Sentinel lymph node mapping and biopsy for early stage oral cavity cancer
Dr Stephen Lai - The University of Texas MD Anderson Cancer Center, Houston, USA
Can you tell us about your discussion at IAOO?
My talk today is going to be about sentinel lymph node mapping and biopsy for early stage oral cavity cancer. So the thought is that in early stage oral cavity cancer there still is a risk for spread of the cancer from the primary tumour site in the oral cavity, say the tongue or the floor of mouth, to the lymph nodes in the neck. That risk, even when by clinical examination and radiographic examination shows that there are no lymph nodes present, you can still have disease present in approximately 20% or greater of patients. So the traditional therapy for patients in those situations, and sometimes with a certain depth of invasion for the primary tumour, is to go ahead and do an elective neck dissection. The elective neck dissection is certainly diagnostic, it gives you the pathology specimen to analyse and it can be also then therapeutic if you do remove disease.
You have up to about 80% of patients who may have an elective neck dissection who may not have needed it in the first place. So the thought is that you can do sentinel lymph node mapping; you can find out which lymph nodes are at highest risk, or the first echelon lymph nodes, and then you can remove them. Then in that way you are only looking at a sampling of the lymph nodes rather than all of the lymph nodes. The other advantage to this is that the sample of lymph nodes, so if you take out one, two or three lymph nodes, now your pathologist can focus on those few lymph nodes, they can do serial step sectioning and actually assess the entire lymph node, rather than just assessing a portion of, say, twenty, thirty or forty lymph nodes.
Sentinel lymph node mapping and biopsy technology and the surgical technique has been well established in melanoma and in breast. So that’s why it seems to be a useful technique.
How widely is this used in head and neck?
The Europeans have the longest track record with it and so they’ve had… I think it’s become very much standard of care over there. It is used around the world elsewhere; there have certainly been some clinical trials that have been tried, done in the US and in other countries, but I would say that it has the strongest foothold in Europe.
There are new technologies being developed and one of the technologies I’m involved with is something called Lymphoseek, or tilmanocept, and it’s a first in class receptor targeted agent. So it has a radiotracer called technetium that it’s labelled with but the actual agent itself actually binds to a specific receptor on immune cells that are found in the lymph nodes. So it’s thought that it can actually be retained in the lymph nodes and then identified more easily.
Can you explain how your team’s approach to this work?
Trying to get this to work requires… it is a multidisciplinary effort, just like the care of head and neck cancer patients. But certainly you have to have your nuclear medicine colleagues on board because they are the ones who ultimately lead the scintigraphy studies or the SPECT/CT studies. But you have to get approval from the hospital to get the newly labelled agent in; you have to be able to get your patient to the nuclear medicine department and get them injected with this agent prior to the surgery and then have the radiology study done so that you can actually know where the lymph node is going to be.
Do you see this becoming a standard of care?
It’s gaining traction. It’s an attractive alternative to doing an elective neck dissection. But I would caution that it is really for a specific subset of patients. It’s also important, as it is being adopted, that we study it carefully rather than simply taking it on board. The nice thing about some of the new agent tilmanocept is that it actually has an FDA indication in the United States for use in head and neck cancer. But even with that indication it still merits careful study. The D’Cruz study that was published in The New England Journal recently certainly helps to settle the issue that has existed for a long time about elective neck dissection versus therapeutic neck dissection. Now the question of elective neck dissection versus sentinel lymph node deserves the same kind of carefully designed study to address the differences between the two approaches.
