9 Reporting in Brachytherapy: Dose and Volume Specification

194 Reporting in Brachytherapy

8 Intracavitary Brachytherapy for Cervix Cancer: Definition of Concepts, Quantities, Doses and Volumes for Reporting 8.1 Introduction-The “historical systems” Intracavitary brachytherapy for cervix carcinoma has been and is one of the most efficient radiotherapy techniques. This is due mainly to two factors. The anatomical conditions allow insertion of intrauterine and intravaginal sources in contact with the target volume. Secondly, because of the effects of the “inverse square law”, high doses are delivered to the target volume and the dose decreases rapidly with the distance to the source. This has two practical consequences: a benefit related to the protection of the organs at risk, but difficulty in treating lesions with extension (e.g., to the parametrium) with brachtherapy alone necessitating combination of brachytherapy with external beam therapy. 8.1.1 Milligram.hour In the original Stockholm and Paris systems, the treatment was reported in terms of the amount of radium (in milligrams) and the duration of the application in hours (26,37,53,54,94,111). For example, in the Paris system, typically three intrauterine tubes (10 + 10 + 15 mg) and 2 vaginal tubes (15 + 15 mg) were used and the applications lasted for 6 days (Fig 6.21) (80).

Fig 6.21 : The historical Paris system. Typical radium application for a treatment of cervix carcinoma consisting of : 3 individualized vaginal sources (one in each lateral fornix and one central in front of the cervical os), 1 intrauterine source made of 3 radium tubes (in so called tandem position). Possible variations of the Paris system include : 2 vaginal sources (or only one) in case of a narrow cavity : only 2 intrauterine radium tubes (or only one) in case of short uterus. The active length of the