A dosimetric evaluation of flattening filter-free volumetric modulated arc therapy in nasopharyngeal carcinoma

Abstract

Purpose:To explore the dosimetric effects of flattening filter-free (FFF) beams in volumetric modulated arc therapy (VMAT) of nasopharyngeal carcinoma via a retrospective planning study.Materials and Methods:A linear accelerator (LINAC) was prepared to operate in FFF mode and the beam data were collected and used to build a model in TPS. For 10 nasopharyngeal carcinoma (NPC) cases, VMAT plans of FFF beams and normal flattened (FF) beams were designed. Differences of plan quality and delivery efficiency between FFF-VMAT plans and filter filtered VMAT (FF-VMAT) plans were analyzed using two-tailed paired t-tests.Results:Removal of the flattening filter increased the dose rate. Averaged beam on time (BOT) of FFF-VMAT plans was decreased by 24.2%. Differences of target dose coverage between plans with flattened and unflattened beams were statistically insignificant. For dose to normal organs, up to 4.9% decrease in V35 of parotid grand and 4.5% decrease in averaged normal tissue (NT) dose was observed.Conclusions:The TPS used in our study was able to handle FFF beams. The FFF beam prone to improve the normal tissue sparing while achieving similar target dose distribution. Decreasing of BOT in NPC cases was valuable in terms of patient's comfort.

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

“…This was in line with the several previous studies in which reduction of TT of 20–50% have been reported 17,20,21. Because of this advantage, the use of FFF beams has been extended to VMAT treatment of nasopharynx22 and prostate23 cancers. Nevertheless, despite the FFF beam technology demonstrated attractive practical advantages over the conventional beam IMRT, the understanding of the biological effect of such a high dose rate treatment on body tissues which may have consequence on late toxicities is still not certain and needs to be proven by longer term clinical studies.…”

Comparison of Flattening Filter and Flattening Filter-Free Volumetric Modulated Arc Radiotherapy in Patients with Locally Advanced Nasopharyngeal Carcinoma

“…Many factors can affect the application of VMAT in patients with NPC, including the large planning target volume (PTV), the proximity of vital normal tissues, which make the planning of radiation treatment of NPC cases challenging [24]. Therefore, the aims of the present study were present study were to investigate the therapeutic role of the flattening filter-free (FFF) mode in volumetric modulated arc therapy (VMAT) compared with the flattening filter (FF) mode in patients with locally advanced nasopharyngeal carcinoma (NPC).…”