3768 - Outcomes of Reduced Elective Nodal Radiation Dose for Laryngeal, Hypopharyngeal and p16 Negative Oropharyngeal Cancers

K. Zakeri¹, T. Shang¹, Y. Yu¹, L. Chen¹, A. Shamseddine¹, J. J. Kang², C. J. Tsai³, E. Sherman⁴, R. J. Wong⁵, S. McBride¹, D. Gelblum¹, N. Riaz¹, and N. Y. Lee¹; ¹Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, ²Yale University, New Haven, CT, ³Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada, ⁴Department of Medical Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, ⁵Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): Reducing elective nodal irradiation dose can decrease treatment toxicity and improve quality of life for head and neck cancer patients. The elective radiotherapy doses for laryngeal, hypopharyngeal, and p16 negative oropharyngeal cancers range from 44-63 Gy. We hypothesized that a lower dose of 40 Gy may be as effective and less toxic. Materials/

Methods: We sought to determine the effectiveness of reducing elective radiotherapy doses to 40 Gy for a consecutive cohort of laryngeal, hypopharyngeal, and p16 negative oropharyngeal squamous cell carcinomas. The primary outcome measure was solitary elective nodal recurrence.
Results: The cohort included 73 consecutive patients from December 2020 to March 2023. All patients were treated with 40 Gy in 2 Gy daily fractions to the elective nodal volume followed by an optional cone down of 10-20 Gy around the primary tumor and final cone down to 70 Gy for all gross primary and nodal disease. All patients received concurrent chemotherapy, except for two patients that received concurrent cetuximab. Primary sites included 35 larynx, 24 oropharynx, 11 hypopharynx, 2 unknown primary, and 1 synchronous oropharynx and hypopharynx cancer. Most patients were male (73%), had T3 or T4 tumors (64%), and node positive disease (68%). All patients with oropharynx cancer or unknown primary had p16 negative disease. Among larynx cancers, there were 4, 14, and 17 patients with p16 positive, p16 negative, and unknown p16 status, respectively. Among hypopharynx cancers, there were 9 and 2 patients with p16 negative and unknown p16 status, respectively. The median follow up was 18.9 months (IQR: 11.9 – 24.5 months). There were no cases of solitary elective nodal recurrence. There were 14 cases of local or distant recurrence, 1 second primary, and 6 competing deaths in the absence of local or distant recurrence. Four patients had locoregional recurrence, 8 had distant recurrence, and 2 had simultaneous locoregional and distant recurrence. All patients who experienced locoregional recurrence failed in the 70 Gy target volume. One patient failed simultaneously in the 70 Gy volume, the elective 40 Gy volume, and outside the elective field in the neck. Another patient failed simultaneously in the 70 Gy volume and outside of the elective field.
Conclusion: Reduction in elective nodal radiation dose did not lead to solitary elective nodal recurrences for laryngeal, hypopharyngeal, and p16 negative oropharyngeal squamous cell carcinomas. This strategy can be implemented without compromise in locoregional control while reducing toxicity.