Radiofrequency Ablation of Spinal Metastases: Patient Selection, Goals of Therapy, Follow-Up Care

[Michael Barraza]
What are the primary indications and the goals of radiofrequency ablation therapy for spinal lesions?

[Sonny Bagla]
The primary goal is to get patients out of pain. So, to palliate these patients, they obviously have advanced disease by nature of the fact that they have bone metastases. Our primary goal is get them out of pain so that they can go on and live a good quality of life and stay on their systemic therapy, which many patients cannot tolerate because they're in so much back or pelvic pain that they don't want to tolerate their systemic therapy. The secondary goals are more about preventing a delayed skeletal event, preventing that severe compression or retropulsion. We don't follow patients with serial imaging who come in with your typical osteoporotic compression fracture, but if you do follow your oncologic patients, you will note that those patients who have lesions in the spine, when left untreated, end up going on to fracture. They end up coming back with epidural extension in time. And those are the types of events we're trying to prevent as a secondary effect of the procedure.

[Michael Barraza]
What are you looking for in terms of size and location of lesions in identifying appropriate targets for ablation?

[Jason Levy]
So, there's really no size criteria. The most common thing that serves as an exclusion is a neurologic compromise, so somebody who has neurologic symptomatology. I will treat occasional patients with multiple lesions, but I'm not going to treat somebody if they can't come into my clinic and say, "I hurt here and here." I need them to be able to localize where the pain is. Now, it's not always perfect, a lot of these patients will get wrap-around pain and our ER colleagues may have worked them up with a CT pulmonary angiogram to start with and sure enough it's actually a T5 met. But, the bottom line is I want the imaging to match the location of pain. If they just have diffuse pain, it's very hard to improve upon that and we usually refer those to our radiation colleagues.

[Sonny Bagla]
Yeah. I would agree. In those patients who I'd say are not candidates, we tend to shy away from patients who have diffuse disease all up and down the spine and don’t really have a focal spot that you can say, "This is where the pain is." Those patients might be better for a wider net of EBRT and/or biologic or bone stabilizing agents. Obviously, there are some patients who we turn down just because they're surgical candidates. Some of these patients have such instability that they do need fixation, and so that does happen where you get patients who are so advanced. These cases are important to consult with your spine surgeon and make sure that they have spinal stability. But, I absolutely agree with Jason's methodology, and I think taking that approach really keeps your patient flow consistent. The oncologist in the area, the radiation oncologist, the spine surgeon—they all know the kinds of patients you're going to put on the table and what your goals are for your therapy.

[Michael Barraza]
How do you approach lesions with significant extra spinal extension?

[Sonny Bagla]
We both tend to say, "Don't chase those extra spinal lesions with bone ablation." If you go and turn on a probe, whether it's radiofrequency or any other technology, and you turn that on say in the psoas musculature or somewhere else, you're going to end up having a problem. Patients are going to get resultant pain from burning or freezing that tissue. If you get very aggressive with lesions, that can add to the neural foramina. While you could be a little bit more aggressive there, you definitely run the risk of getting an exiting nerve root injury. You can use thermocouples, and there are protective techniques that you can utilize, but I always make the comment that if you just treat the vast majority of patients who aren't those, you're going to have great results. You're going to make a real big difference in these patients' lives.

[Jason Levy]
Yeah. I agree completely. Everything comes back to what our goals were, and it's pain relief and preventing delayed skeletal events. So, delayed skeletal events, when they occur, they almost always occur in the vertebral body, at least posteriorly. So, really making sure that your ablation is effective posteriorly, in my mind, comes first and foremost. Chasing tumors that are in the paraspinal soft tissues, I find to be both ineffective and overzealous. And, really, the bottom line is there's data to support not chasing that. If you look at some of the older studies, we know that the larger tumor ablations did not result in better pain relief, but in fact, it was just ablation at the bone-tumor interface.

[Michael Barraza]
You talk again about delayed skeletal events. Is there a role of using this for preventing that, beyond just pain palliation? I mean, is there a role for prophylactic ablation on lesions at high risk of fracture?

[Sonny Bagla]
Mike, it's a great question, and it is one that's probably not yet, to my knowledge, well-answered because it's very difficult to stratify those patients. There are grading scales for which certain factors increase the likelihood of instability of a lesion. For example, if that lesion were at a hinge point or if a certain percentage of the bone was replaced. But, because there's not necessarily a set guidance on it, a lot of it is left open to individual interpretation.

[Jason Levy]
Yeah. I agree with you. I mean, there's my opinion and then there's the reality. My opinion is similar to a surgeon who would be looking at something that's got an impending fracture. He'd be going and treating it. I do think that certainly for certain metastases, some of these renal cells, thyroid mets, or other real vascular and/or lytic lesions that really have a high propensity to go into fracture, I personally believe in an approach that is very aggressive upfront. Then you step back and you look at the reality and what almost every payor will accept for an indication. That's not one of them. So, you're put into a little bit of a challenging location if you believe that it is worthwhile, which I do. I agree with Sonny that we don't really have good data for that. Not sure we'll ever get that either.