A retrospective analysis was conducted for 25 patients with recurrent adenoid cystic carcinoma in parotid glandwho were histopathologically diagnosed between January 2015 and October 2019. These patients were treated with 125I interstitial brachytherapy alone, with prescribed doses of 100-120 Gy. The target volume was designed according to the pathological characteristics of ACC and recurrence sites. The pre- and post-operation dosimetric parameters (i.e., local control rates) were calculated using the treatmentplanning system.
Results:
In this study, the local recurrence sites included the superficial lobe (10/25) and deep lobe (7/25) of the parotid gland primarily and the skull base region (four patients) and mastoid posterior region (four patients) secondarily. The number of 125I seeds ranged from 16 to 111, with a median number of 59. The activity of radioactive particles was 18.5-25.9 MBq. The 3- and 5-year local control rates were 81.5% and 61.5%, respectively. No significant differences were found between pre- and post-operative dosimetric parameters such as D90, V100, and V150. There was no significant difference in local control rates among the four different recurrence sites.
Conclusions:
125I interstitial brachytherapy is proven to be an effective approach in the treatment of recurrent adenoid cystic carcinoma in the parotid gland. Satisfying local control rates can be achieved through target delineation performed according to recurrence sites and perineural invasion characteristics of ACC.