Dose-volume histogram analysis of brainstem necrosis in head and neck tumors treated using carbon-ion radiotherapy.

BACKGROUND AND PURPOSE: We aimed to evaluate the relationship between brainstem necrosis and dose-volume histograms in patients with head and neck tumors after carbon-ion radiotherapy.

MATERIAL AND

METHODS

We evaluated 85 patients with head and neck tumors who underwent carbon-ion radiotherapy and were followed-up for ≥12months. Brainstem necrosis was evaluated using the Common Terminology Criteria for Adverse Events (version 4.0).

RESULTS

The median follow-up was 24months, and four patients developed grade 1 brainstem necrosis, with 2-year and 3-year cumulative rates of 2.8% and 6.5%, respectively. Receiver operating characteristic curve analysis revealed the following significant cut-off values: a maximum brainstem dose of 48Gy (relative biological effectiveness [RBE]), D1cm3 of 27Gy (RBE), V40Gy (RBE) of 0.1cm3, V30Gy (RBE) of 0.7cm3, and V20Gy (RBE) of 1.4cm3. Multivariate analysis revealed that V30Gy (RBE) was most significantly associated with brainstem necrosis. The 2-year cumulative rates were 33% and 0% for V30Gy (RBE) of ≥0.7cm3 and <0.7cm3, respectively (p<0.001).

CONCLUSIONS

The present study indicated that the dose constraints might help minimize brainstem necrosis after carbon-ion radiotherapy.