Dosimetric Study of Hybrid Intensity Modulated Radiation Therapy Treatment Plan with Flattened Filter Free Photon Beam for Carcinoma of Breast: Treatment Planning Study
Subhas HALDAR1,Archana DIXIT3,Biplab SARKAR4
1Department of Physics, GLA University, Institute of Applied Science and Humanities, Mathura-India
2Department of Radiotherapy, Saroj Gupta Cancer Centre and Research Institute, Kolkata-India
3Department of Mathematics, GLA University, Institute of Applied Science and Humanities, Mathura-India
4Department of Radiation Oncology, Apollo Multispeciality Hospital, Kolkata-India
DOI : 10.5505/tjo.2022.3783 OBJECTIVE
This study assesses the use of the flattening filter free (FFF) photon beam in hybrid treatment planning for breast carcinoma and the various dosimetric indices of planning target volume (PTV) and organs at risk (OARs).

We selected 15 female breast cancer patients treated with Field-in-Field technique to a dose of 40 Gy/15 fractions. Retrospectively, hybrid intensity-modulated radiation therapy (IMRT) plans with FF, and FFF photon beams were created. To make the hybrid IMRT plan, a planning weightage of 60% (3DCRT): 40% (IMRT) was applied. The dose-volume histograms (DVH) were assessed for various dosimetric indicators for PTV and OARs.

A UDI scoring of 1.090±0.023 and 1.078±0.024 was observed between 6FF_Hybrid and 6FFF_Hybrid treatment plans with p<0.05. ID for I/L lung was 6387±1658.51 (Gy-L) and 6347.056±1643.41 (Gy-L) in 6FF_ Hybrid and 6FFF_Hybrid IMRT plan (p=0.05), respectively. ID value to heart was 2272.52±1086.63 (Gy- L) and 2212.40±1059.49 (Gy-L) in 6FF_Hybrid and 6FFF_Hybrid IMRT plans (p>0.05), respectively. The beam on time (BOT) values of 0.882±0.08 (6FF_Hybrid) and 0.5436±0.07 (6FFF_Hybrid) were reported.

Hybrid IMRT planning with an FFF photon beam offers comparable target coverage, conformality, and homogeneity with greater OAR sparing and faster treatment time. Keywords : Ca-breast; flattened filter free; hybrid plan; intensity-modulated radiation therapy; radiotherapy