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Keywords:

  • Ewing sarcoma;
  • EWS fusion genes;
  • loco-regional sarcoma;
  • P6 protocol;
  • secondary cancer

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

Background

Reported overall survival (OS) rates of patients with localized Ewing sarcoma family of tumors (ESFT) are >80% when treated with the MSKCC P6 protocol. However, it has been associated with a 5.8% incidence of secondary leukemias. A modified P6 (mP6) protocol with reduced exposure to chemotherapy is presented.

Procedure

Thirty-one newly diagnosed ESFT patients were enrolled onto this phase II, single-arm, non-randomized protocol. Courses 1, 2 and 4 consisted of cyclophosphamide 4.2 g/m2, doxorubicin 75 mg/m2, and vincristine 2 mg/m2 (CDV). Cycles 3 and 5 consisted of ifosfamide 9 g/m2 and etoposide 500 mg/m2 (IE). Course 5 ifosfamide was 14 g/m2 if necrosis was <90%.

Results

Twenty-four patients had loco-regional disease and seven had metastases. The 4-year event-free survival (EFS) rate for patients with localized tumors is 83% and overall survival (OS) is 92%. The 3-year EFS rate for patients with distant metastases is 28% and OS rate is 42%. EWS-FLI1 fusion genes were detected in 17 cases (74%) and EWS-ERG in six cases (26%). Type 1 EWS-FLI1 variant was present in 6/7 metastatic patients and 3/16 loco-regional cases (P = 0.001). None of the patients experienced tumor progression before remission. All relapses occurred within 2 years from the end of treatment and local relapses (n = 3) happened in patients who did not receive radiation therapy. No secondary malignancies have been observed, median follow-up of 4.3 years for surviving patients.

Conclusions

In this pilot study, the mP6 protocol produced a complete remission rate of 83% at 4 years in non-metastatic ESFT reducing the risk of secondary malignancies. Pediatr Blood Cancer 2011;57:69–75. © 2011 Wiley-Liss, Inc.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

Ewing sarcoma family of tumors (ESFT) is the second most common bone malignancy in children, accounting for approximately 40% of all bone cancers 1. ESFT is characterized by a specific balanced chromosomal translocation which fuses the amino-terminal domain of the EWSR1 gene or, in rare cases, the TLS/FUS gene, to the DNA-binding domain of one of five ETS genes 2. The transcripts resulting from these fusion genes can be detected using the reverse transcriptase-polymerase chain reaction (RT-PCR) technique. RT-PCR provides a higher sensitivity than conventional cytological analysis to detect tumor cells in bone marrow (BM) and peripheral blood (PB). Previous studies have reported that among patients with local-regional ESFT, RT-PCR positivity of BM correlates with a high risk of adverse outcome and significantly poorer disease-free survival rates 3. Thus, RT-PCR analysis of BM might be useful to classify localized and metastatic patients at diagnosis.

Treatment of ESFT has improved over the last two decades with reported durable remissions in 50–70% of non-metastatic patients 4. In 1995, the group at MSKCC published the P6 protocol showing a successful induction of remission in patients with local-regional disease and good initial responses with dose-intensive and short-term chemotherapy in patients with distant metastases 5. A subsequent and extended outcome data on 68 patients (44 localized) with ESFT treated with the P6 protocol showed a 4-year EFS and OS for patients with localized disease of 82% and 89%, respectively. Patients with detectable metastatic disease at diagnosis had a significantly worse prognosis, with a 4-year EFS rate of 12% and OS rate of 17.8% 6.

In 1998, the MSKCC group reported a cumulative incidence of therapy related acute myelogenous leukemias (t-AML) and myelodysplastic syndromes (MDS) at 40 months of 8% in survivors of the P6 protocol 7. The latest report from the MSKCC group 6 details three patients experiencing secondary MDS/t-AML out of 44 non-metastatic patients, which makes a 7% incidence in the population with longest overall survival. This and other experiences suggested that repetitive use of high-dose alkylating agents given with topoisomerase-II inhibitors is strongly leukemogenic, even with modest cumulative doses of each drug. The two well-described kinds of t-AML/MDS occurred, namely, those associated with topoisomerase-II inhibitors and marked by early emergence of t-AML with translocations of the MLL gene at chromosome band 11q23, and those associated with alkylating agents and marked by an MDS, whole or partial deletions of chromosomes 5 or 7, and a latency period of 2–8 years 8, 9.

