2Department of Radiation Oncology, İzmir City Hospital, İzmir-Türkiye DOI : 10.5505/tjo.2024.4429 OBJECTIVE
To evaluate the effect of volumetric changes in the bladder and rectum on clinical target volume (CTV) and organs at risk doses during adjuvant radiotherapy in gynecologic cancers.
METHODS
The study included 19 patients with gynecologic cancer who received adjuvant radiotherapy. Nineteen
planning computed tomography scans and 171 megavoltage computed tomography (MVCT) scans were
evaluated retrospectively. All structures were re-contoured on MVCT images using MIM software. The
isodoses obtained from the reference plan were loaded onto the contoured MVCT images, and dosevolume
histogram-based analysis was performed.
RESULTS
Analyses showed that patients with a bladder volume of ?300 cc at the time of planning had lower bladder
volumes (p=0.03) and higher mean bladder doses (p=0.04) during treatment compared with planning.
Bladder volume deviation was found to be significantly higher in patients with a bladder volume of ?300 cc
at the time of planning (p=0.002). The mean treatment CTV V95% values of patients with planning bladder
volumes of <150 cc, 150?300 cc, and ?300 cc were 97.2%, 98.7%, and 98.9%, respectively (p=0.005).
CONCLUSION
Bladder and rectum filling have a critical impact on patients receiving adjuvant radiotherapy for gynecologic
cancer. For optimal results, the bladder volume should be planned between 150 and 300 cc.