Association between Tooth Extraction 2 Weeks before Radiotherapy and Osteoradionecrosis in Patients with Advanced Oral and Oropharyngeal Cancer.

Osteoradionecrosis (ORN) is the most serious late adverse event in standard treatment for locally advanced oral and oropharyngeal cancers. The clinical guidelines recommend dental extractions be completed at least 2 weeks before the start of radiotherapy to reduce the risk of ORN development. However, to what extent tooth extraction 2 weeks before radiotherapy, as recommended by the guidelines, reduces the risk of ORN development is unclear. This study was conducted to examine the association between tooth extraction 2 weeks before radiotherapy and ORN development. The study included patients aged ≥18 years who received chemoradiotherapy with 3-weekly cisplatin or radiotherapy alone for locally advanced oral and oropharyngeal cancer at the head and neck surgery of Miyagi Cancer Center in Japan between 2011 and 2018. Additional oral care (AOC) was provided to the patients between 2011 and 2014; however, because of the downsizing of dentistry in 2015, usual oral care (UOC) was provided to the patients between 2015 and 2018. In the AOC group, all dental infection foci and teeth with poor prognosis in the radiation field were removed 2 weeks before radiotherapy. The cumulative incidence of ORNs was calculated using the Kaplan-Meier method, and multivariate analyses were performed using the Fine-Gray model with death as a competing risk for ORN development. Ninety-three patients were analyzed, 43 in the AOC and 50 in the UOC. The cumulative incidence rate of ORN in the AOC group was lower than that in the UOC group (0.071 vs. 0.415, p < 0.001). The hazard ratio (HR) for the incidence of ORN in the AOC group versus that in the UOC group was lower (HR, 0.108, 95% CI 0.019-0.606). In the subgroup analysis, HRs were lower in the following groups: male (0.062, 0.009-0.425), Eastern Cooperative Oncology Group performance status 0 (0.141, 0.028-0.700), without diabetes (0.135, 0.029-0.635), drinkers with a Sake index of ≥60 (0.033, 0.002-0.518), advanced cancer of clinical stage Ⅳ (0.151, 0.025-0.909), concurrent chemotherapy (0.126, 0.022-0.702), total cisplatin dose of ≥200 mg/m (0.055, 0.007-0.411), and dental risk factors (0.061, 0.007-0.537). This study showed that extraction of at-risk teeth 2 weeks before radiotherapy reduced the risk of ORN development by approximately 90%. However, these results are based on a retrospective observational study conducted at only one center. Thus, future multivariate studies conducted at multiple centers, with death as a competing risk, are needed.