Main Session
Sep 29
PQA 04 - Gynecological Cancer, Head and Neck Cancer

2761 - Risk-Adapted Ipsilateral Mucosal Radiation Volumes for Head and Neck Carcinoma of Unknown Primary: A Single-Institution Experience and Dosimetric Analysis

10:45am - 12:00pm PT
Hall F
Screen: 16
POSTER

Presenter(s)

Houda Bahig, MD, PhD Headshot
Houda Bahig, MD, PhD - Centre Hospitalier de l'Universite de Montreal, Montreal, QC

P. Harris1, P. F. Nguyen-Tan2, E. J. Filion3, O. Ballivy4, A. Christopoulos1, T. Ayad5, L. Guertin6, E. Bissada6, P. Tabet1, D. Soulieres1, L. Létourneau-Guillon7, and H. Bahig8; 1Centre Hospitalier de l'Université de Montréal (CHUM), Montreal, QC, Canada, 2Centre Hospitalier De L'Universite De Montreal (CHUM), Montreal, QC, Canada, 3CHUM (The University of Montreal Hospital Centre), Montreal, QC, Canada, 4Centre Hospitalier de l'Université de Sherbrooke, Sherbrooke, QC, Canada, 5Division of Otolaryngology-Head & Neck Surgery, Centre Hospitalier de l'Université de Montréal (CHUM), Montreal, QC, Canada, 6Division of Otolaryngology-Head and Neck Surgery, Centre Hospitalier de l'Université de Montréal (CHUM), Montreal, QC, Canada, 7Department of Radiology, Centre Hospitalier de l'Université de Montréal (CHUM), Montreal, QC, Canada, 8Department of Radiation Oncology, Centre Hospitalier de l'Université de Montréal (CHUM), Montréal, QC, Canada

Purpose/Objective(s): The optimal radiotherapy (RT) field extent and mucosal coverage for head and neck cancer of unknown primary (HNCUP) remain subjects of debate. This study presents long-term institutional outcomes of HNCUP management, utilizing a p16-based strategy to tailor RT fields, with a focus on disease-free survival (DFS), overall survival (OS), and dosimetric analysis. The hypothesis is that risk-adapted radiation was associated with survival outcomes comparable to those obtained with standard radiotherapy field extent.

Materials/Methods: We conducted a retrospective review of HNCUP patients treated with curative-intent radiotherapy at a single institution between 2009 and 2023. Risk-adapted RT volumes were as follows: for p16+ disease, RT volumes included the ipsilateral naso- and oropharyngeal mucosa with lymph node regions, while p16- disease, RT volumes encompassed the ipsilateral pharyngeal mucosa and larynx, along with lymph node irradiation. DFS and OS were evaluated for the entire cohort (n=145), with additional subgroup analysis by p16 status. A dosimetric analysis was performed for a subset of patients with available data.

Results: A total of 145 patients treated between 2009 and 2023. P16 status was positive, negative or unknown in 56%, 20% and 24% of patients. As per AJCC 8th edition, stagings were as follow : stage I (n=25), stage II (n=45), stage III (n=18), stage IVA (n=36), stage IVB (n=21) (p16+ n=81, p16- n=29, unknown n=35). Median follow-up was 41.7 months (range: 1.5–181.5 months). For the entire cohort, 2- and 5-year OS was 94.0% and 88.4%, respectively. OS at 5 years was 86.9% p16+ vs. 69.2% p16-, p=0.087. Rate of local and regional recurrence was 3% and 3%, respectively, with no difference in recurrence patterns by p16 status. Risk-adapted RT volumes in p16+ plans were associated with statistically significant reduction in mean dose to the ipsilateral parotid, retropharyngeal muscles, esophagus and larynx with absolute differences of 0.9 Gy, 2.5 Gy, 1 Gy and 0.4 Gy, respectively.

Conclusion: Risk-adapted ipsilateral mucosal irradiation yields favorable outcomes in HNCUP.