Novalis LINAC Radiosurgery and Radiotherapy for Chordomas and Chondrosarcomas of the Skull Base

Cranial neoplasia (benign), 2008

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Speaker

Jason S. Hauptman, MD, PhD

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Description

Jason Hauptman, MD, from the University of California Los Angeles discusses their study of Novalis linear accelerator radiosurgery and radiotherapy for skull base chordomas and chondrosarcomas. He begins by giving an overview of chordomas, which are benign but locally invasive and difficult to treat. He goes into studies examining their treatment with radiosurgery. He then delves into the study completed by the UCLA neurosurgery department, including rationale, methods and results.

Transcript

I am J. Hauptman. I'm from UCLA. I'm a resident in neurosurgery. It's a pleasure to be here. Thank you very much for having me. It's a pleasure to be able to present my data, but more importantly to get three days off of residency. Thank you. Thank you, everybody. Knowing neurosurgery, I don't think I can take off from Santa Barbara, and they might make me. I don't know, yeah. Might be a little far to drive to L.A. So, what I did here was, during my short time on the stereotactic radiosurgery service, so, I wanted to look at our experience of chordomas and chondrosarcomas of the skull base, because our experience is limited, and in the literature, particularly with LINAC radiosurgery and radiotherapy, experience is limited and numbers are small, as are ours. But, hopefully, this will contribute to our knowledge of how to treat these. A lot of people helped me, including Dr. De Salles, my mentor, Dr. Selch, and Dr. Agzaryan. They taught me everything I know about physics, which isn't much.

Why do we do this? Chordomas are histologically benign tumors thought to arise from the notochord. We know that. Even though they're histologically benign, their behavior is extremely invasive, and patients experience multiple recurrences. It's a characterization of the disease. And the consensus approach that we take to these is we operate first, we radiate second as an adjunctive therapy. The literature shows that we've used Gamma Knife, LINAC, proton beam therapy, and they've all shown good tumor control rates. Not great, good. And they're all characterized by limited experience except save for a few, which have some relatively large members.

Just some examples, this is the Pittsburgh group and their experience of Gamma Knife radiosurgery which shows about a 62%, 63% tumor control rate at five years. This is a review of Dartmouth's experience... Sorry, a review at Dartmouth regarding proton beam therapy showing about a 75% tumor control rate over 33 months. And this is a small study out of Stanford showing about a 70% control rate using LINAC. That's over three years or four years. So what did I do? I looked at treatment plans and medical charts of patients we treated, and then using DVHs I looked at the amount of dose that the brainstem received, the optic apparatus received, and the pituitary gland and stalk received, hopefully to maybe draw a conclusion about whether those patients experienced pituitary failure or visual field deficits, so on and so forth.

So over a period of 8 years, a total of 14 patients received 15 total treatments. We had mostly chordomas, one kind of sarcoma. And all of them at least had surgery once. Total of 10 radiotherapy, 5 radiosurgery. This is a demographic breakdown. So these are about, you know, 50 years old was the mean age for SRT and 63 for SRS. And the mean time from diagnosis to radiation was about 1800 days. Two-thirds of these treatments were for post-surgical residual tumor. That is, they had surgery, they had residual, they got their radiation, whereas five treatments were from recurrent disease years after surgery.

Breaking down the locations of these tumors, about half were clival or petroclival. One was primarily located in the CP angle, and the 40% were parasellar and cavernous sinus. And, overall, our follow-up was so-so. A lot of that, I think, is because a lot of these patients were referred from very far away, and we tried our best to kind of keep tabs on them. So I'm gonna present to you as best as we have. Five were lost to clinical follow-up and two were lost to radiographic follow-up. So we do have good radiographic follow-up on the majority of patients. I mean, if we exclude those who were lost to follow-up, our clinical follow-up is pretty good, almost 1000 days of clinical follow-up. And our radiographic follow-up was also almost 1000 days. So we have a pretty significant radiographic and clinical follow-up on the ones that we do have follow-up.

