A Dosimetric Comparison between Three Different External Photon Beam Techniques for Accelerated Partial Breast Irradiation

Francesca Bonfantini, Elena De Martin, Tommaso Giandini, Maria Luisa Fumagalli, Anna Cavallo, Valentina Pinzi, Michela Dispinzieri, Eliana La Rocca, Riccardo Valdagni, Roberto Agresti, Laura Fariselli, Laura Lozza, Emanuele Pignoli and Maria Carmen De Santis

Department of Medical Physics Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Italy
Department of Health, Fondazione IRCCS Istituto Neurologico Carlo Besta, Italy
Department of Neurosurgery Radiotherapy Unit, Fondazione IRCCS Istituto Neurologico Carlo Besta, Italy
Department of Radiotherapy Unit 1, Fondazione IRCCS Istituto Nazionale dei Tumori, Italy
Department of Oncology and Hemato-ncology, University degli Studi di Milano, Italy
Department of Breast Surgery Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy

^*Correspondance to: Maria Carmen De Santis 

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Abstract:

Objectives: To evaluate the advantages and limits of CyberKnife (CK) compared to the two external beams Radiotherapy (RT) Techniques, Three Dimensional Conformal Therapy and Volumetric Modulated Arc Therapy(3D-CRT and VMAT) for Accelerated Partial Breast Irradiation (APBI). A dosimetric study was conducted with special focus on dose to organs at risk (OAR), target coverage and technical features.Methods: Ten consecutive early-stage breast cancer patients were selected and for each one of them, three treatment plans were generated for 3DCRT, VMAT and CK. Dosimetric parameters, extracted from the dose volume histograms, were used to evaluate the differences in terms of PTV coverage and OAR sparing among the irradiation techniques. Conformity Index (CI) and Homogeneity Index (HI) were also compared.Results: VMAT and CK provided equivalent dose conformity, with CIs significantly higher compared to 3D-CRT technique. Besides, VMAT achieved the best results in terms of HI and target coverage (p<0.05). Significant differences were observed in the OAR dosimetric data, except for heart. 3DCRT achieved the best results in terms of the dose to the whole contra-lateral breast as regards technical features. The treatment session time is usually longer for CK (on average 60 min) than for VMAT and 3DCRT techniques (15 to 20 min).Conclusion: In this dosimetric comparison, all RT techniques are feasible to deliver APBI.CK and VMAT provide higher conformity than 3D-CRT, although with 3D-CRT we observed a reduction of the dose to the OAR. In CK treatment organ motion is controlled and, despite the longer treatment times, the delivery accuracy is expected to be better than 3D-CRT and VMAT, especially if motion management systems are not used. Advances in Knowledge: 1) CK treatment allows to reduce safely the PTV margin, achieving both optimal PTV coverage and a better sparing OAR. 2) This study can provide an important guidance to select the right RT technique for APBI.

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Cite the Article:

Bonfantini F, De Martin E, Giandini T, Fumagalli ML, Cavallo A, Pinzi V, et al. A Dosimetric Comparison between Three Different External Photon Beam Techniques for Accelerated Partial Breast Irradiation. Clin Oncol. 2018; 3: 1501.