Abstract
Purpose: To identify the continual diversity between flattening photon beam (FB) and Flattening Filter Free (FFF) photon beams for localized prostate cancer; and to determine potential benefits and drawbacks of using unflattened beam for this type of treatment. Methods : Eight prostate cases including seminal vesicles selected for this study. The primary planning target volume (PTV P ) and boost planning target volume (PTV B ) were contoured. The total prescription dose was 78 Gy (56 Gy to PTV P and an additional 22 Gy to PTVB). For all cases, treatment plans using 6MV with FB and FFF beams with identical dose-volume constraints, arc angles and number of arcs were developed. The dose volume histograms for both techniques were compared for primary target volume and critical structures. Results: A low Sigma index (FFF: 1.65 + 0.361; FB: 1.725 + 0.39) indicating improved dose homogeneity in FFF beam. Conformity index (FFF: 0.994 + 0.01; FB: 0.993 + 0.01) is comparable for both techniques. Minimal difference of Organ at risk mean dose was observed. Normal tissue integral dose in FB plan resulted 1.5% lower than FFF plan. All the plans displayed significant increase (1.18 times for PTV P and 1.11 for PTB B ) in the average number of necessary MU with FFF beam. Conclusion : Diversity between FB and FFF beam plans were found. FFF beam accelerator has been utilized to develop clinically acceptable Rapid Arc treatment plans for prostate cancer with 6 MV. --------------------------------- Cite this article as : Rout BK, Muralidhar KR, Ali M, Shekar MC, Kumar A. Dosimetric study of RapidArc plans with flattened beam (FB) and flattening filter-free (FFF) beam for localized prostate cancer based on physical indices. Int J Cancer Ther Oncol 2014; 2 (4):02046. DOI : 10.14319/ijcto.0204.6
Highlights
Cancer is the major cause of leading deaths in the 21st century in world with 14.1 million cases and 8.2 million deaths occurred in 2012.1 Among them, prostate cancer stands as important due to risk of secondary malignancies associated with intensity modulation radiation therapy (IMRT) with conventional 3-Dimentional conformal radiotherapy (3D-CRT).[2]
We found that MU was 675 ± 36.66 for flattened beam (FB) plans and 796 ± 88.11 for Flattening Filter Free (FFF) beam plans in PTVP
The increased NTID can be attributed to the softer photon spectrum and resultant higher skin dose from FFF beams
Summary
Cancer is the major cause of leading deaths in the 21st century in world with 14.1 million cases and 8.2 million deaths occurred in 2012.1 Among them, prostate cancer stands as important due to risk of secondary malignancies associated with intensity modulation radiation therapy (IMRT) with conventional 3-Dimentional conformal radiotherapy (3D-CRT).[2]. Intensity-modulated radiotherapy (IMRT) technology for localized intermediate risk prostate tumor/cancer allows less toxicity in comparison to 3D-CRT.[5]
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