P49.02 Simultaneous Integrated Boost IMRT (54 Gy) versus Conventional IMRT (45 Gy) Twice Daily Combined With Chemotherapy for LS-SCLC

Twice-daily thoracic radiotherapy (TRT) with concurrent chemotherapy is standard for limited-stage small-cell lung cancer (LS-SCLC). However, the importance of twice-daily simultaneous integrated boost intensity-modulated (SIB-IMRT) has not been clearly defined in LS-SCLC. Therefore, we compared SIB-IMRT dose escalation (54 Gy) to gross tumor volume versus conventional (IMRT) standard-dose (45 combined patients We previously conducted a prospective study on target volumes LS-SCLC (Cancer, 2020, 126(4), 840-849). In that study, from 2012-2017, 85 received IMRT postchemotherapy volume, as group this retrospective analysis. group, prescribed was 45 Gy at 1.5 per fraction both planning (PGTV) and clinical (PCTV). From 2015-2019, 40 were treated group. 54Gy 1.8Gy twice daily PGTV, 45Gy 1.5Gy PCTV. All 125 chemoradiotherapy after completion 2 cycles induction cisplatin-etoposide 4 6 total. progression free survival (PFS) overall (OS) between treatment groups by using Kaplan-Meier method Cox proportional hazards regression before propensity score matching (PSM). Overall, median follow-up 19.4 months, PFS OS 12.9 23.1 respectively. The showed longer than those (median reached 11.5 months; p = 0.003). 35.0 20.3 2-year rate 73.5% 38.8%, respectively ( =0.018 ). After PSM, (35 cases each group), respectively, which (PFS 8.0 0.001, 19.0 0.011) (fig 1). For toxicity, grade acute esophagitis more common but grade≥3 grade≥2 pneumonitis no difference two groups. patients, daily) PGTV benefited greatly. Our results suggest SIR-IMRT safe effective should be further evaluated large trial.