Previous studies have suggested that molecular progression of disease in patients with EGFR-mutant NSCLC, as measured by sequential plasma EGFR T790M, may precede radiological progression, as measured by Response Evaluation Criteria in Solid Tumors (RECIST).
However, the impact of these measures on timing of treatment changes and patient outcomes has not been examined, wrote Jordi Remon, MD, of Paris (France)–Saclay University and colleagues, in Annals of Oncology.
The European Organization for Research Treatment and Cancer Lung Cancer Group designed a phase 2 clinical trial known as APPLE to evaluate the use of sequential plasma EGFR T790M and determine the optimal sequencing for gefitinib and osimertinib in patients with EGFR-mutant NSCLC.
The researchers reported results from two randomized arms of the APPLE trial. In arm B, 52 patients received gefitinib until emergence of circulating tumor DNA (ctDNA) EGFR T790M mutation, based on the cobas EGFR test v2 (a real-time PCR test), or progression of disease based on Response Evaluation Criteria in Solid Tumors (RECIST). In arm C, 51 patients received gefitinib until disease progression based on RECIST. Both arms then switched to osimertinib. Patients randomized to a third arm (arm A) received osimertinib upfront until progression of disease based on RECIST, and they were not included in the current study.
The primary endpoint was progression-free survival (PFS) while receiving osimertinib at 18 months in patients who were originally randomized to gefitinib, then switched to osimertinib at the emergence of circulating tumor DNA. Secondary endpoints included PFS, overall response rate, overall survival, and brain PFS.
Patients entered the study between November 2017 and February 2020. A total of 75% and 65% of those in arms B and C, respectively, were female, approximately 65% had the mutation EGFR Del19, and approximately one-third had baseline brain metastases. In arm B, 17% of patients switched to osimertinib based on the emergence of ctDNA T790M mutation before progressive disease based on RECIST. The median time to molecular disease progression was 266 days.
More patients in arm B met the primary endpoint of PFS while receiving osimertinib at 18 months (67.2%) than in arm C (53.5%), after a median follow-up of 30 months.
As for secondary endpoints, the median PFS in the two arms was 22.0 months and 20.2 months, respectively. Median overall survival was 42.8 months in arm C and was not reached in arm B. The median brain PFS was 24.4 months for arm B and 21.4 months for arm C.
The benefits seen in the osimertinib patients may be due in part to the timing of the switch to correspond with molecular or radiological disease progression, the researchers wrote in their discussion.
In the future, more research is needed to determine whether molecular monitoring may impact patients’ outcomes, compared with monitoring based on radiological progression, they said.
The findings were limited by several factors, mainly the rapid evolution in the treatment landscape of EGFR-mutant NSCLC, the researchers noted.
Osimertinib is currently considered the preferred first-line treatment by most physicians, they said. “The APPLE trial is the first prospective study supporting the role of dynamic adaptive strategies based on ctDNA monitoring in patients with EGFR-mutant advanced NSCLC.”
The study was supported by AstraZeneca. Lead author Dr. Remon had no financial conflicts to disclose. Corresponding author Dr. Dziadziuszko disclosed honoraria for consultancy or lectures from AstraZeneca, Roche, Novartis, MSD, Takeda, Pfizer, Amgen, and Bristol-Myers Squibb.