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

extensive lymphovascular space invasion (LVSI) or multifocality larger margins along the vaginal wall may be applied [12, 17]. An example of the above-mentioned target concept in the treatment of a locally advanced primary vaginal tumour is shown in figure 5. There is currently no specific recommendation for target volume definition in image-guided brachytherapy as a single modality. Traditionally, this was the gross tumour volume with a safety margin of 10 – 20 mm along the vaginal wall.

time of diagnosis prior to the start of EBRT and at the time of brachytherapy is mandatory. The tumour shrinkage observed during chemoradiation is taken into account for target volume definition, which consists of three target volumes. The following section refers to a brachytherapy boost after conventionally fractionated EBRT of 45 to 50 Gy in 1.8-2.0 Gy per fraction: GTV-T res : The GTV-T res is the remaining visible and palpable residual macroscopic tumour during gynaecological examination at the time of brachytherapy. On T2-weighted MRI this is visualized as a remaining mass with hyper-intense to isointense signal intensity, within the initial tumour extension at diagnosis [12]. CTV-T HR : The high-risk clinical target volume includes the GTV T res and any abnormal thickened or irregular vaginal wall within the initial tumour extension before EBRT. On T2-weighted MRI the thickened or deformed wall typically has a more hypo-intense appearance. In case of tumours infiltrating the paravaginal or parametrial space at diagnosis, so called “grey zones“ can be observed, and are included in the CTV-T HR . “Grey zones” are considered as signs of tumour regression in terms of conversion of tumour cells into fibrotic tissue and are defined as areas with hypo-isointense signal intensity on T2-weighted MRI occurring within the initial tumour extension in the paravaginal or parametrial space [12]. CTV-T IR : The intermediate risk clinical target volume should include all significant microscopic disease adjacent to the CTV THR. Practically, the CTV-T IR should minimally encompass the initial tumour extension at diagnosis adapted to the anatomical situation at brachytherapy including a safety margin of at least 0.5 cm in tissue around the CTV-T HR , limited by previously unaffected anatomical borders (primary vaginal cancer). In patients with vaginal recurrences with high risk histologies (e.g., serous cancer),

8. TECHNIQUE

8.1 Application techniques Intracavitary (IC) as well as interstitial (IS) implants are used, often in combination. In both, intracavitary and interstitial implantation, different dose rates can be used. High-dose rate (HDR) and pulsed-dose rate (PDR) schedules are nowadays the most frequent choices, while low-dose-rate brachytherapy (LDR) is on the decline. Iridium-192 sources are mainly used for HDR and PDR afterloaders [19]. Cobalt-60 sources are also used as an alternative. 8.1.1 Intracavitary brachytherapy Different vaginal applicators are commercially available: metallic or plastic colpostats, cylinders of different diameters with or without peripheral needles, ring applicators, split rings with or without vaginal caps (serving as a multichannel cylinder) or a vaginal mould, to be adapted to the anatomy of the patient, the volume and the topography of the tumour (Figure 6). In tumours of the upper third

Figure 6. Examples for applicator types for vaginal brachytherapy*: 1a, b: intracavitary multichannel cylinders in different diameters; 2a, b: intracavitary/interstitial multichannel cylinder with a perineal template (four peripheral needles in cylinder and tissue, two needles in paravaginal tissue); 3a, b: ovoid-type intracavitary and interstitial applicator (one needle shown) tandem; 4a, b: ring-type applicator with three needles inserted through vaginal caps and ring. Many applicators include optional intrauterine tandem, as shown in panel 4. *Disclaimer: Example products were selected solely to represent different applicators types.