Frequency of osteoradionecrosis of the lower jaw after radiotherapy of oral cancer patients correlated with dosimetric parameters and other risk factors.

Objectives: Osteoradionecrosis (ORN) of the lower jaw is a serious late complication after radiotherapy in patients with oral cavity cancer. The aim of this study is to generate more insight into which patient- and treatment-related factors are associated with the development of ORN in oral cavity cancer patients undergoing postoperative radiotherapy.

Material And Methods: Retrospective evaluation and comparison of 44 patients with ORN (event group 1) matched according to 45 patients without ORN (control group 2) who received postoperative radiotherapy of oral cavity squamous cell carcinoma at our institution between 2012 and 2020. Dosimetric factors that favor the occurrence of ORN should be detected. The cumulative occurrence rate of ORN was calculated according to the Kaplan-Meier method and analyzed by Cox regression and log-rank test.

Results: The median time to develop ORN was 18 months (3-93 months) after radiotherapy. Dental status before radiotherapy (RT) treatment (HR 4.5; 1.8-11.5) and dosimetric parameters including Dmean > 45 Gy (HR 2.4; 1.0-5.7), Dmax > 60 Gy (HR 1.3; 1.1-2.8) and planning target volume (PTV) proportion > 40% intersection with the lower jaw (HR 1.1; 1.0-1.1) were significantly associated with ORN.

Conclusion: The results of this retrospective study reveal that oral cavity cancer patients who underwent pre-RT dental surgery as well as dosimetric parameters using Dmax > 60 Gy, higher mean doses > 45 Gy and more than 40% PTV intersection with the lower jaw bone are independent risk factors for ORN. These findings can assist in the management of patients undergoing RT for head and neck cancer regarding ORN prevention.

Clinical Relevance: Poor oral hygiene and desolate dental status as well as high radiation doses to the mandibular bone significantly increase the risk of developing osteoradionecrosis. Before irradiating a patient with oral cavity cancer, an appointment with the dentist should be made and teeth sanitized if necessary. Likewise, maximum radiation doses to the lower jaw should be minimized.