Retrospective analysis of tooth extraction and osteoradionecrosis after low-dose rate brachytherapy for patients with tongue cancer.

Objectives: This study aimed to investigate the incidence of osteonecrosis of the jawbones (ORN) after tooth extraction in patients undergoing low-dose rate brachytherapy (LDR-BT) and assess its safety.

Methods: This study retrospectively analyzed 145 patients with tongue cancer treated at Hiroshima University Hospital from 2007 to 2021 with LDR-BT using 192Ir or 198Au alone, LDR-BT and external beam radiotherapy (EBRT) with or without chemotherapy, and LDR-BT with chemotherapy. Patients' mandible and maxilla were protected with spacers. Forty-seven patients underwent tooth extraction, and the incidence, site, and relationship of ORN with tooth extraction were recorded. A subgroup of 26 patients received additional EBRT to the neck after dissection for late cervical lymph node metastases.

Results: Of 145 patients, six (4.1%) developed ORN on the same side of the mandible as LDR-BT, and EBRT was performed before and/or after LDR-BT on the sites where ORNs developed. Five of 47 (10.6%) patients who underwent tooth extraction after LDR-BT developed ORN. ORN incidence was 1.8% (2/109) in the LDR-BT and/or chemotherapy group and 11.1% (4/36) in the combination LDR-BT and EBRT and/or chemotherapy group for primary tongue cancer. Different irradiation methods (LDR-BT and/or chemotherapy and combination LDR-BT and EBRT and/or chemotherapy) and the presence or absence of tooth extraction showed significant differences (p = 0.0335 and p = 0.0139, respectively) with or without ORN.

Conclusions: Mandibular tooth extraction should be avoided on the side of LDR-BT in combined EBRT cases. However, tooth extraction is feasible using a spacer in LDR-BT and/or chemotherapy.