PURPOSE:To evaluate the potential usage of flattening filter-free (FFF) photon beams in the treatment of prostate cancer.
METHODS AND MATERIALS: Volumetric-modulated arc therapy (VMAT) treatment planning was performed for 7 patients using TrueBeam(®) linear accelerator and photon beams with (X6, X10) and without (X6FFF, X10FFF) flattening filter. Prescribed dose was 19 × 3 Gy = 57 Gy. One or two 360° arcs with dose rate of 600 MU/min for flattened beams, and 1,200 MU/min for FFF beams were used.
RESULTS: No difference was detected between the four beams in PTV coverage, conformity, and homogeneity. Mean body dose and body volume receiving 50% of the prescribed dose decreased with increasing mean energy (r(2) = 0.8275, p < 0.01). X6FFF delivered 3.6% more dose compared with the X6 (p < 0.01). X10FFF delivered 3.0% (p < 0.01), and the X10 5.8% (p < 0.01) less mean body dose compared with X6. There was a significant increase in the mean dose to the rectum for the X10 compared with X6 (2.6%, p < 0.01). Mean dose to the bladder increased by 1.3% for X6FFF and decreased by 2.3% for X10FFF. Using a single arc and FFF, treatment time was reduced by 35% (2 SD = 10%).
CONCLUSION: FFF beams resulted in dose distributions similar to flattened beams. X10FFF beam provided the best solution, sparing rectum and bladder and minimizing whole-body dose. FFF beams lead to a time efficient treatment delivery, particularly when combined with hypofractionated VMAT.
Written by:
Zwahlen DR, Lang S, Hrbacek J, Glanzmann C, Kloeck S, Najafi Y, Streller T, Studer G, Zaugg K, Luetolf UM. Are you the author?
Department of Radiation Oncology, University Hospital Zurich, Zurich, Switzerland.
Reference: Int J Radiat Oncol Biol Phys. 2012 May 7. Epub ahead of print.
doi: 10.1016/j.ijrobp.2011.10.019
PubMed Abstract
PMID: 22572080
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