Multidisciplinary experts discuss the role of concurrent radiation in the treatment of renal cell carcinoma.
Elizabeth Wulff-Burchfield, MD: Dr McKay, I have 1 other question to ask you. It sounds as if you’re a superuser of SBRT [stereotactic body radiation therapy], and you collaborate with your radiation oncology colleagues for metastasis-directed therapy, which is so important. I agree that we’re going to be doing so much of that in the future to completely move past the narrative that radiation isn’t helpful for renal cell carcinoma. If you had a patient whom you thought might get metastasis-directed therapy even though they need systemic [therapy], are there regimens you favor or disfavor in the setting of receiving radiation?
Rana McKay, MD: We just published an analysis looking at cabozantinib given concurrently with radiation therapy. It looked at different patterns of use of cabozantinib, specifically with SBRT. There are variable practices about patients stopping their TKI [tyrosine kinase inhibitor] when they’re getting radiation, whether they continue their TKI, and for how long you hold the TKI prior to radiation. This is getting a little nuanced, but the site you’re radiating probably matters. In the context of bone metastases, the toxicity is probably limited. In the context of soft tissue or any abdominal-based metastases, erring on the side of holding makes sense. There are variable practices.
When I have a patient who’s on 1 given regimen, I try to maximize that regimen to its fullest before I say that somebody has progressed and is done with that treatment. A lot of things are [done differently] on trial vs clinical practice. For example, dose modification and titration. I’ll have patients who may be on 20 mg of cabozantinib and have a little progression. It’s not to a large degree, but you can see that they’re trending in the wrong direction. We say, “Let’s see what we can do. You’re on cabozantinib 20 mg, but do you think you can tolerate 40 mg 2 or 3 days a week? Let’s try to do that.” There are a lot of nuances. This is the art of treating patients in the clinic. I don’t think that’s in the guidelines per se. From seeing a lot of patients and having experience with working with these drugs, you can develop a style around how to adjust dosing and maximize the benefit of any given regimen before you close the door on that regimen.
Elizabeth Wulff-Burchfield, MD: Absolutely. There’s nothing an oncologist hates more than throwing the baby out with the bath water. We don’t have an unlimited number of treatments for essential hypertension, let alone any metastatic solid tumor. That’s an important grounding philosophy. Like you, I’ll do things like that or have folks who are so frail from cancer-related symptoms at the beginning of their treatment that we have to dose reduce their cabozantinib down to 20 mg. Later, if we’re trying to get them higher serum levels and things like that, we may be able to scoot it back up.
You’re right: there’s absolutely no way to capture that in trials. I’m open in disclosing my motivations and rationale with patents about that. [I want them to] understand that it might be standard to discontinue a regimen and start a different one; however, I want to make sure we extend that benefit. It’s completely sound ethically and medically. It’s great to hear that others are doing similar things.
Transcript edited for clarity.