<i>In vivo</i> dosimetric impact of breast tissue expanders on post‐mastectomy radiotherapy

Gee, Harriet E.; Bignell, Fiona; Odgers, David; Gill, Simran; Martin, Darren; Toohey, Joanne; Carroll, Susan

doi:10.1111/1754-9485.12403

Cited by 29 publications

(25 citation statements)

References 21 publications

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“…Gee et al25 reported an average 7% dose reduction to skin surface in a sample of PMRT patients with tissue expanders using opposing tangent beams, and Chatzigiannis et al17 reported 7% to 13% dose reduction with the expander in place for two 6 MV tangential photon beams, and our study showed 5.5%~6.6% dose reduction in the skin area for the conventional plan. The dose reduction increased to 15.6%~15.8% when we only used one beam in the conventional plan, which is close to 22% reduction reported by Damast et al16 for a single 6 MV beam.…”

Section: Resultssupporting

confidence: 56%

“…However, it seems that the tissue expander used in this study was the most popular type used in the US and other countries according to literature14, 15, 16, 17, 24, 25, 31 and Pinnacle is one of the most widely used TPS worldwide, which means our model is applicable to most clinics. The methodology used in this study is generally applicable and clinics that use different brands of tissue expanders or TPS could create their own model and improve their dosimetric accuracy by using our approach.…”

Section: Resultsmentioning

confidence: 99%

“…The in vivo film measurement one side at a time for one PMRT patient treated with 15 MV beams concurred with ex vivo results, while TLD measurements for six patients treated with 15 MV beams showed smaller dose variation (86%~101% of prescription dose). They recommended using 15 MV photons with compensating bolus to treat patients; Chatzigiannis et al17 used Monte Carlo (MC) simulation and found 7% to 13% dose reduction with the expander in place for two 6 MV tangential photon beams, and around 6% dose reduction for 18 MV beams; Chen et al18 reported that tissue expanders with metal ports will increase dose heterogeneity and reduce dose coverage significantly for patients treated with 6 MV or 18 MV opposed tangent photon fields; Sharabi et al reported in an abstract19 5%~20% dose attenuation due to the metallic port and claimed a nondeformable implant model of the port was created based on manufacture specifications, but they did not show the details of the model or validate the dosimetric accuracy of the model; Trombetta et al20 initially reported that no significant change in dose distributions was found for an opposed pair of 6 MV photon beams delivered to a breast phantom containing a metallic port, but later drew a conflicting conclusion in a separate paper21 that the metallic port must be taken into account in the dose calculations; Strang et al22 used TLD measurements and concluded that radiation doses around the tissue expander were unaltered; Srivastava et al23 conducted measurements in a water phantom using a small ion chamber (IC) and concluded that dose perturbation caused by metallic port in photon beams was 5%~20% and this perturbation could not be predicted by TPS; Zabihzadeh et al24 used MC simulation and found a dose enhancement about 15% in front of the port and a dose reduction of about 10% at 5 cm under the port; Gee et al25 used radiochromic films as in vivo dosimeter and found an average 7% dose reduction to skin surface in a sample of PMRT patients with the tissue expander present during radiotherapy.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of the metallic port in breast tissue expanders for photon radiotherapy

Yoon

Xie

Heins

et al. 2018

J Applied Clin Med Phys

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The purpose of this study was to model the metallic port in breast tissue expanders and to improve the accuracy of dose calculations in a commercial photon treatment planning system (TPS). The density of the model was determined by comparing TPS calculations and ion chamber (IC) measurements. The model was further validated and compared with two widely used clinical models by using a simplified anthropomorphic phantom and thermoluminescent dosimeters (TLD) measurements. Dose perturbations and target coverage for a single postmastectomy radiotherapy (PMRT) patient were also evaluated. The dimensions of the metallic port model were determined to be 1.75 cm in diameter and 5 mm in thickness. The density of the port was adjusted to be 7.5 g/cm3 which minimized the differences between IC measurements and TPS calculations. Using the simplified anthropomorphic phantom, we found the TPS calculated point doses based on the new model were in agreement with TLD measurements within 5.0% and were more accurate than doses calculated based on the clinical models. Based on the photon treatment plans for a real patient, we found that the metallic port has a negligible dosimetric impact on chest wall, while the port introduced significant dose shadow in skin area. The current clinical port models either overestimate or underestimate the attenuation from the metallic port, and the dose perturbation depends on the plan and the model in a complex way. TPS calculations based on our model of the metallic port showed good agreement with measurements for all cases. This new model could improve the accuracy of dose calculations for PMRT patients who have temporary tissue expanders implanted during radiotherapy and could potentially reduce the risk of complications after the treatment.