This is a breakdown of the patients who received stereotactic radiotherapy. They all received anywhere between 28 and 42 fractions, anywhere from 50 to 75 Gy. Most received intensity and modulation technique. There were a few that did not. For fractionated therapy, the mean tumor volume was approximately 30 cc's, the mean prescribed dose, 60 Gy, and the mean maximum dose that actually the [inaudible 00:05:12.005] was at 67.4 Gy. And in these treatments, when we looked at the deviations, approximately 8% of brainstem volume, 42% or 43% pituitary stalk volume, and 9.5% of optic apparatus volume was contained in the 80% isodose line. I went a little overboard with the animations, [inaudible 00:05:36], excuse me.

In this group, there were two patients who experienced tumor recurrence, 22%. That's two out of nine that we had good follow-up on. If I count number 10 as a failure because we have no follow-up on him, it's still approximately 70% tumor control rate over the time that we have, which is consistent with part of studies. In patient number four...because this is a question I got at a previous presentation that I described this. We describe failure as radiographic signs of failure, increased theories of enhancement called by a radiologist. In patient four, I defined recurrence as new areas of enhancement. He did not go back to surgery, of his own choice. So I don't know whether that was confirmed by [inaudible 00:06:21.003]. So I can't tell you even for sure whether that was true, recurrent disease or whether, you know, this radiation changes. However, with patient number six, she did go back to surgery. She had new areas of enhancement. She went back to surgery, and that was a recurrent disease. We had one patient that seriously required thyroid replacement, and one patient who had asymptomatic medial temporal lobe changes from radiation.

In our SRS group, with a total of five patients, number four is interesting because she actually had SRT, and she failed. That was the one that actually went to surgery and had additional surgical debulking. She failed and went, actually, to SRS about a year later, and did well since then. In this group, our mean tumor volume was 12 cc's, 13 cc's, with a mean prescribed dose of 17 Gy, and a mean maximum dose of approximately 19 Gy. Again, we really kept brainstem volume low through our high conformality of 0.3%. Forty percent was seen by the pituitary stalking gland, and about 9.7% was seen by the optic apparatus at the 80% isodose line.

Okay. And as for our outcomes here, we had one patient who had a recurrent tumor. Again, he had new areas of enhancement, and he went to surgery, and that was confirmed surgically. And we had one patient who had mildly symptomatic medial temporal lobe changes. Now, that is the same patient that had received SRT a year before. So it's probably not hard to, you know, reason out why she had some radiation changes in the mesial temporal lobe. She had some deja vu and a little bit of headaches, and that's what we ascribe to those radiation changes.

Now, number five, who I think I'm gonna talk about in a second here... Okay. Going backwards. Sorry about that. Number five, we had really lost to follow-up. And according to a report somewhere from a primary care physician outside of our system, I saw that she began to develop multiple cranial neuropathies, and there was no further investigation done. I don't know if she's still alive. And, you know, I don't know if she's received any other imaging, but I would count her as a failure, to be conservative, because it sounds like she recurred. So then we're talking about two or five, or three or five failures, because number two, we really have no clinical follow-up on. So our SRS data is not really as good as our SRT data, but that's really what I wanted to impress, is that our SRT is pretty good.

So in conclusion, stereotactic radiotherapy, more so, I think, than stereotactic radiosurgery, are useful techniques for adjunctive treatments of skull base chordomas and chondrosarcomas. And, of course, as we know that being highly conformal really minimizes the amount of radiation at the brainstem and the optic apparatus in the pituitary see and therefore minimize the morbidities of our treatment. And, of course, we need larger numbers and more studies. I think that goes without saying, but this is a relatively rare pathology. So, I'd like to thank everybody that helped me. Dr. De Salles, Dr. Selch, Dr. Agzaryan, our surgeons that referred us to these patients, and everybody here for listening. Thank you.