A Study on Using Cell-Free Tumor DNA (ctDNA) Testing to Decide When to StartRoutine Treatment in People With Human Papilloma Virus (HPV)- Associated Oropharynx Cancer (OPC)

HPV ctDNA evaluation will be completed using NavDx which is a validated digital droplet PCR (ddPCR) assay that targets primers and hydrolysis probes to specifically detect amplicons within the E6 and E7 genes encoded by high-risk HPV strain 16, and the E7 gene for high-risk HPV strains: 18, 31, 33, and 35.

Research MRI studies will be acquired at Memorial Sloan Kettering using a fast multi-phase spoiled gradient echo sequence. A Gadolinium-based agent will be used for DCE-MRI studies.

The EORTC QLQ H\&N 35 s a validated 35-item site specific assessment tool. The module uses 7 multi-item scales to measure problems with swallowing, senses, speech, social eating and social contact. In addition, 11 single-item scales are utilized in assessing problems with teeth, mouth opening, dry mouth, sticky saliva, coughing, feeling ill, as well as use of analgesics, nutritional supplements, feeding tube and finally, weight gain and weight loss. All of the scales and single item measures range in score from 0 to 100. High scores for the Global Health Status/QoL scale represent high QoL, high scores for the functional scales represent high/healthy levels of functioning, but high scores for the symptom scales/items represent high levels of symptomatology/problems. Scoring the two instruments yields a total of 33 distinct scores and we will examine all of these scored.

The MDADI-HN is a questionnaire scored on a scale of 1 to 5, consisting of global, emotional, functional, and physical subscales. The MDADI-HN evaluates the effects of dysphagia on QOL.

Comprehensive Score for financial Toxicity or COST survey is a validated screening tool to assess objective and subjective questions about treatment-related financial distress. It is scored from 0-44, where lower composite scores reflect greater risk of financial toxicity.

59.4-60 Gy in 1.8-2 Gy fractions: CTV\_primary, Involved/Adjacent to nodal levels. 50 Gy to this volume is allowed as per MSK institutional standards in patients with clear or close margins and 2-4 involved nodes. 45-50.4 Gy in 1.8-2 Gy fractions: Dissected node positive neck: uninvolved levels that are not adjacent to positive node - Dissected node negative neck

30 Gy in 2 Gy fractions: CTV\_primary, CTV\_node-positive neck, CTV\_node-negative neck, received de-escalated postoperative chemoradiation. Adjuvant radiation will be administered as previously outlined. Concurrent chemotherapy will be administered as per standard of care. Cisplatin will be administered concurrently with radiation. For non-cisplatin candidates, carboplatin/5fu will be administered. Reasons for using carboplatin/5FU instead of cisplatin need to be charted in the medical record, but the decision belongs to the treating physician. Cisplatin may be given up to 3 days before the scheduled dates, if necessary for medical or personal reasons