Local tumor control probability to evaluate an applicator‐guided volumetric‐modulated arc therapy solution as alternative of 3D brachytherapy for the treatment of the vaginal vault in patients affected by gynecological cancer

Abstract

The purpose of this study was to evaluate the applicator‐guided volumetric‐modulated arc therapy (AGVMAT) solution as an alternative to high‐dose‐rate brachytherapy (HDR‐BRT) treatment of the vaginal vault in patients with gynecological cancer (GC). AGVMAT plans for 51 women were developed. The volumetric scans used for plans were obtained with an implanted CT‐compatible vaginal cylinder which provides spatial registration and immobilization of the gynecologic organs. Dosimetric and radiobiological comparisons for planning target volume (PTV) and organs at risk (OARs) were performed by means of a dose‐volume histogram (DVH), equivalent uniform dose (EUD), and local tumor control probability (LTCP). In addition, the integral dose and the overall delivery time, were evaluated. The HDR‐BRT averages of EUD and minimum LTCP were significantly higher than those of AGVMAT. Doses for the OARs were comparable for the bladder and sigmoid, while, although HDR‐BRT was able to better spare the bowel, AGVMAT provided a significant reduction of normald2cc, normald1cc, and dmax (p<0.01) for the rectum. AGVMAT integral doses were higher than HDR‐BRT with low values in both cases. Delivery times were about two or three times higher for HDR‐BRT with respect to the single arc technique (AGVMAT1) and dual arc technique (AGVMAT2), respectively. The applicator‐guided volumetric‐modulated arc therapy seems to have the potential of improving rectum avoidance. However, brachytherapy improves performance in terms of PTV coverage, as demonstrated by a greater EUD and better LTCP curves.PACS number: 87

External beam techniques to boost cervical cancer when brachytherapy is not an option—theories and applications

“…In their experience, the CT compatible vaginal cylinder, through providing spatial registration and immobilization of the gynecologic organs, minimized target volume motion variability allowing 2 mm PTV margin. By reducing cervical target volume motion, this applicator allowed lower rectal dose when compared with BT (44).…”

“…The rectal dose to 1 cc (d 1cc ) was (5.09 vs. 6.05 Gy, P=0.02), the bladder d 1cc (6.78 vs. 8.76 Gy, P=0.04) and the median target coverage by the 100% isodose line was (99.1% vs. 50.7%, P<0.05); all favoring SBRT plans (the study however was limited by BT dose prescription to point A) (41). Similarly, the volumetric modulated arc therapy (VMAT) dosimetric plans [generated for 51 gynecologic cancer patients receiving the initial 45-50.4 Gy via three dimensional conformal radiotherapy (3DCRT) and a boost of 6 Gy for maximum dose (d max ) with comparable bladder and bowel dose; however, the integral dose and the PTV coverage favored BT (44). These results are discordant with Georg et al dosimetric study in which image guided BT was superior to EBRT plans using either photon or proton radiotherapy.…”

An Evaluation of the Impact of MR Image Slice Thickness on the Accuracy of High-Dose-Rate Brachytherapy for Gynaecological Cancers

“…Being a relatively new technique in cervical cancer radiation therapy, it has yet to be evaluated in the literature to the extent of other alternatives [208]. That said, a pioneering work by Pedicini et al in 2012 revealed that SBRT delivered in VMAT fashion accomplished an 11% lower rectal d1cc, and a 10% lower bladder d1cc compared to high dose-rate brachytherapy (HDR BT), while requiring nearly 60% less treatment time [206]. Despite this, the mean PTV doses with this technique were up to 55% lower than HDR BT which significantly diminished their tumour control probability.…”

Vaginal cuff brachytherapy in endometrial cancer &ndash; a technically easy treatment?

“…VMAT needed 28% less monitor units compared with IMRT, and treatment duration reduced from 11 to <3 minutes for a dose of 6 Gy. Pedicini et al111,112 compared VMAT, IMRT and 3D-CRT using a vaginal cylinder for vaginal immobilization to 3D brachytherapy. The cylinder was able to reduce the movement in the VMAT course and reduced planning target volume margin to 2 mm.…”