Dosimetric comparison of left sided whole breast irradiation with Tangential wedge beam, electron boosted Tangential wedged beam and asymmetric technique

Background: Irradiation of the adjacent critical structures is inevitable in breast cancer radiotherapy (RT). Our purpose is to assess the dose distribution across the breast tissue and adjacent organs with our institutional asymmetric technique for left-sided breast cancer compared to the standard tangential wedged beam (TWB) and electron-boosted TWB techniques.

Materials and methods: The three RT planning were created for 30 consecutive patients with a focus on proper coverage of the planning target volume (PTV). The irritated doses into the heart, ipsilateral lung, and left anterior descending artery (LAD) were evaluated.

Results: No significant difference was found in the mean values of relative PTV irradiated to 47.5 Gy, PTV dose and the volume of PTV, and critical organs between the treatments. The mean dose (Dmean) irradiated to the heart and LAD was lowest with the electron-boosted TWB. The Dmean to the heart was comparable between the TWB and asymmetric RT techniques, while the Dmean to LAD was significantly reduced with asymmetric technique versus TWB. The heart volume receiving ≥25 Gy and the Dmean to the left lung were significantly decreased with the asymmetric technique compared with TWB. The mean relative lung volume irradiated to ≥20 Gy was comparable between all techniques. The mean central lung distance was also significantly increased from 18.03 ± 4.5 cm with asymmetric RT to 37.47 ± 5.6 cm with TWB and to 27.67 ± 3.8 cm with electron-boosted TWB techniques.

Conclusion: The asymmetric technique is useful for patients with breast cancer on the left side, having acceptable PTV coverage and considerably reduced cardiopulmonary doses.