Validity of High-Dose-Rate Interstitial Brachytherapy as Monotherapy for Mobile Tongue Cancer in Terms of the Acute Mucosal Reaction.

Background: The present study investigated the acute mucosal reaction (AMR) after high-dose-rate interstitial brachytherapy at 54 Gy/9 fractions (HDR54) as monotherapy administered twice a day for tongue cancer in 13 patients, and attempted to validate HDR54 by comparing the AMR with that of our previously reported HDR at 60 Gy/10 fractions (HDR60), and low-dose-rate interstitial brachytherapy at approximately 70 Gy (LDR70).

Methods: The European Organization for Research on Treatment of Cancer/ Radiation Therapy Oncology Group scoring system with modifications (score: 1-4.5) was used to evaluate AMR. The time courses of the AMR scores of HDR54 were recorded. The time courses of the AMR of HDR54, HDR 60, and LDR70 were each divided into 6 phases and compared.

Results: The number of cases in the HDR54 group with a lower score (1-2) at the time of the initial response was significantly higher (12 cases) than those in the HDR60 group (1 case) (p=0.0077) and LDR70 group (1 case) (p=0.0077). In the HDR54 group, the time between the end of treatment and appearance of the first response was significantly longer (median: 3 days) than those in the HDR60 group (median: 1 day) (p<0.001) and LDR70 group (median: 1 day) (p<0.001). No significant differences were observed in the maximum score, its duration, or other parameters.

Conclusions: The results indicated that the AMR of HDR54 started later and was gentler and more easily tolerated than the other two methods, suggesting the validity of HDR54 in terms of AMR.