|
|
|
|
|
|
|
|
|
|
|||||||
 |
 |
 |
||||||||||
|
Advancing the Treatment of LymphedemaBy Maude Veech
Not many areas of medicine still draw heavily from 19th century knowledge, but the understanding of the lymphatic system has been hampered in just such a way. Thus, it has been impossible to prevent or cure lymphedema, a painful dysfunction of the lymphatic system that can result from cancer treatments. Today, M. D. Anderson researchers are breaking barriers in lymphatic medicine. Not only is the institution developing new ways to image the almost invisible lymphatic system, it is also among the first to offer surgery to treat lymphedema. With further research, specialists hope to better understand metastasis via the lymphatic system and to prevent lymphedema altogether. “You’d think that in 2009 we’d have a good understanding of the lymphatic system, but we don’t,” said David W. Chang, M.D., a professor in the Department of Plastic Surgery and clinical medical director of the Plastic Surgery Center. “Not fully understanding the lymphatic system and its anatomy—as we do with the vascular system, for instance—is one reason it is so hard to prevent and treat lymphedema. It also prevents us from explaining why some patients develop lymphedema and others do not.” Lymphedema basics Lymphedema, characterized first by swelling and later by inflammatory fibrosis in tissues near damaged or missing lymph nodes, is caused by a failure of the lymphatic system to drain properly. Primary lymphedema develops spontaneously, while secondary lymphedema is caused by treatment, injury, or infection. About 200 million people worldwide suffer from secondary lymphedema caused by parasites, mostly in underdeveloped regions. In developed nations, lymphedema is usually a byproduct of cancer treatment—in fact, it is one of the worst side effects of removing one or more lymph nodes, which is often done to determine how far a cancer has spread. Radiation treatment to cancerous lymph nodes can also cause lymphedema. Breast cancer patients are among those most likely to develop lymphedema, with about 20%–30% experiencing it to some extent, usually in the upper arms. However, lymphatic system problems can also develop in the legs or elsewhere following treatment for cancers in the pelvis or other locations. Historically, the only treatments readily available for lymphedema were compression, massage, and other palliative measures. “Some physicians have tried using liposuction or taking the radical approach of removing skin and muscle to offer relief to patients,” Dr. Chang added. However, the effectiveness of such approaches remains controversial. New treatment option M. D. Anderson is one of the first centers to offer a new procedure known as lymphaticovenular bypass to reroute the fluid that has built up. The procedure is performed using general anesthesia and is minimally invasive, requiring two to five small incisions. Using microsurgical tools, the surgeon redirects lymphatic fluid into tiny veins, allowing it to drain out of the affected area. Patients generally can return home within 24 hours. In a recently reported prospective analysis, Dr. Chang found that 19 of 20 breast cancer patients with lymphedema who underwent lymphaticovenular bypass had significant improvements in their symptoms. Researchers compared measurements of patients’ affected arms and healthy arms to quantify the benefits of the surgery. After bypass, there was a mean reduction in the volume difference between the healthy and affected arms of 29% at 1 month, 33% at 3 months, 39% at 6 months, and 25% at 1 year. Dr. Chang has performed more than 30 such surgeries, and his group now has data documenting sustained symptom alleviation over 3 years. Though the surgery appears to be most effective before fibrosis develops, almost any breast cancer patient with stage I, II, or III lymphedema of the upper extremities is a candidate, and the procedure can also be performed for lymphedema in the legs. Dr. Chang is now planning a larger prospective trial of lymphaticovenular bypass for upper and lower extremity lymphedema in conjunction with collaborators from the Department of Surgical Oncology. Visualizing the lymphatic system Dr. Chang has also worked closely with Hiroo Suami, Ph.D., clinical research program coordinator in the Department of Plastic Surgery, who has been studying the anatomy of the lymphatic system since 2001. A specialist in gross anatomy, Dr. Suami is employing a novel method for imaging the lymphatic system and aims to develop a modern map of the system. The maps of the lymphatic system currently taught in medical schools originated in France over 100 years ago. “They made a diagram—not photos, but a diagram. We don’t know how accurate that is,” Dr. Suami said. Modern imaging can help create a better anatomical model and illustrate how lymphedema occurs, he added.
But Dr. Suami’s research goes beyond exploring the mechanisms of lymphedema. “We want to understand how the lymphatic system works so we can understand its role in spreading cancer,” he said, noting that the lymph nodes are among the most common sites of early cancer metastasis. To do this, Dr. Suami has developed animal models that allow him to inject orange lead oxide directly into the lymphatic vessels of living rats and mice. He has also had a great deal of success with human cadavers, using a microscope to guide the injection and then studying differences between cadavers with and without lymphedema. To visualize the lymphatic system, Dr. Suami injects the orange lead oxide directly into the lymphatic vessels. A contrast medium, lead oxide can be recorded by radiography, computed tomography, or three-dimensional computed tomography. “We also plan to use an infrared camera system in the near future to study the lymphatic vessels in living animals,” Dr. Suami said. Currently, only limited visualization of the lymphatics can be obtained in clinical practice. For example, during sentinel lymph node biopsy, physicians inject dye and radioactive tracers to identify the lymph nodes closest to a tumor, those that are most likely to contain metastasis. “However, the sentinel lymph node biopsy technique can only identify the nodes and surrounding vessels near the injection area,” Dr. Suami said. “By injecting lead oxide into the lymphatic vessels, I can delineate comprehensive pathways.” Another difference is that sentinel node biopsy is only used in primary operative cases because previous operations disturb lymph flow, Dr. Suami said. “But my technique can be applied in postoperative cases to see changes in the lymphatics,” he explained. Future implications If reliable methods of mapping the lymphatic system can be developed, cancer surgeons could spare more of the healthy lymphatic system during lymph node removal. “Perhaps we can keep the lymphatic vessels visible using colored dye during operations for cancer,” Dr. Chang said. “That would help us preserve the essential lymphatics and remove cancerous lymph nodes without damaging others.” And while lymphaticovenular bypass surgery can potentially relieve the misery of lymphedema, Drs. Chang and Suami hope that someday their research will make the surgery obsolete. “Right now, we can help reduce lymphedema, but there is no cure. Once we learn why lymphedema develops in some cases and not others, we may be able to prevent it,” Dr. Chang said.For more information, call Dr. Chang or Dr. Suami at 713-794-1247. Other articles in OncoLog, June 2009 issue:
Home/Current Issue | Previous Issues | Articles by Topic | Patient Education ©2009 The University of Texas M. D. Anderson Cancer Center |
|||||||||
TOP