Safety and Tolerability of Low Dose Radiotherapy Concurrent SBRT and PD-1 Inhibitors in Advanced NSCLC.

This exploratory phase I study will be conducted in West China Hospital, Sichuan University. A dose escalation of low dose radiotherapy (LDRT) and partial SBRT, 3 patients per cohort (a total of 9 patients) will be enrolled to determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT). All eligible patients will receive LDRT + partial SBRT at different dose levels (decried as below), followed by PD-1 inhibitors starting within 7 days after radiation completed. PD-1 inhibitors will be given at doses as recommended in the instruction manual every 3 weeks until disease progression, unacceptable toxicities, the patient withdraws informed consent, or PD-1 inhibitors reaches a maximum of up to 48 months. Patients in the dose escalation will receive LDRT + partial SBRT at 3 cohorts with increasing dose levels: 2 Gy (2 Gy/f) + 10 Gy (10 Gy/f) in 1 fraction in dose level 1; 4 Gy (2 Gy/f) + 20 Gy (10 Gy/f) in 2 fractions in dose level 2; 6 Gy (2 Gy/f) + 30 Gy (10 Gy/f) in 3 fractions in dose level 3.