Evaluation of the dosimetric impact of applying flattening filter‐free beams in intensity‐modulated radiotherapy for early‐stage upper thoracic carcinoma of oesophagus

Abstract

IntroductionFlattening filter-free (FFF) radiation beams have recently become clinically available on modern linear accelerators in radiation therapy. This study aimed to evaluate the dosimetric impact of using FFF beams in intensity-modulated radiotherapy (IMRT) for early-stage upper thoracic oesophageal cancer.MethodsEleven patients with primary stage upper thoracic oesophageal cancer were recruited. For each patient, two IMRT plans were computed using conventional beams (Con-P) and FFF beams (FFF-P), respectively. Both plans employed a five-beam arrangement and were prescribed with 64 Gy to (planning target volume) PTV1 and 54 Gy to PTV2 in 32 fractions using 6 MV photons. The dose parameters of the target volumes and organs at risks (OARs), and treatment parameters including the monitor units (MU) and treatment time (TT) for Con-P and FFF-P were recorded and compared.ResultsThe mean D5 of PTV1 and PTV2 were higher in FFF-P than Con-P by 0.4 Gy and 0.3 Gy, respectively. For the OARs, all the dose parameters did not show significant difference between the two plans except the mean V5 and V10 of the lung in which the FFF-P was lower (46.7% vs. 47.3% and 39.1% vs. 39.6%, respectively). FFF-P required 54% more MU but 18.4% less irradiation time when compared to Con-P.ConclusionThe target volume and OARs dose distributions between the two plans were comparable. However, FFF-P was more effective in sparing the lung from low dose and reduced the mean TT compared with Con-P. Long-term clinical studies are suggested to evaluate the radiobiological effects of FFF beams.

Comparison between flattening filter‐free (FFF) and flattened photon beam VMAT plans for the whole brain radiotherapy (WBRT) with hippocampus sparing

“…Thus, the FFF beams yielded a little bit better results in target volume coverage and conformity than the FF beams. The dosimetry advantage for target can be neglected by the FFF mode; these results are similar to those of other studies 18,19 . The FFF mode can increase the peripheral dose of the target area with nonuniform tissues, such as SBRT for lung cancer 20 …”

“…The dosimetry advantage for target can be neglected by the FFF mode; these results are similar to those of other studies. 18,19 The FFF mode can increase the peripheral dose of the target area with nonuniform tissues, such as SBRT for lung cancer. 20 The development of advanced techniques is increasing the feasibility of hippocampal avoidance during WBRT, resulting in greater memory preservation and quality of life of patients.…”