2Department of Radiation Oncology, Dokuz Eylül University Faculty of Medicine, İzmir-Türkiye
3Department of Physics, Dokuz Eylül University Faculty of Science, İzmir-Türkiye DOI : 10.5505/tjo.2025.4574 OBJECTIVE
To compare reference-line (RL) and "inverse" optimization (IO) on organs at risk (OAR) and clinical target volume (CTV) doses in patients receiving vaginal cuff (VC) brachytherapy (BT).
METHODS
CT images of 20 patients were used who received VC BT using "Stump" applicator after external-beam RT
(EBRT). Reference-line optimization (RLO) was performed to the line composed of 8 symmetrical points
at 0.5cm from the applicator's surface. Dose was prescribed to CTV in IO with introduction of optimization
goals (CTV: D98%≥85%, D90%≥100%, V100%≥92.5%, and OARD2ccEQD2 total doses: Bladder ≤9000
cGy, rectum, sigmoid, and bowel ≤7000 cGy). Using Wilcoxon Signed-Rank test, 2 different optimization
techniques were compared with respect to their effects on CTV dose-volume parameters and OAR D2cc.
RESULTS
Significantly lower D2ccEQD2 doses could be obtained with IO compared to RLO (p<0.001, p=0.004,
p=0.001, and p=0.001 for bladder, rectum, sigmoid, and bowel, respectively). Significantly higher
doses could be obtained with RLO for CTV D90% and V100% (p<0.001, and p<0.001, respectively).
D%50/D%90 is significantly lower in IO (p<0.001). It was detected that CTV criteria could be met in all
cases where OAR criteria of ≤7000cGy was violated only for rectum in 1 case in IO and 3 cases in RLO.
CONCLUSION
In both types of optimizations, desired criteria are met for CTV while they may not be met constantly in
all cases. The resultant significant difference in favor of IO regarding OARs supports the routine clinical
use of IO in VC BT.