Objectives: To investigate abscopal effect (AbE) in oligometastatic non-small cell lung cancer patients treated with SBRT in combined with PD1.

Methods: 12 non-small cell lung cancer (NSCLC) patients with metastatic tumors, which were EGFR negative, ALK negative, and Met negative, were involved in the research registry. The SBRT was given to all metastatic tumors except primary lung disease which is not suitable for SBRT, SBRT was given followed by granulocyte-macrophage colony-stimulating factor (GMSF) for 2 weeks. PD-1 antibody (pembrolizumab) was given concurrently and afterward. Of these patients, SBRT group(5) received SBRT (30Gy delivered in 5 fractions for 5 successive days) . In PD1 group (4) no SBRT given. In the SBRT + PD1(3) group, three different doses (8Gy x1, 30 Gy in 5 and 30 Gy in 10) was given to each patient individually, the metastases in the same patient will receive the same designed dose accordingly.

Results: In the SBRT group, one patient showed AbE in primary site. In PD1 group, pseudoprogression were seen in one primary tumors, but no AbE seen. Lastly, in the SBRT + PD1 group, primary site AbE seen in all patient.

Conclusions: The AbE are likely associated with PD1 and SBRT stage IV oligo metastases NSCLC. More studies are needed to clarify if AbE are associated with SBRT dosage once given the PD1 concurrently.