16 Cervix Carcinoma

Cervix Cancer 311

6.3 Postoperative Brachytherapy If there is no residual disease, the CTV is the vaginal cuff with 5 mm depth into the vaginal wall; if there is residual disease the CTV encompasses residual macroscopic and/or microscopic disease plus a safety margin of 2 - 3 centimeters. Techniques This chapter and the following describe intracavitary preoperative brachytherapy and definitive brachytherapy in the intact cervix. Interstitial parametrial brachytherapy and postoperative vaginal brachytherapy are described in detail elsewhere (chapter on interstitial gynaecologic brachytherapy, (17) and endometrial cancer (15)). 7.1 General introduction 7.1.1 Intracavitary techniques based on modern afterloading devices All classical techniques used radium-226 which was introduced with the applicator. All modern techniques developed in the 1950`s and 1960`s are based on afterloading devices ( 60 Co, 137 Cs, 192 Ir), where the application and the irradiation are separated from each other. All these devices use intrauterine and intravaginal sources. However, several different approaches have been developed over past decades with a significant range of applicators: mainly different sized standard applicators with ovoids or with a ring and individualised moulded applicators. Many of these applicator systems (rigid, fixed or semifixed, metallic or plastic) - except the individualised moulded applicators - are nowadays commercially available for LDR/MDR/HDR/PDR brachytherapy, usually in combination with afterloading devices. These applicators imitate in principle the basic classical and modern application techniques as described below: Paris (intrauterine catheter plus corks/ovoids), Manchester (intrauterine catheter plus ovoids), Stockholm (intrauterine catheter plus plate). The modern commercially available applicators come in different presentations (ovoid-type (with or without shielding), ring-type) and with different names mainly representing traditional schools (“Manchester-style”, “Fletcher-style” etc.). They are applicable for the different radioactive sources nowadays in use, which are most frequently Cesium-137 and Iridium-192. The indivualised moulded applicators represent the most individualized approach, but it is also possible to use adaptations of standard rigid applicators to fit in most clinical situations: different lengths, angles and curvatures of the intrauterine catheter; different shapes and sizes of ovoids or rings; rectal shielding in the ovoids; rectal retractors; fixed or non fixed geometry. The majority of them are used with individualised vaginal packing. For different forms of treatment planning, CT- and/or MRI compatible applicators are available (based on the ovoid or ring type). There are few publications about the advantages and disadvantages of the different applicators. To assess the different application techniques, multiple variables have to be taken into consideration: above all, the potential of adjusting to different anatomical and pathological situations; size and form of the vaginal sources with or without integrated shielding; spacing between the vaginal sources; length, curvature, and angle of the intrauterine catheters; fixed or nonfixed geometry between ovoids/ring and intrauterine catheter; variability of loading (ring/ovoids and intrauterine catheter); capability for sparing rectum and bladder; potential for treating extended vaginal and parametrial tumour extension. 7