Is There a Role for SRS and WBRT for Brain Metastases in HER2+ BC?
Ryan Jones, MD, reflects on factors to consider when selecting stereotactic radiosurgery vs whole-brain radiotherapy including performance status, extracranial control, number of lesions, and CNS progression.
Erika Hamilton, MD: Ryan, this is something that I struggle with actually a lot in the clinic: SRS (stereotactic radiosurgery) versus whole-brain radiation therapy [WBRT]. When do you decide to do 1 versus the other?
Ryan Jones, MD: I was thinking of the timeline because I might have done her radiosurgery.
Erika Hamilton, MD: It's because she did well.
Ryan Jones, MD: [laughs] Yes![There are] a few key features for deciding on SRS versus whole brain [radiation]: certainly. [The] performance status of the patient [and] extracranial control or patterns. If I see it flourishing outside the brain, [it] gives me pause over what I am going to see in a few months if I'm just addressing these lesions locally. Still, the overall theme at present is avoiding whole brain [radiation] at all costs. If we're going to do it, can we justify a hippocampal sparing or so-called hippocampal avoidance style to try to minimize long-term cognitive effects or the incidence of significant fatigue after whole-brain radiation? I was trained at a very progressive place. We retreated many lesions, commonly 15, 20, or more with SRS and then kept monitoring and repeating if necessary.
With these drugs coming out that are helping us with intracranial disease of all volumes, but in particular, I'd say, conceptually, this idea of micrometastatic disease is that [we] can reliably help with—we can then take care of—bigger spots, maybe in the combination of how we're working together. I'm encouraged that number will keep shifting up as to when can we justify radiosurgery of [a] higher and higher number of lesions, but it's also limited by technology [and] what's in your region. To the audience listening, you might think, “Well, [the] radiation oncologist I work with doesn't routinely do this for more than 5 lesions.” It could be [that] technology is limiting that provider, because it takes some pretty advanced equipment to treat many lesions in a time that's practical for a clinic.
Erika Hamilton, MD: Absolutely. In follow-up to that, if brain metastases progress or if there are new lesions, how do you decide when you continue what I like to call “spot welding” with SRS versus when you pull the trigger for the brain at that point?
Ryan Jones, MD: The first MRI (magnetic resonance imaging) or the first couple of MRIs after a surgery can be tricky as to whether you're just seeing this transient kind of pseudo-progression and progression after that we see with some agents. We'll talk about this more later.
I'm curious still—as we see these drugs with activity—how these therapies might play together. We've seen some in the setting of radiosurgery with immunotherapy, suggesting that we're improving response by delivering the 2 together. I take pause with subtle changes on the first MRI, as in, let’s watch closely. Let's not jump to surgery or radiosurgery and repeat if the patient's asymptomatic. Certainly, we’ll use steroids or try to help symptoms if symptomatic. I'd say that for the topic of repeat. [And what was the] second part of your question?
Erika Hamilton, MD: If you have new lesions, do you continue using SRS?
Ryan Jones, MD: I do if at all possible. I'm a believer in it if the number of lesions, disease pattern, and performance status of the patient can justify it.
Erika Hamilton, MD: That makes sense.
Transcript has been edited for clarity.
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