Preliminary Results about Application of Intensity-Modulated Radiotherapy to Reduce Prophylactic Radiation Dose in Limited-Stage Small Cell Lung Cancer

To evaluate the clinical outcomes of simultaneous dose reduction of elective nodal area with intensity-modulated radiotherapy (SIR-IMRT) versus conventional IMRT (C-IMRT) in patients with limited-stage small-cell lung cancer (LS-SCLC), patients with LS-SCLC who received definitive SIR-IMRT or C-IMRT were retrospectively analyzed. In SIR-IMRT group, the prescribed dose was 60Gy to the planning gross target volume (PTVG), and 54Gy to the planning target volume (PTV). In the C-IMRT group, the prescribed dose was 60Gy to the whole PTV. Radiation-related toxicities were estimated according to Common Terminology Criteria for Adverse Events (version 3.0). The primary endpoint was loco-regional recurrence-free survival (LRFS), and the secondary endpoints include overall survival (OS) and toxicities. LRFS and OS were estimated with Kaplan-Meier method. After propensity score matching, 84 patients were included in this study, with 42 patients in each group. Fifty-eight patients experienced treatment failure. Grade 3 and above radiation-induced lung toxicity developed in 2 patients in SIR-IMRT group and 5 patients in C-IMRT group, respectively. Grade 3 and above radiation-related esophagitis was observed in 3 patients and 5 patients, respectively. The 1-, 3-year LRFS rates of the SIR-IMRT group and C-IMRT group were 90.4%, 73.3% and 87.1%, 45.0%(P=0.025), respectively. Reducing the irradiation dose to the elective nodal region may reduce radiation-induced toxicities without compromising local-regional control and overall survival.