrane with a contiguous underlying space and the eye is so small, injecting the usual volume of tracer used for sentinel node biopsy in other locations caused the agent to spread on the surface of the eye and drain to nonspecific nodal basins. By using a smaller needle and decreasing the volume, she was able to identify the sentinel node or nodes successfully. To illustrate how the use of sentinel lymph node biopsy can affect the treatment of eye tumors, Dr. Esmaeli related the case of a 58-year-old man who had a conjunctival melanoma removed from the surface of his eye. Ultrasonography and magnetic resonance imaging found no disease in his lymph nodes. In this situation, the standard of care is to wait and see if the melanoma metastasizes, which can occur in as many as 30% of conjunctival melanomas. Instead, the man’s local ophthalmologist referred him to M. D. Anderson, where Drs. Esmaeli and Ross performed a sentinel lymph node biopsy and identified three sentinel nodes. One turned out to be histologically positive for metastatic melanoma, and the patient’s melanoma was upgraded from stage I to stage III. “Sentinel node biopsy drastically changed this patient’s treatment; instead of just waiting for his metastatic disease to become clinically obvious, we found his microscopic lymph node metastasis early, and he had neck dissection, radiation therapy, and was enrolled in a phase III trial for systemic interferon,” said Dr. Esmaeli. “For aggressive malignancies of the conjunctiva and eyelid, sentinel lymph node biopsy is an important advance because we would otherwise miss microscopic nodal involvement in these patients.” Sentinel lymph node biopsy has also been modified for more common tumors. In colon cancer, the procedure is used solely for staging purposes, to help the oncologists decide whether to administer chemotherapy. Performing a sentinel lymph node biopsy in place of a complete lymph node dissection in patients with colon cancer does not reduce surgical morbidity because there are no side effects associated with removing the mesenteric lymphatics. Thus, lymphatic mapping is sometimes performed ex vivo when there is too much fatty tissue inside the body to see the nodes. In ex vivo mapping, the surgeons inject the localization agents, resect the tumor and the lymphatics, and then remove any positive nodes for analysis. While the false-negative rates of sentinel lymph node biopsy are higher in colon cancer than in melanoma or breast cancer, there is hope that the rates will improve with the development of more sensitive pathologic techniques. As more patients enroll in clinical trials of these experimental sentinel lymph node biopsies, surgical oncologists will continue to perfect the procedure so that staging and even survival benefits may be realized for patients with many different kinds of tumors. For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789. Other articles in OncoLog, September 2003 issue:
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