In 2001, we modified the original P6 (hereby mP6) protocol by: (1) reducing the number of chemotherapy cycles down to five, three CDV and two IE, in order to decrease the risk of secondary tumors; (2) using higher doses of ifosfamide (2.8 g/m2/day instead of 1.8 g) post-surgery in cases with poor histological response; and (3) using dexrazoxane before doxorubicin to prevent early cardiotoxicity and therefore changed the 24 hr original administration of doxorubicin into 1 hr infusion. The main objective of the protocol was to reproduce a 4-year EFS of ≥80% for non-metastatic ESFT patients while reducing the risk of secondary malignancies.

The purpose of this pilot study is to report the institutional experience accumulated since 2002 with the mP6 regimen in pediatric patients with ESFT.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

Patients

From January 2002 to August 2009, 31 newly diagnosed, previously untreated ESFT patients were enrolled onto this phase II, single-arm, non-randomized evaluation of the mP6 protocol. All patients diagnosed during the enrolment period were eligible. Histologic and immunohistochemical evaluation of primary tumors were consistent with the diagnosis of ESFT in all cases. Molecular diagnosis was performed before patient recruitment. The mP6 protocol was approved by the HSJDBCN Institutional Review Board, and signed informed consent was obtained from all patients or legal guardians before initiation of treatment. Pre-treatment extent of disease evaluation for each patient included computed tomography (CT) and/or magnetic resonance imaging of the primary site; CT of the chest (and/or abdomen and pelvis, when appropriate); a technetium-99m bone scan; histologic and molecular evaluation of 2–4 bone marrow aspirates, and histologic and immunohistochemical analysis of two biopsies from iliac crest sites. Patients with local-regional disease had tumors confined to the region of the primary site of disease. Patients with distant metastases had radiographic, pathologic and/or molecular biology evidence of tumor at any site distant from the primary site.

Molecular Analysis

Tumors were analyzed by RT-PCR and sequencing when a frozen fragment was available and by fluorescence in situ hybridization (FISH) in the rest of cases. FISH was carried out as previously described 10.

RNA was isolated with TriReagent (Sigma, St. Louis, MO), according to manufacturer's instructions. cDNA synthesis was performed with 1 µg total RNA in the presence of 2.5 µM random hexamers and M-MLV. Aliquots of cDNA were simultaneously amplified with primers for the control gene TATA-binding protein (TBP) and with three different primer pairs to analyze ESFT fusion genes: one to detect both EWS-FLI1 and EWS-ERG fusions, one to detect specifically EWS-FLI1 fusions, and a third primer pair specific for EWS-ERG fusions (Supplemental Table I). Cell lines A673, SK-N-ES1, A4573, and TTC466 were used as positive controls for type 1, type 2, type 3 EWS-FLI1, and EWS-ERG, respectively. Non-template controls were included in each run. Seven microliters of each PCR product were run in 2% agarose gels to check amplicon sizes. The rest was purified and sequenced in an Applied Biosystems 3130 Genetic Analyzer.

Two to four bone marrow (BM) aspirates were collected from each patient in EDTA tubes and processed as individual samples. Mononuclear cells were isolated by density gradient upon receipt. They were analyzed by qRT-PCR in patients whose primary tumor expressed type 1 or type 2 EWS-FLI1 transcripts. The rest of BMs were analyzed by RT-PCR and gel electrophoresis, using the same primer pairs and conditions described above. When the fusion gene of a primary tumor was unknown, both qRT-PCR and conventional RT-PCR were performed.

Cell lines were serially diluted in normal BM mononuclear cells to estimate bone marrow infiltration. RNA of serially diluted cell lines was isolated and cDNA synthesis was performed in parallel with bone marrow aspirate samples. Aliquots of these cDNAs were amplified with primers and probes for EWS-FLI1 transcripts (5′-AGC CAA GCT CCA AGT CAA TAT AG-3′, 5′-TCC TCT TCT GAC TGA GTC ATA AG-3′ and probe 5′-FAM-AAC AGA GCA GCA GCT ACG GGC AGC A-TAMRA-3′) and for abl as control gene 11.

