3729 - Impact of Titanium Plate Reconstruction and Dental Amalgam on Risk of Osteoradionecrosis in Oral Cavity Cancer Patients Receiving Intensity Modulated Radiation Therapy

A. Shah¹, C. Oh², J. M. Karp³, J. Xiao⁴, L. Moses⁵, U. Duvvuri⁵, C. Hill⁶, A. Jacobson⁷, T. Tran⁷, M. Persky⁷, Z. Li⁸, B. Schmidt⁹, D. J. Byun¹⁰, and K. S. Hu¹; ¹Department of Radiation Oncology, NYU Langone Health, New York, NY, ²Biostatistics, Department of Population Health, NYU Langone Health, New York, NY, ³NYU Langone Medical Center, New York City, NY, ⁴New York University Grossman School of Medicine, Department of Radiation Oncology, New York, NY, ⁵NYU Langone Health, New York, NY, ⁶Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, ⁷NYU Langone Medical Center, New York, NY, ⁸Department of Medical Oncology, NYU Langone Health, New York, NY, ⁹New York University School of Dentistry, New York (and vicinity), NY, ¹⁰Department of Radiation Oncology, NYU Grossman School of Medicine, New York, NY

Purpose/Objective(s): Osteoradionecrosis (ORN) is a well-known side effect after intensity modulated radiation therapy (IMRT) to the head and neck. Patients with titanium plate reconstruction or with extensive in field dental amalgams may be at increased risk of ORN due to scatter radiation and increased dose heterogeneity to the bone. We studied the impact of these factors on ORN and locoregional recurrence (LRR) in oral cavity patients. Materials/

Methods: We retrospectively identified patients receiving IMRT for oral cavity cancer from 2014-2023. Patient demographics, IMRT dose and field, concurrent chemotherapy, smoking history, reconstruction details, number of dental amalgams on CT simulation scan, and LRR data were correlated with risk of ORN. Patients with reirradiation or brachytherapy were excluded. Reconstructions were classified as requiring metal or not. Dental amalgams were identified on the CT simulation scan within the 50 Gy isodose line (IDL). Wilcoxon rank sum test, Pearson’s chi-squared test, Linear and logistic regression, Kaplan-Meier analysis with logrank test and Fisher’s exact test were used to analyze the data.
Results: 148 patients were treated to the oral cavity definitively (n=13) or adjuvantly (n=135). Median age was 62 years. Median follow-up was 16 months. Over 80% of the patients were stage III or IV. 30 patients had reconstruction with a metal plate while 84 patients had reconstruction without a metal plate or no reconstruction (n=34). The most common IMRT dose was 60 Gy, with 98 patients receiving bilateral neck treatment.16.2% of patients (n=24) developed ORN, either spontaneously (87%) or after undergoing tooth extraction (13%). Median time to ORN after completion of IMRT was 23 months. 2-year actuarial risks of ORN for all patients, those with a metal plate reconstruction, and no metal plate reconstruction were 14.6%, 20.0%, and 15.6%, respectively. 44 patients had at least 1 dental amalgam within the 50 Gy IDL. 45 patients developed LRR. On univariate analysis, reconstruction with a metal plate was not a risk factor for developing ORN (p=0.719). LRR was not significantly different in patients with or without a metal plate (p=0.652) or in those who developed ORN (p=0.885). Median time to LRR was not significantly different in patients with or without a metal plate (6 months vs 4 months, p=0.098, respectively). 2-year actuarial risks of LRR for all patients, those with a metal-plate reconstruction, and no metal-plate reconstruction were 32.2%, 28.9%, and 35.3%, respectively. Though not statistically significant, every additional dental amalgam in the 50 Gy IDL increased the risk of ORN by 29% (OR 1.29, 95% CI 0.91-1.79, p=0.13).
Conclusion: Although there is a theoretical concern of increased dose heterogeneity due to scatter radiation from metal plate reconstruction and in field dental amalgams, we did not find an increased risk of ORN. We found a positive correlation between increasing number of dental amalgams in the 50 Gy IDL and risk of ORN.