Cure: hematopoietic SCT
The first curative allogeneic SCT to a thalassemia patient from an
human leukocyte antigen (HLA) identical sibling donor was
reported in 1982.79 Since then, _ 3000 successful transplantations
have been reported.80 The probability of overall event-free survival
has been recently reported as high as 89%-97% for patients with no
advanced disease and of 80%-87% for patients with advanced
disease.81
Donor selection is of great importance because transplantations
may fail or be lethal resulting from immunologic complications.
The best results have been obtained with HLA-matched siblings.
The preparatory regimen includes administration of busulfan
fludarabine and cyclophosphamide, which in combination can
eradicate the thalassemia clone, enhance immunosuppression, and
facilitate sustained allogeneic engraftment.82 There are several risk
factors, including hepatomegaly _ 2 cm, portal fibrosis, and inadequate
iron chelation therapy, that can influence the outcome of
SCT. Patients are typically classified into 3 risk groups: class 1,
those with no risk factors; class 2, those with 1 or 2 risk factors; and
class 3, those with all risk factors.81
The administration of cyclosporine and methylprednisolone
together with a short course of methotrexate has been recommended
as GVHD prophylaxis with an outcome of 8% moderate
and 2% severe GVHD manifestations.83 Advances in conditioning
regimens have considerably improved the outcomes of class 3
patients younger than 17 years. However, these favorable results
have not been reproduced in older, more heavily iron-overloaded
patients, and they remain at high risk for transplantation-related
mortality.84
Approximately 10% of SCT patients are transfusion-free for
years, although they experience persistent mixed hematopoietic
chimerism.85 This suggests that only a few engrafted donor cells are
sufficient for correction of donor phenotype. Approximately 30%
subsequently reject their grafts.84 Those who deteriorate and
require further transfusion support may benefit from a second
transplantation with nonmyeloblative conditioning to restore normal
Hb levels.81
Despite a successful engraftment, previously iron-overloaded
patients may require phlebotomy after transplantation to prevent
the risks of residual iron excess causing hepatic fibrosis or other
endocrine complications.86 Moreover, growth failure and/or hypogonadism
and infertility can develop after the chemotherapeutic
preparative conditioning for transplantation or secondary to iron
excess. Persistent iron excess can be normalized by phelobotomy
after successful engraftment. Long-term post-transplantation survival
in some patients may also be affected by previously acquired
hepatitis C, which can be treated with ribavirin and peginterferon.
85 Rare cases of myelodysplastic syndrome and carcinoma
have been reported in some centers.86,87
Another option is to use matched unrelated donor if a matched
sibling is not available or when patients are not compliant with
conventional therapy. In one series of 27 patients, 70% of
27 patients were alive and transfusion-independent for _ 3 years
using matched unrelated donor. However, 40% developed GVHD
and a third had chronic GVHD.88 In another series of
49 thalassemic children from Thailand, there was no difference in
the outcome of 28 patients transplanted from a related donor
compared with 21 who received stem cells from unrelated donor.89
A few patients who failed the first transplantation underwent a
second transplantation. Although the preliminary results are encouraging,
90 this approach requires more clinical data before it can be
recommended.
Cure: hematopoietic SCTThe first curative allogeneic SCT to a thalassemia patient from anhuman leukocyte antigen (HLA) identical sibling donor wasreported in 1982.79 Since then, _ 3000 successful transplantationshave been reported.80 The probability of overall event-free survivalhas been recently reported as high as 89%-97% for patients with noadvanced disease and of 80%-87% for patients with advanceddisease.81Donor selection is of great importance because transplantationsmay fail or be lethal resulting from immunologic complications.The best results have been obtained with HLA-matched siblings.The preparatory regimen includes administration of busulfanfludarabine and cyclophosphamide, which in combination caneradicate the thalassemia clone, enhance immunosuppression, andfacilitate sustained allogeneic engraftment.82 There are several riskfactors, including hepatomegaly _ 2 cm, portal fibrosis, and inadequateiron chelation therapy, that can influence the outcome ofSCT. Patients are typically classified into 3 risk groups: class 1,those with no risk factors; class 2, those with 1 or 2 risk factors; andclass 3, those with all risk factors.81The administration of cyclosporine and methylprednisolonetogether with a short course of methotrexate has been recommendedas GVHD prophylaxis with an outcome of 8% moderateand 2% severe GVHD manifestations.83 Advances in conditioningregimens have considerably improved the outcomes of class 3patients younger than 17 years. However, these favorable resultshave not been reproduced in older, more heavily iron-overloadedpatients, and they remain at high risk for transplantation-relatedmortality.84Approximately 10% of SCT patients are transfusion-free foryears, although they experience persistent mixed hematopoieticchimerism.85 This suggests that only a few engrafted donor cells aresufficient for correction of donor phenotype. Approximately 30%subsequently reject their grafts.84 Those who deteriorate andrequire further transfusion support may benefit from a secondtransplantation with nonmyeloblative conditioning to restore normalHb levels.81Despite a successful engraftment, previously iron-overloadedpatients may require phlebotomy after transplantation to preventthe risks of residual iron excess causing hepatic fibrosis or otherendocrine complications.86 Moreover, growth failure and/or hypogonadismand infertility can develop after the chemotherapeuticpreparative conditioning for transplantation or secondary to ironexcess. Persistent iron excess can be normalized by phelobotomyafter successful engraftment. Long-term post-transplantation survivalin some patients may also be affected by previously acquiredhepatitis C, which can be treated with ribavirin and peginterferon.85 Rare cases of myelodysplastic syndrome and carcinomahave been reported in some centers.86,87Another option is to use matched unrelated donor if a matchedsibling is not available or when patients are not compliant withconventional therapy. In one series of 27 patients, 70% of27 patients were alive and transfusion-independent for _ 3 yearsusing matched unrelated donor. However, 40% developed GVHDand a third had chronic GVHD.88 In another series of49 thalassemic children from Thailand, there was no difference inthe outcome of 28 patients transplanted from a related donorcompared with 21 who received stem cells from unrelated donor.89A few patients who failed the first transplantation underwent asecond transplantation. Although the preliminary results are encouraging,90 this approach requires more clinical data before it can berecommended.
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