@misc{oai:repo.qst.go.jp:00065721,
 author = {Kanematsu, Nobuyuki and Matsufuji, Naruhiro and Inaniwa, Taku and Matubara, Hiroaki and Yamamoto, Naoyoshi and Miyamoto, Tadaaki and 兼松 伸幸 and 松藤 成弘 and 稲庭 拓 and 松原 礼明 and 山本 直敬 and 宮本 忠昭},
 month = {Jun},
 note = {Purpose: Malignant pleural mesothelioma is a rare form of cancer that is most commonly caused by exposure to asbestos and developes in pleura of internal chest wall and outer linining of lungs. The incidence of mesothelioma can take anywhere from 20 to 50 years after exposure to asbestos before it shows obvious symptoms. Treatment options for mesothelioma include surgery, chemotherapy, conventional radiation therapy, and their combinations although the prognosis is typically poor. Ion beam therapy is an advanced form of radiotherapy utilizing the physical and biological advantage of energetic ions, namely the Bragg peak of dose at a controlled depth in body, for cancer treatment. Recent advancement of beam scanning techniques has enabled exceedingly conformal dose formation for large and irregular-shaped tumors. The present work aims to evaluate the feasibility of scanning ion beam therapy for radical treatment of mesothelioma like surgery.
Methods: A diagnostic PET/CT image series of a patient with malignant mesothelioma in the left pleura was used in this study. A clinical target volume (CTV) was defined to include the entire left pleura of inner 5 mm and outer 10 mm from the chest wall or to the median line of the ribs. In this feasibility study, all uncertainties for organ motion, patient setup, and beam delivery were ignored. We used the treatment planning system for scanning carbon-ion beam therapy at the National Institute of Radiological Sciences, in which in-house carbon-ion beam algorithms were built on a base system provided by Elekta, AB. Two opposing beams in the anterior and posterior directions were planned to cover only respective near-side halves of the CTV so that the carbon ions would not deeply penetrate into the lung tissue. Their scanning sequences were individually optimized with the other being fixed, where the clinical dose was evaluated with correction for relative biological effectiveness (RBE) originally defined for 10% survival fraction of human salivary grand tumor cells.
Results: Due to dose contribution of each beam to the opposite half of the CTV, the respective beam-optimization steps have to be repeated alternately, which took about one hour in total. Figure 1 shows the resultant dose distribution. Despite the highly irregular shape and the beam junction, the CTV dose was moderately uniform. For the normal lung tissue, defined as the left lung volume excluding the CTV, less than 50% of the volume received 50% of the dose prescribed to the tumor, which may suggest that the lung will possibly remain healthy. However, influences of various uncertainties, especially diaphragm motion and heartbeat, must be considered and mitigated if necessary before the proposed method can be practical. Optimum dose fractionation scheme and adequacy of the RBE will have to be investigated and validated in future clinical studies.
Conclusion: In the treatment planning study using a diagnostic image of a patient with malignant mesothelioma in the left pleura, we have demonstrated the feasibility of scanning ion beam therapy to treat the pleura with possible sparing of the lung tissue., CARS 2014 Computer Assisted Radiology and Surgery 28th International Congress and Exhibition},
 title = {Treatment planning study of scanning ion beam therapy for malignant pleural mesothelioma},
 year = {2014}
}