The Clinical Potential of Intensity Modulated Proton Therapy

Lomax, Anthony; Pedroni, E.; Rutz, Hans; Goitein, Gudrun

doi:10.1078/0939-3889-00217

Cited by 147 publications

(122 citation statements)

References 24 publications

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“…The experience with IMPT at Paul Scherrer Institut (Switzerland) demonstrated a potential for improved tissue sparing in a number of sites, including intracranial, nasopharyngeal and paraspinal lesions (14)(15)(16)(17)(18). While intensity-modulation has been identified as a means to achieve prostate dose escalation (12), IMPT treatment of prostate cancer has not yet been performed anywhere.…”

Section: Introductionmentioning

confidence: 99%

Radiotherapy Treatment of Early-Stage Prostate Cancer with IMRT and Protons: A Treatment Planning Comparison

Trofimov

Nguyen

Coen

et al. 2007

International Journal of Radiation Oncology*Biology*Physics

199

163

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Purpose-To compare intensity-modulated photon radiotherapy (IMRT) with 3D-conformal proton therapy (3D-CPT) for early stage prostate cancer, and explore the potential utility of intensitymodulated proton therapy (IMPT).Methods-Ten patients were planned with both 3D-CPT (2 parallel-opposed lateral fields) and IMRT (7 equally spaced coplanar fields). Prescribed dose was 79.2 Gy (or cobalt Gray-equivalent, CGE for protons) to the prostate gland. Dose-volume histograms, dose conformity, and equivalent uniform dose (EUD) were compared. Additionally, plans were optimized for 3D-CPT with nonstandard beam configuration, and for IMPT assuming delivery with beam scanning.Results-At least 98% of the PTV received the prescription dose. IMRT plans yielded better dose conformity to the target, while proton plans achieved higher dose homogeneity, and better sparing of rectum and bladder in the range below 30 Gy/CGE. Bladder volumes receiving over 70 Gy/CGE (V 70 ) were reduced, on average, by 34% with IMRT vs. 3D-CPT, while rectal V 70 were equivalent. EUD from 3D-CPT and IMRT plans were indistinguishable within uncertainties, for both bladder and rectum. With the use of small-angle lateral-oblique fields in 3D-CPT and IMPT, the rectal V 70 was reduced by up to 35% compared to the standard lateral configuration, while the bladder V 70 increased by less than 10%.Conclusions-In the range over 60 Gy/CGE, IMRT achieved significantly better sparing of the bladder, while rectal sparing was similar with 3D-CPT and IMRT. Dose to healthy tissues in the range below 50% of the target prescription was substantially lower with proton therapy.

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Section: Introductionmentioning

confidence: 99%

Radiotherapy Treatment of Early-Stage Prostate Cancer with IMRT and Protons: A Treatment Planning Comparison

Trofimov

Nguyen

Coen

et al. 2007

International Journal of Radiation Oncology*Biology*Physics

199

163

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“…The newly developed intensity-modulated proton therapy (IMPT), which can be delivered with the spot scanning method, has been shown to yield superior dose distributions to photon intensity-modulated radiotherapy (IMRT), with the added advantage of a significant reduction in the volume of healthy normal tissues exposed to low-to-medium doses. 3 In spite of almost 43,000 patients treated with protons worldwide, there are still few published controlled clinical trials comparing protons and light ions to x-ray radiation therapy. 4 There is a growing number of particle therapy facilities around the world.…”

mentioning

confidence: 99%

Current status of radiotherapy with proton and light ion beams

Greco

Wolden

2007

Cancer

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Several model studies have shown potential clinical advantages with charged particles (protons and light ions) compared with 3D-conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) in many disease sites. The newly developed intensity-modulated proton therapy (IMPT) often yields superior dose distributions to photon IMRT, with the added advantage of a significant reduction in the volume of healthy normal tissues exposed to low-to-medium doses. Initially, the major emphasis in clinical research for proton and light ion therapy was dose escalation for inherently radioresistant tumors, or for lesions adjacent to critical normal structures that constrained the dose that could be safely delivered with conventional x-ray therapy. Since the advent of IMRT the interest in particle therapy has gradually shifted toward protocols aimed at morbidity reduction. Lately the emphasis has mostly been placed on the potential for reduced risk of radiation-induced carcinogenesis with protons. Compared with 3D-CRT, a 2-fold increase has been theoretically estimated with the use of IMRT due to the larger integral volumes. In the pediatric setting, due to a higher inherent susceptibility of tissues, the risk could be significant, and the benefits of protons have been strongly emphasized in the literature. There is a significant expansion of particle therapy facilities around the world. Increasing public awareness of the potential benefits of particle therapy and wider accessibility for patients require that treating physicians stay abreast of the clinical indications of this radiotherapy modality. The article reviews the available literature for various disease sites in which particle therapy has traditionally been considered to offer clinical advantages and to highlight current lines of clinical research. The issue of radiation-induced second malignancies is examined in the light of the controversial epidemiological evidence available. The cost-effectiveness of particle therapy is also discussed. Cancer 2007;109: 1227-38. 2007 American Cancer Society.KEYWORDS: radiotherapy, proton therapy, light ions, intensity modulated radiotherapy, second cancers. C harged particles (protons and light ions) have a finite range in tissues. The interaction probability to cause ionization increases as they lose velocity traversing through tissues, so that a peak of dose occurs at a depth proportional to the energy of each particle. Beyond this peak no further dose deposition occurs. This phenomenon was described by William Bragg over 100 years ago.1 The dose peak may be 'spread out' to achieve a plateau of uniform dose to precisely cover the target while sparing adjacent normal structures. Passively scattered beams of a certain aperture can be produced by means of range-shifting modulators of variable thickness providing spread-out Bragg peaks (SOBP) for clinical use. The recent introduction of the spot scanning method represents a major advance in particle therapy.2 In this method, small pencil beams of a certain

