Dosimetric Parameters Predicting Tooth Loss after Carbon Ion Radiotherapy for Head and Neck Tumors

Abstract

Background: Tooth loss reduces quality of life; however, little is known about tooth loss caused by carbon ion radiotherapy (CIRT). Here, we aimed to elucidate the incidence of tooth loss post-CIRT for head and neck tumors and to identify risk-predictive dosimetric parameters. Methods: This study enrolled 14 patients (i.e., 171 teeth in total) with head and neck non-squamous cell carcinoma. All patients received CIRT comprised of 57.6 or 64.0 Gy (relative biological effectiveness, RBE) in 16 fractions. Dose–volume analysis of the teeth was performed using receiver operating characteristic (ROC) curve analysis with VX (i.e., the volume irradiated with X Gy (RBE)). Results: The median follow-up period was 69.1 months. The median time of tooth loss was 38.6 months. The 5 year cumulative incidence of tooth loss was 13.3%. The volume of irradiated teeth was significantly greater for the lost teeth than for the remaining teeth throughout the dose range. Using the cut-offs calculated from ROC curve analysis, V30–V60 showed high accuracy (i.e., >94%) for predicting tooth loss, with V50 being the most accurate (cut-off, 58.1%; accuracy, 0.95). Conclusions: This is the first report to examine the incidence of tooth loss post-CIRT and to identify risk-predictive dosimetric parameters.

Dose–volume constraints for head‐and‐neck cancer in carbon ion radiotherapy: A literature review

“…A different study focused on the incidence of tooth loss after CIRT of 14 patients (171 teeth) with HN non‐SCCs 29 . The patients were treated with 57.6 or 64 Gy (RBE) in 16 fractions.…”

“…More than half of the teeth that exceeded the V30–V60 cut‐off values fell out within 5 years. Kubo et al recommend the use of V50 < 58.1% as a constraint because V50 showed the highest diagnostic performance among the DVH parameters 29 …”

“…Table 1 summarizes the dose–volume constraints recommended by previous studies 2,17–31 . We divided the constraints into hard and soft.…”

“…Previous studies have associated various constraints with OAR complications related to the HN cancer CIRT 2,17–31 . This review provides an extensive list of constraints for HN cancer CIRT based on the Japanese RBE models.…”

Carbon-ion Radiotherapy for Inoperable Head and Neck Bone and Soft-tissue Sarcoma: Prospective Observational Study

“…Furthermore, preventing acute adverse events can also reduce the occurrence of late adverse events (14-16). Late adverse events such as osteoradionecrosis (21,22), trismus (23), nasolacrimal duct obstruction (24), tooth loss (25), brainstem necrosis (26), brain injury (27), and optic nerve injury (28) have been reported. In the future, we intend to develop a C-ion RT plan considering these dose indicators of onset; thus, the incidence of adverse events is anticipated to be reduced compared with that of the present study.…”