Correspondence

Access to Bone Marrow Transplantation for Chronic Myeloid Leukemia

N Engl J Med 1995; 332:823March 23, 1995

Article

To the Editor:

In their study comparing the rates of allogeneic bone marrow transplantation for chronic myeloid leukemia in 10 countries (Oct. 20 issue), Silberman et al.1 found that Swedish patients were the most likely to receive transplants. In an editorial in the same issue,2 Schroeder discusses possible methodologic reasons for the observed differences. He correctly stresses the importance of the accuracy of the number of cases of chronic myeloid leukemia, as well as the number of bone marrow transplantations. Underestimation of the frequency of the disease in Sweden would lead to overestimation of the country's performance, as compared, for example, with that of the United States.

Since 1989, all patients in Sweden under the age of 60 years with newly diagnosed chronic myeloid leukemia have been referred to hematologists for consideration of high-dose chemotherapy and early transplantation. Demonstration of the Philadelphia translocation by cytogenetic examination of bone marrow or polymerase chain reaction is required for the diagnosis. This requirement may result in the exclusion of less than 10 percent of patients who would otherwise receive a diagnosis of chronic myeloid leukemia. All cases of chronic myeloid leukemia in Sweden are reported to the national cancer registry. In contrast, Silberman et al. compiled U.S. data from two registries, covering 10 percent of the population. In our opinion, the different rates of transplantation in Sweden and the United States cannot be attributed to underestimation of the rate of chronic myeloid leukemia in Sweden.

Anders Wahlin, M.D., Ph.D.
Umeå University Hospital, S-901 85 Umeå, Sweden

Bengt Simonsson, M.D., Ph.D.
Akademiska Hospital, S-751 85 Uppsala, Sweden

2 References

1. 1

   Silberman G, Crosse MG, Peterson EA, et al. Availability and appropriateness of allogeneic bone marrow transplantation for chronic myeloid leukemia in 10 countries. N Engl J Med 1994;331:1063-1067
   Full Text | Web of Science | Medline

2. 2

   Schroeder SA. Rationing medical care -- a comparative perspective. N Engl J Med 1994;331:1089-1091
   Full Text | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Wahlin and Simonsson correctly point out that the difference between rates of transplantation in the United States and Sweden cannot be attributed to underestimation of the rate of chronic myeloid leukemia in Sweden.

We would also like to comment on several issues raised in the editorial by Schroeder. He states that “for seven of the countries the incidence of leukemia was projected from small samples.” Cancer registries covering the entire populations were used for six countries (Canada, Denmark, the Netherlands, New Zealand, Sweden, and the United Kingdom). For Australia, the registry represented approximately 85 percent of the population. For the United States, we relied on data from the Surveillance, Epidemiology, and End Results Program, an established source of data on the incidence of cancer for more than two decades. We are not aware of published research that would support the view that better methods of finding cases of chronic myeloid leukemia in the United States may help explain why the rates of bone marrow transplantation for this type of leukemia are relatively low.

The editorial states that we “unintentionally excluded the elderly” from our comparison. In fact, our study of allogeneic bone marrow transplantation was intended to focus on the nonelderly, because they are less likely than the elderly to have coexisting conditions, which can make it difficult to interpret data on patterns of care. Our general interest in the role of private insurance also led us to focus on the population not covered by Medicare.

Schroeder states that according to our article, “differences in the treatment of chronic myeloid leukemia mirror well the efficiency and effectiveness of various countries' medical care systems.” We did caution that we could not “assume that our findings apply to other complex procedures, or to a wider range of medical interventions.”

In summary, we believe that there was little evidence presented that the observed differences in rates of transplantation resulted from methodologic flaws in our study.

George Silberman, M.A.
Marcia G. Crosse, Ph.D.
Eric A. Peterson, M.Phil.
General Accounting Office, Washington, DC 20548

Author/Editor Response

Why is the reported incidence of chronic myeloid leukemia 1¹/2 to 2 times as high in the United States as in Sweden? Drs. Wahlin and Simonsson refute one hypothesis: that diagnosed cases are underreported in Sweden. Two other hypotheses remain: that chronic myeloid leukemia is underdiagnosed in Sweden as compared with the United States, and that there are real cross-national differences stemming from genetic or environmental factors (or both). The differences in the incidence rates among the countries are substantial (as shown in Table 2 of the article by Silberman et al.), although the reasons for these differences remain unclear.

Steven A. Schroeder, M.D.
Robert Wood Johnson Foundation, Princeton, NJ 08543-2316