25 Oesophageal Cancer

Oesophageal Cancer Brachytherapy

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 10/06/2019

and define it as an intermediate risk CTV zone (IR CTV) as this area may still contain significant microscopic disease.

(Create Medic Ltd, Yokohama, Japan; http://www.createmedic. co.jp/english/) (fig. 27.8). In general, the larger applicators are used preferentially, whereas applicators with smaller diameters are reserved for highly obstructing lesions. It is always advisable to use the largest possible diameter to improve the dose gradient at the mucosa and the depth dose (see figure 27.9 and table 27.1). Themost serious problem is an obstructive tumour, where difficulties may occur even in placing an applicator with a small diameter. As these tumours usually are rather rigid, it is difficult to dilate the lumen mechanically. If no dilation is possible - e.g. in rigid recurrent lesions -, a small diameter applicator is introduced and the high tumour surface dose with a significant overdosage to the mucosa and submucosa are considered in the dose prescription. The chosen dose per fraction is in this context a trade-off to achieve the maximal acceptable mucosal dose. A shrinking volume strategy can be used in multiple fraction regimens in order to minimize mucosal doses and in consequence therapy-related toxicity. In these highly obstructive cases, laser surgery may be an alternative to mechanical dilatation to clear the lumen prior endoluminal brachytherapy. If there is a wide oesophageal lumen, the diameter of even a large diameter (bougie) applicator (14-16 mm) may not be sufficient to fill the entire lumen. In certain situations, balloon applicators with at least two channels may be used, which allow for a better fit with larger lumen diameters. These applicators are commercially available (CreateMedic Ltd, Yokohama, Japan).These large diameter applicators may be used for the lower, medium or upper third of the oesophagus. The balloon (usually about at least 6 cm in length) can be filled with a dilute contrast medium up to a diameter of 20 mm leading to a large distance up to 10 mm between the source and the surface of the balloon (tumour/oesophageal mucosa). The outer surface of applicators usually carries a scale in cm similar to endoscopes. 8.2. Patient Preparation The application should preferably be performed using an endoscope. Fluoroscopic guidance alone should be used only when endoscopic guidance is not available. HDR treatments may be performed on an outpatient basis. However, the risk of post-procedural serious complications (e.g. bleeding, perforation, mediastinitis) with immediate necessity for emergency treatment should be considered and discussed with the patient. The patient must be fasting on the morning of treatment and intravenous access should be secured. Application is facilitated by sedation and a vagolytic agent. Local anaesthesia of the oral cavity and oro-hypopharynx is needed to introduce the endoscope and applicator. In fluoroscopy assisted applications, a recent barium swallow should be available - the barium swallow should not be performed more than 2 - 3 days before the application. This documents the actual pathologic situation precisely. A recent barium swallow is only unnecessary in recently stented patients or in patients with a wide lumen. However, barium swallow excludes an existing pre-treatment fistula. 8.3. Application Methods Depending on whether endoscopy or fluoroscopy is used, there are different methods for application appropriate for the individual pathologic situation. The goal is always to match the applicator

7.B. Palliative Indications In palliative situations, it is usually not possible to entirely cover the gross tumour volume with endoluminal brachytherapy. The historical approach in these cases, as used in palliative endobronchial brachytherapy, is to prescribe the dose at 1 cm distance from the source axis, deep into the tumour mass, accepting that the cancer lesion is usually not covered in depth by an adequate tumour sterilizing dose (fig. 27.6). The downsizing effect of the previously irradiated brachytherapy fractions, however, may be used to achieve a better coverage of the actual tumour lesion in multiple-fraction procedures. Although in palliative settings depth dose delivery can be suboptimal, it is always important to treat the malignant stricture over an adequate length. Around the GTV visible on barium swallow or at endoscopy a composite CTV-PTV margin of 2 cm is taken. It is very helpful to indicate the CTV/PTV borders with radiopaque (clip) marking. 8.1. Applicator Types For patient comfort and logistic reasons, HDR-brachytherapy should be preferred. However, LDR(PDR) brachytherapy may be also used [Vuong et al. Okawa et al.]. The applicators are single catheters, allowing the treatment of cylindrical shaped PTVs. There are several variations in the construction of the applicators: pure cylindrical, with an inflatable double lumen, or bougie type with a gradually increasing diameter to facilitate the mechanical dilation of stenotic disease. Importantly, dilation by bougies must be carried out by experienced gastro-entorologists, because there is a significant danger of perforation and bleeding. The diameters of these applicators vary greatly. Bougie-type oesophageal applicators between 18F (Ø 6 mm) and 45F (Ø 15 mm) for both afterloaders Flexitron and microSelectron along with an applicator fixation mask for use in a wide oesophageal lumen are available by Nucletron (an Elekta company, Elekta AB, Stockholm, Sweden; https://www.elekta.com/brachytherapy/) as well as small-diameter applicators between 6 and 8 mm for palliative treatments. Single-use bougies between 24F (Ø 8 mm) and 36F (Ø 12 mm) along with a universal 2 mm-diameter applicator are provided by Eckert & Ziegler (BEBIG GmbH, Berlin, Germany; https://www.bebig.com/home/products/hdr_brachytherapy/) for the afterloaders SagiNova and MultiSource. Varian offers bougie oesophageal applicators between 8 mm to 14 mm diameter for the afterloaders VariSource and GammaMed plus (VarianMedical Systems Inc, Palo Alto, USA; https://www.varian.com/oncology/ solutions/brachytherapy). All applicators available on the market are CT- compatible. See also fig. 27.7. In addition, Buzurovic et al. have successfully tested in collaboration with Ancer Medical (Hialeah, FL, USA) a novel multi-balloon self-centring applicator [50, Buzurovic et al.]. This central source catheter surrounded by five equally spaced, 2cm (individually inflatable up to 2.3 cm) balloons allows the treatment of an active length of 10 cm. Balloon applicators are also well established and used in Japan 8. TECHNIQUE