Novel Hybrid Scattering- and Scanning-Beam Proton Therapy Approach

Abstract

Purpose: To determine whether a hybrid intensity-modulated proton therapy (IMPT) and passive scattered proton therapy (PSPT) technique, termed HimpsPT, could be adopted as an alternative delivery method for patients demanding scanning beam proton therapy. Patients and Methods: We identified 3 representative clinical cases-an oropharyngeal cancer, skull base chordoma, and stage III non-small-cell lung cancer-that had been treated with IMPT at our center. We retrospectively redesigned these cases using HimpsPT. The PSPT plans for all three cases were designed with the same prescriptions as those used in the IMPT plans. In this way, the whole treatment was delivered using alternating or sequential PSPT and IMPT. Results: All HimpsPT plans met the clinical dose criteria and were of similar quality as the IMPT plans. In the skull base case, the mixed plan was more effective at sparing the brain stem because the sharp penumbra of the aperture in the PSPT plans was not present in the IMPT plans. The HimpsPT plans were more robust than the clinical IMPT plans generated without robust optimization. Conclusion: The HimpsPT delivery technique can achieve a treatment-plan quality similar to that of IMPT, even in the most challenging clinical cases. In addition, at centers equipped with both scattering and scanning beam capabilities, the HimpsPT technique may allow more patients to benefit from scanning beam technology.

Early Axial Growth Outcomes of Pediatric Patients Receiving Proton Craniospinal Irradiation

“…[27] Our study found a significantly reduced growth suppression on univariate analysis but this was not reproduced on multivariate analysis. Other institutions have also reported use of alternate partial vertebral body irradiation strategies [1], conformal thecal sac-only p-CSI using intensity-modulated proton therapy (IMPT), and PBS that spares ossification centers [28, 29]. In addition, novel imaging techniques such as dual energy CT and prompt gamma imaging may reduce range uncertainty and permit more precise dose delivery.…”