Isocenter bilateral tangential fields combined with intensity-modulated radiotherapy for synchronous bilateral whole breast irradiation

Objective To investigate the dose characteristics and outcomes of a single isocenter bilateral tangential fields (IBTF) combined with intensity-modulated radiotherapy (IMRT) in bilateral breast radiotherapy (BBR). Methods Fourteen female patients with synchronous bilateral breast cancer (SBBC) after breast-conserving surgery (BCS) were enrolled in this study. All patients received BBR using IBTF combined with IMRT at a conventional (50 Gy/25f) or hypofractionated (43.5 Gy/15f) dose. For patients with invasive cancer, the additional tumor bed boost was given with sequential electron radiation or simultaneously photon IMRT. The coverage, uniformity and short-term clinical efficacy were evaluated. Results The number of the irradiation field was 8-11, including 4-7 intensity-modulated fields. The bilateral breast PTV dose coverage reached 95% in all plans. For the tumor bed, the mean dose coverage was (95.54±1.33)%(left) and (94.19±1.03)%(right) using photon, and (90.25±8.79)%(left) and (85.28±8.35)%(right) using electron. The average V20 of bilateral lungs was (16.69±3.90)%. The cardiac Dmean was 5.48 Gy. Three patients presented with grade Ⅱ acute skin toxicities. No ≥ grade Ⅱ pneumonitis was observed. No recurrence occurred with the median follow-up time of 30.1 months. Eleven patients showed excellent cosmetic results. Conclusion BBR using IBTF combined with IMRT is efficacious and safe for patients with SBBC after BCS. Key words: Breast neoplasm/adjuvant radiotherapy; Radiation technique; Short-term efficacy