Intensity-modulated vaginal brachytherapy applicator and single- and multi-channel applicators in vaginal cuff brachytherapy

Purpose:
To compare the dosimetric performance of vaginal intensity-modulated brachytherapy (IM-BRT) applicator and single- (SC-BRT) and multi-channel brachytherapy (MC-BRT) applicators for vaginal cuff brachytherapy (VC-BRT).

Material and methods:
Fifteen patients with uterine-confined endometrium cancer who received adjuvant VC-BRT were included in this study. IM-BRT, SC-BRT, and MC-BRT treatment plans were created for two different clinical target volume (CTV) definitions: 1. Standard CTV, called CTVs; and 2. Virtually defined CTV, called CTVv, with asymmetrical tumor extension > 5 mm in thickness. Plan comparison was performed using dose-volume histogram (DVH) and treatment planning parameters.

Results:
According to DVH analysis, D₉₈ for CTVv and D2 for both CTVs and CTVv showed statistically significant differences between IM-BRT and SC-BRT plans, but there was no significant difference between IM-BRT and MC-BRT plans in terms of D₉₈ and D₂ for both CTVs and CTVv. Additionally, for CTVv plans, IM-BRT was found to be significantly superior to SC-BRT for the rectum (D_2cc, V_5Gy, and V_7Gy), bladder (D_2cc and V_7Gy), and small bowel (D_2cc, V_5Gy, and V_7Gy). On the other hand, DVH parameters of the sigmoid showed large difference between IM-BRT and SC-BRT plans, but it was not statistically significant. Similarly, the use of IM-BRT applicator demonstrated a noticeable dose reduction in all defined OARs when compared with MC-BRT applicator, but statistically significant for the rectum V_7Gy (p = 0.03) only.

Conclusions:
While the IM-BRT applicator is still in pre-clinical phase, our investigation demonstrated the proof-of-concept in real patient treatment plans with promising dosimetric results compared with SC-BRT and MC-BRT plans in selected patient group.