mP6 Therapy

The mP6 protocol consists of five cycles of chemotherapy. Two days of high-dose cyclophosphamide and 3 days of 1-hr infusion doxorubicin and vincristine (CDV) were given during cycles 1, 2, and 4. The CDV courses consisted of cyclophosphamide 4.2 g/m2, doxorubicin 75 mg/m2, and vincristine 2 mg/m2. Cycles 3 and 5 consisted of ifosfamide and etoposide (IE) given as 1-hr infusions on five consecutive days. IE courses: ifosfamide 9 g/m2 and etoposide 500 mg/m2. Course 5 ifosfamide was 14 g/m2 (2.8 g/m2/day × 5) if necrosis was <90%. Cyclophosphamide and ifosfamide were given with vigorous hydration, anti-emetics, and an equivalent daily dose of mesna administered as a continuous 24-hr intravenous infusion. Each cycle begins shortly after the patient's post-nadir neutrophil count reached 500/µl and the platelet count reached 75,000/µl. After each cycle of chemotherapy, granulocyte colony-stimulating factor was used to shorten the duration of neutropenia. Surgical resection was scheduled after recovery from course 3 and radiotherapy (RT) was scheduled after completion of all chemotherapy. Gross total resection (GTR) is defined as the surgical excision of the entire visible tumor, regardless of the presence of microscopic disease at the margins. In general, 40–45 Gy was administered for microscopic margins and 50–56 Gy was administered for gross disease. All patients underwent GTR, RT, or both.

Patients received periodic extent of disease evaluations. These evaluations included CT or magnetic resonance imaging of the primary site; CT of the chest, abdomen, and pelvis; and 2–4 bone marrow aspirates.

Whenever possible, a GTR was performed after cycle 3 of chemotherapy and the specimens obtained were evaluated for degree of necrosis. The anti-tumor effect of the chemotherapy is defined, for the primary tumor only, as follows: complete response (CR) when there was no detectable tumor; very good partial response (VGPR), when more than 90% of the tumor was necrotic; partial response, when more than 50% of the tumor was necrotic; and patients were considered to have stable disease when less than 50% of the tumor was necrotic. Progressive disease was defined as any radiographic evidence of a significant (≥25%) increase in tumor size or appearance of new metastatic lesions. Patients who underwent surgical resections at diagnosis and patients with unresectable primary tumors were not assessed for histologic response.

Statistical Methods

Event-free survival (EFS) and overall survival (OS) were estimated by the methods of Kaplan–Meier 12. An event was defined as relapse or progression of disease, a treatment-related secondary neoplasm, or as death at any time after the initiation of therapy. An event affecting the OS was defined as death from any cause. The log-rank test was used to evaluate the significance of differences in EFS and OS between groups of patients 13. The Fisher exact test was used to investigate correlations between variables. The statistical significance of several prognostic factors (primary tumor site and volume, presence of metastases, and type of fusion gene) was determined by univariate analyses.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

From January 2002 to August 2009, 31 patients with newly diagnosed ESFT were enrolled onto the mP6 protocol. Patient's characteristics are listed in Table I. Twenty-four patients (77%) had local-regional disease and seven patients (22%) had distant metastases at diagnosis. Nineteen patients (61%) were male, and 12 patients (39%) were female. The median age at diagnosis was 9.3 years for all patients (range, 5 months to 17 years). The EFS for all patients is 69% (95% CI, 54–83% at 4 years) and the OS is 78% (95% CI, 66–90% at 4 years), as shown in Figure 1.

Table I. Clinical and Biological Characteristics of the Patients
Pt#AgeFusion genePrimary siteTumor size (cm3)MetastasesBM analysisRXSurgery%RTConsol.RelapseStatusF/up
  1. Pt#: patient number. Age at diagnosis: y, years; m, months. Fusion gene: FISH, diagnosis done by fluorescence in situ hybridization on paraffin tissue and therefore fusion type is unknown. Primary site: CNS, central nervous system. Metastases: BM, bone marrow. Bone marrow (BM) analysis: Dx: diagnosis; F/up: follow-up; NA: not available. Radiological (RX response): PR, partial response; CR: complete response. Surgery: DX, diagnosis; GTR, gross total resection; TX, therapy. %: percentage of necrosis in the second-look specimen. RT, radiation therapy; brachy, brachytherapy. Consol.: Consolidation therapy. G/D, gemcitabine + docetaxel protocol. ABMT: autologous bone marrow transplantation. Status: DOD, dead of disease; NED: non-evidence of disease; AWD = alive with disease. F/up: in months.

