Safety and Tolerability Evaluation of Sintilimab in Combination With Radiation in Stage IV NSCLC Patients

This exploratory phase I study will be conducted in two steps: Step A: A low dose radiotherapy (LDRT) dose escalation, 6 patients per cohort (a total of 18 patients) will be enrolled to determine the maximum tolerated dose (MTD), dose-limiting toxicity (DLT) and recommended dose for expansion (RDE) for lung LDRT. Step B: A lung LDRT dose expansion All eligible patients will receive lung SBRT dosed at 30 Gy in 3 fractions, in combination with LDRT at different dose levels (decried as below) starting from the 2nd day of SBRT, followed by sintilimab monotherapy starting within 7 days after radiation completed. Sintilimab will be given at 200mg every 3 weeks until disease progression, unacceptable toxicities, the patient withdraws informed consent, or sintilimab reaches a maximum of up to 24 months. Patients in the dose escalation will receive lung LDRT at 3 cohorts with increasing dose levels: 2 Gy in 1 fraction in dose level 1, 4 Gy in 2 fractions in dose level 2, 10Gy in 5 fractions in dose level 3. A cohort of 17 patients will receive lung LDRT at the RDE determined during the dose escalation phase in combination with SBRT and Sintilimab to obtain additional safety and response data.