ESTRO 2024 - Abstract Book

S265

Brachytherapy - Gynaecology

ESTRO 2024

To compare two-dimensional (2D) and three-dimensional (3D) planning in exclusive vaginal brachytherapy (VBT) in postoperative endometrial cancer (PEC) patients considering vaginal-cuff relapses (VCR) and late complications in organs at risk (OAR).

Material/Methods:

We conducted a retrospective analysis of 212 consecutive PEC patients treated with exclusive high-dose rate VBT. Group 1: 102 patients who underwent VBT treatment after 2D planning and received 4 to 5 sessions of 4-6Gy and 4 sessions of 5-6Gy from 2004 to 2011. Group 2 included 110 patients who received VBT after 3D planning and were treated with either 3x6Gy or 2x7.5Gy from 2012 to 2021. In both groups, the prescribed dose was administered at a depth of 5mm from the applicator surface. The active source length was 2.5 cm for both 2D and 3D planning techniques. VCR were analyzed during follow-up. Late toxicities were prospectively assessed using the RTOG scoring system for the bladder and rectum and the objective LENT-SOMA criteria for late vaginal complications (LVC). Equivalent doses in 2Gy fractions EQD2(α/β=10) and EQD2(α/β=3) received at 5mm of vaginal surface and to vaginal mucosa surface were calculated. Although the use of vaginal dilators was recommended in all the patients, their use was not registered in Group 1. The statistical analysis was performed using R version 4.3.1, which included descriptive analysis, and Chi-square and Student’s t-tests.

Results:

Both groups had similar characteristics regarding prognostic factors (Table 1). The mean total follow-up was 55.74 (SD 9.76) months, 56.88 (SD 8.22) in Group 1 and 54.69 (SD 10.94) in Group 2. No VCR was detected in this series. Grades 2 and 3 LVC appeared in 13 (12.7%) patients in Group 1 and in 10 (9.1%) patients in Group 2 (p value:0.392). Grade 1 late rectal toxicity was observed in one patient in Group 1 and 2 patients in Group 2. Grade 1 late bladder toxicity was detected in one patient in Group 1. The overall prescribed mean EQD2(α/β=10) was 28.32 (SD 4.78) and 22.68 (SD 1.11) in Groups 1 and 2, respectively (p<0.01), while the mean EQD2(α/β=3) was 36.09(SD 6.31) and 31.78(SD 0.67) in Groups 1 and 2, respectively (p<0.01). The mean EQD2(α/β=10) received in vaginal mucosa surface was 54.79 (SD 14.3) in Group 1 and 42.36 (SD 3.16) in Group 2 (p<0.01).