Flattening filter-free technique in volumetric modulated arc therapy for lung stereotactic body radiotherapy: A clinical comparison with the flattening filter technique

Abstract

Abstract. The present study sought to evaluate the impact of the flattening filter-free (FFF) technique in volumetric modulated arc therapy for lung stereotactic body radiotherapy. Its clinical safety and availability were compared with the flattening filter (FF) method. The cases of 65 patients who underwent lung volumetric modulated arc therapy-stereotactic body radiotherapy (VMAT-SBRT) using FF or FFF techniques were reviewed. A total of 55 Gy/4 fractions (fr) was prescribed for peripheral lesions or 56 Gy/7 fr for central lesions. The total monitor units (MU), treatment time, dose to tumors, dose to organs at risk, tumor control (local control rate, overall survival, progression-free survival) and adverse events between cases treated with FF and cases treated with the FFF technique were compared. A total of 35 patients were treated with conventional FF techniques prior to November 2014 and 30 patients were treated with FFF techniques after this date. It was revealed that the beam-on time was significantly shortened by the FFF technique (P<0.01). Other factors were similar for FFF and FF plans in respect to conformity (P=0.95), homogeneity (P=0.20) and other dosimetric values, including total MU and planning target volume/internal target volume coverage. The median follow-up period was 18 months (range, 2-35). One-year local control rates were 97.1 and 90.0% in the FF group and FFF groups, respectively (P=0.33). Grade 3 pneumonitis was observed in 5.8% of FF patients and 3.4% of FFF patients (P=1.00). No other adverse events ≥grade 3 were observed. The results of the study suggest that VMAT-SBRT using the FFF technique shortens the treatment time for lung SBRT while maintaining a high local control rate with low toxicity.

Salvage stereotactic body radiotherapy for post‑operative oligo‑recurrence of non‑small cell lung cancer: A single‑institution analysis of 59�patients

“…The median interval between initial resection and salvage SBRT for recurrence was 30.5 months (range, 2.0-99.0 months). A total of 20/59 lesions (33.9%) were located in the central area, which is a greater proportion than that in the whole SBRT cohort of University of Tokyo Hospital during the same period (41).…”

“…Patients admitted between September 2010 and March 2013 were treated using a conventional SBRT plan using 6-12 beams, whereas patients admitted from April 2013 onwards were treated using volumetric modulated arc therapy (VMAT)-SBRT with 6 or 10 MV beams using an Elekta-synergy system (Elekta Instrument AB). There was no significant difference in treatment outcome between the two methods (41). VMAT plans were designed using a single partial arc with angle ranges of -40˚ to 180˚ (left lung) or -180˚ to 40˚ (right lung), as previously detailed (37,38,41,42).…”

“…There was no significant difference in treatment outcome between the two methods (41). VMAT plans were designed using a single partial arc with angle ranges of -40˚ to 180˚ (left lung) or -180˚ to 40˚ (right lung), as previously detailed (37,38,41,42). dosimetric planning and plan analysis were performed using Pinnacle 3 .…”

Surface and build‐up dose comparison between Elekta 6 MV flattening filter and flattening‐filter‐free beams using an advanced Markus ionization chamber and a solid water‐equivalent phantom

“…1,2 Flattening-filter-free (FFF) photon beams have been increasingly used for stereotactic hypofractionated radiotherapy due to their much higher dose rate thereby minimizing the delivery time. 3 The shorter treatment time may increase the tumor localization accuracy while reducing patient burden. There have been many articles reporting FFF beam characteristics [4][5][6] ; however, the number of publications reporting surface and build-up dose measurement for the FFF beams is limited.…”

“…In radiation therapy, surface and initial build‐up dose is an important measure to take skin toxicity into account 1,2 . Flattening‐filter‐free (FFF) photon beams have been increasingly used for stereotactic hypofractionated radiotherapy due to their much higher dose rate thereby minimizing the delivery time 3 . The shorter treatment time may increase the tumor localization accuracy while reducing patient burden.…”