title: Adaptive radiotherapy based on the daily regression of a tumor in carbon-ion beam irradiation.
abstract: We propose a new application of adaptive radiotherapy using a scanning beam, taking into account the daily regression of a tumor. No patient-specific hardware (such as collimators and compensating filters) is needed for the scanning technique; thus, it allows re-planning immediately before each fractional irradiation using the sophisticated conformations of dose distributions. We retrospectively modeled the tumor volume regression curves as a function of the dose from the CT images which were taken three times during the treatment course. The daily shape of the tumor was mathematically interpolated assuming constant continuity of the tumor deformation. We simulated the adaptive radiotherapy by optimizing the dose distribution on the estimated daily tumor volume for every fraction. The dose-volume histogram (DVH) for the organ at risk in the adaptive radiotherapy was compared with that of the current clinical protocol. We performed analysis using the CT images of cervical cancer patients who received carbon-ion radiotherapy in broad-beam irradiation. The DVH for the rectum and the sigmoid colon was improved by adaptive radiotherapy considering the inter-fractional tumor regression. The result shows that this approach has possible advantages.
authors.affiliation: The Particle Therapy Cancer Research Institute, University of Oxford, Oxford, UK.
authors.forename: Ai
authors.initials: A
authors.lastname: Nagano
authors.forename: Shinichi
authors.initials: S
authors.lastname: Minohara
authors.forename: Shingo
authors.initials: S
authors.lastname: Kato
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kiyohara
authors.forename: Ken
authors.initials: K
authors.lastname: Ando
mesh_terms: D005260:Female; D063193:Heavy Ion Radiotherapy / Q000009:adverse effects / Q000379:methods*; D006801:Humans; D008954:Models, Biological; D058958:Organs at Risk / Q000528:radiation effects; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*