Safety and efficacy of consolidative stereotactic radiotherapy for oligo-residual EGFR-mutant non-small cell lung cancer after first-line third-generation EGFR-tyrosine kinase inhibitors: a single-arm, phase 2 trial.

Background: Prospective data is limited on the efficacy and safety of consolidative stereotactic radiotherapy (SRT) in metastatic epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) patients harboring oligo-residual disease (ORD) after first-line third-generation EGFR-tyrosine kinase inhibitors (TKIs). Methods: In this single-arm, phase II trial, 61 patients from two academic centers were enrolled from March 2021 to March 2023. All these patients had metastatic EGFR-mutant NSCLC and harbored ORD after first-line third-generation EGFR-TKIs. Consolidative SRT was performed and EGFR-TKIs were not held during SRT. The primary endpoint was progression-free survival (PFS) and the secondary endpoints included overall survival and treatment-related adverse events (TRAEs). A prespecified propensity score matched (PSM) comparison was conducted with a contemporary cohort of patients who developed ORD but received EGFR-TKIs alone. This trial was registered with ClinicalTrails.gov, NCT04764214. Findings: All patients received consolidative SRT. With a median follow-up of 21.1 months, the median PFS was 29.9 (80% CI 22.4-32.4) months and the lower boundary exceeded the predefined threshold, meeting the primary endpoint. TRAEs occurred in 43 (70%) patients, with pneumonitis (27.9%) and esophagitis (26.2%) being the most common toxicities. Four patients (6.6%) reported grade ≥3 TRAEs, each for pneumonitis, esophagitis, leukopenia, and cranial radiation necrosis. PSM analysis showed significantly prolonged PFS in EGFR-TKI + SRT group compared to EGFR-TKI group (HR 0.46, 80% CI 0.20-0.61; Interpretation: Consolidative SRT is associated with an encouraging PFS in first-line third-generation EGFR-TKI-treated metastatic NSCLC patients harboring ORD, with generally acceptable toxicities. Further confirmatory studies are warranted. Funding: Hui Lan Public Welfare and the Chinese Society of Clinical Oncology Foundation.