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Techniques for Treating Bilateral Breast Cancer Patients Using Pencil Beam Scanning Technology.

ABSTRACT: Purpose:Patients with bilateral breast cancer (BBC), who require postmastectomy radiation therapy or radiation as part of breast conservation treatment, present a unique technical challenge. Even with modern techniques, such as intensity modulated radiation therapy or volumetric modulated arc therapy (VMAT), adequate target coverage is rarely achieved without the expense of increased integral dose to important organs at risk (OARs), such as the heart and lungs. Therefore, we present several BBC techniques and a treatment algorithm using intensity-modulated proton therapy (IMPT) for patients treated at our center. Materials and Methods:We describe 3 different BBC treatment techniques using IMPT on patients treated at our center, with comparison VMAT plans to demonstrate the dosimetric benefit of proton therapy in these patients. Following RADCOMP (Radiation Therapy Oncology Group, Philadelphia, Pennsylvania) guidelines, a single physician approved all target volumes and OARs. Plans were designed so that ??95% of the prescribed dose covered ??95% of all targets. Parameters for dosimetric volume histograms for the clinical targets and OARs are reported for the 2 radiation methods. Results:All methods demonstrated acceptable target coverage with 95% of the prescription planning target volume reaching a mean (±?SD) of 98.0% (±?0.87%) and 97.5% (±?2.39%), for VMAT and IMPT plans, respectively. Conformity and homogeneity were also similar between the 2 techniques. Proton therapy provided observed improvements in mean heart dose (average heart mean [SD], 9.98 Gy [±?0.87 Gy] versus 2.12 Gy [±?0.96 Gy]) and total lung 5% prescription dose (V5; mean [SD] total lung V5, 97.9% [±?2.84%]), compared with 39.8% [±?9.39%]). All IMPT methods spared critical OARs; however, the single, 0° anterior-posterior plan allowed for the shortest treatment time. Conclusion:Both VMAT and all 3 IMPT techniques provided excellent target coverage in patients with BBC; however, proton therapy was superior in decreasing the dose to OARs. A single-field optimization approach should be the IMPT method of choice when feasible.

SUBMITTER: Vyfhuis MAL

PROVIDER: S-EPMC6986399 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Techniques for Treating Bilateral Breast Cancer Patients Using Pencil Beam Scanning Technology.

Vyfhuis Melissa A L MAL Zhu Mingyao M Agyepong Benjamin B Nichols Elizabeth M EM

International journal of particle therapy 20190924 2

<h4>Purpose</h4>Patients with bilateral breast cancer (BBC), who require postmastectomy radiation therapy or radiation as part of breast conservation treatment, present a unique technical challenge. Even with modern techniques, such as intensity modulated radiation therapy or volumetric modulated arc therapy (VMAT), adequate target coverage is rarely achieved without the expense of increased integral dose to important organs at risk (OARs), such as the heart and lungs. Therefore, we present seve ...[more]

PMID: 31998816

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Project description:Proton therapy makes use of the favorable depth-dose distribution with its characteristic Bragg peak to spare normal tissue distal of the target volume. A steep dose gradient would be desired in lateral dimensions, too. The widespread spot scanning delivery technique is based, however, on pencil-beams with in-air spot full-widths-at-half-maximum of typically 1 cm or more. This hampers the sparing of organs-at-risk if small-scale structures adjacent to the target volume are concerned. The trimming of spot scanning fields with collimating apertures constitutes a simple measure to increase the transversal dose gradient. The current study describes the clinical implementation of brass apertures in conjunction with the pencil-beam scanning delivery mode at a horizontal, clinical treatment head based on commercial hardware and software components. Furthermore, clinical cases, which comprised craniopharyngiomas, re-irradiations and ocular tumors, were evaluated. The dosimetric benefits of 31 treatment plans using apertures were compared to the corresponding plans without aperture. Furthermore, an overview of the radiation protection aspects is given. Regarding the results, robust optimization considering range and setup uncertainties was combined with apertures. The treatment plan optimizations followed a single-field uniform dose or a restricted multi-field optimization approach. Robustness evaluation was expanded to account for possible deviations of the center of the pencil-beam delivery and the mechanical center of the aperture holder. Supplementary apertures improved the conformity index on average by 15.3%. The volume of the dose gradient surrounding the PTV (evaluated between 80 and 20% dose levels) was decreased on average by 17.6%. The mean dose of the hippocampi could be reduced on average by 2.9 GyRBE. In particular cases the apertures facilitated a sparing of an organ-at-risk, e.g. the eye lens or the brainstem. For six craniopharyngioma cases the inclusion of apertures led to a reduction of the mean dose of 1.5 GyRBE (13%) for the brain and 3.1 GyRBE (16%) for the hippocampi.

