**2.1.3 Chronic myelogenous leukemia (CML)**

CML is rare in childhood and accounts for less than 10% of all childhood leukemia. The treatment of CML has undergone dramatic changes in recent years. Before introduction of HSCT, the standard treatment approach for chronic phase CML was single-agent chemotherapy such as busulfan, hydroxyurea and interferon-alpha, however, treatment rarely produced a true complete remission. After 1980's, allogenic-HSCT was introduced as the only curative therapy for patients with CML. Five large multi-institutional retrospective studies have shown a high rate of long-term disease free survival (55-75% after myeloablative allogeneic HSCT), but survival was accompanied by significant treatmentrelated mortality, especially when unrelated donor allografts were used (Creutzig, 1996; Cwynarski et al., 2003; Millot et al., 2003; Weisdorf et al., 2002). From the 1980's to 2000, allogeneic HSCT was the treatment of choice for younger patients in first chronic phase if an HLA-matched donor was available. Before 1999, CML was the most frequent indication for allogeneic HSCT worldwide. With the approval of imatinib by the FDA in 2001, this tyrosine kinase inhibitor soon became the frontline therapy for newly diagnosed CML patients and transplant rates in CML dropped quickly worldwide (Muramatsu et al., 2010).

65%) (Chessells et al., 1986; Hoogerbrugge et al., 1995) was evident but not statistically

Another factor to consider when deciding whether HSCT is an option for relapse ALL is the phase of leukemia at the time of transplant because it is also highly predictive for the risk of leukemia relapse and death from non-relapse causes. In particular, patients transplanted in relapse with over 30% circulating blast, have very poor survival following HSCT (Kessinger, 1989). Patients transplanted in remission compared to those in relapse have a two to five

In summary the current opinion is that the earlier the relapse the more difficult is to obtain and maintain a second complete remission, so HSCT should be consider as an elective therapeutic option in order to eradicate a resistant disease. Relapse patients who fail to achieve remission prior to transplant have very poor outcome, so HSCT should not be

CML is rare in childhood and accounts for less than 10% of all childhood leukemia. The treatment of CML has undergone dramatic changes in recent years. Before introduction of HSCT, the standard treatment approach for chronic phase CML was single-agent chemotherapy such as busulfan, hydroxyurea and interferon-alpha, however, treatment rarely produced a true complete remission. After 1980's, allogenic-HSCT was introduced as the only curative therapy for patients with CML. Five large multi-institutional retrospective studies have shown a high rate of long-term disease free survival (55-75% after myeloablative allogeneic HSCT), but survival was accompanied by significant treatmentrelated mortality, especially when unrelated donor allografts were used (Creutzig, 1996; Cwynarski et al., 2003; Millot et al., 2003; Weisdorf et al., 2002). From the 1980's to 2000, allogeneic HSCT was the treatment of choice for younger patients in first chronic phase if an HLA-matched donor was available. Before 1999, CML was the most frequent indication for allogeneic HSCT worldwide. With the approval of imatinib by the FDA in 2001, this tyrosine kinase inhibitor soon became the frontline therapy for newly diagnosed CML patients and

transplant rates in CML dropped quickly worldwide (Muramatsu et al., 2010).

significant.

undertaken.


fold reduction in risk of relapse (p=0.0001) (36).

t(9;22) (q34, q11) or BCR-ABL molecular rearrangement t(4;11) (q21, q23) or 11q23 molecular rearrangement


Any one or more of the following:

Hypodiploidy (≤44 chromosomes) - Age ≥10 years and WBC ≥200 x109 /L - Induction failure (day 28 M2 or M3 BM)

WBC ≥100 x109 /L at diagnosis

Day 14 M2 or M3 BM

CD10 negative (CALLA) ALL phenotype

**2.1.3 Chronic myelogenous leukemia (CML)** 

Table 2. Ultra High-Risk Criteria of Childhood ALL in CR1.

Dramatic responses to oral imatinib administration were observed in adult patients with CML (Druker et al., 2001; Hughes et al., 2003). However, clinical experience with imatinib in the pediatric population is limited. Several studies have shown that treatment with imatinib has resulted in prolonged molecular response with limited drug toxicity with comparable results with those in adult patients (Millot et al., 2006). Imatinib is now implemented in the primary treatment regimen for children, but the paucity of evidence on its ability to result in permanent cure and the potential complications that may arise from long-term treatment with imatinib have prevented imatinib from superseding HSCT as the primary means of curative treatment in children. The results of allogeneic HSCT in children with CML are similar to those observed in adults; HSCT-related complications such as transplant-related mortality and graft versus host disease remain significant challenges.

