The clinical utility of circulating tumor DNA (ctDNA) for detecting minimal residual disease (MRD) and for treatment planning postoperatively was a topic of debate at the European Lung Cancer Congress 2024, held in Prague, Czech Republic.
PRO: Prognostic Value
Enriqueta Felip, MD, PhD, of Vall d’Hebron Institute of Oncology in Barcelona, Spain, argued in favor of using liquid biopsy for disease surveillance and decision making about adjuvant therapy.
“In early stage non–small cell lung cancer I think the evidence shows that pretreatment baseline ctDNA levels are clearly prognostic, and also, after surgical resection, the MRD predicts relapse, so we know that at present ctDNA and MRD are strong prognostic markers,” she said.
“I think ctDNA is useful as a noninvasive tool in both settings — at baseline pre surgery and also post surgery — to guide adjuvant therapy decision making,” she added.
Dr. Felip noted that so-called “tumor-informed” assays, such as sequencing of tumor tissue to identify mutations that can then be tracked in plasma samples, are high sensitivity methods, but have a long turnaround time, and approximately one in five patients does not have adequate tumor tissues for analysis.
In contrast, “tumor agnostic” methods rely on epigenetic features such as DNA methylation and cell-free DNA fragmentation patterns to detect tumor-derived DNA, but don’t rely on tumor tissue sample.
Dr. Felip cited a 2017 study published in Cancer Discovery showing that in patients with localized lung cancer post treatment ctDNA detection preceded radiographic progression in 72% of patients by a median of 5.2 months. In addition, the investigators found that 53% of patients had ctDNA mutation profiles that suggested they would respond favorably to tyrosine kinase inhibitors or immune checkpoint inhibitors.
She also pointed to 2022 European Society for Medical Oncology (ESMO) recommendations on the use of ctDNA in patients with cancer, which state that detection of residual tumor DNA after NSCLC therapy with curative intent is associated with a high risk of future relapse, as supported by evidence from multiple studies. The recommendation also states, however, that there is insufficient evidence to recommend ctDNA testing in routine clinical practice in the absence of evidence from prospective clinical trials.
Evidence to support a benefit of ctDNA detection for treatment planning in the adjuvant setting come from several clinical studies, Dr. Felip said. For example, in a 2020 study published in Nature Cancer, investigators found that patients with detectable ctDNA after chemoradiotherapy who had treatment consolidation with an immune checkpoint inhibitor had significantly better freedom from progression compared with patients who had detectable ctDNA but did not receive consolidation immunotherapy.
In the IMpower010 trial, patients who were ctDNA-positive post surgery and received adjuvant atezolizumab (Tecentriq) had a median disease-free survival of 19.1 months, compared with 7.9 months for patients who did not get the immune checkpoint inhibitor, further indicating the value of ctDNA in the adjuvant setting, she said.
Wrapping up her argument, Dr. Felip acknowledged that currently the negative predictive value of ctDNA/MRD is suboptimal.
“However, we have seen that high ctDNA levels pre surgery predict poor outcome, and MRD-positive following definitive therapy is strongly prognostic and has extremely high positive predictive value for recurrence,” she said.
Taken together, the evidence suggests that patients who are ctDNA-positive preoperatively should be considered for neoadjuvant chemotherapy and immune checkpoint inhibition. If ctDNA persists after neoadjuvant therapy, patients should have extensive re-staging before surgery, because their options for pathologic complete response are limited. Patients who are MRD-positive after surgery should be treated with the same therapeutic approach as for patients with metastatic disease, Dr. Felip concluded.