A Phase I/II Study of Chemotherapy Concurrent with Twice-daily Radiotherapy 
Schedules by Intensity Modulated Radiation Therapy Using Simultaneous Integrated Boost for Limited-stage Small Cell Lung Cancer

Twice-daily radiation concurrent with chemotherapy is one of the standard methods for limited-stage small cell lung cancer. The study was to evaluate the feasibility of chemotherapy concurrent with dose-escalating twice-daily radiotherapy by simultaneous integrated boost intensity-modulated radiation therapy (SIB-IMRT) approach in patients with limited-stage small cell lung cancer. Patients with limited-stage small cell lung cancer were included, treated with twice-daily radiotherapy by SIB-IMRT concurrent with chemotherapy of etoposide plus cisplatin. Dose escalation was conducted by "classical" 3+3 methods with three patients enrolled in each dose level. The therapeutic gross tumor volume (GTV) was treated according to three consecutive dose levels i.e., 45 Gy at 1.5 Gy twice daily, 50 Gy at 1.67 Gy twice daily and 54 Gy at 1.8 Gy twice daily. The planning target volume (PTV) received a dose of 45 Gy delivered in 30 fractions of 1.5 Gy. The primary endpoints were acute toxicities. The secondary endpoints in