P05.07 Single-Fraction Carbon ion Radiotherapy for Patients with Early-Stage Lung Cancer with or without Interstitial Pneumonitis

Abstract

Carbon ion radiotherapy (CIRT) is one of the treatment choices for lung cancer. In our institution, we administer 50Gy [relative biological effectiveness (RBE)] in 1 fraction to treat peripheral lung cancer. We retrospectively analyzed the outcomes of this treatment with special regard to prognostic impact of coexistent interstitial pneumonitis (IP). Between June 2011 and May 2018, patients with or without IP who received 50Gy (RBE) in 1 fraction CIRT for peripheral lung cancer and whose tumor diameters were 5 cm or smaller were retrospectively recruited from our database. Toxicities were evaluated using the Common Terminology Criteria for Adverse Events version 4.0. A total of 195 fulfilled the inclusion criteria. There were 33 patients with IP, and all of them except for one patient were inoperable. The median age was 75 years (range 42–95 years), median follow-up time was 39 months (range 2–97 months), and median tumor diameter was 24 mm (range 8–49 mm). Among all the patients, the 3-year overall survival (OS), local control (LC), and disease-free survival (DFS) rates were 86.3%, 94.5%, and 82.0%, respectively. The 3-year OS (58.8%), LC (79.8%), and DFS (56.8%) of patients with IP were significantly worse than those without IP (OS 91.1%, LC 96.7%, and DFS 85.9%; p < 0.001). IP was also a significant risk factor of OS (hazard ratio = 3.0; p = 0.015), LC (hazard ratio = 3.8; p = 0.022), and DFS (hazard ratio = 3.2; p = 0.006) in multivariate Cox analysis. There were 3 patients with grade 3 pneumonitis (all had IP), and 4 patients with grade 2 pneumonitis (2 had IP and 2 did not). Single-fraction CIRT is an effective and safe treatment for early-stage lung cancer, even in patients with IP, although the clinical results of patients with IP are worse than those of patients without IP.