SOME QUESTIONS/ANSWERS ABOUT THE TBI REGISTRY

In the preface of the book "TBI prior BMT" Prof. Gösta Gahrton says: "...Bone marrow transplantation is one of the most important treatment modalities for hematologic malignancies, and total body irradiation is one of the key elements in bone marrow transplantation....Most likely, total body irradiation will continue to be an important part in the conditioning of malignant desease for bone marrow transplantation."

From the early 70's several thousand TBI/BMT treatments have been performed in European centres. The European group for Blood and Marrow Transplantation (EBMT) has collected a few TBI parameters and the results of treatments for evaluation. However, there are serious difficulties in the analysis of the clinical results so far. There are discrepancies in the recorded data, parameters are often defined differently, while data have been determined, recorded, reported and registered in dissimilar ways or incompletely. Parameters have been changed too frequently, usually several at once. Too many clinical, biological and physical parameters determine the cure rate and the failure of treatment, as well as the rates of early and late complication. Experimental data, if available, are not always applicable or comparable to the clinical situation. Many different treatment schedules are applied; different procedures of both medical and physical treatment planning are used; different definitions of target volume, different dosage and timing schedules have been used in combination with other local treatment data; many different techniques of TBI have been developed, regarding the local technical situation and physical experience: different methods of dosimetry, treatment verification and documentation are used. Large centres tend to have a sufficient amount of data for internal studies. They all try not to change any of the parameters if the treatments are succesful.

The EBMT and the Project Managing Group for two projects (1990-1996) supported by the Europen Commission, that concerns bone marrow transplantation, asked a task group of radiophysicists and radiotherapists to suggest guidelines for TBI.

The first step of this task group was to review all the work carried out till then. Basic ideas for the relevant physical parameters of TBI to be reported to the European and international registries (EBMT and IBMTR) were evaluated by the DGMP working group on physical aspects of TBI of the German Association of Medical Physicists and published in the late 80's, as the results and conclusions of the contributions and discussions at the EBMT-EULEP-TBI meeting of Leiden (1982), the ESTRO-TBI meeting of Baden-Baden (1986), the IAEA dosimetry in Radiotherapy meeting of Vienna (1987), the EAR-HBI/TBI meeting of Desden (1987), the DGMP-ÖGMP-EFOMP meeting of Insbruck (1987), the ESTRO-EBMT-EULEP-TBI meeting of Den Haag (1988), taking into account reccomendations of the AAPM task group (report 17) and many review publications. This set of parameters describing the spatial and temporal distribution of dose to target volume and organs at risk was tested during ESTRO-inquiries (34 centres) in 1986 and 1988 (45 centres), in annual DGMP TBI working group meetings (more than 50 centres) as well as by the EULEP/EBMT working group dosimetry of TBI in 1992.

Retrospective evaluation is always unsatisfaying. Prospective studies are demanded. In order to obtain a consensus in reporting TBI parameters to the EBMT registry, the EBMT-TBI task group was founded under the auspices of two EU projects (MR4*-0216-S "Treatment of Hematologic Malignancies by Bone Marrow Transplantation from Volunteer Donors" and BMHI-CT94-0300 "Optimization of Procedures for Treatment of Hematologic Malignancies by Bone Marrow Transplantation from Volunteer Donors"). More than 50 institutions were consulted and their opinions and suggestions were taken into consideration and discussed in several EBMT and EBMT Project Managing Group meetings: Cortina d’Ampezzo (1991), London (1991), Roma (1991), Zurich (1992), Stockholm (1992), Zurich (1995), Vienna (1996).

As a conclusion of all the discussions mentioned above, by which it was very difficult to make any evaluation due to the spread of criteria concerning TBI, the EBMT decided to include a series of TBI parameters into the MED B (page 63). The aim of this TBI registry is then to allow a more precise knowledge of the influence of the dose, dose rate and fractionation, the relationship between TBI and Chemotherapy, the late effects in organs at risk such us lung, kidney, liver, central nervous system, etc.

MED B encourages to fill page 63 for all treatments involving TBI. This page has two parts: the first one has seven lines (regarding administrative data) which have to be filled by the hematologic unit and should be sent to the radiotherapy department before TBI. The rest of this page must be filled by the radiophysicist group and returned to the hematologic unit once TBI is performed.

TBI registry will participate in the AL/CL/MM working parties to coordinate efforts while it will continue collaborating with the Late Effects working party, rather than working as a separate group. Considering the discussions and conclussions of these meetings, the corresponding reports will be ellaborated.

A web page has been created with this aim. The address is as follows:

Apart from the information which can be achieved from this web page (including the page 63 of MED B itself), which explains and defines every parameter involved, suggestions, comments and clarifications can be addressed to the corresponding electronic mail box.