TURKISH JOURNAL OF ONCOLOGY 2017 , Vol 1 , Num 1
Physical and Radiobiological Dosimetric Comparison of Volumetric Arc Treatment Plans with or without Flattening Filter in Synchronous Bilateral Breast Cancer
Deepali PATIL1,Mukesh ZOPE1,Richa MADHAWI2,Shraddha RAJ2,Kunal KISHOR2,Seema DEV2,Rajesh SINGH2,Devraj SINGH3
1Department of Medical Physics, State Cancer Institute, Indira Gandhi Institute of Medical Sciences, Patna-India
2Department of Radiation Oncology, State Cancer Institute, Indira Gandhi Institute of Medical Sciences, Patna-India
3Department of Physics, Veer Bahadur Singh Purvanchal University, Jaunpur-India DOI : 10.5505/tjo.2024.4346

Summary

OBJECTIVE
This study aimed to evaluate the dosimetric and radiobiological differences between 6MV flattened filter (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.