Project description:AimsTwenty per cent of patients with non-small cell lung cancer present with stage III locally advanced disease. Precision radiotherapy with pencil beam scanning (PBS) protons may improve outcomes. However, stage III is a heterogeneous group and accounting for complex tumour motion is challenging. As yet, it remains unclear as to whom will benefit. In our retrospective planning study, we explored if patients with superior sulcus tumours (SSTs) are a select cohort who might benefit from this treatment.Materials and methodsPatients with SSTs treated with radical radiotherapy using four-dimensional planning computed tomography between 2010 and 2015 were identified. Tumour motion was assessed and excluded if greater than 5 mm. Photon volumetric-modulated arc therapy (VMAT) and PBS proton single-field optimisation plans, with and without inhomogeneity corrections, were generated retrospectively. Robustness analysis was assessed for VMAT and PBS plans involving: (i) 5 mm geometric uncertainty, with an additional 3.5% range uncertainty for proton plans; (ii) verification plans at maximal inhalation and exhalation. Comparative dosimetric and robustness analyses were carried out.ResultsTen patients were suitable. The mean clinical target volume D95 was 98.1% ± 0.4 (97.5-98.8) and 98.4% ± 0.2 (98.1-98.9) for PBS and VMAT plans, respectively. All normal tissue tolerances were achieved. The same four PBS and VMAT plans failed robustness assessment. Inhomogeneity corrections minimally impacted proton plan robustness and made it worse in one case. The most important factor affecting target coverage and robustness was the clinical target volume entering the spinal canal. Proton plans significantly reduced the mean lung dose (by 21.9%), lung V5, V10, V20 (by 47.9%, 36.4%, 12.1%, respectively), mean heart dose (by 21.4%) and thoracic vertebra dose (by 29.2%) (P < 0.05).ConclusionsIn this planning study, robust PBS plans were achievable in carefully selected patients. Considerable dose reductions to the lung, heart and thoracic vertebra were possible without compromising target coverage. Sparing these lymphopenia-related organs may be particularly important in this era of immunotherapy.

Project description:BackgroundAlthough pencil beam scanning (PBS) is the most conformal method for proton beam therapy (PBT) delivery, it is unknown if outcomes differ compared to treatment with passive scatter/uniform scanning (PS/US). This analysis compares patient reported outcomes (PRO) changes following PBS and PS/US for prostate cancer (PC) in a prospective multicenter registry study.MethodsWe evaluated PROs with the Expanded Prostate Cancer Index Composite (EPIC) instrument for men with localized PC enrolled in PCG 001-09 (NCT01255748). PROs were assessed at baseline and through 12 months of follow-up. We compared mean changes in EPIC scores, as well as the proportions of men experiencing a one- and two-fold minimally important difference (MID) in domain scores, between PBS and PS/US. Multivariate analyses (MVAs) were performed to further evaluate the association between proton modality and PRO changes.ResultsThree-hundred-and-four men completed EPIC at baseline; 72 received PBS and 232 received PS/US. The average quality-of-life (QOL) declines from baseline through 12 months did not significantly differ between the two groups. The proportion of men reporting a 1-MID decline at 12 months for PBS and PS/US was 34.3% and 27.4%, respectively, for urinary QOL (P = 0.27); 40. 1% and 40.9% for bowel QOL (P = 0.36); and 30. 1% and 36.6% for sexual QOL (P = 0.94). Corresponding 2-MID declines for PBS and PS/US were observed in 26.9% and 13.2% of men for urinary QOL (P = 0.01), 35.3% and 29.1% for bowel QOL (P = 0.33); and 16.4% and 18.1% for sexual QOL (P = 0.76). The association between proton modality and 2-MID changes in urinary QOL at 12-months remained significant on MVA (P = 0.007).ConclusionsThe results of this analysis show differences between PBS and PS/US with regards to two-fold MID changes in urinary function at 12 months, but no differences for average score declines over time. Future studies evaluating PRO measures between the two PBT modalities are warranted.

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Techniques for Treating Bilateral Breast Cancer Patients Using Pencil Beam Scanning Technology.

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Techniques for Treating Bilateral Breast Cancer Patients Using Pencil Beam Scanning Technology.

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