A leading endoscopic surgeon said that removing complex esthesioneuro blastomas can be achieved using accepted oncological principles, and that the early results appear comparable to outcomes achieved with conventional surgery.
Obviously, this is a work in progress, said Carl H. Snyderman, MD, Professor of Otolaryngology at the University of Pittsburgh Medical Center (UPMC), in delivering the Presidential Lecture at the 111th annual meeting of the Triological Society held in conjunction with the Combined Otolaryngology Spring Meeting.
Looking at our own limited experience, we have now treated 24 patients for esthesioneuroblastomas, Dr. Snyderman said, describing his collaboration with Ricardo Carrau, MD, and Amin Kassam, MD, at the UPMC Center for Skull Base Surgery. He reported on 17 of those patients with at least one year of follow-up.
The early results are very encouraging. We have had only one recurrence in this group of 17 patients. We have had two patients with positive margins, he said, including one patient whose tumor involvement above the orbit required transition to an open approach.
We have followed patients for a mean of 31 months, so we are getting respectable numbers, he said.
Dr. Snyderman said, however, that he was concerned about endoscopic procedures that were not performed using oncologic principles designed to give patients the best possible chance for a cure. I am dismayed to see that many of the reports are doing what I would call a nononcologic resection, he said. They are not resecting the dura in all patients; they are not taking the olfactory bulb and olfactory nerves. They are not striving for the same defect that would be done with an open approach.
The margins of resection should be the same as with open approaches. Endoscopic approaches are not an excuse for performing an incomplete tumor resection. We shouldn’t be cutting corners.
Dr. Snyderman said that a fully endoscopic approach can be employed in resection of the difficult tumors. We can do so with adherence to oncological principles, he said. I want to warn you that you should adhere to oncological resection including the dura and olfactory nerves if the skull base is involved until we have good long-term data. Don’t rely on radiation therapy to sterilize the margins. We do have reconstructive options, the use of vascularized flaps to maximize the healing.
I want to caution that there is a steep learning curve in doing these surgeries. It wasn’t until we had four or five years experience working as a team on less involved cases that we embarked on the more complex tumors, he said in his lecture.
One cannot be anything but impressed by Dr. Snyderman’s presentation and the facility with which he and his team have been able to remove tumors with potentially less morbidity, commented Paul A. Levine, MD, the Robert W. Cantrell Professor and Chair of the Department of Otolaryngology-Head and Neck Surgery at the University of Virginia Health System in Charlottesville. His presentation demonstrated that a surgeon could expand the technique to all lesions.
However, Dr. Levine cautioned that the use of endoscopic surgery for esthesioneuroblastomas still does not have long-term outcome results needed to declare the procedure ready for prime time. He noted that recurrence of these tumors has to be looked at with a different clock than other cancers, as recurrence often develops more than five years after treatment-sometimes not until 10 years or more after surgery.
Any time there is a paradigm shift, there are several phases of development you have to go through, Dr. Snyderman said. The first one is feasibility. Can this be done? For skull base endoscopy, the first thing we had to do was relearn the anatomy from an endoscopic approach. Second, we had to develop the instrumentation that would allow us to do some of these things-and that is an ongoing enterprise-and then we had to develop surgical techniques that would allow us to take out a complex tumor.
Once you solve those issues, then the next stage is really looking at the safety of what we are doing. Are the morbidities higher? Or are you just exchanging one set of morbidities for a different set? And finally, you need to look at outcomes. We need a critical self-appraisal of what is happening to our patients: What are their survival rates, and what is their quality of life?
I think we are in the second two phases at this point. We have demonstrated feasibility. We have demonstrated the safety, and we are starting to report outcomes data that are relevant, he said.
Dr. Snyderman said that although craniofacial resection remains the gold standard in treating esthesioneuroblastomas, conventional surgery is not without its own set of drawbacks. Open approaches don’t necessarily provide good exposure, he said. Radical resection of high-grade malignancies with skull base involvement is often unsuccessful. Postoperative therapy is often delayed due to concerns about healing or complications.
