ESTRO 2024 - Abstract Book

S1432

Clinical - Head & neck

ESTRO 2024

Osteoradionecrosis (ORN) is an uncommon but morbid complication of head and neck radiotherapy. To mitigate its risk, many UK centres recommend extracting poor prognosis teeth which are likely to be in the high dose radiotherapy field prior to starting radiotherapy (1). However, there is evidence to suggest that pre-radiotherapy extractions may contribute to ORN risk (2). Whilst relationships between various dose metrics and risk of ORN have been described, there remains no agreed single dosimetric constraint for ORN risk. Additionally, there is limited published work describing the correlation of dental extraction sites with ORN location.

Purpose: To assess the relationship between the site of ORN, site of dental extraction and the radiotherapy dose received at that location.

Objectives:

1. To describe the demographics of patients diagnosed with ORN in our centres. 2. To look at the relationship between site of dental extraction and site of ORN. 3. To look at the relationship between the mandible maximal dose (Dmax) and the site of ORN. 4. To calculate the Dmax at the ORN site in patients whose extraction site correlated with the site of ORN, and in patients where there was no correlation.

Material/Methods:

We performed a retrospective review of patients in our regional head and neck centres who developed ORN following radiotherapy in the definitive or postoperative setting for head and neck cancer between 1994-2022. A list of patients with ORN who have been reviewed by oral maxillofacial surgeons and/or restorative dentistry in our region was obtained from their database. Inclusion criteria included histological diagnosis of squamous cell carcinoma (SCC), adenoid cystic carcinoma or sinonasal undifferentiated carcinoma of the head and neck; radical/adjuvant radiotherapy in our regional centres; and a diagnosis of ORN. If the exact site of ORN was not known, the laterality was used. Data on patient demographics (including age, smoking), primary tumour (including subsite, stage), dental assessment (including date and site of extractions), treatment factors (including radiotherapy technique, dose at site of ORN, dental extractions and mandible), and ORN (site and date of diagnosis) were collected. Dose volume parameters of original treatment plans were reviewed, including mean dose to the mandible (Dmean Gy), maximum dose to the mandible (Dmax Gy), dose at exact site of ORN (Gy) and volume receiving 50Gy (V50). The temporal relationship between dental extractions, radiotherapy and ORN was obtained.

Results:

Between 1994 – 2022, 55 patients were identified from our local ORN database. Fourteen were excluded: 7 had no evidence of ORN on notes review; 6 were treated at external centres and their data was not obtainable; and 1 case of NK T-cell lymphoma. 41 patients were included in the analysis. Patient population: Median age at cancer diagnosis was 55 years. 61.0% were current or ex-smokers. 95.1% had SCC. The most common sites of disease were oropharynx and oral cavity (78.0%). Most patients had locally advanced disease (85.4%). Dental extractions occurred in 68.3% pre-radiotherapy and 34.1% post-radiotherapy.