There is a general consensus for the need for HSCT in patients with imatinib resistance or those with advance-phase (accelerated and blast phase). (Table 3). However, issues such as when to undertake HSCT in chronic-phase CML pediatric patients or how best to treat patients who have relapsed after HSCT are still controversial. When considering HSCT vs imatinib in pediatric CML patients in early chronic phase, one must consider that the objective for treatment of childhood CML is not palliation, but cure. Hence, the possible adverse effects that stem from long-term tyrosine kinase weigh more heavily in the childhood CML population. HSCT still remains an important treatment option especially for younger patients with CML depending on physician and patient preferences. As a result of multiple clinical trials in adults that have documented great results with the use of imatinib in CML in chronic phase (87% of patients treated with imatinib showed complete cytogenetic response at 18 months with 3.3% disease progression) (O'Brian et al., 2003), this results have been applied to children, and imatinib is now also the front-line treatment for childhood CML.


Adapted from Swerdlow, 2008; Speck, 1984.

Table 3. Definition of Accelerated Phase and Blast Phase Chronic Myeloid Leukemia (by WHO2008 and IBMTR Criteria)

Hematopoietic Stem Cells Therapeutic Applications 355

Table 5. Recommendation for Definitions of Treatment Response to Imatinib Used in Early

Children suffering from NHL(Burkitt, lymphoblastic, diffuse large B cell and anaplastic large cell lymphoma) even with stages III/IV have excellent results when treated with firstline chemotherapy and radiation therapy. Long term EFS is between 60-90%(Cairo et al., 2007; Gerrad et al., 2008; Link, 1997; Patte et al., 2007). However**,** for refractory or recurrent Burkitt's, diffuse large cell and lymphoblastic lymphoma, the long term survival is only 10- 20% (Atr, 2001; Cairo, 2003) In contrast**,** for refractory or recurrent anaplastic large

Several studies have shown that patients with chemosensitive recurrent diseases can achieve long-term disease free survival after HSCT. In a recent study by Thomas Gross published in 2010, he examined the role of HSCT for patients less than 18 years with the four different histologic subtypes receiving autologous or allogeneic HSCT (sibling & unrelated) from 1990-2005. To date this is the largest study done for refractory/relapse NHL. He concluded that EFS rates were lower for patients not in complete remission at HSCT, regardless of donor type. After adjusting for disease status, 5-year EFS were similar after allogeneic and autologous HSCT for diffuse large B cell (50% vs 52%), Burkitt's (31% vs 27% and anaplastic large cell lymphoma (46% vs 35%). However, EFS was higher for lymphoblastic lymphoma after allogeneic HSCT (40% vs 4% p<0.01). Predictors of EFS for progressive or recurrent disease after HSCT included disease status at HSCT and use of allogeneic donor for

HSCT (auto & allo) can be effective in salvaging children and adolescents with refractory or recurrent NHL and results are superior if complete remission can be achieved prior to

HSCT. Allogeneic donor is preferred for patients with lymphoblastic lymphoma.

Chronic Phase. Modified from Suttorp M, et al, 2011 and Baccarani M et al, 2009.

lymphoma, up to 60% of patients may achieve long-term survival (53).

**2.2 Lymphomas** 

lymphoblastic lymphoma.

**2.2.1 Non hodgkin's lymphoma (NHL)** 

The evaluation of the response to tyrosine kinase treatment is made through hematologic, cytogenetic and molecular testing (table 4). The overall evaluation should lead to a classification of treatment response as optimal, suboptimal or failure (table 5). For patients in early chronic phase who achieve an optimal response, the drug should be continued until allogeneic HSCT is undertaken. In those patients who fail to respond, second-generation tyrosine kinase inhibitors and HSCT need to be considered. In suboptimal responders, imatinib may be continued, possibly at a higher dosage, or second-generation tyrosine kinase inhibitors may be introduced (Lee & Chung, 2011) Prospective cooperative studies are needed to address this complex issue in young patients with CML.

Complete hematologic response


Partial hematologic response


Cytogenetic response (in patients with complete hematologic response)

1. Complete response; No Ph-positive metaphase cells


Molecular response


Adapted from Faderls, et al, 1999.


Table 5. Recommendation for Definitions of Treatment Response to Imatinib Used in Early Chronic Phase. Modified from Suttorp M, et al, 2011 and Baccarani M et al, 2009.

