DEEPALİ PATIL, MUKESH ZOPE, RİCHA MADHAWI, SHRADDHA RAJ, KUNAL KISHOR, SEEMA DEVI, RAJESH SINGH, DEVRAJ SINGH
Turkish Journal of Oncology - 2024;39(4):411-422
OBJECTIVE This study aimed to evaluate the dosimetric and radiobiological differences between 6MV flattened fitler (FF) and flattening filter-free (FFF) using the volumetric modulated arc (VMAT) technique for synchronous bilateral breast cancer (SBBC). METHODS Three SBBC patients underwent radiotherapy with 6X_FF beams using VMAT treatment plans, delivering a dose of 50 Gy in 25 fractions. Retrospectively, plans with five partial arc 6X_FFF beams using VMAT treatment plans were generated, maintaining identical parameters. The evaluation included a comparison of dosimetric planning indices, target coverage, and OAR (organ at risk) sparing, as well as NTCP (normal tissue complication probability) radiobiological parameters of OARs. RESULTS There was no significant difference observed in the Conformity Index (CI), Homogeneity Index (HI), and V95% in planning target volume (PTV) in both treatment plans. The mean NTCP values of the Poisson- LQ model for pulmonary pneumonitis and cardiac mortality were 2.47% and 0.19%, respectively, in 6X_FF treatment plans. In comparison, the corresponding NTCP values for pulmonary pneumonitis and cardiac mortality in the 6X_FFF plans were 2.16% and 0.18%, respectively. Statistical analysis using the NTCP model (Poisson-LQ and Lyman-Kutcher-Berman) revealed similar outcomes between 6X_FF and 6X_FFF VMAT plans across the assessed endpoints for the heart and lungs. CONCLUSION 6X_FFF photon beams offer a treatment plan for SBBC patients that maintains similar target coverage while improving the preservation of organs and minimizing the biological effects, as compared to 6X_FF VMAT plans.
