Long-Term Results of a Phase II Clinical Trial of Radiation Volume and Dose De-intensification Following Transoral Robotic Surgery and Neck Dissection for Human Papillomavirus-Associated Oropharyngeal Squamous Cell Carcinoma.
prospective_cohort · Level II
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- Record sourced from PubMed, PMID 41999781.
- Also identified by DOI 10.1016/j.ijrobp.2026.04.015.
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Abstract
We conducted a Phase II clinical trial reducing both dose and volume of adjuvant radiation in patients with HPV-associated OPSCC. We also examined whether postoperative circulating tumor DNA (ctDNA) was prognostic for outcomes. Eligible patients had pT0-T3 pN0-N1 HPV-associated OPSCC (AJCC 8<sup>th</sup> Ed.) treated with primary transoral robotic surgery (TORS) and neck dissection. Adjuvant RT was delivered in 25 fractions over 5 weeks. We reduced RT volumes in two ways: the primary oropharyngeal resection bed was omitted in select patients (pT1-T2 tumors with negative margins and no LVI or PNI), and the contralateral neck targets were reduced to mirror the pathologically-involved ipsilateral nodal levels. We also reduced RT doses: 50Gy was given to primary resection beds requiring treatment and to ipsilateral neck levels with pathologically-positive nodes. 45Gy was delivered to other at-risk ipsilateral nodal regions and the contralateral neck. Concurrent chemotherapy was prescribed for positive margins and ENE, although optionally omitted when ENE was ≤1mm. Baseline HPV ctDNA was collected after surgery and measured at 3 subsequent timepoints. We enrolled 150 patients between October 2018 and June 2022. One patient withdrew, leaving 149 patients treated per protocol. At a median follow-up of 48 months [IQR: 38-59 months], no patients developed local recurrence while two experienced regional recurrences. The estimated five-year LRC rate was 98.0% (95% CI: 95.3%-100%). Both regional recurrences were successfully salvaged. Ten patients (6.7%) developed distant metastases and three (2.0%) died of disease. At 24-months post-RT, median MDASI-HN scores were dysphagia-2, xerostomia-2, and interference with work-0. For 79 patients with available blood samples, detectable postoperative HPV ctDNA was associated with subsequent metastatic disease but not LRC. Now with mature follow-up, our adjuvant RT strategy with reduced doses and volumes maintained high locoregional control with favorable toxicity in selected patients with HPV-associated OPSCC.