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.
Explore This IssueOctober 2008
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.