EGFR tyrosine kinase inhibitor therapy continuation with high-dose hypofractionated radiotherapy in EGFR-mutated non-small cell lung cancer (NSCLC) patients with oligoprogressive disease

e21580 Background: EGFR tyrosine kinase inhibitors (TKIs) represent the standard first-line therapy for advanced non-small cell lung cancer (NSCLC) patients with activating EGFR mutations. However, despite initial marked responses, tumors invariably develop acquired resistance to TKIs. Oligoprogression is commonly observed during treatment with oncogene-directed therapies, including EGFR TKIs, and refers to patients who experience disease progression only in limited sites as a result of heterogeneous mechanisms of resistance. The use of local ablative treatments for these resistant lesions may extend the duration of TKI therapy and potentially improve long-term disease control and survival. We e retrospectively analyzed the efficacy of EGFR TKI therapy continuation with high-dose hypofractionated radiation therapy (RT), in EGFR-mutant NSCLC patients with oligoprogressive disease. Methods: Patients with metastatic EGFR mutant NSCLC who developed oligoprogression during first-line treatment with gefitinib were included in this analysis. We evaluated progression-free survival 1 (PFS 1), defined as the time from initiation of TKI therapy until development of oligoprogression or death, and PFS 2, defined as time of focal progression until further progression of disease or death. Overall survival and safety were also assessed. Results: Thirty-six patients were included in the study. The median PFS 1 was 12.5 (4.0-23.2) months. High-dose hypofractionated RT consisted of intensity-modulated RT in 23 patients (64%) and stereotactic radiotherapy in 13 cases (36%). The median PFS 2 was 6.3 (2-12.5) months. Overall survival was 38.7 months (9.0-46.3). The treatment was well-tolerated and no patient had to discontinue TKI therapy because of adverse events during radiotherapy. Conclusions: Our therapeutic strategy, including high-dose hypofractionated RT in addition to TKI therapy, was feasible in the clinical setting and was associated with significant prolongation of disease control and improvement of survival outcomes, while being associated with manageable side effects. Our study further support the use of definitive therapeutic approaches in oligoprogressive disease, especially in oncogene-driven tumors. Molecular profiling of metastatic sites remains crucial to identify novel biomarkers, involved in the development of acquired resistance and oligoprogression, that may be useful to select patients for local treatments.