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Flejmer, A. M., Edvardsson, A., Dohlmar, F., Josefsson, D., Nilsson, M., Witt Nyström, P. & Dasu, A. (2016). Respiratory gating for proton beam scanning versus photon 3D-CRT for breast cancer radiotherapy. Acta Oncologica, 55(5), 577-583
Open this publication in new window or tab >>Respiratory gating for proton beam scanning versus photon 3D-CRT for breast cancer radiotherapy
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2016 (English)In: Acta Oncologica, ISSN 0284-186X, E-ISSN 1651-226X, Vol. 55, no 5, p. 577-583Article in journal (Refereed) Published
Abstract [en]

Background Respiratory gating and proton therapy have both been proposed to reduce the cardiopulmonary burden in breast cancer radiotherapy. This study aims to investigate the additional benefit of proton radiotherapy for breast cancer with and without respiratory gating.

Material and methods Twenty left-sided patients were planned on computed tomography (CT)-datasets acquired during enhanced inspiration gating (EIG) and free-breathing (FB), using photon three-dimensional conformal radiation therapy (3D-CRT) and scanned proton beams. Ten patients received treatment to the whole breast only (WBO) and 10 were treated to the breast and the regional lymph nodes (BRN). Dosimetric parameters characterizing the coverage of target volumes and the cardiopulmonary burden were compared using a paired, two-tailed Student’s t-test.

Results Protons ensured comparable or better target coverage than photons in all patients during both EIG and FB. The heterogeneity index decreased from 12% with photons to about 5% with protons. The mean dose to the ipsilateral lung was reduced in BRN patients from 12 Gy to 7 Gy (RBE) in EIG and from 14 Gy to 6-7 Gy (RBE) in FB, while for WBO patients all values were about 5-6 Gy (RBE). The mean dose to heart decreased by a factor of four in WBO patients [from 1.1 Gy to 0.3 Gy (RBE) in EIG and from 2.1 Gy to 0.5 Gy (RBE) in FB] and 10 in BRN patients [from 2.1 Gy to 0.2 Gy (RBE) in EIG and from 3.4 Gy to 0.3 Gy (RBE) in FB]. Similarly, the mean and the near maximum dose to left anterior descending artery (LAD) were significantly lower (p<0.05) with protons in comparison with photons.

Conclusion Proton spot scanning has a high potential to reduce the irradiation of organs at risk and other normal tissues for most patients, beyond what could be achieved with EIG and photon therapy. The largest dose sparing has been seen for BRN patients, both in terms of cardiopulmonary burden and integral dose.

National Category
Cancer and Oncology
Identifiers
urn:nbn:se:liu:diva-123274 (URN)10.3109/0284186X.2015.1120883 (DOI)000375566700008 ()
Note

Funding agencies:  LiU Cancer research network at Linkoping University; Region Ostergotland; ALF Grants from Region Ostergotland (Sweden)

Available from: 2015-12-09 Created: 2015-12-09 Last updated: 2017-04-24
Flejmer, A. M., Dohlmar, F., Nilsson, M., Stenmarker, M. & Dasu, A. (2015). Analytical Anisotropic Algorithm versus Pencil Beam Convolution for treatment planning of breast cancer: implications for target coverage and radiation burden of normal tissue. Anticancer Research, 35(5), 2841-2848
Open this publication in new window or tab >>Analytical Anisotropic Algorithm versus Pencil Beam Convolution for treatment planning of breast cancer: implications for target coverage and radiation burden of normal tissue
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2015 (English)In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 35, no 5, p. 2841-2848Article 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
Keywords
breast radiotherapy, dose calculation algorithm, analytical anisotropic algorithm, pencil beam convolution, planning guidelines
National Category
Cancer and Oncology
Identifiers
urn:nbn:se:liu:diva-117854 (URN)000354267200045 ()25964565 (PubMedID)
Available from: 2015-05-11 Created: 2015-05-11 Last updated: 2017-12-04
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-1375-9246

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