Dual-isocentric volumetric modulated arc therapy in synchronous bilateral breast cancer irradiation: A dosimetric study

Abstract

Introduction: In synchronous or metachronous breast cancer, bilateral breast irradiation is one of the major problems of radiation oncology. In this study, dosimetric radiation treatment of bilateral breast cancer (BBC) in two cases of synchronous bilateral mammary cancer will be discussed. In this study, a conformal radiotherapy (RT) plan for bilateral breast irradiation is discussed over two cases with synchronous BBC (sBBC). Materials and Methods: Two cases with sBBC requiring irradiation of dual breasts and regional nodal areas were chosen. Data from bilateral breast irradiation studies were used rather than dose recommendations used in unilateral breast irradiation for organs at risks. The dual-isocentric four-half-arc option was utilized in volumetric-modulated arc therapy (VMAT) plans. The dynamic sliding window method with fixed gantry angle was utilized in intensity-modulated radiation therapy (IMRT) plans. Results: Both IMRT and VMAT plans were chosen for the patients. D95% of the planning target volume supplied the desired dose prescription in the VMAT and IMRT plans of Case 1 and in the IMRT plan of Case 2, whereas the VMAT plan of Case 2 did not achieve the desired dose prescription at the target. The conformity index (CI) was the ideal plan in Case 1's VMAT plan, while Case 2's VMAT plan deviated greatly in terms of the CI value. The VMAT and IMRT plans of Case 1 and the IMRT plan of Case 2 were considered to be more homogeneous plans than the value closest to zero in terms of homogeneity index, whereas the VMAT plan of Case 2 was not considered homogeneous. Conclusion: It is recommended that in sBBC RT confined to breast only dual isometric, four half arc VMAT is an appropriate plan.

Keywords

• dual isocenter
• partial volumetric modulated arc therapy
• synchronous bilateral breast cancer