Long-Term Outcomes of Ablative Carbon-Ion Radiotherapy for Central Non-Small Cell Lung Cancer: A Single-Center, Retrospective Study

Simple Summary Ablative radiotherapy for central early stage non-small cell lung cancer (NSCLC) is controversial in its feasibility and optimal dose prescription due to the risk of severe pneumonia and adverse events associated with mediastinal organs. Carbon-ion radiotherapy (CIRT) is a promising modality of radiotherapy with steep and linear dose distribution and high biological efficacy. We retrospectively analyzed the long-term results of ablative CIRT using 68.4 Gy in 12 fractions for central early stage NSCLC. Irradiation doses to lungs and mediastinal organs such as bronchus and esophagus were controlled and no serious mediastinal organ-related adverse events occurred. In addition, the efficacy was not inferior to that reported in previous studies, including photon SBRT or proton radiotherapy. This means that our CIRT regimen is expected to have a relatively high safety profile for central NSCLC with tumor and organ at risk (OAR) proximity.Abstract The aim of this study is to assess the efficacy and safety of ablative carbon ion radiotherapy (CIRT) for early stage central non-small cell lung cancer (NSCLC). We retrospectively reviewed 30 patients who had received CIRT at 68.4 Gy in 12 fractions for central NSCLC in 2006-2019. The median age was 75 years, and the median Karnofsky Performance Scale score was 90%. All patients had concomitant chronic obstructive pulmonary disease, and 20 patients (67%) were considered inoperable. In DVH analysis, the median lung V5 and V20 were 15.5% and 10.4%, and the median Dmax, D0.5cc, D2cc of proximal bronchial tree was 65.6 Gy, 52.8 Gy, and 10.0 Gy, respectively. At a median follow-up of 43 months, the 3-year overall survival, disease-specific survival, and local control rates were 72.4, 75.8, and 88.7%, respectively. Two patients experienced grade 3 pneumonitis, but no grade >= 3 adverse events involving the mediastinal organs occurred. Ablative CIRT is feasible and effective for central NSCLC and could be considered as a treatment option, especially for patients who are intolerant of other curative treatments.