Role of Microbiome as a Biomarkers in Locoregionally-Advanced Oropharyngeal Squamous Cell Carcinoma 2

This is a single-centre feasibility study designed to assess the safety, tolerability and engraftment of MET-4 bacterial strains when given in combination with chemoradiotherapy (CRT). The study will involve a prospective cohort of 30 patients diagnosed with Locoregionally-Advanced Oropharyngeal Squamous Cell Carcinoma (LA-OPSCC) to be treated with CRT as per standard of care at Princess Margaret Cancer Centre. All patients enrolled will receive MET-4 in addition to standard CRT. MET-4 is administered orally as an initial daily loading dose over 2 days followed by a daily maintenance dose of MET-4 and will be administered until week 4 of CRT or unacceptable toxicity whichever occurs earlier and in the absence of criteria to discontinue MET-4. This protocol does not determine eligibility to receive treatment with concurrent CRT. It is anticipated that patient accrual will be completed within 12 months.

Inclusion Criteria: 1. Signed written and voluntary informed consent. 2. Patient must be willing and able to provide: -Oropharyngeal swab, stool and blood specimen at protocol specified time points. 3. Age \> 18 years, male or female. 4. Patient must be diagnosed with histologically confirmed squamous cell carcinoma of the oropharynx (soft palate, tonsils, base of tongue). 5. Patients must be eligible for curative-intent concurrent treatment with radiotherapy and chemotherapy. Exclusion Criteria: 1. Any condition that, in the opinion of the Investigator, would interfere with patient safety, or evaluation of the collected specimen and interpretation of study result. 2. Subjects unable to swallow orally administered medications or any subjects with gastrointestinal disorders likely to interfere with absorption (e.g. bowel obstruction, short gut syndrome, blind loop syndrome, ileostomy etc). Subjects with colostomies may be enrolled. 3. Pregnant or planning to get pregnant in the next 6 months.