In this JCO Precision Oncology Article Insights episode, Natalie DelRocco summarizes "Real-Time Monitoring in Renal Cell Carcinoma With Circulating Tumor DNA: A Step Forward, but How Far?" by Zeynep B. Zengin et al. published on February 28, 2025.

TRANSCRIPT

The guest on this podcast episode has no disclosures to declare.

Natalie DelRocco: Hello, and welcome to JCO Precision Oncology Article Insights. I'm your host, Natalie DelRocco, and today we will be discussing the editorial, "Real-Time Monitoring in Renal Cell Carcinoma With Circulating Tumor DNA: A Step Forward, but How Far?"

This editorial by Zengin and Kotecha discusses the impact of circulating tumor DNA (ctDNA) and its potential applications in renal cell carcinoma - we'll call this RCC for the remainder of the podcast.

This article was published in February of 2025, and I think this is really timely because ctDNA is currently an emerging biomarker of interest in many different cancers. Having shown promise in certain cancers, other types of cancers are really targeting ctDNA to see if it can be used as a prognostic or a predictive biomarker in their specific field of oncology. Sometimes it is found that ctDNA is a prognostic marker that's associated with outcome, but it's not always clear whether it is a predictive biomarker that can help modify treatment and to what extent it could be helpful modifying treatment.

This is what the authors of this editorial really focus on. They focus on the applications of ctDNA in RCC by interpreting the accompanying article, "Longitudinal Testing of Circulating Tumor DNA in Patients With Metastatic Renal Cell Carcinoma" by Basu et al.

So, the editorial authors begin by giving examples of cancers where ctDNA has been shown to be useful in cancer monitoring - for example, locally advanced urothelial carcinoma - and they give examples of when it has not been shown to be useful in monitoring colorectal cancer. And this just highlights the variability of ctDNA as a biomarker. It's not always a useful biomarker, but sometimes it is.

The authors note that RCC may fall into the latter category - that is, the "not useful" category - due to the low ctDNA shedding which characterizes RCC. However, metastatic RCC - we'll call this ‘mRCC’ for the remainder of the podcast - may be a target for use of ctDNA clinically due to advanced assay development, according to the authors. Basu et al, in the original work that the editorial accompanies, showed in a retrospective study of 92 patients with mRCC that ctDNA detectability was associated with poorer PFS, regardless of receipt of active treatment versus no receipt of active treatment. That's important because ctDNA can be directly affected by therapy.

The authors of the editorial believe that this is a particularly promising result for a few reasons. Firstly, the estimated hazard ratios were quite large. A hazard ratio of 3.2 was seen in the active treatment group versus a hazard ratio of 18 was observed in the no-active-treatment group. I will note that a hazard ratio of 18 with an extremely wide confidence interval is an unusual observation. So, when interpreting this result, I would consider the direction and magnitude of the effect to be suggestive of promise but needing to be validated in the future to improve precision. And the authors of the editorial do agree with this; they note the same.

The authors also note that a single-patient example was used to show how that ctDNA positivity can be used in mRCC to monitor and prompt imaging if disease progression is suspected. And then that way, disease progression can be caught earlier. That to say, there is a real target for clinical use, which isn't always the case. Sometimes we know that ctDNA is associated with outcome, but we don't quite know how we can modify when we know that ctDNA is positive. In this case, the editorial authors show that we can use ctDNA positivity to monitor patients for disease progression.

Despite the promise of the study, the editorial does highlight that the study inherits typical retrospective study limitations. For example, there is a heterogeneous cohort. There is variability in data collection, particularly nailing down specific time points, which can always be a challenge when collecting biological samples as part of a study. And small sample size - although 92 patients is great for renal cell carcinoma, it is a challenging sample size with respect to precision of those hazard ratio estimates, which we've already talked about.

The authors additionally note that ctDNA could be used to direct therapy, not just to monitor for disease progression. So, both monitoring and changing therapy would certainly require further study and validation, which is discussed by the authors of this editorial. We would want larger, prospective studies showing the same association before we would be comfortable modifying treatment for patients based on their ctDNA positivity level.

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