A comparison of the biological effective dose of 50-kV electronic brachytherapy with (192)Ir high-dose-rate brachytherapy for vaginal cuff irradiation
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Authors
Rava, PaulDvorak, Tomas
Markelewicz, Robert J. Jr.
Hiatt, Jessica R.
Sternick, Edward S.
MacAusland, Stephanie G.
Huber, Kathryn
Wazer, David E.
Hepel, Jaroslaw T.
UMass Chan Affiliations
Department of Radiation OncologyDocument Type
Journal ArticlePublication Date
2012-09-01Keywords
BrachytherapyEndometrial Neoplasms
Female
Humans
Iridium
Radiation Dosage
Radioisotopes
Rectum
Urinary Bladder
Vagina
Neoplasms
Oncology
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PURPOSE: Advantages for electronic brachytherapy (EBT) of the vaginal cuff include decreased physical dose to the bladder and rectum. Here we compare (192)Ir with EBT using biological effective dose (BED) to account for the different radiobiological effectiveness (RBE) predicted for low-energy x-rays. METHODS AND MATERIALS: Fifteen data sets from five consecutive postoperative endometrial cancer patients treated with EBT were analyzed. Treatment planning was performed using PLATO software. The dose was prescribed as 21Gy in three fractions to a depth of 0.5cm. Physical dose, BED(3), and BED(10) were evaluated for the mucosa, bladder, and rectum. An RBE value of 1.5 was used for BED calculations. RESULTS: Mucosal physical dose is 28.4% greater with EBT (36.6 vs. 28.5Gy, p<0.05). However, the BED(10) is increased by 79.1% (55.6 vs. 99.6Gy, p<0.05) and the BED(3) by 71.5% (118.8 vs. 203.7Gy, p<0.05). The physical dose (dose to 50% volume of the organ) to the bladder (9.3 vs. 6.6Gy, p<0.05) and rectum (7.2 vs. 4.2Gy, p<0.05) are reduced with EBT. BED(3) to the rectum and bladder are also reduced but to a lesser extent (13 vs. 8.3Gy, p<0.05; 18.9 vs. 14.7Gy, p=0.06, respectively). CONCLUSIONS: BED takes into account the higher RBE of low-energy photons generated with EBT and provides a more accurate estimate of the biological effect. When using EBT, physical dose may underestimate the biological effect on the vaginal mucosa and overestimate the benefit for the bladder and rectum. Dose adjustment for EBT based on BED should be considered. rights reserved.Source
Brachytherapy. 2012 Sep-Oct;11(5):402-7. doi: 10.1016/j.brachy.2011.08.004. Epub 2011 Oct 12. Link to article on publisher's siteDOI
10.1016/j.brachy.2011.08.004Permanent Link to this Item
http://hdl.handle.net/20.500.14038/47924PubMed ID
21996539Related Resources
Link to Article in PubMedae974a485f413a2113503eed53cd6c53
10.1016/j.brachy.2011.08.004