%0 Journal Article
%T Biological equivalence between LDR and PDR in cervical cancer: multifactor analysis using the linear-quadratic model
%A Jos¨¦ Guilherme Couto
%A Isabel Bravo
%A Rui Pirraco
%J Journal of Contemporary Brachytherapy
%D 2011
%I Termedia Publishing House
%X Purpose: The purpose of this work was the biological comparison between Low Dose Rate (LDR) and Pulsed DoseRate (PDR) in cervical cancer regarding the discontinuation of the afterloading system used for the LDR treatments atour Institution since December 2009. Material and methods: In the first phase we studied the influence of the pulse dose and the pulse time in the biologicalequivalence between LDR and PDR treatments using the Linear Quadratic Model (LQM). In the second phase,the equivalent dose in 2 Gy/fraction (EQD2) for the tumor, rectum and bladder in treatments performed with both techniqueswas evaluated and statistically compared. All evaluated patients had stage IIB cervical cancer and were treatedwith External Beam Radiotherapy (EBRT) plus two Brachytherapy (BT) applications. Data were collected from 48 patients(26 patients treated with LDR and 22 patients with PDR). Results: In the analyses of the influence of PDR parameters in the biological equivalence between LDR and PDRtreatments (Phase 1), it was calculated that if the pulse dose in PDR was kept equal to the LDR dose rate, a small therapeuticloss was expected. If the pulse dose was decreased, the therapeutic window became larger, but a correction inthe prescribed dose was necessary. In PDR schemes with 1 hour interval between pulses, the pulse time did not influencesignificantly the equivalent dose. In the comparison between the groups treated with LDR and PDR (Phase 2) weconcluded that they were not equivalent, because in the PDR group the total EQD2 for the tumor, rectum and bladderwas smaller than in the LDR group; the LQM estimated that a correction in the prescribed dose of 6% to 10% was ne -cessary to avoid therapeutic loss. Conclusions: A correction in the prescribed dose was necessary; this correction should be achieved by calculatingthe PDR dose equivalent to the desired LDR total dose.
%K brachytherapy
%K cervical cancer
%K LDR
%K PDR
%K EQD2
%K LQM
%U http://www.termedia.pl/Biology-Contributions-Biological-equivalence-between-LDR-and-PDR-in-cervical-cancer-multifactor-analysis-usingthe-linear-quadratic-model,54,17413,1,1.html