Vancomycin and Radiation for Non-Small Cell Lung Cancer

Randomized Pilot Inclusion * Patients planned to receive Stereotactic Body Radiotherapy (SBRT) to a biopsy-proven or clinically-suspected NSCLC * Age \>18 years' old * Patient capable of giving informed consent Randomized Pilot Exclusion * Use of antibiotics, antifungal, antivirals or antiparasitics during the 4 weeks prior to registration * Active infection with oral temperature \>100°F * Use of corticosteroids, methotrexate or immunosuppressive drugs during the 4 weeks prior to registration * Use of chemotherapy during the 4 weeks prior to radiotherapy or during radiotherapy. Chemotherapy cannot begin before the collection of the 30-day post treatment sample (S4). * Documented history of HIV, HBV or HCV * Active uncontrolled gastrointestinal disorders such as inflammatory bowel disease, moderate/severe irritable bowel syndrome, persistent, infectious gastroenteritis, colitis or gastritis, persistent or chronic diarrhea of unknown etiology, Clostridium Difficile infection (within 2 years of lung cancer diagnosis) or Helicobacter Pylori infection (untreated) * Major surgery of the GI tract, with the exception of cholecystectomy and appendectomy, in the past five years. Any major bowel resection at any time * Patients on anti-diarrheal medications * Patients on probiotics Safety Trial Inclusion * Patients planned to receive precision hypofractionated radiation (SBRT or an ablative dose of radiation is used if SBRT is not appropriate or if insurance does not approve - i.e. \> 30 Gy in 10 fraction equivalent) to all sites of oligoprogressive NSCLC who progressed after 1st line systemic therapy for metastatic disease which included immunotherapy or a tyrosine kinase inhibitors (TKI) for NSCLC * The number of sites of progression are \< 5 sites. * Age \>18 years' old * Patient capable of giving informed consent Safety Trial Exclusion * Evidence of untreated CNS or leptomeningeal disease * Use of antibiotics, antifungal, antivirals or antiparasitics during the 4 weeks prior to registration * Active infection with oral temperature \>100°F * Use of oral corticosteroids, methotrexate or immunosuppressive drugs during the 4 weeks prior to registration * Use of chemotherapy during the 4 weeks prior to radiotherapy or during radiotherapy. Chemotherapy cannot begin before the collection of the 30-day post treatment sample (S3). * Documented history of HIV, HBV or HCV * Patients on daily anti-diarrheal medications * Use of probiotics during the 4 weeks prior to radiotherapy or during radiotherapy