#### **2.2 Lymphomas**

354 Advances in Hematopoietic Stem Cell Research

The evaluation of the response to tyrosine kinase treatment is made through hematologic, cytogenetic and molecular testing (table 4). The overall evaluation should lead to a classification of treatment response as optimal, suboptimal or failure (table 5). For patients in early chronic phase who achieve an optimal response, the drug should be continued until allogeneic HSCT is undertaken. In those patients who fail to respond, second-generation tyrosine kinase inhibitors and HSCT need to be considered. In suboptimal responders, imatinib may be continued, possibly at a higher dosage, or second-generation tyrosine kinase inhibitors may be introduced (Lee & Chung, 2011) Prospective cooperative studies

1. Complete normalization of peripheral blood counts with leukocyte count <10x109/L

4. No signs or symptoms of disease with disappearance of palpable splenomegaly

are needed to address this complex issue in young patients with CML.

3. No immature cells, such as blasts, promyelocytes, metamyelocyte


2. platelet count <50% of the pretreatment count but >450xx109/L 3. persistent splenomegaly but <50% of the pretreatment extent

1. Complete response; No Ph-positive metaphase cells

3. Partial response; 1-34% Ph-positive metaphase cells 4. Minor response; 35-90% Ph-positive metaphase cells

Cytogenetic response (in patients with complete hematologic response)

2. Major response; 0-35% Ph-positive metaphase cells (complete+partial)

1. Complete molecular response; bcr-abl mRNA undetectable by RT-PCR

2. Major molecular response; > 3-log reduction of bcr-abl mRNA

Table 4. Criteria for Cytogenetic and Hematologic Remission in CML.

Complete hematologic response

2. Platelet count <450x109/L

Partial hematologic response

Molecular response

Adapted from Faderls, et al, 1999.

1. persistence of immature cells or

#### **2.2.1 Non hodgkin's lymphoma (NHL)**

Children suffering from NHL(Burkitt, lymphoblastic, diffuse large B cell and anaplastic large cell lymphoma) even with stages III/IV have excellent results when treated with firstline chemotherapy and radiation therapy. Long term EFS is between 60-90%(Cairo et al., 2007; Gerrad et al., 2008; Link, 1997; Patte et al., 2007). However**,** for refractory or recurrent Burkitt's, diffuse large cell and lymphoblastic lymphoma, the long term survival is only 10- 20% (Atr, 2001; Cairo, 2003) In contrast**,** for refractory or recurrent anaplastic large lymphoma, up to 60% of patients may achieve long-term survival (53).

Several studies have shown that patients with chemosensitive recurrent diseases can achieve long-term disease free survival after HSCT. In a recent study by Thomas Gross published in 2010, he examined the role of HSCT for patients less than 18 years with the four different histologic subtypes receiving autologous or allogeneic HSCT (sibling & unrelated) from 1990-2005. To date this is the largest study done for refractory/relapse NHL. He concluded that EFS rates were lower for patients not in complete remission at HSCT, regardless of donor type. After adjusting for disease status, 5-year EFS were similar after allogeneic and autologous HSCT for diffuse large B cell (50% vs 52%), Burkitt's (31% vs 27% and anaplastic large cell lymphoma (46% vs 35%). However, EFS was higher for lymphoblastic lymphoma after allogeneic HSCT (40% vs 4% p<0.01). Predictors of EFS for progressive or recurrent disease after HSCT included disease status at HSCT and use of allogeneic donor for lymphoblastic lymphoma.

HSCT (auto & allo) can be effective in salvaging children and adolescents with refractory or recurrent NHL and results are superior if complete remission can be achieved prior to HSCT. Allogeneic donor is preferred for patients with lymphoblastic lymphoma.

Hematopoietic Stem Cells Therapeutic Applications 357

indicative of AML, such as organomegaly or non-random chromosomal aberrations such as

Another relevant question in this respect is whether patients with advanced MDS benefit from pre-HSCT chemotherapy or not. Current results indicate this is not the case, as outcome did not differ according to blast percentage <5%, 5-19% or >20% in directly

In summary, patients diagnosed with advanced MDS should be treated with allogeneic-HSCT, which may even include less suitable donors such as mismatched or haploidentical

Neuroblastoma (stage IV beyond the age of 1 year, or high risk factors in lower stage) is still the only indication where the benefit of high-dose therapy with autologous HSCT has been

Although to date the published results do not show an unequivocal benefit for consolidation with high-dose therapy, children and adolescents with solid tumors might undergo autologous HSCT after high-dose chemotherapy within clinical research trial, preferably as

Brain tumors: children with medulloblastoma and high-grade gliomas responsive to

In general, allogeneic HSCT cannot be recommended in children with solid tumors. Allogeneic HSCT may be undertaken in the context of a clinical protocol in specialized

BMF syndromes include a broad group of diseases of varying etiologies in which hematopoiesis is abnormal or completely arrested in one or more cell lines. BMF can be acquired aplastic anemia (AA) or can be congenital, as part of such syndromes as Fanconi anemia (FA), Diamond Blackfan anemia (DBA), and Shwachman Diamond syndrome (SDS). The estimated incidence of BMF is 2 per million in Europe, with higher rates in Asia,

HSCT using an HLA-matched related donor is the treatment of choice for severe acquired aplastic anemia, resulting in long-term survival rates of over 90% If an HLA-compatible

donors if this is the only available choice for a particular patient.

part of first –line treatment strategies in the following situations:

 Soft tissue sarcoma: stage IV or in responding relapse. Germ cell tumors: after a relapse or with progressive disease.

