Head and Neck Cancer

PV 02 - Poster Viewing Q&A - Session 2

MO_28_2918 - Osteoradionecrosis after Radiotherapy for Head and Neck Cancer: Incidence, Risk Factors, and Mandibular Dose-Volume Effects

Monday, September 16
10:45 AM - 12:00 PM
Location: ASTRO Innovation Hub

Osteoradionecrosis after Radiotherapy for Head and Neck Cancer: Incidence, Risk Factors, and Mandibular Dose-Volume Effects
S. F. M. Aarup-Kristensen1,2, C. R. Hansen1,3, and J. Johansen1,2; 1Department of Clinical Research, University of Southern Denmark, Odense, Denmark, 2Department of Oncology, Odense University Hospital, Odense, Denmark, 3Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark

Purpose/Objective(s): The incidence of osteoradionecrosis (ORN) may have declined during the era of 3D to IMRT-based radiotherapy (RT) of head and neck cancer (HNC). We aimed at determining the incidence of mandibular ORN in the modern era of radiotherapy, with proper consideration to possible risk factors, including surgery and mandibular dose-volume effects.

Materials/Methods: The cohort consisted of 1,224 patients treated with 3D RT or IMRT for carcinoma of the oral cavity, pharynx or larynx between 2007-2015 in a single academic HNC center. Patients were treated to 66-68 Gy (95% dose to 98% PTVF volume) with either 3D-CRT or IMRT, depending on treatment year. Dose planning was performed in Pinnacle3. All patients were routinely evaluated by a hospital oral and maxillofacial surgeon before the start of RT and all patients had follow-up at the center. ORN cases were defined from clinical observations at follow-up or by oral and maxillofacial hospital code diagnostics. Patient demographics, including smoking, tumor characteristics and dental status were expanded by data obtained from a national database. A nested case-control study used all ORN cases matched with two controls (1:2). The mandible was delineated on axial slices in a treatment planning system for dose calculation. Multivariable Cox regression analysis (MVA) was applied using demographic and treatment variables combined with dosimetric data.

Results: Of 1,224 patients, 51 were recorded with ORN (4.2%) with a median time to event of 10 months (range 1.5-89) after RT. Median follow-up time was 22 months (0.3-95). Average mean mandibular dose was 39.1 Gy, mean D1cc was 63.6 Gy. In univariable analysis, smoking (HR 1.60, p=0.02), surgery involving the mandible and/or pre-RT tooth extraction (HR 2.68, p=0.004), as well as mean mandibular dose (HR 1.05, p=0.003) were all significantly associated with the development of ORN. All dose parameters were related to ORN except for max dose to < 1cc. Mean mandibular dose was selected for MVA. In the Cox regression model, mean mandibular dose and surgery/tooth extraction remained significant predictors of for ORN, HR 1.04 (1.008-1.08) and 2.14 (1.08-4.24), respectively, while smoking did not retain its power (p=0.08, HR 1.43).

Conclusion: The onset of mandibular ORN was early, and the incidence low (4.2%) in this large HNC cohort treated with 3D RT/IMRT. In the nested case-control analysis, mandibular surgery/pre-RT tooth extraction and treatment dose were associated with the development of ORN. This raises the question whether a more conservative approach should be adopted when eliminating dental foci prior to RT. Mean mandibular dose is still to consider. With an average mean mandibular dose around 40 Gy, the risk of ORN was less than 5% after 3DCRT/IMRT.

Author Disclosure: S.F. Aarup-Kristensen: None. C.R. Hansen: None.

Svend Aarup-Kristensen, PGY-1

Odense University Hospital

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