After nearly 30 years of dedication, the International Bone Marrow Transplant Registry (IBMTR) and the Autologous Blood and Marrow Transplant Registry (ABMTR), by nearly any criterion, can be considered a success. The Registry contains over 120,000 patient records that are an invaluable source of information on both autologous and allogeneic bone marrow transplantations. Through the voluntary efforts of more than 350 institutions, it annually registers over 20% of all transplants occurring in nearly 50 countries and, by some estimates, nearly half of all transplants in North America.
The IBMTR/ABMTR has evolved to become an invaluable resource to physicians and researchers around the world. Perhaps the strongest indication of its value is the vehemence with which Registry data and methods are occasionally attacked and conclusions from the large data sets dismissedin science, this is often a good indication that the traditional paradigms are being successfully challenged.
Strengths and Weaknesses of Imperfect Data
Clinical trial purists argue that inherent selection biases severely compromise the value of Registry data, and that valid treatment comparisons come only from prospective, randomized trials. This issue is too broad to be considered in detail here, but the continuing broad-based, long-term, and voluntary cooperation of large numbers of investigators around the world is a clear indication of the value of the Registry to the field.
Although there clearly are other limitations to the use of Registry data, it is fair to say that the major limitation is the lack of comparable control data from a registry of patients not treated by transplantation. However, the Registry has not allowed the good to become the prisoner of the perfect. The clinical world is not always perfect, and we can often learn much from imperfect information. Indeed, the imperfections of Registry data result in a certain reserve and humility, which is sometimes lacking in analyses of randomized trial results. The rest of oncology would do well to develop similar comprehensive data sets.
As with many areas of clinical research, the major strength and weakness of the Registry is one and the same: the homogenization of data from many varied sources. The best gets lumped in with the worstin essence a regression to the mean. The number of patients from any given institution may be small, the treatments varied, and the skill and depth of the support teams heterogeneous. In my mind, this limits the use of Registry data in selecting the "best" treatment approach.
On the other hand, the broad-based nature of the Registry provides an unparalleled opportunity for identifying factors that may contribute to variations in outcome and to understanding the state of the art of the whole field for policy considerations. In addition, it currently offers the only realistic method of collecting data on transplant treatment of rare diseases.
Selective and Long-Term Benefits
As it becomes even larger, the Registry will serve an increasingly important role in the study of rare events, particularly for unraveling the etiology of unusual toxicities. Rare events are inherently difficult to study in medicine; through its voluntary nature and its broad-based participation, the Registry provides the opportunity to benefit individual patients with unusual syndromes by allowing their physicians to gain insights from the experience of other transplant institutions with these rare events.
Because data are collected over an extended period, issues affecting survivorship can be identified and properly addressed during active treatment periods, even when such effects do not appear for many years. This fact could be one of the Registry’s greatest strengths.
In the end, perhaps the greatest overall value of the Registry is its ability to facilitate the generation of hypotheses. Three factorsthe large size of the database; the varied nature of the patients, diseases, sites, and physicians; and the intrinsic curiosity of the participating memberscombine to provide the proper seed and soil for the intellectual restlessness and intercourse that conceives and ignites new ideas. Finally, the development of randomized trials is truly facilitated by Registry dataagain, all oncology would be well served by similar systematically collected data from nontransplant settings.
As a clinical scientist who for many years has been skeptical of the role of the Registry, I must admit that there is great value here. The hope is that 30 years from now the Registry will no longer be needed because its use has led to greater therapeutic success.