Dosimetric Evaluation of Target Volume in Breast Boost Radiotherapy: Comparison of Electron and Photon Beam

Background and purpose: Breast‑conserving surgery followed by radiation therapy to the whole breast is now recognized as a standard strategy in patients with breast cancer. Recommended technique for radiotherapy is whole breast irradiation followed by boost to the tumor bed. This study aimed to compare the dosimetric parameters of electron and photon beams for boosting irradia­tion in post‑lumpectomy patients of breast cancer. Materials and methods: This analytical study included 50 patients of post‑lumpectomy breast cancer. Treatment Planning System (TPS) was used to compare the plans for electron beam and photon beam boost irradiation. The organs at risk (OAR) consist of heart, ipsilateral lung, and skin. Target-volume coverage, Conformity Index (CI), Homogeneity Index (HI), and doses to OAR were compared. Results: Photon plans represented a considerably better CI and HI for the planning target volumes (PTV), compared to the electron beam plans. Regarding OAR sparing, the V1Gy and Dmean in heart and ipsilateral lung with photon beam were significantly higher than electron beam (P<0.05). Conclusion: Dosimetric analysis revealed that CI index, HI index, and PTV coverage were significantly better in photon boost plans, while OAR dosimetry conveyed a significant reduction in ipsilateral lung and heart doses with electron beam plans.