Ulka Vaishampayan, MD: What about adding stereotactic radiation with the goal of controlling metastatic disease, both locally as well as systemically?

Rana R. McKay, MD: That’s an excellent question, Ulka: What’s the role of SBRT [stereotactic body radiation therapy]? We saw data from the SABR [stereotactic ablative radiotherapy] trial. This was a trial that looked at the role of SBRT and showed benefit. There’s more talking about the abscopal effect of radiation as opposed to true data out there. I really want to commend the authors of 2 abstracts that were presented at GU ASCO [American Society of Clinical Oncology Genitourinary Cancers Symposium]. Hans Hammers, MD, PhD, and Cristina Masini, MD, both presented data of the role of SBRT in the context of I/O [immuno-oncology] therapy. The NIVES trial was a phase II, single-arm trial that looked at patients treated with nivolumab and SBRT. The response rate was underwhelming, about 17.5% in this trial. The response rate is below what we would see with historic controls in a patient population that was predominantly naïve of a prior checkpoint inhibitor.

Dr Hammers presented data on nivolumab-ipilimumab combined with SBRT from the RADVAX trial, and response rates were higher, on the order of around 56%. It’s good to have these data out there. I think these data really highlight that this approach is feasible, this approach is safe, but I think we need more data to really prove the role of SBRT as being truly synergistic with nivolumab and ipilimumab.

There are other questions to be asked about SBRT. What is the role in the context of patients who have oligometastatic disease, when treating with an almost curative intent and trying to radiate all visible sites of disease? Also, is there a potential role in the context of oligoprogression post-I/O where you can maintain an I/O backbone and then treat with SBRT to the oligoprogressive sites? I think these are unmet questions in the field. Sumanta Kumar Pal, MD, gave a very sobering discussion on these 2 abstracts and the data that are out there about the role of SBRT. I think we need to see more data before we really implement this in practice.

Ulka Vaishampayan, MD: I agree. He actually showed the comparison to standard ipilimumab-nivolumab-only data, and there really wasn’t a big difference with the addition of SBRT. So definitely very sobering clinical trial data. At least from the preclinical trials and preliminary studies, the thought was that this would add quite a bit to the immunotherapy. Any other comments?

Mehmet Asim Bilen, MD: Ulka, I agree with you and Rana. I think a possible area where we can use radiation down the road may be if someone has a symptomatic primary tumor. In that case, we can entertain SBRT. In addition to that, we have patients with IVC [inferior vena cava] tumor thrombus. There’s nice data from NRG Oncology on this group of patients. When they radiate IVC tumor thrombus, they have a pretty good outcome. It turns out that they had a very high PD-L1 [programmed death-ligand 1] expression. So, combining this with immunotherapy may be an important area of study. And the third area that we can think about it is, once we have the PD-L1 PET [positron emission tomography] results, using radiation to the cold tumor may make it hot. And then, combining with radiation therapy might also be possible. I think the jury is still out, but hopefully we can learn from those trials and come up with a good combination.

Transcript Edited for Clarity