This exploratory phase I study will be conducted in two steps:~Step A: 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), dose-limiting toxicity (DLT) and recommended dose for expansion (RDE) for lung LDRT and partial SBRT.~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.~Step B: A dose expansion of LDRT + partial SBRT A cohort of 5 patients will receive lung LDRT and partial SBRT at the RDE determined during the dose escalation phase in combination with PD-1 inhibitors to obtain additional safety and response data.
This pilot phase I trial aims to investigate the safety and tolerability of low dose radiotherapy (LDRT) and concurrent partial stereotactic body radiation therapy (SBRT) in combination with programmed cell death-1 (PD-1) inhibitors in Stage IV non-small cell lung cancer (NSCLC) patients who have failed standard therapy. At least 14 participants will be enrolled in this study. All will take part at West China Hospital, Sichuan University.