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“…The optimisation used by the Deutsches Krebsforschungszentrum (Heidelberg, Germany) inhouse TPSs for particle therapy (KonRad, Heidelberg, Germany), is the worst-case dose distribution approach [55]. The worst-case dose distribution was introduced by Lomax et al [56] and is a method of combining multiple dose distributions into a single one. For a voxel inside the target volume the minimum dose to this voxel is stored and for a voxel outside of the target volume the maximum dose is stored.…”

Section: Optimisation Functions For Robust Proton Planningmentioning

confidence: 99%

“…In this optimisation it is assumed that the range uncertainties for each Bragg peak are correlated, so that at the target the range uncertainty is accumulated and effects within the target are ignored. The dose from each beamlet was calculated Treatment planning optimisation in proton therapy at multiple ranges; three ranges between 2 and 5 mm were used, and these were the nominal, maximum and minimum range uncertainties [56]. The set-up uncertainty was modelled as a shift of the target inside a sphere with a radius equal to the maximum set-up uncertainty.…”

Section: Optimisation Functions For Robust Proton Planningmentioning

confidence: 99%

Treatment planning optimisation in proton therapy

McGowan¹,

Burnet²,

Lomax³

2013

BJR

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ABSTRACT. The goal of radiotherapy is to achieve uniform target coverage while sparing normal tissue. In proton therapy, the same sources of geometric uncertainty are present as in conventional radiotherapy. However, an important and fundamental difference in proton therapy is that protons have a finite range, highly dependent on the electron density of the material they are traversing, resulting in a steep dose gradient at the distal edge of the Bragg peak. Therefore, an accurate knowledge of the sources and magnitudes of the uncertainties affecting the proton range is essential for producing plans which are robust to these uncertainties. This review describes the current knowledge of the geometric uncertainties and discusses their impact on proton dose plans. The need for patient-specific validation is essential and in cases of complex intensity-modulated proton therapy plans the use of a planning target volume (PTV) may fail to ensure coverage of the target. In cases where a PTV cannot be used, other methods of quantifying plan quality have been investigated. A promising option is to incorporate uncertainties directly into the optimisation algorithm. A further development is the inclusion of robustness into a multicriteria optimisation framework, allowing a multi-objective Pareto optimisation function to balance robustness and conformity. The question remains as to whether adaptive therapy can become an integral part of a proton therapy, to allow re-optimisation during the course of a patient's treatment. The challenge of ensuring that plans are robust to range uncertainties in proton therapy remains, although these methods can provide practical solutions. The ability to create and deliver the ideal treatment plan, where the target volume receives 100% of the prescribed dose and normal tissue receives 0%, is the holy grail of radiation therapy [1]. It is, however, impossible to achieve this perfect balance. Instead, multiple trade-offs are required to achieve a clinically acceptable plan, so the problem becomes one of optimisation. There are many factors that can affect how ''optimised'' a patient's treatment can be. This review focuses on the challenges of proton therapy plan optimisation, particularly in regard to range uncertainties, and how to incorporate them into the plan evaluation and verification process.The nature of proton therapy makes the aim of cure without complications potentially more achievable, owing to the highly localised deposition of dose in the characteristic Bragg peak [2]. This relates predominantly to the ability to deliver high doses of radiation close to normal tissue structures, which would be dose limiting in conventional X-ray treatments, and to the finite range of protons, which results in a reduced integral dose to surrounding normal tissues.From a clinical perspective, the exact role of proton therapy has yet to be defined. However, for childhood cancers, proton therapy delivers a lower dose to tissues around the tumour than X-rays, resulting in less growth disturbance and l...

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The Clinical Potential of Intensity Modulated Proton Therapy

Cited by 147 publications

References 24 publications

Radiotherapy Treatment of Early-Stage Prostate Cancer with IMRT and Protons: A Treatment Planning Comparison

Radiotherapy Treatment of Early-Stage Prostate Cancer with IMRT and Protons: A Treatment Planning Comparison

Current status of radiotherapy with proton and light ion beams

Treatment planning optimisation in proton therapy

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