Inclusion Criteria:

• Age ≥ 18 years.
• Body weight > 30 kg.
• Primary non small cell lung cancer treated previously on PACIFIC regimen (concurrent chemoradiation followed by durvalumab for stage III lung cancer).
• Progression during duvalumab administration or within 6 months after completion of final durvalumab infusion.
• Extracranial lesion > 4 cm amenable to grid therapy.
• Patients with brain metastases are permitted to enroll.
• Patients with polymetastatic disease are permitted to enroll.
• Patients with local recurrence are permitted to enroll.
• Patients who do not have rapid polymetastatic progression (at the discretion of the enrolling physician).
• Patients who have not had SBRT within 1 month of enrolment.
• Patients may receive conventional palliative radiation to other symptomatic metastatic disease.
• ECOG Performance Status (Dronca, Liu, et al.) 0-2.
• The following laboratory values obtained ≤15 days prior to registration:
  • Hemoglobin ≥ 9.0 g/dL;H
  • Absolute neutrophil count (ANC) ≥ 1500/mm^3;
  • Platelet count ≥ 100,000/mm^3;
  • Total bilirubin ≤ 1.5 x ULN or direct bilirubin ≤ULN if total bilirubin is > 1.5 x ULN;
  • Alanine aminotransferase (ALT) and aspartate transaminase (AST) ≤ 2.5 x ULN (≤ 5 x ULN for patients with liver involvement);
  • Creatinine OR glomerular filtration rate (GFR) ≤ 1.5 x ULN; OR
  • GFR > 60 mL/min for patients with creatinine > 1.5 x ULN.
• Negative pregnancy test done ≤ 7 days prior to registration, for persons of childbearing potential only.
• Persons able to become pregnant OR able to father a child must be willing to use an adequate method of contraception while on treatment and for 120 days after last treatment.
• Life expectancy ≥ 12 weeks.
• Provide written informed consent..
• Willingness to provide mandatory blood specimens for correlative research.
• Willing to return to Mayo Clinic for follow-up (during the Active Monitoring Phase of the study).

Exclusion Criteria:

• < 18 years of age.
• Any of the following because this study involves an investigational agent whose genotoxic, mutagenic and teratogenic effects on the developing fetus and newborn are unknown:
  • Pregnant persons;
  • Nursing persons;
  • Persons of childbearing potential OR able to father a child who are unwilling to employ adequate contraception.
• Co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the prescribed regimens.
• Active autoimmune disease requiring systemic treatment, documented history of severe autoimmune disease, or a syndrome that requires systemic steroids or immunosuppressive agents.
• NOTE: Exceptions are allowed for:
  • Vitiligo;
  • Resolved childhood asthma/atopy;
  • Intermittent use of bronchodilators or inhaled steroids;
  • Daily steroids at dose of ≤10mg of prednisone (or equivalent);
  • Local steroid injections;
  • Stable hypothyroidism on replacement therapy;
  • Stable diabetes mellitus on non-insulin therapy;
  • Sjögren’s syndrome.
• Uncontrolled intercurrent illness including, but not limited to:
  • Ongoing or active infection requiring systemic therapy;
  • Interstitial lung disease;
  • Serious, chronic gastrointestinal conditions associated with diarrhea (e.g., Crohn’s disease or others);
  • Known active hepatitis B (i.e., known positive HBV surface antigen (HBsAg) reactive);
  • Known active hepatitis C (i.e., positive for HCV RNA detected by PCR);
  • Known active tuberculosis (TB);
  • Symptomatic congestive heart failure;
  • Unstable angina pectoris;
  • Unstable cardiac arrhythmia; or
  • Psychiatric illness/social situations that would limit compliance with study requirements (e.g., substance abuse).
• History of myocardial infarction ≤ 6 months, or congestive heart failure requiring use of ongoing maintenance therapy for life-threatening ventricular arrhythmias.
• Receiving any other investigational agent which would be considered as a treatment for the primary neoplasm.
• Hypersensitivity to durvalumab or any of its excipients.
• Previous adverse event attributed to durvalumab or other PD-1 or PD-L1 directed therapy that led to drug discontinuation.
• History of Grade ≥ 3 immune-related adverse event or any grade of immune-related neurologic or ocular adverse event while receiving immunotherapy.
  • Note: Patients who had endrocrine adverse events ≤ Grade 2 are allowed to enroll if they are stable on appropriate replacement therapy and asymptomatic.
• Other active malignancy < 6 months prior to registration.
  • EXCEPTIONS: Non-melanotic skin cancer, papillary thyroid cancer, prostate cancer, or carcinoma-in-situ of the cervix, or others curatively treated and now considered to be at less than 30% risk of relapse.