Comparison of brachytherapy with advanced EBRT techniques (intensity-modulated radiotherapy–stereotactic body radiotherapy)
Brachytherapy has intrinsic advantages compared to modern EBRT techniques, mainly intensity-modulated radiotherapy (IMRT) and stereotactic body radiotherapy (SBRT), due to the close contact between radioactive sources and volume to treat. IMRT has generally been used to irradiate the pelvis but with less toxicity.104 The main drawback to the use of EBRT techniques is that the vagina moves, so there is a risk of geographical “miss of target”, which leads to increased margins and higher integral doses to small bowel.105 Average VC movement for 11 patients was 16.2 ± 8.3 mm during an EBRT course, with a maximum movement of 34.5 mm.106 Large variations in bladder and rectum volumes correlate with significant displacement of the VC.107 Aydogan et al108 concluded that IMRT could be an alternative to HDR brachytherapy and provided a suitable immobilization system. Both techniques, brachytherapy and IMRT, covered the target volume well, but brachytherapy produced higher doses. In order to control vaginal movements an applicator-guided IMRT technique has been proposed.109 It was used to compare 3D conformal radiotherapy (3D-CRT), IMRT and volumetric-modulated arc therapy (VMAT) in irradiating the VC.110 Dose coverage was similar across the three techniques. VMAT showed the highest level of conformity and produced a significant reduction in rectal and bladder volumes compared with 3D-CRT. VMAT needed 28% less monitor units compared with IMRT, and treatment duration reduced from 11 to <3 minutes for a dose of 6 Gy. Pedicini et al111,112 compared VMAT, IMRT and 3D-CRT using a vaginal cylinder for vaginal immobilization to 3D brachytherapy. The cylinder was able to reduce the movement in the VMAT course and reduced planning target volume margin to 2 mm. EBRT techniques always delivered higher integral doses but reduced rectal doses compared with brachytherapy. VMAT produced a uniform dose distribution, while VCB doses were much higher than the prescription. No direct cost comparisons between these modalities have been published, but three fractions of VCB course with one image study has been calculated to cost between US$1235 and $1293,95 while four to five fractions of SBRT for lung cancer cost $10616.113
In summary, we believe that despite the widespread use of the VCB and the simplicity of its performance, several technical subjects have to be considered by the radiation oncologists aside from the usual groups of risk involved in patient selection. The technical subjects reported so far have been reviewed here, although additional research is merited, such as the impact of VCB on survival, dose–fractionation direct comparisons or the use of short schedules.
The authors would like to thank Phil Hoddy for language editing.
The authors report no conflicts of interest in this work.
Sebastià Sabater,1 Ignacio Andres,1 Veronica Lopez-Honrubia,1 Roberto Berenguer,1 Marimar Sevillano,1 Esther Jimenez-Jimenez,2 Angeles Rovirosa,3 Meritxell Arenas,4
1Department of Radiation Oncology, Complejo Hospitalario Universitario de Albacete, Albacete, 2Department of Radiation Oncology, Hospital Son Espases, Palma de Mallorca, 3Department of Radiation Oncology, Hospital Clinic, Barcelona, 4Department of Radiation Oncology, Hospital Universitari Sant Joan, Reus, Spain
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