Main Session
Sep
29
PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3482 - Long-Term Efficacy and Toxicity of Pencil-Beam Scanning Proton and Carbon Ion Radiotherapy for Head and Neck Adenoid Cystic Carcinoma: A Decade of Experience
Presenter(s)
Xiyin Guan, MD - Shanghai Proton and Heavy Ion Center, Shanghai,
X. Guan1, X. Chen2, Y. Li3, X. Xing4, and C. Hu1; 1Department of Radiation Oncology, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, Shanghai, China, 2Department of Radiation Oncology, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, shanghai, China, 3Department of Radiation Oncology, Shanghai Proton and Heavy Ion Center, Fudan University Cancer Hospital, ShangHai, China, 4Fudan University Shanghai Cancer Center, Shanghai, China
Purpose/Objective(s):
This study evaluated the long-term survival outcomes, prognostic factors, and late toxicities of patients with head and neck Adenoid cystic carcinoma (ACC) treated with PBS proton therapy and/or carbon ion radiotherapy over a ten-year period.Materials/Methods:
This retrospective analysis included 102 consecutive patients with head and neck ACC treated at a single institution between May 2016 and June 2025. All patients received curative-intent radiotherapy using PBS technology. Elective neck irradiation was omitted for patients with prior recurrent/metastatic disease, ACC originating in the orbit or trachea, or early-stage (T1-2) lesions; all others received elective neck irradiation. Treatment modalities included PBS-CIRT alone (n=90), PBS-PT alone (n=2), or mixed-modality therapy.Results:
The median follow-up was 47.2 months (range: 8–113). The cohort included 41 males and 61 females, with a median age of 45 years (range: 18–83). Histological subtypes were cribriform/tubular (n=49), solid (n=13), mixed (n=6), and unclassified (n=34). Primary sites included salivary glands (n=23), oral cavity (n=21), nasal cavity/paranasal sinuses (n=19), lacrimal gland (n=12), nasopharynx (n=11), and others (n=16). At presentation, 11 patients had distant metastasis, 12 had node-positive disease, and 65 had T3–T4 stage disease (69 patients were stage III–IV). Treatment intent was definitive (n=70), postoperative (n=20), or re-irradiation (n=12). Elective neck irradiation was performed in 63 patients. The 3-year and 5-year outcomes were: LRC: 80.9% and 72.0%; DMFS: 76.0% and 69.0%; PFS: 62.8% and 51.6%; OS: 91.7% and 76.4%, respectively. Multivariate analysis identified T3–T4 stage as an independent adverse prognostic factor for OS (HR=12.2, p=0.015) and node-positive status for PFS (HR=5.95, p<0.001). Grade =3 acute toxicities included oral mucositis (n=46) and airway stenosis (n=1). Late grade =3 toxicities occurred in 10 patients: radiation-induced brain injury (n=3), osteoradionecrosis (n=3), ocular injury (n=1), tumor ulceration with hemorrhage (n=2), and trismus (n=1).Conclusion:
PBS-based proton and carbon ion radiotherapy demonstrates durable long-term local control and favorable overall survival for head and neck ACC, even in advanced-stage and re-irradiation settings. Our institutional protocol utilizing risk-adapted dose escalation based on resection status—63–66.5 Gy(RBE) in 18–19 fractions for R0–R1; 70–73.5 Gy(RBE) in 20–21 fractions for R2/biopsy-only; and 60–66 Gy(RBE) in 20–22 fractions for re-irradiation (all at 3.0–3.5 Gy(RBE)/fraction)—effectively balances tumor control with an acceptable toxicity profile. These findings suggest that particle therapy should be considered a standard-of-care option, particularly for patients with high-risk features such as advanced T-stage or nodal involvement.