Twice-Daily Thoracic Radiotherapy by Intensity-Modulated Radiation Therapy (IMRT) or Simultaneous Integrated Boost (SIB) IMRT With Concurrent Chemotherapy for Limited-Stage Small Cell Lung Cancer Patients? A Propensity-Score Matched Analysis

Purpose/Objective(s) Concurrent chemoradiotherapy is the standard treatment for limited-stage small-cell lung cancer patients (SCLC), but the optimal dose and schedule of radiotherapy have not been established. Materials/Methods We retrospectively reviewed the clinical records of limited-stage SCLC patients treated with twice-daily thoracic radiotherapy by intensity modulated radiotherapy (IMRT) or Simultaneous integrated boost IMRT (SIB-IMRT) with concurrent chemotherapy between December 2009 to December 2017. The patients were divided into two groups according to the radiotherapy dose. The patients of SIB-IMRT group received 57Gy at 1.9Gy twice-daily to the gross tumor volume (GTV), 51Gy at 1.7Gy twice-daily to the clinical target volume (CTV) and 45Gy at 1.5Gy twice-daily to the planning target volume (PTV), and the patients of IMRT group received 45Gy at 1.5Gy twice-daily to PTV. A 1:1 propensity score matching (PSM) was applied to balance observable potential confounding factors between two groups. Primary endpoint was progression-free survival (PFS). Overall survival (OS), objective tumor response (ORR) and treatment-related toxicities were also evaluated. Statistical analyses were conducted using SPSS version 22.0 and statistical significance was defined as P Results A total of 112 patients were enrolled in our study, including 71 patients in IMRT group and 41 patients in SIB-IMRT group. After PSM, the clinical features were well balanced between two groups included 37 patients each. ORR in IMRT group and SIB-IMRT group were 94.6% (35/37) and 97.3% (36/37), respectively. Median PFS was 17.54 months in IMRT group vs 34.92 months in SIB-IMRT group (P = 0.047). Median OS was 38.52 months in IMRT group vs 63.41 months in SIB-IMRT group (P = 0.261). The incidence of grade 3-4 treatment-related toxicities was 43.24% (32/74), and there was no significant difference between two groups (P = 0.639). Conclusion Compared with IMRT, the high dose of twice-daily thoracic radiotherapy by SIB-IMRT approach with concurrent chemotherapy for the patients with limited-stage SCLC were well-tolerated and may improve PFS, but PFS improvement didn't result in significant advantage in OS.