ctDNA Shows Promise for Assessing Lung Cancer Treatment Response

Mark G. Kris, MD


January 27, 2022

This transcript has been edited for clarity.

Hello. This is Mark Kris from Memorial Sloan Kettering, talking today about circulating tumor DNA (ctDNA), an emerging technology for use in perioperative patients. Recently, there have been a number of presentations about the use of ctDNA measurements in patients receiving pre- or postoperative therapies. These are critical therapies because they are given with the intention of improving the chance for cure.

All three of the presentations I'm going to mention have one thing in common: They used the so-called tumor-informed panel. The investigators took the patients' tumor tissue, looked for cancer-related genes in that tumor tissue, and then looked for those same genes in the patient's blood. That technology is going to become very important, as shown in these presentations.

I made one of these presentations at the European Society for Medical Oncology (ESMO) Immuno-Oncology virtual meeting in Geneva. In our study, we were able to find genes in the majority of patients who had tumor tissue available. These patients were preoperative surgical candidates. In 72% of these, we were able to find and track ctDNA. When we tracked the DNA in the blood, we saw that the falling levels of DNA were associated with shrinkages of the cancer radiographically — the degree of shrinkage seen in this case in the neoadjuvant examination at the time of surgery and examining the resection specimen after neoadjuvant therapy. Ultimately, the major pathologic responses were associated with clearing or falling DNA as well. Perhaps the most interesting observation is that when you put this DNA information together with the major pathologic response information, all of the patients who had clearance of ctDNA and had a major pathologic response were disease free. I believe that eventually we will use this ctDNA data in conjunction with other measures of benefit to reach a more precise assessment of therapy benefit, and eventually it may be helpful for prognosis as well.

Two other studies also used this technology. One was earlier this year, presented by Patrick Forde at the American Association for Cancer Research meeting. They associated changes in ctDNA using another tumor-informed assay. In that study, using the Archer assay, they were able to show that the ctDNA clearance was associated with a complete pathologic response. So again, combining this information provides a more precise measurement of the benefit of therapy.

Another presentation at ESMO Immuno-Oncology, by Caicun Zhou, looked at the Natera assay, another tumor-informed assay, in a trial of adjuvant atezolizumab. This group showed that patients who had clearance of their ctDNA after surgery had the greatest benefit from subsequent atezolizumab therapy. And even those patients who did not have clearance experienced some benefit of the atezolizumab therapy. In addition, they assessed the degree of benefit associated with whether or not PD-L1 was present. Those patients who had PD-L1 expression experienced the greatest benefit from the atezolizumab. For patients who didn't have PD-L1 expression, where you wouldn't expect atezolizumab to have this greater benefit, they didn't see it.

I believe that ctDNA-informed testing will become more and more useful, both in clinical trials and ultimately in the care of patients with early-stage lung cancers. These tumor-informed assays are going to be standards of care and provide physicians and patients a better estimate of the effectiveness of therapy going forward.

Mark G. Kris, MD, is chief of the thoracic oncology service and the William and Joy Ruane Chair in Thoracic Oncology at Memorial Sloan Kettering Cancer Center in New York City. His research interests include targeted therapies for lung cancer, multimodality therapy, the development of new anticancer drugs, and symptom management with a focus on preventing emesis.

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