113 yEWS-FLI1 type 1Astragalous<200LungsNegativePRAmputation at Dx Yes LungsDOD35 m
25 yEWS-FLI1 type 1Vertebral body<200BMPositive at DxCRGTR100YesG/DBM and BoneDOD49 m
38 yEWS-FLI1 type 1Rib<200Lungs, liver, BMPositive at Dx and F/upCRGTR100YesG/DBone, BM, liverDOD20 m
48 yEWS-FLI1 type 1Pelvic bones<200Lungs, BMPositive at DxPRGTR4LungG/DNoNED27 m
511 yEWS-FLI1 (10-5)Vertebral body and rib<200LungsNegativePRGTR100YesG/DNoNED10 m
65 mEWS-FLI1 type 1Femur<200BMNAPRGTR95noABMTLocalNED96 m
74 yEWS-FLI1 type 1Femur<200Lungs and BMPositive at Dx and F/upPRGTR93noABMTLocal and BMDOD23 m
810 mEWS-FLI1 type 2Subcutaneous tissue<200NoNegativeCRGTR at Dx Brachy NoNED24 m
917 yEWS-FLI1 type 1Subcutaneous tissue<200NoNegativeCRGTR at Dx Yes NoNED60 m
103 yEWS-ERG (7-7)CNS<200NoNegativeCRGTR at Dx Yes NoNED48 m
1115 yEWS-FLI1 type 1Femur<200NoNegativeCRGTR Yes NoNED24 m
1213 yEWS-FLI1 (9-7)Femur>200NoNegativePRGTR80Yes NoNED66 m
1311 yEWS-FLI1 type 1Humerus<200NoNegativeCRGTR100Yes NoNED54 m
1411 yEWS-ERG (7-9)Tibia<200NoNegativePRGTR Yes NoNED48 m
1515 yFISHChest wall-epidural>200NoNAPRPartial resection95YesABMTNoNED96 m
168 yEWS-FLI1 (7-7)Chest wall-epidural>200NoNegativeCRGTR100Yes NoNED42 m
176 yEWS-ERG (10-6)Chest wall>200NoPositive at F/upCRGTR100Yes Lungs and BMDOD26 m
186 mFISHChest wall>200NoNegativeCRGTR at Dx no LocalNED15 m
1913 yEWS-ERG (7-6)Vertebral body-epidural<200NoNegativePRGTR100Yes NoNED10 m
209 yEWS-ERG (7-6)Chest wall<200NoNegativePRGTR at Dx Yes NoNED9 m
218 yEWS-ERG (7-6)Femur<200NoNegativePRGTR70Yes NoNED8 m
2214 yFISHTibia<200NoNAPRGTR25YesABMTNoNED96 m
2317 yFISHEpidural<200NoNACRGTR at DX YesABMTNoNED96 m
249 yFISHChest wall>200NoNAPRGTR100YesABMTNoNED84 m
2510 yFISHVertebral body-epidural<200NoNegativeCRGTR100Yes NoNED72 m
2612 yEWS-FLI1 type 2Pelvis<200NoNegativeCRGTR90Yes LungsAWD54 m
275 yEWS-FLI1 type 2Pelvis>200NoNegativePRGTR end of TX100Yes NoNED17 m
2812 yFISHPelvis>200NoNACRGTR100Yes LungsDOD27 m
299 yFISHPelvis>200NoNAPR  Yes NoNED96 m
3015 yEWS-FLI1 (7-7)Pelvis<200NoNegativeCRGTR100Yes NoNED36 m
318 yEWS-FLI1 type 2Pelvis<200NoNAPR  YesABMTNoNED96 m
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Figure 1. Overall and EFS survival for all patients.

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Molecular Analysis

Eight tumors were analyzed by FISH and 23 by RT-PCR. Rearrangement of the EWS gene was observed in the eight tumors examined by FISH. Among cases analyzed by RT-PCR, EWS-FLI1 fusion genes were detected in 17/23 cases (73.9%) and EWS-ERG in 6/23 cases (26%). Among EWS-FLI1 fusions, 9/17 were type 1 (52.9%), 4/17 were type 2 (23.5%), and other fusions were detected in four patients (23.5%) (Table I). An example of RT-PCR analysis performed in a tumor with type 1 EWS-FLI1 expression is shown in Figure 2A.

