Effect of 3-Dimensional Interstitial High-Dose-Rate Brachytherapy With Regional Metastatic Lymph Node Intensity-Modulated Radiation Therapy in Locally Advanced Peripheral Non-Small Cell Lung Cancer: 5-Year Follow-up of a Phase 2 Clinical Trial

We aimed to reveal the 5-year clinical outcomes of 3-dimensional (3D) interstitial high-dose-rate (HDR) brachytherapy with regional metastatic lymph node intensity modulated radiation therapy (IMRT) for locally advanced peripheral non-small cell lung cancer (NSCLC), which has been shown to have low toxicity and improved 2-year survival rates in patients with this disease.In this phase 2, single-arm, open-label clinical trial, 83 patients with locally advanced peripheral NSCLC were enrolled (median follow-up [range], 53.7 [4.3-120.4] months). All eligible patients received 3D interstitial HDR brachytherapy with regional metastatic lymph node IMRT. The primary endpoint was overall survival (OS). Secondary endpoints were local recurrence-free survival, regional recurrence-free survival, progression-free survival, distant metastasis-free survival, toxicities, and quality of life.The final analysis included 75 patients (19 [25.3%] females, 56 [74.7%] males; median [range] age, 64 [44-80] years; stage IIIA, 34 [45.3%]; stage IIIB, 41 [54.7%]). At the latest follow-up, 32 (42.7%) patients had survived. The median OS was 38.0 months (5-year OS, 44.5%; 95% confidence interval [CI], 33.8%-58.6%). Local recurrence-free survival, recurrence-free survival, and distant metastasis-free survival at 5 years were 79.2% (95% CI, 68.5%-91.5%), 73.6% (95% CI, 61.5%-88.1%), and 50.3% (95% CI, 38.3%-66.1%), respectively. The dominant failure pattern was distant disease, corresponding to 40% (30 of 75) of patients and 65.2% (30 of 46) of all failures. Two (2.7%) patients developed grade 1 acute pneumonitis. Grade 2 and 3 acute esophagitis occurred in 11 (14.7%) and 4 (5.3%) patients, respectively. No late radiation-related grade ≥2 late adverse events were observed.3D interstitial HDR brachytherapy with regional metastatic lymph node IMRT for locally advanced peripheral NSCLC shows significant OS and has a low toxicity rate. Additional evaluation in a phase 3 trial is recommended to substantiate these findings.