Osteogenic sarcoma: the value of HSCT is not yet clear.

shown by randomized trials (Ladenstein et al., 2008; Matthay et al., 2009).

chemotherapy in an attempt to avoid or postpone radiotherapy.

t(8;21) or inversion(16).

**2.4 Solid tumors** 

transplanted patients (Stary, 2005).

 Neuroblastoma ( high risk, >CR1) Ewing's sarcoma (high risk or >CR1).

Wilm's tumor: relapse.

**2.5 Bone marrow failure (BMF)** 

perhaps resulting from environmental factors.

**2.5.1 Acquired severe aplastic anemia (AA)** 

centers.

### **2.2.2 Hodgkin's disease (HD)**

Autologous HSCT is the standard therapy for patients with HD in first chemosensitive relapse or second complete remission (CR) as shown by two prospective randomized clinical trials (Linch et al., 1993; Schmitz et al., 2002)

Currently, there is no indication for autologous HSCT in first CR, even in patients with bad prognostic features at diagnosis (Federico et al., 2003; Proctor et al., 2002).

For primary refractory patients or for patients in chemorefractory relapse, autologous HSCT has only a small chance of inducing long-term remission (Lazarus et al., 1999; Sweetenham et al., 1999). As part of a clinical protocol for patients with resistant HD, autologous HSCT might be considered as an initial debulking therapy to be followed by an allogeneic HSCT as consolidation therapy (Carella et al., 2000).

Allogeneic HSCT has mainly been used as salvage therapy for multiply relapsed or refractory HD. A retrospective analysis indicates that reduced intensity conditioning allogeneic HSCT can improve the outcome of HD patients that relapse after an autologous HSCT (Thomson et al., 2008). Its impact in the long term outcome of these patients has still to be prospectively evaluated. HSCTs from HLA-identical sibling donors and well-matched unrelated donors give a similar outcome (Anderlini et al., 2008).

#### **2.3 Myelodysplastic syndrome (MDS)**

MDS is rare in children an allogeneic HSCT from a sibling donor or a well-matched unrelated donor is currently the only curative therapy that is available for children with de novo MDS, JMML or secondary MDS. MDS is a heterogeneous disorder, characterized by a clonal stem cell disease with ineffective hematopoiesis which is morphologically abnormal. MDS in children differs from MDS in adults, as children more frequently suffer from hypocellular MDS. De novo MDS can be further classified as refractory cytopenia (RC; previously known as refractory anemia or RA), RA with excess of blast (RAEB) and RAEB in transformation (RAEBt).

The European working party on myelodysplastic syndrome (EWOG-MDS) reported their retrospective results on 63 children with RC (Kardos et al., 2003). Over 40% of patients had hypocellular marrows. Almost 50% of children with monosomy 7 progressed to advanced MDS within 2 years from diagnosis. By contrast, patients with hypocellular RC with a normal karyotype, may experience a long stable course before progression to generalized marrow failure occurs. Therefore, in patients with monosomy 7, HSCT should be performed soon after the diagnosis has been established. This is also advised for patients with advanced MDS (RAEB or RAEBt), and for patients with hypercellular RC, or with other clonal aberrations. In some patients the differentiation between hypocellular RC with a normal karyotype and aplastic anemia may be difficult, and in such patients a "watch and wait" strategy may be considered with repeated bone marrow evaluation before a final decision on diagnosis and therapy is made.

After the introduction of the new WHO definition of acute myeloid leukemia, which lowered the threshold to diagnose AML from 30 to 20% blasts, there has been a debate whether RAEBt should be classified and treated as MDS or AML (VArdiman, 2002). One approach is to build in some observation time to assess progression, and to look for signs indicative of AML, such as organomegaly or non-random chromosomal aberrations such as t(8;21) or inversion(16).

Another relevant question in this respect is whether patients with advanced MDS benefit from pre-HSCT chemotherapy or not. Current results indicate this is not the case, as outcome did not differ according to blast percentage <5%, 5-19% or >20% in directly transplanted patients (Stary, 2005).

In summary, patients diagnosed with advanced MDS should be treated with allogeneic-HSCT, which may even include less suitable donors such as mismatched or haploidentical donors if this is the only available choice for a particular patient.
