Abstract
Carbon-ion radiation is a high linear energy transfer radiation, and is associated with high levels of biological effects. In addition, it has an excellent dose concentration, thus allowing effective radiation therapy with less damage to the surrounding organs. Here, we report the favorable therapeutic effects of carbon-ion radiation therapy on postoperative residual or recurrent tumors, which are often difficult to treat. The study was conducted on 52 cases of postoperative residual or recurrent tumors of the oral and maxillofacial region, including the parotid glands, treated with carbon-ion radiation therapy at the National Institute of Radiological Sciences between April 1997 and August 2013. Adenoid cystic carcinomas accounted for 26 cases (50%), and locally advanced Stage T4 tumors accounted for 39 cases (75%). The treatment was conducted using 57.6 or 64 GyE in 16 fractions over 4 weeks. The median observation period was 47.7 months. The local control and crude survival rates were 84.6% and 76.8%, respectively, at 3 years, and 75.2% and 63.2%, respectively, at 5 years. As for adverse reactions, Grade 3 mucositis was found in 12 cases during the acute stage, although recovery to Grade 1 or lower occurred in all cases during the later stages. Our results suggest that carbon-ion radiation therapy is an effective local treatment for radioresistant locally advanced recurring tumors that are difficult to treat using other methods.
