Inclusion Criteria:

          -  Patient is planned to receive Stereotactic Body Radiotherapy (SBRT) to a biopsy-proven
             NSCLC

          -  Age 18 years old or older

          -  Patient capable of giving informed consent

        Exclusion Criteria:

          -  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

          -  Chronic constipation (bowel movements less frequent than every other day)

          -  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