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Radford et al. 487<br />

1 2 3 4 5 6 7 8 9 10 11 12<br />

Patient number<br />

Figure 1. FISH analysis of pretransplant bone <strong>marrow</strong> or peripheral <strong>blood</strong> stem cell spec<br />

imens from patients developing posttransplant MDS. Dotted line indicates threshold for a p<br />

itive sample. The specimen from patient 1 was analyzed using two separate markers.<br />

DISCUSSION<br />

High-dose chemotherapy or chemoradiotherapy is now part of the st<strong>and</strong>ard<br />

therapeutic approach to a variety of high-risk malignancies, <strong>and</strong> its use is now<br />

being investigated in the management of a variety of nonmalignant disorders as<br />

well. 9<br />

Exp<strong>and</strong>ed application of this technology has been accompanied by<br />

increasing recognition of the potential for development of secondary myelodys­<br />

plasias. However, despite the common use of the term "posttransplant MDS" in<br />

reference to these conditions, it is possible that the clonal "transforming event"<br />

leading to posttransplant MDS may originate in the prior conventional-dose<br />

therapy rather than in the course of the HDC/<strong>autologous</strong> transplant process itself,<br />

since most patients undergoing HDC/<strong>autologous</strong> <strong>transplantation</strong> have previously<br />

received conventional-dose chemotherapy <strong>and</strong>/or radiotherapy.<br />

Most previous analyses have addressed this issue indirectly, using X-<br />

chromosome inactivation patterns or comparisons of the extent <strong>and</strong> duration of<br />

conventional-dose chemotherapy in patients who developed posttransplant MDS<br />

with those who did not. 10-12<br />

Others have used conventional cytogenetic analysis to<br />

study small numbers of patients with posttransplant MDS. 6<br />

Results of these<br />

analyses have been conflicting; most authors have suggested that posttransplant<br />

MDS results from the patient's prior conventional-dose therapy, 710-12<br />

whereas the<br />

authors of a recent large study of breast cancer patients concluded that the high-<br />

dose chemotherapy was the causative factor. 6

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