25 Oesophageal Cancer

Oesophageal Cancer Brachytherapy

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

diameter to the oesophageal lumen diameter in its maximum extension.This avoids eccentric applicator positions, under-dosage to the tumour and over-dosage to the healthy tissue and treats as far as possible beyond the steep slope of the depth dose curve. The application may be performed in a dedicated brachytherapy room. Artificial teeth are removed. The patient lies on the left side as usual for oesophageal endoscopy. A sedative drug and a vagolytic agent are given intravenously. Extensive local anaesthesia is applied to the oral cavity, the oro- and hypopharynx (nomeals are allowed for 2 - 3 hours afterwards). The oro- and hypopharynx are then digitally palpated to determine the individual anatomical situation. In endoscopy assisted applications, the surface of the endoscope is covered with local anaesthetic gel and then introduced between two fingers placed into the oropharynx to lead the tip of the endoscope towards the proximal aperture of the oesophagus. With the patient swallowing, the endoscope is then introduced into the oesophagus. The proximal and distal end of the tumour are inspected by the endoscopist and the radiotherapist. The distances in cm from the teeth are noted and compared to the results of pre-therapeutic examinations. If localisation is difficult because of changes since pre-therapeutic imaging, the proximal and distal tumour end may be documented by two anterior-posterior radiographs with the tip of the oesophagoscope at the respective tumour margin. Radio-opaque markers should be used to document the distal and the cranial ends of the actual tumour at first brachytherapy. A flexible guide wire (>twice the length of the oesophagoscope) is advanced through the biopsy channel and placed far beyond the distal tumour margin, preferably within the stomach (fig. 27.12). The oesophagoscope is then withdrawn over the guide wire which remains in place. The applicator (open end or with perforated guiding tip) with a diameter larger than the biopsy channel (> 2mm) is advanced using the guide wire as glide path to the correct position. If an applicator with a small diameter (<= 2 mm) is to be used, it can be directly placed under endoscopy through the biopsy channel (as in bronchus). If the applicator with a diameter larger than 2 mm has a closed end, it has to be introduced alongside the oesophagoscope, which may be difficult in obstructive lesions. In fluoroscopy assisted applications, a semiflexible applicator with a scale is covered with local anaesthetic gel. The applicator is introduced between two fingers which are placed in the oropharynx to guide the tip of the applicator towards the proximal aperture of the oesophagus. With the patient swallowing, the applicator is then introduced into the oesophagus. It is gently advanced avoiding any significant pressure against resistant tissue. As the tumour region is reached - according to the known distance from the teeth - it is advanced even more cautiously. In obstructive lesions the resistance increases and must be gently overcome. After passing the obstruction, further advancement becomes easy again. To avoid perforation, the radiation therapist performing the application without the support of a gastro-enterologist should never try to overcome resistance by force. After the applicator has been placed correctly, the distance between the tip of the applicator and the teeth is noted andmarked. If an inner tube is needed, this can now be introduced into the outer tube ("applicator"). If there are difficulties with introducing the applicator, the Seldinger technique with a guide wire can be used. In such cases the guide wire (> twice the length of the tube) is put into a semi-flexible gastric tube with an open distal end. The gastric tube is gently introduced into the oesophagus with the patient actively swallowing and then

carefully advanced well beyond the distal end of the tumour, preferably into the stomach. The gastric tube is removed over the guide wire leaving the guide wire in place. The applicator can then be carefully introduced into the patient over the guide wire, which is finally removed (fig. 27.12). The guide wire based Seldinger technique offers in addition to localization accuracy, procedural safety. Ideally this will be performed with interdisciplinary expertise of the specialized cooperating gastroenterologist. The application can also be done through the nose with the patient sitting upright. Local anaesthesia is applied.The guide wire and later the applicator is then introduced through the nose.This procedure is only possible for small diameter applicators up to 6-8 mm.

9. TREATMENT PLANNING

After placement of the /applicator and before 2D or 3D imaging a calibrated marker wire is inserted to enable definition of the correct stepping source positioning in the applicator. This is not necessary when using applicators with inner markers at their distal end (see section 8). 9.A. Curative indications Curative indications require high precision treatment.The treatment planning is preferably based on 3D imaging. Planning on CT is possible, but should be supplemented by endoscopic placement of radio-opaque clips to delineate the CTV. MRI allows discrimination of the GTV from the non-invaded oesophageal wall, or the residual GTV and grey zones after initial (chemo)radiotherapy. If PET-CT is available, it may be of additional value to accurately determine the GTV. 9.A.1. Radical brachytherapy for superficial tumours After delineation of the GTV on CT or MRI a CTV margin of 1 cm is delineated in the oesophageal wall, as well as a PTVmargin of an additional 1 cm in the longitudinal direction to take account of possible displacement of the applicator in the oesophageal lumen. Dose prescription should be defined by the D90 of the PTV. For comparison with other cases and other centres dose recording and reporting should contain the prescription depth from the surface of the catheter, as well as the reference dose at 5 mm mucosal depth (fig. 27.13). 9.A.2. Boost after (chemo)radiotherapy 2D planning (see in detail GEC-ESTRO Handbook of BT first edition chapter 24) Two orthogonal X-rays are takenwith the applicator and themarker wire in place. The position of the applicator on the radiographs is carefully checked and compared to the pre-treatment barium swallow, looking at anatomical landmarks (carina, vertebral bodies, aortic notch) or clips.The tip of the applicator should reach several centimetres beyond the distal end of the visible tumour to adequately cover the length of the PTV. The Length of the Planning Target Volume (PTL) is determined considering tumor length (GTL), safety margins for subclinical extension (CTL) and positional uncertainties e.g. catheter