No more transplantation in CML?

Allogeneic stem cell transplantation has been considered the only curative therapy for chronic myeloid leukemia (CML). However, since 1999 the number of transplantations reported to scientific groups has substantially dropped.

In this issue, Hehlmann and colleagues report the results of a large randomized study comparing allogeneic stem cell transplantation versus the best available drug treatment. Of 621 patients included in the study, 354 were eligible for stem cell transplantation and 135 patients actually received a matched transplant. The patients included in the group that did not undergo transplantation were treated with interferon and hydroxyurea, or low-dose AraC and then with imatinib at the time the drug was available. The results of this important study demonstrate the superiority of the drug treatment group with a significantly better outcome. The difference is marked at 3 years after diagnosis, the 2 curves being indistinguishable at 8 years.

There has been substantial progress in recent years in the management of CML with the remarkable efficacy of imatinib. Before the imabinib era, the treatment of CML patients was restricted to allogeneic stem cell transplantation or interferon-based regimen. These therapies were indicated in the majority of patients younger than 70 years. Allogeneic transplantation was considered for patients younger than 40 years for those with a matched related donor. Although the optimal timing of transplantation was frequently discussed, a number of papers have shown little difference in long-term outcome among patients who underwent transplantation in the first 12 months after diagnosis compared with those who underwent transplantation after 1 year. Although the procedure carries a risk of death, it is obvious that transplantation is still considered as the only curative therapy with patients in complete response without any maintenance therapy. Interferon (IFN)–based regimens are no longer used as front-line therapy. However, the combination of IFN and AraC has been considered the gold standard until imatinib demonstrated its superiority.^1,2  Despite the toxicity of this combination, the treatment induced complete cytogenetic responses in patients who could tolerate 2 or 3 years of the treatment. Of interest, patients who achieved sustained cytogenetic responses had significant survival improvement. A similar observation has been published with imatinib. Given the recent update of the International Randomized Study of Interferon and STI 571 (IRIS) trial,²  it is obvious that any comparison between transplantation and imatinib would conclude in imatinib's favor. Allogeneic stem cell transplantation could again play a role in case of imatinib resistance. But the recent impressive results of the second generation of tyrosine kinase inhibitors^3,4  will probably delay the time of transplantation in the course of the disease. However, these new inhibitors could also be used for reducing the tumor burden before performing stem cell transplantation. Nevertheless, the study of Hehlmann et al clearly reinforces the message previously published⁵  that allogeneic stem transplantation cannot be recommended for front-line therapy.