Shirai K, et al. – The relationship between brainstem necrosis and dose–volume histograms, was explored in patients with head and neck tumors after carbon–ion radiotherapy. This study reported that the dose constraints appeared to help minimize brainstem necrosis after carbon–ion radiotherapy.

Methods

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

Results

• As per observations, the median follow-up was 24months.
• Results reported the development of grade 1 brainstem necrosis in four patients, with 2-year and 3-year cumulative rates of 2.8% and 6.5%, respectively.
• The following significant cut-off values were unveiled by receiver operating characteristic curve analysis: a maximum brainstem dose of 48Gy (relative biological effectiveness [RBE]), D1cm³ of 27Gy (RBE), V40Gy (RBE) of 0.1cm³, V30Gy (RBE) of 0.7c³, and V20Gy (RBE) of 1.4cm³.
• A significant association between V30Gy (RBE) and brainstem necrosis was revealed by multivariate analysis.
• In addition, the 2-year cumulative rates were 33% and 0% for V30 Gy (RBE) of ≥0.7 cm³ and 3, respectively (p