He said that the major benefit of an endonasal endoscopic approach to these tumors is better visualization. Perhaps that better visualization translates into better margins and into decreased risk of local recurrence, Dr. Snyderman said. We can see small vessels and dissect tumors without damaging the vessels, and that may prove important to functioning of the optic nerve.
We are not transgressing normal tissues to reach the tumor, and perhaps that will have a decreased risk of tumor seeding and have a less adverse effect on tumor growth factors. We also can get patients into adjunctive therapy sooner, and that may have a beneficial effect on outcome.
Contraindications and Limitations
Dr. Snyderman acknowledged that there are contraindications for doing an endonasal approach. Our golden rule is that if you have to move nerves and vessel to get there, it is not the best approach, he said. So if we have a tumor on the backside of the optic nerve, we might better use an open approach. We are never going to take out acoustic neuromas through the nose because they are on the wrong side of the nerves.
He advised colleagues that there may be limits to what can be achieved with endoscopic dissection of esthesioneuroblastomas and other malignancies, including whether the entire tumor can be removed using endoscopic approaches. Another limit is the individual doctor’s comfort level in dealing with complications, neural injury, and reconstruction.
Dr. Snyderman said that duration of surgery might also be a limiting factor, as some of the operations can be lengthy. They certainly can take a toll on the surgeon, he said.
He demonstrated in his talk that one of the main concepts of endoscopic endonasal surgery involves access of the endonasal corridor. This provides you with direct access to tumors, he said. There is no easy way to get there except through the nose. It gets you right to the base of the tumor. The goal is avoiding displacement of neurovascular structures. This becomes no-retraction, no-touch brain surgery.
I think that this is really the only true form of team surgery. You have two disciplines working together simultaneously, and neither one alone can achieve the goals of the surgery. There are lots of benefits from working together. It has been a tremendous advantage.
Dr. Snyderman said that when surgeons use an endoscopic approach, there is no difference in dissection goals as compared with conventional surgery. We use both nostrils so that we can operate with both hands. We often start by debulking the tumor and collapsing the tumor onto itself, and that gives us access to the margins of the tumor. We then perform an extracapsular dissection. There is no pulling of tumors. We are not just pulling tumors out through the nose. There is very gentle retraction, he said.
The majority of the time we will use a two-suction dissection technique. One suction provides very gentle retraction. It is not enough traction to tear vessels on the back side of the tumor, and the other suction is a dissector, he explained.
In removal of esthesioneuroblastomas, Dr. Snyderman said, we start by debulking the portion of the tumor that is hanging in the nasal cavity. We identify the landmarks around the margins of the tumor. We find the margins in the front sinus anteriorly, the nasal septum inferiorly, and the orbit laterally.
Then we start removing the bone around the margins of the tumor to expose the dura. The dura is incised at the margins of the skull base, and finally there is complete resection of the dura, the olfactory bulb, and the olfactory tract. There is no retraction of the frontal lobes, but we are still achieving the same resection and we are having excellent visualization. There is nothing blind about this technique.
The defect created is the same that is achieved in conventional approaches. He said that the defect can be covered with vascularized flaps. One thing that we have learned over the last decade is the use of a Foley balloon as an external bolster to maintain support during the early healing period.
He said that cerebrospinal fluid leaks that were a major complication in early endonasal procedures have been corrected with the use of flaps. With use of the septal mucosa flap, we have decreased our leak rate down from about 25 percent to about 5 to 10 percent. In fact, our leak rate is now 4 percent overall and 7 percent in high-flow leak situations, which is comparable for what has been reported in the open approach, he said.
We have to remember that the extent of surgery is determined by the biological behavior of the tumor, Dr. Snyderman said. The endoscope is just a tool. It is not the endoscope versus the microscope. It is about choosing the best approach for the patient and the tumor.
Dr. Snyderman disclosed that he has possible financial conflicts of interest with Karl Storz Endoscopy America and Stryker Navigation and Instruments.
©2008 The Triological Society