Single versus multichannel applicator in high-dose-rate vaginal brachytherapy optimized by inverse treatment planning

Abstract

PurposeTo retrospectively compare the potential dosimetric advantages of a multichannel vaginal applicator vs. a single channel one in intracavitary vaginal high-dose-rate (HDR) brachytherapy after hysterectomy, and evaluate the dosimetric advantage of fractional re-planning.Material and methodsWe randomly selected 12 patients with endometrial carcinoma, who received adjuvant vaginal cuff HDR brachytherapy using a multichannel applicator. For each brachytherapy fraction, two inverse treatment plans (for central channel and multichannel loadings) were performed and compared. The advantage of fractional re-planning was also investigated.ResultsDose-volume-histogram (DVH) analysis showed limited, but statistically significant difference (p = 0.007) regarding clinical-target-volume dose coverage between single and multichannel approaches. For the organs-at-risk rectum and bladder, the use of multichannel applicator demonstrated a noticeable dose reduction, when compared to single channel, but statistically significant for rectum only (p = 0.0001). For D2cc of rectum, an average fractional dose of 6.1 ± 0.7 Gy resulted for single channel vs. 5.1 ± 0.6 Gy for multichannel. For D2cc of bladder, an average fractional dose of 5 ± 0.9 Gy occurred for single channel vs. 4.9 ± 0.8 Gy for multichannel. The dosimetric benefit of fractional re-planning was demonstrated: DVH analysis showed large, but not statistically significant differences between first fraction plan and fractional re-planning, due to large inter-fraction variations for rectum and bladder positioning and filling.ConclusionsVaginal HDR brachytherapy using a multichannel vaginal applicator and inverse planning provides dosimetric advantages over single channel cylinder, by reducing the dose to organs at risk without compromising the target volume coverage, but at the expense of an increased vaginal mucosa dose. Due to large inter-fraction dose variations, we recommend individual fraction treatment plan optimization.

American Brachytherapy Task Group Report: Adjuvant vaginal brachytherapy for early-stage endometrial cancer: A comprehensive review

“…Multi-channel vaginal cylinders have the advantage of customizing dose to either deliver asymmetric doses or avoid adjacent normal structures [94,95]. The multi-channel cylinder has been shown to decrease dose to the bladder and rectum but at the expense of increased vaginal mucosa dose [96]. Patients with large lesions or those that are >5mm thick may benefit from a multi-channel cylinder, but they may still be difficult to adequately treat without delivering excess dose to the vaginal surface [97].…”

Vaginal Cuff Brachytherapy in Endometrial Cancer

“…It should be kept in mind that multi-catheter cylinders may reduce the rectum and bladder dose, but may cause a dose increase in the vaginal mucosa. [55] In some cases, the vaginal apex can be seen as a "dog ear" shaped pocket because of the vaginal fornix remnants. These conditions can be best treated with vaginal molds, multichannel applicators, or ovoid applicators.…”

Film based verification of calculation algorithms used for brachytherapy planning-getting ready for upcoming challenges of MBDCA

“…Self-developing dosimetry films have been used to verify dose distributions, and their use has been well documented [ 20 , 21 , 22 , 23 ]. However, they need to be adapted to the technical capacities of the particular facility [ 24 ]. Our department is preparing to introduce MBDCA soon.…”