new research: Sentinel Lymph Node Mapping for Cervical and Endometrial Cancer Continues to Evolve

Elsevier Global Medical News. 2010 Aug 11, D Brunk

Fewer than 10% of gynecologic oncologists use sentinel lymph node mapping for cervical cancer, and less than 5% use it for endometrial cancer, according to Dr. Nadeem R. Abu-Rustum. To his mind, these rates are "a shame" in today's clinical practice.

"A lot of people are much more interested in learning newer, much more expensive techniques instead of investing in trying to understand the disease process, and do the operation in a more fine-tuned, precise way, to target the lymph nodes that are potentially involved with disease," said Dr. Abu-Rustum, director of minimally invasive surgery for the gynecology service in the department of surgery at Memorial Sloan-Kettering Cancer Center, New York.
Dr. Abu-Rustum has been an investigator for several published studies of sentinel lymph node mapping in both types of cancer. The technique promotes a more precise, fine-tuned operation and reduces the risk of leg lymphedema and other side effects to patients, he contends. It also provides the pathologist with a better specimen, and allows clinicians to be more accurate in the way they stage and define metastases.

"Sentinel lymph node mapping is for people who have negative, normal appearing lymph nodes," he said. "It's taken years for it to become accepted as standard of care in breast cancer and melanoma.

"I think that in cervical cancer and endometrial cancer, we will probably move slowly away from complete lymphadenectomy to sentinel lymph node mapping. We will never stop doing pelvic lymphadenectomy, but we can abbreviate it and make it more fine-tuned and more precise to the lesion."

Sentinel lymph node mapping in cervical and endometrial cancer complements current trends in minimally invasive surgery, agreed Dr. Michael Frumovitz, a gynecologic oncologist at the University of Texas M.D. Anderson Cancer Center, Houston. "The general philosophy of sentinel nodes is, 'can you be oncologically safe by removing less?' " he said. "That fits in very well with a minimally invasive mentality of 'can we make smaller incisions and do less invasive surgeries oncologically and still be oncologically safe?' "

Sentinel lymph node mapping techniques for cervical cancer "are pretty well worked out," Dr. Frumovitz said. "I think we need one or two large studies to prove that it is reliable and valid."

Blue Dye and Tc-99 - or Blue Dye Alone?
Most gynecologic oncologists use a combined injection of patent blue dye and technetium-99m radioactive colloid (Tc-99), injecting intradermally at the junction between the tumor and the normal tissue of the cervix, according to Dr. Frumovitz. "If the patient has had a prior cone biopsy and there's no visible tumor, then we inject in four quadrants," he explained. "You then allow some time for the substances to be taken up and transported to the regional lymph nodes. Then you open up the lymph node basins, and you look both using your eyes and using a handheld gamma counter to detect where those substances have localized."
To date, detection rates for cervical cancer have ranged from 80% to 100% in published studies, Dr. Abu-Rustum said. In early studies clinicians used both Tc99 and blue dye, "because this has been the recommendation from many other specialties to improve your detection rate," he said.

"But as your experience gets better, you may be able to use just blue dye. Many of the breast surgeons, as they get better, stop using Tc-99 and they just use blue dye. That's what we've done in gynecologic oncology as well. The advantage of using Tc-99 with blue dye is that it probably still provides you with the highest chance of finding these lymph nodes."

Endometrial Injection Site Not Defined
Less is known about the success of sentinel lymph node mapping in endometrial cancer because there is no clear-cut injection site. Some use the cervix, but that technique negates ovarian drainage of the uterus, Dr. Frumovitz said.

"Ideally, you would inject around the tumor like you would for all other sites, but to do that in endometrial cancer is very difficult," he said. "There are some centers that have tried to do it hysteroscopically - trying to visualize the tumor with a hysteroscope then injecting around it. We've had varying rates of success, anywhere from 40% at our center to 90% in studies done in Italy and Japan. It's a very difficult technique to do. For something to become widely used by everyone, it needs to be a little simpler."

Dr. Abu-Rustum maintains that a cervical injection is sufficient for sentinel lymph node mapping of endometrial cancer because the main drainage of the uterus "comes out through the main lymphatic channels and bundles of blood vessels that are between the cervix and the uterus. It's an anatomic reality."

To date, detection rates for endometrial cancer in published studies have ranged from 50% to 100%, Dr. Abu-Rustum said. In his opinion, the learning curve for sentinel lymph node mapping of both cervical and endometrial cancer is about 30 cases. "It's really an individual technique," he said. "It's the same story in breast cancer: You have to have a dedicated surgeon, a dedicated pathologist, and a commitment to doing a certain number of cases before you start changing your practice."

Preoperative Alternatives - Are They Cost Effective?
Other preoperative techniques to detect sentinel lymph nodes include planar lymphoscintigraphy and, more recently, SPECT-CT. In a study of sentinel lymph node mapping in 40 women with endometrial cancer and 10 with cervical cancer conducted by Dr. Abu-Rustum and his associates (Gynecol. Oncol. 2010;117:59-64), planar lymphoscintigraphy alone detected sentinel lymph nodes in 8 of the cervical cancer patients (80%) while SPECT-CT localized nodes in all 10 patients (100%). In endometrial cancer, planar lymphoscintigraphy alone detected sentinel lymph nodes in 30 patients (75%) while SPECT-CT localized nodes in all 40 patients (100%).

"I think SPECT-CT can give you an edge over planar lymphoscintigraphy," Dr. Abu-Rustum said. "If you inject Tc-99 and you take a plain x-ray, it may show you where hot spots are, but it's not going to tell you where these are anatomically. When you do the SPECT-CT, you can tell anatomically where that lymph node is. It gives you an edge over planar imaging as far as accuracy and localization. There is a cost to this, of course. Not all institutions have it. But in terms of evolving technology, this has an advantage."

In the opinion of Dr. Frumovitz, preimaging with planar lymphoscintigraphy or SPECT-CT provides minimal information that can't be obtained at the time of surgery. "We're not going to change our incision based on that imaging," he said.

"For example, in cervix cancer we know that [disease is] going to drain to the pelvic nodes. Which of those nodes, we don't know, but we're going to look for those nodes during surgery. So using a SPECT-CT is just adding cost, added time for the patient, and added pain for the patient, because it hurts."

Dr. Abu-Rustum predicts that increasing numbers of gynecologic oncologists will begin to perform sentinel node mapping for cervical and endometrial cancers.

"Like everything in medicine there is always a lot of resistance initially, but with time things can open up and become more accepted," he said. "I suspect that as time goes on, more people will adopt this technology because there is more doubt about performing lymphadenectomy for normal-appearing lymph nodes."

Dr. Abu-Rustum and Dr. Frumovitz reported no conflicts of interest