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- Flejmer, Anna M., et al.
(författare)
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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
- 2015
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Ingår i: Anticancer Research. - : International Institute of Anticancer Research. - 0250-7005 .- 1791-7530. ; 35:5, s. 2841-2848
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Flejmer, Anna M., et al.
(författare)
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Potential benefit of scanned proton beam versus photons as adjuvant radiation therapy in breast cancer
- 2015
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Ingår i: International Journal of Particle Therapy. - 2331-5180. ; 1:4, s. 845-855
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To investigate the feasibility of using scanned proton beams as adjuvant radiation therapy for breast cancer. Long-term cardiopulmonary complications may worsen the quality of life and reduce the positive contribution of radiation therapy, which has been known to improve long-term control of locoregional disease as well as the long-term survival for these patients.Materials and Methods: Ten patients with stage I-III cancer (either after mastectomy or lumpectomy, left- or right-sided) were included in the study. The patients were identified from a larger group where dose heterogeneity in the target and/or hotspots in the normal tissues qualified them for irregular surface compensator planning with photons. The patients underwent planning with 2 scanned proton beam planning techniques, single-field uniform dose and intensity-modulated proton therapy, and the results were compared with those from irregular surface compensator. All volumes of interest were delineated and reviewed by experienced radio-oncologists. The patients were prescribed 50 GyRBE in 25 fractions. Dosimetric parameters of interest were compared with a paired, 2-tailed Student t test.Results: The proton plans showed comparable or better target coverage than the original photon plans. There were also large reductions with protons in mean doses to the heart (0.2 versus 1.3 GyRBE), left anterior descending artery (1.4 versus 6.4 GyRBE), and the ipsilateral lung (6.3 versus 7.7 GyRBE). This reduction is important from the point of view of the quality of life of the patients after radiation therapy. No significant differences were found between single-field uniform dose and intensity-modulated proton therapy plans.Conclusion: Spot scanning technique with protons may improve target dose homogeneity and further reduce doses to the organs at risk compared with advanced photon techniques. The results from this study indicate a potential for protons as adjuvant radiation therapy in breast cancer and a further step toward the individualization of treatment based on anatomic and comorbidity characteristics.
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