A preliminary study on effect of carbon ion radiotherapy on bone marrow suppression

Objective To explore the effect of carbon ion radiotherapy (CIRT) on the bone marrow adjacent to or within the treatment fields, and to observe the bone marrow toxicities after CIRT alone. Methods Twenty-one patients with malignant tumors of different body parts and treated with CIRT in Heavy Ion Center, Wuwei Cancer Hospital were analyzed retrospectively. The data of white blood cells, neutrophils, hemoglobin, platelets, lymphocytes and globulin before treatment, 7, 14 and 28 ​d during treatment, and 1 and 3 months after treatment were collected. Hematological toxicities were measured according to the Common Terminology Criteria for Adverse Events (CTCAE, Version 4.03) criteria. Dose-volume histogram parameters were obtained for all patients and analyzed for their correlation with myelosuppression. Univariate analysis was performed for patients’ sex, age group, tumor site, radiation dose, and Karnofsky performance score (KPS) was used as an independent factor to find predictors factors for the risk of myelosuppression. Results CIRT minimized the dose radiated to the bone marrow. Overall, volume receiving 3 GyE(V3) or more of the bone marrow were less than 0.5%, especially V5 less than 0.1%. No patients treated with carbon ion radiotherapy developed grade III or IV myelosuppression. Seven patients (33.3%) developed grade I myelosuppression and one patient (4.8%) developed grade II myelosuppression, and most of them showed reduced white blood cell counts. There were no significant differences in hemoglobin and globulin levels before and after CIRT. Univariate analysis did not find any statistically significant predictors for myelosuppression. Conclusions CIRT is effective in preserving bone marrow function regardless of tumor site. Patients receiving CIRT alone have a low incidence of grade I−II myelosuppression and a mild effect on globulins. There was no significant correlation between occurrence of myelosuppression and the dose and site irradiated by CIRT.