Cytoreductive Stereotactic Body Radiotherapy with Tyrosine Kinase Inhibitors for Intrathoracic Oligoprogressive EGFR-mutated Lung Cancer

Abstract Background: Epidermal growth factor receptor (EGFR) mutated non-small cell lung cancer (NSCLC) shows an impressive initial response to EGFR tyrosine kinase inhibitors (EGFR-TKI). However, resistance invariably develops, commonly involving the site of initial gross disease. Cytoreductive stereotactic body radiotherapy (SBRT) for thoracic oligoprogressive disease (OPD) may effectively delay progression through EGFR-TKI therapy.Methods: From a prospectively maintained IRB-approved institutional registry, we identified 23 patients consecutively treated between 2011-2019 with thoracic SBRT and received EGFR-TKI within 6-months of SBRT. Radiographic progression-free (PFS) and overall survival (OS) were estimated using Kaplan-Meier analysis. Toxicity and patient-reported Edmonton Symptom Assessment Scale (ESAS) scores were reviewed.Results: Median follow-up after SBRT was 20-months (range, 4-100), and the median age was 68-years (range, 33-89). Most patients were females (n=21;91.3%). RT dose was 50-60 Gy in 5-10 fractions. EGFR-TKI administered were erlotinib, osimertinib and gefitinib in 15, 5, and 3 patients, respectively. Median PFS and OS following SBRT were 8-months and 31-months, respectively. 1-year PFS and OS were 34.8% and 78.3%. The median duration of EGFR-TKI therapy was 26-months (1-91). Most patients progressed in new distant sites, most commonly bones (n=5;21.7%) and distant lung (n=4;17.4%), with only 2/23 patients having initial progression within the SBRT field. Grade-2 pneumonitis (n=2) and rib fracture (n=1) were noted radiation-related toxicities. Dominant ESAS symptoms were fatigue (21.7%), pain (8.7%), and loss of appetite (8.7%).Conclusions: For EGFR-mutated NSCLC patients with thoracic OPD on EGFR-TKI, SBRT was well tolerated, resulted in changes in subsequent patterns of failure, lengthened PFS, and prolongs the duration of initial TKI therapy.