Subjects with front-line or relapsed NSCLC or relapsed HNSCC who are intended to receive standard of care immune checkpoint inhibitors without a contraindication to Stereotactic Body Radiation Therapy (SBRT) to a single cancer deposit greater than 1 cm (metastasis or primary cancer) will be enrolled. Subjects will receive standard of care (SOC) immune checkpoint inhibitors and within 2 weeks of initiation, and will receive either: