title: Evaluation of the dosimetric impact of applying flattening filter-free beams in intensity-modulated radiotherapy for early-stage upper thoracic carcinoma of oesophagus.
abstract: BACKGROUND
  Flattening 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.
  
  
  METHODS
  Eleven 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.
  
  
  RESULTS
  The mean D 5 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 V 5 and V 10 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.
  
  
  CONCLUSIONS
  The 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.
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Wuzhe
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Zhixiong
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Zhining
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Weisheng
authors.initials: W
authors.lastname: Fang
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Peibo
authors.initials: P
authors.lastname: Lai
authors.affiliation: Department of Radiation Oncology, Cancer Hospital of Shantou University Medical College Shantou, Guangdong, China.
authors.forename: Jiayang
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Health Technology and Informatics, Hong Kong Polytechnic University Hung Hom, Kowloon, Hong Kong.
authors.forename: Vincent Wc
authors.initials: VW
authors.lastname: Wu
keywords: Flattening filter-free radiation beam; oesophagus cancer; radiation dosimetry; radiotherapy; static beam intensity -modulated radiotherapy