This is a minimal risk feasibility study involving the analysis of patient samples and does not involve any therapeutic intervention. The study will involve a prospective cohort of up to 60 patients diagnosed with Locoregionally-Advanced Oropharyngeal Squamous Cell Carcinoma (LA-OPSCC) treated with chemoradiotherapy (CRT) at Princess Margaret Cancer Centre.

To assess the feasibility of microbiome evaluation in LA-OPSCC patients undergoing CRT using samples collected by four different methods: Saliva, Oropharyngeal swab over the tumor site (OP), Stool, and Rectal swab (optional).

This study is investigating the role of oral microbiota as a biomarker in LA-OPSCC. This is a minimal risk study involving the analysis of patient samples and does not involve therapeutic intervention. This protocol does not determine eligibility to receive treatment with concurrent radiotherapy and chemotherapy. It is anticipated that patient accrual will be completed within 12 months.

The study will involve a prospective cohort of up to 60 patients diagnosed with LA OPSCC treated with CRT at Princess Margaret Cancer Center.

Inclusion Criteria:

1. Signed written and voluntary informed consent.
2. Patient must be willing and able to provide collection for saliva, OP swab and stool specimen analyses at 2 time points. Rectal swab is optional.
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:

- 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.

Subjects diagnosed with locoregionally-advanced oropharyngeal squamous cell carcinoma