Inclusion Criteria:

   - PRIOR TO STEP 1 REGISTRATION INCLUSION:

   - Pathologically (histologically or cytologically) proven diagnosis of squamous cell
   carcinoma of the oral cavity, including the oral (mobile) tongue, floor of mouth
   (FOM), mucosal lip, buccal mucosa, lower alveolar ridge, upper alveolar ridge,
   retromolar gingiva (retromolar trigone; RMT), or hard palate prior to registration

   - Appropriate stage for study entry (T1-2N0M0; American Joint Committee on Cancer [AJCC]
   8th edition [ed.]) based on the following diagnostic workup:

      - History/physical examination within 42 days prior to registration

      - Imaging of head and neck within 42 days prior to registration

         - PET/CT scan or contrast neck CT scan, or gadolinium-enhanced neck magnetic
         resonance imaging (MRI) or lateral and central neck ultrasound; diagnostic
         quality CT is preferred and highly recommended for the PET/CT when possible.

         - Imaging of chest within 42 days prior to registration; chest x-ray, CT chest
         scan (with or without contrast) or PET/CT (with or without contrast)

   - Surgical assessment within 42 days prior to registration. Patient must be a candidate
   for surgical intervention with sentinel lymph node (SLN) biopsy and potential
   completion neck dissection (CND) or elective neck dissection (END)

      - Surgical resection of the primary tumor will occur through a transoral approach
      with anticipation of resection free margins

   - Zubrod performance status 0-2 within 42 days prior to registration

   - For women of child-bearing potential, negative serum or urine pregnancy test within 42
   days prior to registration

   - The patient or a legally authorized representative must provide study-specific
   informed consent prior to study entry

   - Only patients who are able to read and understand English are eligible to participate
   as the mandatory patient reported NDII tool is only available in this language

   - PRIOR TO STEP 2 RANDOMIZATION:

   - FDG PET/CT required prior to step 2. Note: FDG PET/CT done prior to step 1 can be
   submitted for central review.

      - PET/CT node negative patients, determined by central read, will proceed to
      randomization.

      - PET/CT node positive patients will go off study, but will be entered in a
      registry and data will be collected to record the pathological outcome of neck
      nodes for diagnostic imaging assessment and future clinical trial development

         - NOTE: All FDG PET/CT scans must be performed on an American College of
         Radiology (ACR) accredited scanner (or similar accrediting organization)

   - The patient must complete NDII prior to step 2 registration

Exclusion Criteria:

   - PRIOR TO STEP 1 REGISTRATION EXCLUSION:

   - Definitive clinical or radiologic evidence of regional (cervical) and/or distant
   metastatic disease

   - Prior non-head and neck invasive malignancy (except non-melanomatous skin cancer,
   including effectively treated basal cell or squamous cell skin cancer, or carcinoma in
   situ of the breast or cervix) unless disease free for ≥ 2 years

   - Diagnosis of head and neck squamous cell carcinoma (SCC) in the oropharynx,
   nasopharynx, hypopharynx, and larynx

   - Unable or unwilling to complete NDII (baseline only)

   - Prior systemic chemotherapy for the study cancer; note that prior chemotherapy for a
   different cancer is allowable

   - Prior radiotherapy to the region of the study cancer that would result in overlap of
   radiation therapy fields

   - Patient with severe, active co-morbidity that would preclude an elective or completion
   neck dissection

   - Pregnancy and breast-feeding mothers

   - Incomplete resection of oral cavity lesion with a positive margin; however, an
   excisional biopsy is permitted

   - Prior surgery involving the lateral neck, including neck dissection or gross injury to
   the neck that would preclude surgical dissection for this trial. Prior thyroid and
   central neck surgery is permissible; biopsy is permitted. Note: Borderline suspicious
   nodes that are ≥ 1 cm with radiographic finding suggestive of NOT malignant should be
   biopsied using ultrasound-guided (U/S-guided) fine-needle aspiration (FNA) biopsy

   - Underlying or documented history of hematologic malignancy (e.g., chronic lymphocytic
   leukemia [CLL]) or other active disease capable of causing lymphadenopathy
   (sarcoidosis or untreated mycobacterial infection)

   - Actively receiving systemic cytotoxic chemotherapy, immunosuppressive, anti-monocyte
   or immunomodulatory therapy

   - Currently participating in another investigational therapeutic trial