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Analytical Anisotropic Algorithm versus Pencil Beam Convolution for treatment planning of breast cancer: implications for target coverage and radiation burden of normal tissue
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
Region Östergötland, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Linköping University, Faculty of Medicine and Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences.ORCID iD: 0000-0002-4369-1396
Futurum - Academy for Health and Care, Jönköping.ORCID iD: 0000-0003-1375-9246
Futurum - Academy for Health and Care, Jönköping.ORCID iD: 0000-0002-5238-4988
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2015 (English)In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 35, no 5, 2841-2848 p.Article in journal (Refereed) Published
Abstract [en]

Aim: The present study aimed to investigate the implications of using the analytical anisotropic algorithm (AAA) for calculation of target coverage and radiation burden of normal tissues. Most model parameters, recommendations and planning guidelines associated with a certain outcome are from the era of pencil beam convolution (PBC) calculations on relatively simple assumptions of energy transport in media. Their relevance for AAA calculations that predict more realistic dose distributions needs to be evaluated. Patients and Methods: Forty patients with left-sided breast cancer receiving 3D conformal radiation therapy were planned using PBC with a standard protocol with 50 Gy in 25 fractions according to existing re-commendations. The plans were subsequently recalculated with the AAA and relevant dose parameters were determined and compared to their PBC equivalents. Results: The majority of the AAA-based plans had a significantly worse coverage of the planning target volume and also a higher maximum dose in hotspots near sensitive structures, suggesting that these criteria could be relaxed for AAA-calculated plans. Furthermore, the AAA predicts higher volumes of the ipsilateral lung will receive doses below 25 Gy and smaller volume doses above 25 Gy. These results indicate that lung tolerance criteria might also have to be relaxed for AAA planning in order to maintain the level of normal tissue toxicity. The AAA also predicts lower doses to the heart, thus indicating that this organ might be more sensitive to radiation than thought from PBC-based calculations. Conclusion: The AAA should be preferred over the PBC algorithm for breast cancer radiotherapy as it gives more realistic dose distributions. Guidelines for plan acceptance might have to be re-evaluated to account for differences in dose predictions in order to maintain the current levels of control and complication rates. The results also suggest an increased radiosensitivity of the heart, thus indicating that a revision of the current models for cardiovascular complications may be needed.

Place, publisher, year, edition, pages
International Institute of Anticancer Research, 2015. Vol. 35, no 5, 2841-2848 p.
Keyword [en]
breast radiotherapy, dose calculation algorithm, analytical anisotropic algorithm, pencil beam convolution, planning guidelines
National Category
Cancer and Oncology
Identifiers
URN: urn:nbn:se:liu:diva-117854ISI: 000354267200045PubMedID: 25964565OAI: oai:DiVA.org:liu-117854DiVA: diva2:811356
Available from: 2015-05-11 Created: 2015-05-11 Last updated: 2016-04-27
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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