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Figure 2. Example of molecular analysis by RT-PCR (A) of EWS fusion genes (EWS) and housekeeping gene TATA-binding protein (TBP). In lane 1: A673 (type 1 EWS-FLI1); lane 2: SK-ES-1 (type 2 EWS-FLI1); lane 3: A4573 (type 3 EWS-FLI1); lane 4: tumor #4 (type 1 EWS-FLI1); and 5: non-template control. Sensitivity of qRT-PCR was determined by 10-fold serial dilutions of A673 cells in normal mononuclear cells (B): X-axis: log10 dilutions; Y-axis: log10 of normalized expression values (2−ddCT). Dilution 1:105 has been used as calibrator sample (normalized expression value = 1; log101 = 0).

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Cytologic examination of bone marrow specimens was conducted in all cases at diagnosis and by molecular analysis in 23 patients. During follow-up, samples were examined by either cytologic or molecular analysis. Sensitivity of qRT-PCR was 1:105 (Fig. 2B) and sensitivity of conventional RT-PCR was 1:104 (not shown). Four of the 23 patients (17.4%) examined by RT-PCR analysis were positive at diagnosis. In three of these patients, bone marrow infiltration was only detected by qRT-PCR. The fourth patient was initially diagnosed at another hospital, where molecular analysis was not available, but bone marrow involvement was important enough to be diagnosed by cytologic examination. He was then referred to our center, where qRT-PCR was also positive.

A total of 5/23 patients (21.7%) had a BM positive RT-PCR analysis at any time point. Among 19 samples with adequate material for both molecular analysis and cytology, morphologic assessment did not detect the presence of ESFT cells in 13/19 samples (68%) with positive RT-PCR.

Of note, 6 of the 7 metastatic patients had type 1 EWS-FLI1 fusion, whereas 4 of the 16 loco-regional cases showed type 1 EWS-FLI1 fusion (P = 0.001). All the EWS-ERG and type 2 EWS-FLI1 fusion genes were detected in loco-regional cases.

Non-Metastatic Disease

Twenty-four patients had no evidence of clinical, radiographic, or micrometastatic disease. The median age at diagnosis was 10.47 years (range, 6 months to 17 years). Six patients had their primary tumor arising in the appendicular skeleton, eight in the axial skeleton (six pelvic tumors and two in the vertebral bodies), two in the subcutaneous tissue, two in the epidural components of the CNS and six in the chest wall. The median follow-up time for surviving patients is 4.3 years from the initiation of therapy (range, 8 months to 8 years). The 4-year EFS is 83% (95% CI, 71–100%) and OS 92% (95% CI, 74–100%) (Fig. 3). No patients with local-regional disease experienced progression while receiving therapy.

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Figure 3. Overall survival based on the presence of metastatic disease at diagnosis. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

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Four relapses occurred 12, 13, 20, and 24 months from diagnosis. Two of these patients had their primary tumor in the chest wall and the pelvis. The median time to relapse was 17 months. All four patients had GTR and completed therapy achieving a complete response. Three relapsed with systemic disease and one had a local relapse, the only patient of the 24 who did not receive RT. This patient (pt#18, Table I) had GTR as a diagnostic procedure and no radiation because of her age at the time of consolidation (9 months), and the radiation field involved (left chest wall).

Doses of radiation ranged from 42 to 54 Gy. One patient (pt#8, Table I) with a subcutaneous gluteal primary tumor had a complete surgical resection at diagnosis and received brachytherapy after completion of chemotherapy because of his age at the time of consolidation (18 months) and involved radiation field (pelvic floor and scrotum).

Twenty-two patients (92%) underwent GTR a median of 3 months after the initiation of therapy. Six patients (two each with subcutaneous, epidural, and chest wall primary tumors) had GTR as a diagnostic procedure before the mP6 protocol. Five patients with disease not amenable to GTR (n = 3) or with poorly responsive disease (n = 2), received myeloablative chemotherapy with autologous stem-cell rescue in addition to the mP6 protocol. None of them have relapsed. One of these patients (pt#25, Table I) developed a self-limited MDS which did not require therapy.

