Pattern of Recurrence Analysis in Metastatic EGFR-Mutant NSCLC Treated with Osimertinib: Implications for Consolidative Stereotactic Body Radiation Therapy

Despite the impressive response rate to osimertinib, acquired resistance remains an obstacle to achieving long-term tumor control in metastatic epidermal growth factor receptor-mutant non-small cell lung cancer. Stereotactic body radiation therapy (SBRT) plays a growing role in the management of oligometastatic disease. We investigated the patterns of residual disease and progression on osimertinib, as well as the predictors of candidates for consolidative SBRT.The serial scans of patients with metastatic epidermal growth factor receptor-mutant non-small cell lung cancer treated with osimertinib were retrospectively reviewed. Disease progression in residual sites, new sites, and both residual and new sites were classified as residual-site recurrence (RR), new-site recurrence (NR), and combined RR and NR (RNR), respectively. Logistic regression analysis was performed to identify predictors of candidates for consolidative SBRT.Ninety-seven patients were enrolled. The median time to maximal osimertinib response was 2.6 months. Twenty-six patients (26.8%) with oligoresidual disease were identified as candidates for consolidative SBRT at time of maximal response. Stage T1-2 before initiation of osimertinib (P = .046) was the independent predictor of consolidative SBRT eligibility. During a median follow-up of 10.9 months, disease progression was documented in 50 (51.5%) patients, and 70% of them experienced oligoprogression. Twenty-five (50%) patients developed disease progression in originally involved sites, 11 (22%) had new metastases, and 14 (28%) experienced disease progression in both original and new metastatic sites. Forty-six patients had progressive disease after experiencing initial stable disease or objective response to osimertinib. RR occurred in 20 (43.5%) of these patients, NR in 14 (30.4%), and RNR in 12 (26.1%). Notably, within the subgroup of patients eligible for consolidative SBRT, RR was observed in 6 (54.5%) patients, RNR in 3 (27.3%), and NR in 2 (18.2%).The majority of progressive disease on osimertinib was within residual lesions in initially involved sites. Consolidative SBRT may prolong time to progression in a selected subgroup of patients, which merits further investigation.