Particle Therapy and Radiation Oncology Division
Introduction
At our hospital, radiation therapy including particle therapy is focused on 2 aspects of cancer treatment: first, clinical confirmation of the safety and efficacy of radiation therapy and second, the development of treatment techniques that are more precise and easy to apply.
Clinical Trials and Practice
Many in-house, multiinstitutional, and JCOG clinical trials have been conducted. Two prospective studies of combined chemo- and radiotherapy for treating head and neck cancers were performed. Both these studies showed that the combined modality regimen (121, 122) was feasible. Seventy patients with hypopharyngeal carcinoma who had been treated with accelerated radiotherapy were retrospectively analyzed. The 2-year local control rate was approximately 70%, and the overall treatment duration was the only identified prognostic factor (32). The complete response (CR) rate was retrospectively analyzed in patients with head and neck cancer who had received chemoradiotherapy. In these patients, the CR rate at 6 months was found to be a better surrogate endpoint than that at 4 weeks or at 3 months (123).
In chemoradiotherapy for carcinoma of the thoracic esophagus, the treatment regimen of chemotherapy and the technique of radiotherapy (RT) have been changed. Radiation-induced pneumonitis has been analyzed among 43 patients who completed the treatment according to the new technique. Among them, Grade 2 and Grade 3 pneumonitis was observed in 2 and 1 patient, respectively. Our new RT technique has been considered to be safe.
Quality assurance is one of the most important issues in multiinstitutional clinical studies. Several investigations on this issue were, hence, performed (124, 125).
The preliminary outcome of 14 patients with olfactory neuroblastoma who had been treated with proton beam therapy (PBT) was analyzed (126). Over a median follow-up period of 40 months, the 5-year local progression-free and overall survival rates were 84% and 93%, respectively. No serious acute and late toxicity was observed.
Technological Development
Respiratory-gated (RG) radiotherapy is useful for minimizing the volume of normal tissues that is irradiated as a result of the shifting of internal structures during respiratory movements. Although dose distributions can be expected to improve by using this technique, the actual absorbed dose distributions have not been clearly elucidated. Therefore, absorbed dose distributions have been experimentally determined using a phantom system that simulates patient respiration.
Proton-irradiated volume can be confirmed by detection, by means of a positron emission tomography (PET) apparatus, of pair annihilation gamma rays from the positron emitter nuclei, which are generated by the reaction between irradiated proton nuclei and the nuclei in the irradiation target. In the proton treatment room, a beam ON-LINE PET system has been installed, and clinical data collection has been initiated. The same experiment was also carried out using high energy X-rays (127).
● T. Ogino ●
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