Survey of the use of the ICRU 38 in recording and reporting cervical cancer brachytherapy

Abstract

Background: A survey on the practice of reporting intracavitary cervix cancer brachytherapy (LDR and HDR) in clinical practice (CP) and in literature (LIT) was performed on the occasion of a workshop, ‘ICRU 38: The Basis for a Revision’, which took place at the Annual GEC ESTRO meeting in Naples in 1998.

Materials and methods: The answers (n=85) to a specific questionnaire which had been sent to all ESTRO members (n=1600), were evaluated. In parallel, a systematic survey on the literature reporting cervix cancer brachytherapy since 1985 was performed using the MEDLINE database. The main recommendations for reporting as given in the ICRU 38 were addressed for both surveys: technique; total reference air kerma (TRAK); dose specification to the target volume ‘60 Gy reference volume’, to organs at risk ‘ICRU rectum and bladder point’ and other reference points and time–dose pattern. In addition, some other items were investigated such as mg h, Point A, B, and in vivo dosimetry in bladder and rectum.

Results: Issues related to technique (source, machine and applicator type) and to time–dose pattern are reported in the majority of patients in CP and LIT. The same applies for the following parameters: Point A is indicated in 76% (LDR) to 89% (HDR) in CP, in 60% (LDR) to 96% (HDR) in LIT. Rectum and bladder ICRU points are recorded in 55% (HDR) to 90% (LDR) and 58% (HDR) to 84% (LDR), respectively, in CP. On the other hand, TRAK is given in 14% (HDR) to 43% (LDR) in CP, in 0% (HDR) to 10% (LDR) in LIT. ‘60 Gy reference volume’ is recorded in 18% (HDR) to 51% (LDR) in CP, in 0% (HDR) to 17% (LDR) in LIT. Rectum and bladder ICRU points are reported in 18% (LDR) to 28% (HDR) and 14% (HDR) to 29% (LDR), respectively, in LIT. Other reference points and in vivo dosimetry measurements are given in a low percentage. Dose rate and overall treatment time is reported in 10–44%.

Conclusion: Recording and reporting in CP and in LIT meets the recommendations as given in ICRU 38 to different degrees. Specific items such as TRAK and the ‘Reference volume’ have only limited penetration into CP and LIT, which applies in particular to centers using HDR brachytherapy. The discrepancies between CP and LIT may be due to the well-known delay between change in CP and its translation into LIT. In order to arrive at a more common language for the better exchange of clinical results, it seems to be necessary to adapt some terms and recommendations. In particular, comprehensive concepts are needed for reporting dose to points and volumes in the target and in critical organs, according to the new potential from imaging and computer technology and from modern radiobiological insights, bridging the gap between LDR and HDR brachytherapy.

Introduction

Exchange of clinical results between radiation oncology centers requires uniformity and agreement on the methods used to specify the doses and the volumes to which these doses are delivered. To avoid confusion, an agreement has also to be reached on definitions of terms and concepts necessary for reporting irradiation techniques.

The International Commission on Radiation Units and Measurements (ICRU) has been involved for several decades in an effort to improve uniformity in concepts, definitions, dose specification and dose determination in radiation therapy. ICRU Report 29, ‘Dose specification for reporting external beam therapy with photons and electrons’ was published in 1978 [12]. It was superseded in 1993 by ICRU Report 50 [14] ‘Prescribing, recording and reporting photon beam therapy’. A ‘Supplement to Report 50’ (ICRU Report 62) has been published in July 1999 [18]. A similar report is in preparation for electron beam therapy.

In brachytherapy, ICRU Report 38 ‘Dose and volume specification for reporting intracavitary therapy in gynaecology’ was published in 1985 [13] and in 1997, ICRU Report 58 ‘Dose and volume specification for reporting interstitial therapy’ appeared [17].

ICRU Report 38 was prepared more than 15 years ago. During the subsequent period, important changes took place in the field of brachytherapy, among them: dramatic progress in imaging, more powerful and accurate 3-D treatment planning, availability of better and safer therapy equipment, and the development of high dose rate (HDR) and pulse dose rate (PDR) stepping source brachytherapy.

An evaluation and possibly a revision of Report 38 then appeared to be appropriate. In addition to the changes mentioned above, a revision would have to take into account to a large extent the way in which ICRU 38 was perceived and applied by the radiation oncology community in general, which is actually the ‘end user’ of the ICRU Reports. A closer exchange and collaboration with the users is indeed required to prepare a useful report. In that respect, the GEC-ESTRO (Groupe Européen de Curiethérapie) devoted a full day of its annual meeting (May 1998, Naples, Italy) to the discussion of ICRU Report 38 [31] and, in particular the question of the needs for a revision was raised [10], [32], [40]. The discussion was prepared by a survey of a questionnaire sent to all ESTRO members before the meeting [10] and a thorough revue of the literature data since 1985 [40]. A compiled critical analysis of the survey of the questionnaire [10] and of the literature (see Further reading list) is presented here. Before presenting the analysis of these two surveys, it appears to be useful to recall some of the principles and approaches, on which ICRU Report 38 was based.