9 Reporting in Brachytherapy: Dose and Volume Specification

198 Reporting in Brachytherapy

Rationale Point A and the related concepts were introduced in 1934-38 (76). Since then in many centres modifications have been introduced to the location of point A or to the concept of point A itself. The above definition of point A is recommended in this report taking into account recent developments in brachytherapy equipment and the diversity of methods of application. As can be seen from Fig 6.24 A-C, it permits an easy and unambiguous localisation of point A and can be used with different methods of application. Although it is recognised that the steep dose gradient around the sources always makes the choice of any one point particularly difficult, the dose at point A is considered to be relevant for prescribing and reporting the intracavitary application in cervix treatment. The doses at point(s) A, from the brachytherapy application must always be reported. The doses delivered to point(s) A by external beam therapy must also be reported. This recommendation is justified by the fact that point A has been used and is still used today for prescribing and reporting brachytherapy in a majority of centres world wide, providing a large amount of clinical information. Furthermore, many literature reports have shown that the dose at point A is related to outcome in terms of tumour control and side effects (29,83,87,108). 8.3.2 Reporting dose at reference points related to bony structures Reporting dose at reference points related to well defined bony structures and lymph node areas is particularly useful when intracavitary brachytherapy is combined with external beam therapy, or followed by surgery. 8.3.3 Pelvic wall reference point

Fig 6.25 : Determination of the right (RPW) and left (LPW) pelvic wall reference points (see text). (From Chassagne and Horiot [16]). The pelvic wall reference point, as proposed by Chassagne and Horiot (1977) (16) , is intended to be representative of the absorbed dose at the distal part of the parametrium and at the obturator lymph nodes (Fig 6.25) It can be visualised on AP and lateral radiographs and related to fixed bony structures. On a AP radiograph, the pelvic-wall reference point is located at the intersection of the following lines :