18. Primary vaginal cancer and vaginal recurrences - The GEC-ESTRO Handbook of Brachytherapy

Primary vaginal cancer and vaginal recurrences

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 01/09/2023

Figure 7. Comparison of loading patterns for intracavitary multichannel cylinder implants, all with dose prescribed at a dose point to 5mm tissue depth. (a) Central channel loading only, (b) equal loading of central and peripheral channels, (c) peripheral needle loading only. Note variations in distribution of surface doses for different loading, as well as the variation of the shape of the 100% isodose.

Figure 8. Differences and challenges in brachytherapy planning of a locally advanced vaginal tumour by an intracavitary or intracavitary and interstitial approach. Re-used with permission from Westerveld et. al. [7]. A transversal and coronal T2-weighted MRI of the anatomy and target volume is shown. (a) Target volume is delineated in red. (b) The use of intracavitary brachytherapy alone in a standard intracavitary plan with dose prescription to 5 mm tissue depth results in underdosage of the target. Target volume [red] is not covered by 100% of the prescribed dose [blue]. (c) The use of intracavitary brachytherapy alone in a suboptimal intracavitary plan has an improved, yet still not optimal, coverage of the target and the dose to the vaginal mucosa is too high (200–400% of prescribed dose). (d) The use of an optimal combined intracavitary and interstitial plan has good coverage of the target and good sparing of the organs at risk.

of uninvolved vaginal mucosa is achieved by selection of the largest cylinder the patient can accommodate. Shielding inside cylinders has been used to protect part of the vaginal wall, rectum, bladder or urethra. However, with the rise of MRI as a primary imaging modality for treatment planning, MRI-compatible multichannel applicators have become more popular. In addition to the central catheter, these multichannel IC applicators have peripheral source channels close to the cylinder surface, which are equally spaced, about every 5 mm, and cover the whole circumference of the cylinder. This allows an increased number of degrees of freedom for dwell point activation. The whole vagina can be treated with these cylinders. Multichannel versions allow for an increased dose in the region of the CTV-T HR , while keeping the dose on the uninvolved side of the applicator as low as needed.

of the vagina, the technique is analogous to that in cervix cancer with a uterus in situ (see techniques in cervical cancer, chapter 16) and similar applicators can be used including an intra-uterine tandem. 3D printing of patient-anatomy adapted applicators instead of the mould technique is an upcoming technique. For all applicator types, metallic components have gradually been replaced by plastic, as MRI has become the gold standard imaging modality for gynaecological IGABT treatment planning. There are different applicators dedicated to vaginal tumours. In vaginal cylinders the sources are located within a central linear catheter. These cylinders are typically available with diameters of 2 to 4 cm (Figure 6, panel 1 and 2). Following the inverse square law, the dose is higher when closer to the central source. Therefore, sparing