29 Skin Cancer

Skin Cancer

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 30/04/2017

Fig. 31.4: Hand-made flaps using 5mm bolus and plastic tubes taped to the surface (from Maroñas et al, 2011, with permission [51] )

Fig. 31.3: Esteya system

8.1 Contact Brachytherapy (Plesiotherapy) 8.1.1 Surface contact applicators The surface applicators are cup-shaped shielded applicators with a single dwell position. Their shielding is used to reduce the dose to normal tissue and focalizing the treatment volume. The use of these applicators is indicated on flat surfaces where there is good contact without air gaps and small target areas smaller than 3 cm. Several surface contact applicators are available for use with PDR or HDR afterloaders such as the Leipzig applicators™ (Fig. 1) [9, 10, 11, 12]. The Valencia applicators™ (Fig. 2) are an improved modification that gives a more homogeneous dose to the skin [13, 14]. Current Valencia applicators version covers 20 and 30mmfield diameter sizes. There is a new version in progress covering up 50 mm in diameter field size [15]. Electronic brachytherapy is an alternative to the radionuclide based surface applicators [16]. Because of their very low energy (50-69.9 kV) no shielded room is required. There are three systems currently available: Xoft Axxent™ [17, 18], Esteya™ [19] (Fig. 3), and IntrabeamTM.

8.1.2 Flaps Flaps are constructed with plastic tubes (diameter 1.6 - 2mm, 5 or 6 French) and strips of tape (Fig. 31.4). This allows the treatment of large flat or slightly curved skin areas such as the forehead, legs, and the back. The mats are simply taped or fixed to the skin. No anaesthesia is needed. Flaps of different size and inter source spacing can be constructed. These applicators can be used with PDR or HDR afterloading machines. They are not suitable for very curved areas, or areas where skinmay move during treatment (such as the peri-oral area, shoulder, groin....). Diverse flexible flaps with the plastic tubes placed at an exact distance from the surface (usually 5mm) are available: Elekta Freiburg Flap, the Varian Catheter Flap set, and the Harrison-Anderson-Mick (HAM) from Mick Radio- Nuclear Instruments (now E&Z Bebig, Berlin, Germany). They can be cleaned, re-sterilised and used several times. The Freiburg flap applicator™ is made of small spheres 10mm of diameter joined to get a flexible layer that can adapt to the curvature of round areas of the head (Fig. 5). Then the 5mm source-surface distance is guaranteed. Taking into account the shape of the applicator and the surrounding air between spheres, the deviations on a typical flap have been evaluated withMonte Carlo for a standard plan, resulting in a dose reduction of 5% as compared to TG43 in infinite water [20]. The Varian catheter flap has 5 mm between the catheters and