抄録
Traditionally, cervical brachytherapy has been prescribed to point A.
However, since the Groupe Européen de Curiethérapie and European Society for Radiotherapy＆ Oncology guidelines were published, image-guided brachytherapy has become an emerging technique. The purpose of this study was to evaluate the high-risk clinical target volume （HR-CTV） coverage and analyze dose-volume histograms
for organs at risk in point A prescription of high-dose-rate brachytherapy. A total of 68 patients with locally advanced cervical cancer were treated with three-dimensional conformal external beam radiation therapy and brachytherapy from December 2012 to March 2017. Fractions of 6Gy for a total of 12-24Gy were delivered at point A by brachytherapy to all patients. Following each brachytherapy application, a pelvic computed tomography scan was performed and imported into a three-dimensional brachytherapy treatment planning system. In this study, the HR-CTV, bladder, and rectum were re-delineated according to Report 89 of the International Commission on Radiation Units and Measurements using the magnetic resonance images at the time of diagnosis, and the dose-volume histogram of each structure was analyzed. The median age of patients at diagnosis was 67 years （range, 31-91 years）. Mean HR-CTV D90 for all patients was 558.3cGy （range, 228.7-1005.1cGy） and the mean HR-CTV D90 within each clinical T stage was: Ib, 646.4cGy; 2a, 579.3cGy; 2b, 545.2cGy; 3a, 556.6cGy; 3b, 451.3cGy; and 4, 497.9cGy. HR-CTVD90 was correlated with HR-CTV. The mean D2cm3 was 678.1cGy for the bladder and 511.9cGy for the rectum. Using point A-based dose prescription, HR-CTV coverage was insufficient, especially in cases with a large tumor volume or a high T stage. Image-guided brachytherapy is expected to improve HR-CTV coverage while keeping rectal and bladder doses within acceptable levels.
