A simple brachytherapy technique for early anal carcinoma.

Abstract

It is widely recognised that the most suitable anal carcinoma for brachytherapy is a T1−2 anal margin carcinoma, although low T1−2 anal canal lesions may also be effectively implanted, particularly if external beam radiotherapy has preceded the brachytherapy. The present paper describes a technique of mixed interstitial and intracavitary radiotherapy for small anal carcinomas. The technique facilitates the parallel and ideally spaced implantation of needles and, by secure fixation of the implant template and anal intracavitary source, some screening of uninvolved anal circumference may be maintained throughout therapy. The typical applicator consists of an acrylic (perspex) rod 2 cm in diameter and 6 cm in length, fitted with a flat flange plate at one end (Fig. 1). A second detachable thick flange acts as an alignment jig. The rod is centrally bored to receive a standard disposable intrauterine applicator (Amersham International PLC) which is retained in the rod by a pinch screw. A crescentic coaxial cut-out, machined to a depth of 5 cm, accepts a low-melting-point alloy (Cerrobend) insert. The attached flange plate is securely sutured in position through holes situated in its perimeter, and the flange plate also contains the needle guide holes in the predetermined locations. The array of holes in the 2 cm thick alignment jig coincide precisely with the needle guide holes in the flange plate and a dowel provides positive location.