Implications of the findings
The researchers’ findings are important because establishing an MRD-driven approach to treating early-stage NSCLC would facilitate escalation of standard-of-care treatment only for those patients at high risk for relapse, thereby overcoming a key challenge in conventional adjuvant drug-trial design, Dr. Abbosh said.
“If we take a patient population with high-risk early-stage disease who have undergone potentially curative resection of their cancer and we offer these patients adjuvant chemotherapy or adjuvant chemoradiation therapy, then we can improve 5-year survival outcomes in this population,” Dr. Abbosh said. “This is striking because, if we give the same treatment in the metastatic setting, we only see a progression-free survival benefit of a short number of months.”
This suggests a potential “vulnerability of low-burden residual cancer to systemic treatment following surgery,” he added. “So if we want to improve outcomes further in non–small cell lung cancer, we really need to focus on innovation in the early-stage space.”
Dr. Abbosh said he and colleagues demonstrated that “personalized cell-free DNA enrichment can detect low-frequency variant DNA in an accurate manner.
“We’ve shown that preoperative ctDNA shedding is associated with utility of ctDNA as an MRD biomarker and that MRD surveillance can lead to detection of relapse in advance of standard-of-care-imaging,” he said. “We feel that the field is now ready for MRD-driven adjuvant trials.”
Questions to be answered
Invited discussant Corey J. Langer, MD, of Penn Medicine in Philadelphia, outlined “fundamental questions” raised by the findings.
“We need more information on the staging and demographics of those who were MRD positive versus MRD negative,” he said.
Dr. Langer also asked about the findings for shedders versus nonshedders.
“Does this mean nonshedders fare better? This needs to addressed formally,” he said.
Another question is whether the assay “simply enables us to detect relapse sooner and increase anxiety,” or if the trajectory and outcomes in those who prove MRD positive ahead of radiographic manifestations can actually be altered.
A study comparing standard observation with early immunotherapy or chemoimmunotherapy in patients with MRD-positive radiographically occult relapse or progression – using progression-free and overall survival, along with time without symptoms of disease or relapse – would be useful, Dr. Langer said.
“A hazard ratio of 0.8 or less would be meaningful,” he added. “In this regard, there are trials looking at enhanced adjuvant treatment both in colorectal and breast cancer, and trials planned in advanced non–small cell [lung cancer].”
Dr. Langer also said it would be interesting to know if the assay can be used as an adjunct to diagnosis in frailer patients with inaccessible tumors or equivocal biopsy results or to avoid invasive procedures in patients who are stereotactic radiation candidates.
“The jury is still out on this,” he said.
TRACERx is funded by University College London in collaboration with Cancer Research UK. Dr. Abbosh disclosed relationships with AstraZeneca, Novartis, Roche Diagnostics, Bristol Myers Squibb, Achilles Therapeutics, and Archer Diagnostics. Dr. Langer reported grant/research support and/or scientific advisory work for multiple companies.
SOURCE: Abbosh C et al. AACR 2020, Abstract CT023.