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Section: Resultssupporting

confidence: 56%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modeling of the metallic port in breast tissue expanders for photon radiotherapy

Yoon

Xie

Heins

et al. 2018

J Applied Clin Med Phys

View full text Add to dashboard Cite

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“…The generic reference to ‘breast reconstruction’ was intended to capture all articles addressing the type and timing of breast reconstruction. Two authors independently reviewed abstracts of all studies published between 1985 and 2014, and the full texts of those studies published in 2015–2017. Levels of clinical evidence (LoE) were evaluated for each publication and scored from I to V by employing Oxford criteria.…”

Section: Methodsmentioning

confidence: 99%

International multidisciplinary expert panel consensus on breast reconstruction and radiotherapy

Nava

Benson

Audretsch

et al. 2019

British Journal of Surgery

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Background Conflicting evidence challenges clinical decision‐making when breast reconstruction is considered in the context of radiotherapy. Current literature was evaluated and key statements on topical issues were generated and discussed by an expert panel at the International Oncoplastic Breast Surgery Meeting in Milan 2017. Methods Studies on radiotherapy and breast reconstruction (1985 to September 2017) were screened using MEDLINE, Embase and CENTRAL. The literature review yielded 30 controversial key questions. A set of key statements was derived and the highest levels of clinical evidence (LoE) for each of these were summarized. Nineteen panellists convened for dedicated discussions at the International Oncoplastic Breast Surgery Meeting to express agreement, disagreement or abstention for the generated key statements. Results The literature review identified 1522 peer‐reviewed publications. A list of 22 key statements was produced, with the highest LoE recorded for each statement. These ranged from II to IV, with most statements (11 of 22, 50 per cent) supported by LoE III. There was full consensus for nine (41 per cent) of the 22 key statements, and more than 75 per cent agreement was reached for half (11 of 22). Conclusion Poor evidence exists on which to base patient‐informed consent. Low‐quality studies are conflicting with wide‐ranging treatment options, precluding expert consensus regarding optimal type and timing of breast reconstruction in the context of radiotherapy. There is a need for high‐quality evidence from prospective registries and randomized trials in this field.

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“…12,13 For patients with TE that uses an IMP, the known inaccuracies of convolution algorithms may have a limited clinical impact. 21,22 The high-density magnet is generally more than 1 cm away from patient tissue, so inaccuracies in lateral scatter dose are confined to the saline filling the TE and the IMP itself. AAA's underestimation of attenuation through the IMP might affect the accuracy of the dose calculated in the "dose shadow" region.…”

Section: Introductionmentioning

confidence: 99%

Modeling AeroForm tissue expander for postmastectomy radiation therapy

Dziemianowicz

Gardner

Snyder

et al. 2019

J Applied Clin Med Phys

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The AeroForm chest wall tissue expander (TE) is a silicon shell containing a metallic CO 2 reservoir, placed surgically after mastectomy. The patient uses a remote control to release compressed CO 2 from the reservoir to inflate the expander. AeroForm poses challenges in a radiation therapy setting: The high density of the metallic reservoir causes imaging artifacts on the planning CT, which encumber structure definition and cause misrepresentation of density information, in turn affecting dose calculation. Additionally, convolution‐based dose calculation algorithms may not be well‐suited to calculate dose in and around high‐density materials. In this study, a model of the AeroForm TE was created in Eclipse treatment planning system (TPS). The TPS model was validated by comparing measured to calculated transmission through the AeroForm. Transmission was measured with various geometries using radiochromic film. Dose was calculated with both Varian’s Anisotropic Analytical Algorithm (AAA) and Acuros External Beam (AXB) algorithms. AAA and AXB were compared using dose profile and gamma analyses. While both algorithms modeled direct transmission well, AXB better modeled lateral scatter from the AeroForm TE. Clinical significance was evaluated using clinical data from four patients with AeroForm TEs. The AeroForm TPS model was applied, and RT plans were optimized using AAA, then re‐calculated with AXB. Structures of clinical significance were defined and dose volume histogram analysis was performed. Compared to AXB, AAA overestimates dose in the AeroForm device. Changes in clinically significant regions were patient‐ and plan‐specific. This study proposes a clinical procedure for modeling the AeroForm in a commercial TPS, and discusses the limitations of dose calculation in and around the device. An understanding of dose calculation accuracy in the vicinity of the AeroForm is critical for assessing individual plan quality, appropriateness of different planning techniques and dose calculation algorithms, and even the decision to use the AeroForm in a postmastectomy radiation therapy setting.

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In vivo dosimetric impact of breast tissue expanders on post‐mastectomy radiotherapy

Abstract: Dose is attenuated in the 'shadow' of the tissue expander port in patients receiving PMRT. This is likely to be clinically insignificant for most, but centres should undertake appropriate measurements before utilising TPS predictions.

Cited by 29 publications

References 21 publications

Modeling of the metallic port in breast tissue expanders for photon radiotherapy

Modeling of the metallic port in breast tissue expanders for photon radiotherapy

International multidisciplinary expert panel consensus on breast reconstruction and radiotherapy

Modeling AeroForm tissue expander for postmastectomy radiation therapy

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