9 Reporting in Brachytherapy: Dose and Volume Specification

Reporting in Brachytherapy 155

1 Introduction Exchange of information and clinical results between radiation oncology centres requires uniformity and agreement on the methods used to specify the doses and the volumes to which these doses have been delivered. This requires an agreement on definitions of terms and concepts necessary to report irradiation techniques. The ICRU recognised the importance of uniformity in reporting: it has been involved for several decades in an effort to harmonise the concepts, definitions of terms, dose and volume specification and dose determination in radiation therapy. Several reports have been published for external beam therapy (ICRU 42,44,47). “Dose and volume specification for reporting intracavitary therapy in gynecology“ was published in 1985 (43) (a revision is at the moment in preparation). „Dose and volume specification for reporting interstitial therapy“ was published in 1997 (45). This chapter is based mainly on the recommendations of the International Commission on Radiation Units and Measurements (43,44,45,47,48) and the recent GEC-ESTRO recommendations (86). The prescription of a treatment is the responsibility of the radiation oncologist (or the radiation oncology team) in charge of the patient. It is not the aim of this chapter (nor the role of the ICRU) to make recommendations about the treatment prescription, i.e., about the general rationale of the treatment, dose level or technical aspects of the treatment. In fact, different methods of treatment prescription are used at present by different radiation oncologists or in different radiotherapy centres, depending on local tradition, personal training and experience, and local conditions. For example, for cervix brachytherapy, some centres prescribe the treatment in terms of the TRAK (or mg.h which is its “historical” equivalent). Many prescribe the dose at point A, while more recently, some centres orientate their prescription towards volume evaluation. The maximum “tolerable” dose to organs at risk is also used as a prescription method . In interstitial therapy, some centres prescribe the minimum dose to the CTV, others the “Mean Central Dose”, others the dose on the envelope surface encompassing the CTV, etc. In endoluminal brachytherapy, the dose is prescribed at different distances from the centre of the source or at different depths in the tissues. For example, in endovascular brachytherapy, the dose is prescribed at 2 mm from the source axis, or at 1 or 2 mm from the tissue surface, etc. 1.1.2 Recording the radiation treatment Recording the treatment parameters as completely and accurately as possible in the patient chart must be performed in a radiation therapy department for several purposes: - to ensure further care and follow-up of the patients, - to keep treatment conditions reproducible, safe and constant, 1.1 From prescribing to recording and reporting 1.1.1 Treatment prescription