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Impact of physiological breathing motion for breast cancer radiotherapy with proton beam scanning
Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Oncology.ORCID iD: 0000-0001-8425-8110
Department of Physics, Stockholm University, Stockholm, Sweden.
Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Medicine and Health Sciences.ORCID iD: 0000-0001-7193-4458
Medical Radiation Physics, Stockholm University and Karolinska Institutet, Stockholm, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Purpose: This study aims to investigate the impact of breathing motion on proton breast treatment plans.

Material and methods: The study cohort was composed of twelve thoracic patients who had CT datasets acquired during breath-hold at inhalation, breath-hold at exhalation and in free-breathing mode. Proton treatment plans were designed for the left breast for the breathhold at inhalation phase and subsequently recalculated for the breath-hold at exhalation phase or designed for the CT acquired in free-breathing mode and recalculated for the extreme breath-hold phases. Four plans were evaluated for each patient: two with three fields and two with one field. The dosimetric features of the plans were compared from the point of view of their coverage of the target and the doses to the organs at risk. The statistical significance of the difference in parameters was tested with a paired, two tailed Student t-test.

Results: Breathing motion led to a degradation of the dose coverage of the target (HI increased from 4-7% to 8-11%). Exhalation tended to decrease the lung burden [average dose 3.1-4.5 Gy(RBE)], while inhalation increased it [average dose 5.8-6.8 Gy(RBE)]. The individual values depended on the field arrangement. Smaller differences were seen for the heart [average dose 0.1-0.2 Gy(RBE)] and the LAD [1.9-4.6 Gy(RBE)]. The differences in dosimetric parameters for various breathing phases were small and their expected clinical impact is consequently quite small.

Conclusion: The results indicated that the dosimetric parameters of the plans corresponding to the two extreme breathing phases are similar, thus suggesting that breathing might have little impact for the chosen beam arrangements with proton scanned beams.

National Category
Cancer and Oncology
Identifiers
URN: urn:nbn:se:liu:diva-127369OAI: oai:DiVA.org:liu-127369DiVA: diva2:922582
Available from: 2016-04-23 Created: 2016-04-23 Last updated: 2016-05-04Bibliographically approved
In thesis
1. Radiation burden from modern radiation therapy techniques including proton therapy for breast cancer treatment - clinical implications
Open this publication in new window or tab >>Radiation burden from modern radiation therapy techniques including proton therapy for breast cancer treatment - clinical implications
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The purpose of this thesis was to study the clinical implications of modern radiotherapy techniques for breast cancer treatment. This was investigated in several individual studies.

Study I investigated the implications of using the analytical anisotropic algorithm (AAA) from the perspective of clinical recommendations for breast cancer radiotherapy. Pencil beam convolution plans of 40 breast cancer patients were recalculated with AAA. The latter plans had a significantly worse coverage of the planning target volume (PTV) with the 93% isodose, higher maximum dose in hotspots, higher volumes of the ipsilateral lung receiving doses below 25 Gy and smaller volumes with doses above 25 Gy. AAA also predicted lower doses to the heart.

Study II investigated the implications of using the irregular surface compensator (ISC), an electronic compensation algorithm, in comparison to three‐dimensional conformal radiotherapy (3D‐CRT) for breast cancer treatment. Ten breast cancer patients were planned with both techniques. The ISC technique led to better coverage of the clinical target volume of the tumour bed (CTV‐T) and PTV in almost all patients with significant improvement in homogeneity.

Study III investigated the feasibility of using scanning pencil beam proton therapy for regional and loco‐regional breast cancer with comparison of ISC photon planning. Ten patients were included in the study, all with dose heterogeneity in the target and/or hotspots in the normal tissues outside the PTV. The proton plans showed comparable or better CTV‐T and PTV coverage, with large reductions in the mean doses to the heart and the ipsilateral lung.

Study IV investigated the added value of enhanced inspiration gating (EIG) for proton therapy. Twenty patients were planned on CT datasets acquired during EIG and freebreathing (FB) using photon 3D‐CRT and scanning proton therapy. Proton spot scanning has a high potential to reduce the irradiation of organs‐at‐risk for most patients, beyond what could be achieved with EIG and photon therapy, especially in terms of mean doses to the heart and the left anterior descending artery.

Study V investigated the impact of physiological breathing motion during proton radiotherapy for breast cancer. Twelve thoracic patients were planned on CT datasets during breath‐hold at inhalation phase and breath‐hold at exhalation phase. Between inhalation and exhalation phase there were very small differences in dose delivered to the target and cardiovascular structures, with very small clinical implication.

The results of these studies showed the potential of various radiotherapy techniques to improve the quality of life for breast cancer patients by limiting the dose burden for normal tissues.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2016. 64 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1505
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-127370 (URN)10.3384/diss.diva-127370 (DOI)978-91-7685-850-9 (Print) (ISBN)
Public defence
2016-06-01, Hugo Theorell, Campus US, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2016-04-27 Created: 2016-04-23 Last updated: 2016-05-13Bibliographically approved

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Flejmer, Anna M.Josefsson, DanDasu, Alexandru
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