25 Oesophageal Cancer

Oesophageal Cancer Brachytherapy

13

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

Curative Treatment: Radial dose distribution Larger diameter catheter ASL 80 mm

Palliative treatment: radial dose distribution endo-oesophageal catheter ASL 80 mm

Curative Treatment: Radial dose distribution Larger diameter catheter ASL 80 mm

Palliative treatment: radial dose distribution endo-oesophageal catheter ASL 80 mm

Endo-oesophageal Catheter Diameter 12mm

Endo-oesophagealCatheter Diameter 4mm

100 % Prescribed dose at 6 + 3 = 9 mm (Curative intent)

100 % Prescribed Dose at 10 mm from the source axis at 10 mm Reference depth dose (5 mm from applicator) 148 % PD

Reference depth dose (5 mm from applicator) 79 % in tissue Maximum dose at applicator surface 155 % PD on surface 200 % PD in applicator 400 % PD in applicator

Maximum dose at applicator surface 540 % PD on surface 400 % PD in tissue 200 % PD in tissue

Oesophageal wall

Fig 24.5. Radial dose distribution of endoluminal brachytherapy with curative intent for oesophageal cancer using a large diameter (12 mm) applicator. ASL is 80mm with 2mm step size and geometrical optimisation on distance. The prescription isodose covers the CTV. The high dose isodoses (200%, 400%) are inside the applicator. The maximum surface dose is 155% of the Prescribed Dose. The Reference Isodose at 5mm from the catheter is 79% of the Prescribed Dose. distribution of endoluminal brach therapy with curative intent for oesophageal cancer using a large diameter (12 mm) applicator. ASL is 80mm with 2mm step size and geometrical optimisation on distance. The prescription isodose covers the CTV. The high dose isodoses (200%, 400%) are inside the applicator. The maximum surface dose is 155% of the Prescribed Dose. The Reference Isodose at 5mm from the catheter is 79% of the Prescribed Dose. Fig. 27.5. Radial

Fig 24.6 Radial Dose distribution around a small (4mm) endoluminal applicator for a large obstructive oesophageal cancer in a palliative setting. The ASL is 80mmm with 2mm step size and geometrical optimization on distance. Dose prescription is at 10 mm from the source axis. The higher doses (200-400%) are in tissue and not in the applicator as is the case in curative treatment with a large size applicator. The reference depth dose at 5 mm from the applicator is at 148% Fig. 27.6. Radial dose distribution around a small applicator (4 mm). The ASL is 80 mm with 2 mm step size and geometrical optimisation on distance. The maxi um surfa e dose is 540% of the prescribed dose at 10 mm. The 200% and 400% isodoses are in the tissues (tumour and / or oesophageal wall).

Fig. 27.8. Japanese double balloon applicators, inflatable to 15mm diameter and 20mm (Create Medic Ltd, Yokohama, Japan; http://www.createmedic.co.jp/english/).

Fig. 27.7. Example of bougie type intraluminal oesophageal applicators, between 18F (Ø 6 mm) and 45F (Ø 15 mm) with an applicator fixation mask.

Fig. 27.9. Surface doses in relation to applicator diameter for an endo-oesophageal source of 80 mm ASL with 2 mm step size and geometrical optimization on distance. With dose prescription at 3 mm (yellow line) from the applicator surface doses decrease from 394% to128 % for diameters ranging from 2 to 26 mm. The gradient is steeper when dose is prescribed at 5 mm from 604% to 140% (blue line), and range from 1057% to 74% in case of prescription at 1 cm. See also table 27.1. It is shown that 12 mm is the minimum diameter of the applicator to avoid >200% of the prescribed dose to the mucosal surface.