Brachytherapy with 198Au grains for cancer of the floor of the mouth: relationships between radiation dose and complications

Objective This study aimed to retrospectively evaluate the radiation dose and complications in soft tissue and mandible caused by Au-198 grain brachytherapy alone or the combination with other modalities in patients with the cancer of the floor of the mouth. Materials and methods Twelve patients with T1 (n = 5) and T2 (n = 7) squamous cell carcinoma of the floor of the mouth, who were treated with Au-198 grain brachytherapy alone (n = 5) or the combination of external beam radiotherapy (EBRT) and/or chemotherapy and Au-198 grain brachytherapy (n = 7) from January 2005 to December 2016, were included. The relationships between the radiation dose and the complications of the soft tissue or mandible were investigated. Results Seven of 12 patients had died. Of these 7 patients, one with T1 and 2 with T2 had died of the causes related to the cancer of the floor of the mouth. Two with T1 and 2 with T2 had died of other diseases. Two patients had grade 2 complications of the soft tissue and mandible. These patients were treated by the combination of EBRT and/or chemotherapy and Au-198 grain brachytherapy and irradiated with 123 or 139 Gy in total dose, respectively. And one of these patients was treated by the chemotherapy in addition to EBRT. Conclusion Our study showed that the combination of EBRT and Au-198 grains brachytherapy for the floor of the mouth cancer patients might be associated with risks of developing complications of soft tissue ulcer and mandibular bone necrosis.