In this study, we evaluate dosimetric advantages of using patient‐specific aperture system with intensity‐modulated proton therapy (IMPT) for head and neck tumors at the shallow depth. We used four types of patient‐specific aperture system (PSAS) to irradiate shallow regions less than 4 g/cm2 with a sharp lateral penumbra. Ten head and neck IMPT plans with or without aperture were optimized separately with the same 95% prescription dose and same dose constraint for organs at risk (OARs). The plans were compared using dose volume histograms (DVHs), dose distributions, and some dose indexes such as volume receiving 50% of the prescribed dose (V50), mean or maximum dose (Dmean and Dmax) to the OARs. All examples verified in this study had decreased V50 and OAR doses. Average, maximum, and minimum relative reductions of V50 were 15.4%, 38.9%, and 1.0%, respectively. Dmax and Dmean of OARs were decreased by 0.3% to 25.7% and by 1.0% to 46.3%, respectively. The plans with the aperture over more than half of the field showed decreased V50 or OAR dose by more than 10%. The dosimetric advantage of patient‐specific apertures with IMPT was clarified in many cases. The PSAS has some dosimetric advantages for clinical use, and in some cases, it enables to fulfill dose constraints.
The purpose of this paper is to describe an outline of a proton therapy system in Nagoya Proton Therapy Center (NPTC). The NPTC has a synchrotron with a linac injector and three treatment rooms: two rooms are equipped with a gantry and the other one is equipped with a fixed horizontal beamline. One gantry treatment room has a pencil beam scanning treatment delivery nozzle. The other two treatment rooms have a passive scattering treatment delivery nozzle. In the scanning treatment delivery nozzle, an energy absorber and an aperture system to treat head and neck cancer have been equipped. In the passive treatment delivery nozzle, a multi-leaf collimator is equipped. We employ respiratory gating to treat lung and liver cancers for passive irradiation. The proton therapy system passed all acceptance tests. The first patient was treated on February 25, 2013, using passive scattering fixed beams. Respiratory gating is commonly used to treat lung and liver cancers in the passive scattering system. The MLCs are our first choice to limit the irradiation field. The use of the aperture for scanning irradiation reduced the lateral fall off by half or less. The energy absorber and aperture system in scanning delivery is beneficial to treat head and neck cancer.
BackgroundTwo prospective phase II trials were designed to assess the efficacy and safety of image-guided proton therapy (IGPT) for either medically inoperable or operable stage I non-small cell lung cancer (NSCLC). The present study reports the interim results of these trials.MethodsFifty-five patients with histologically confirmed stage I NSCLC (IA in 33 patients and IB in 22 patients; inoperable in 21 patients and operable in 34 patients) who received IGPT between July 2013 and February 2017 were analyzed. The median patient age was 71 years (range: 48–88 years). IGPT with fiducial metallic marker matching was performed for suitable patients, and a respiratory gating method for motion management was used for all treatments. Peripherally located tumors were treated with 66 Gy relative biological effectiveness equivalents (Gy(RBE)) in 10 fractions (n = 49) and centrally located tumors were treated with 72.6 Gy(RBE) in 22 fractions (n = 6). Treatment associated toxicities were evaluated using Common Toxicity Criteria for Adverse Events (v.4.0).ResultsMedian follow-up was 35 months (range: 12–54 months) for survivors. For all patients, the 3-year overall survival, progression-free survival, and local control rates were 87% (95% confidence interval: 73–94%), 74% (58–85%), and 96% (83–99%), respectively. Fiducial marker matching was used in 39 patients (71%). Grade 2 toxicities observed were radiation pneumonitis in 5 patients (9%), rib fracture in 2 (4%), and chest wall pain in 5 (9%). There were no grade 3 or higher acute or late toxicities.ConclusionsIGPT appears to be effective and well tolerated for all patients with stage I NSCLC.Trial registrationLung-001, 13–02-09 (9), registered 11 June 2013 and Lung-002, 13–02-10 (10), registered 11 June 2013.
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