All four relapsed patients responded to second-line rescue regimens based on topotecan. One relapsed patient is still alive with disease and one is in second complete remission, 4.5 and 1.5 years, respectively, from diagnosis. Two patients (8%) died as a result of disease progression. None of the patients died as a result of therapy related complications.

Metastatic Disease

Seven patients had distant metastases at diagnosis (Table I). The median age at diagnosis was 7 years (range, 5 months to 13 years). This median age was inferior to that of non-metastatic patients (10.4 years), a difference statistically close to significance (P = 0.068). Two patients had distant metastases to only the lungs, whereas the remaining five patients had some combination of metastases to lung, bone marrow, liver and/or bone. Two of the five patients with metastasis to bone marrow would not have been discovered by cytomorphologic evaluation alone. They did as poorly as the clinically detectable metastatic patients.

Two patients received myeloablative chemotherapy with autologous stem-cell rescue in addition to the mP6 protocol. Since 2006, all metastatic patients received 1 year of maintenance chemotherapy according to the institutional regimen with gemcitabine and docetaxel, as previously reported 14.

Five of the seven patients relapsed, a median of 18 months from the initiation of therapy (range, 10–39 months). Four of the relapses were systemic and two local. One patient, relapsed only locally, was rescued and is the longest survivor. The two local relapses occurred, like in the loco-regional group, in patients who did not receive RT. The 3-year EFS is 28% (95% CI, 40–100%) and OS 42% (95% CI, 37–100%) (Fig. 3).

Patients with limited metastasis to lungs relapsed and died, whereas the patient who survived the longest period (8 years) presented with metastasis only to bone marrow. None of the patients experienced tumor progression before remission and during maintenance treatment. Four patients died as a result of disease progression. The median follow-up time for the three surviving patients is 44 months (range, 10–96 months).

Response to Therapy

Histologic evaluation of response to therapy was performed in the 20 patients who underwent a definitive surgical procedure after the third cycle of chemotherapy (14 with local-regional disease and 6 with distant metastases). Sixteen patients (80%) had a CR or VGPR; 11 of these 20 patients had local-regional disease, and five had distant metastases. Only four patients (20%) had either a partial response or stable disease (three of four patients with local-regional disease and one with distant metastases). No events were observed in these four patients.

The radiological response was evaluated by RECIST criteria after the first three cycles of mP6 chemotherapy and before surgery. It was either CR or PR for all assessable patients (Table I).

Prognostic Features

The detection of metastatic disease at diagnosis was the only significant prognostic factor (P = 0.003 for OS and P = 0.00038 for EFS). On univariate analysis, tumor volume (cut-off value 200 cm3), primary tumor site (axial vs. non-axial skeleton), and fusion gene type were not significant predictors of EFS or OS (Table II). Multivariate analysis could not be performed because of lack of events.

Table II. Univariate Analysis of Poor-Risk Features
 Log rank (Mantel–Cox)
nOSEFS
Volume
 <200 cm322  
 >200 cm390.8520.96
Primary site
 Non-axial20  
 Axial110.8960.849
Gene fusion
 Type 111  
 Non-type 1120.1820.187
Metastases
 No24  
 Yes70.0030.00038

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

The MSKCC P6 protocol, a short-duration and dose-intensified treatment plan, produced excellent long-term disease-free survival and OS rates in patients with local-regional ESFT. Nevertheless, the increased rate of secondary leukemias precluded further intensification and called for modifications. In order to minimize the risk of secondary malignancies, we modified the P6 protocol reducing the total dose of alkylating agents and etoposide, adjusting the dosages of chemo therapy and radiation therapy according to the histologic response, and keeping the rapid surgery after three cycles of chemotherapy. This protocol produced similar survival rates for non-metastatic pediatric ESFT than those achieved with the original P6 protocol.

A low risk (0.4–2.2%) of secondary neoplasias was reported for patients diagnosed with ESFT and treated with moderate-dose combination chemotherapy regimens 4, 15. However, in recent years, the use of protocols that included intensification of alkylators and topoisomerase-II inhibitors has resulted in a significant increase in the incidence of t-AML/MDS 4, 7, 16. There are different explanations on what is the most important risk factor that predispose to secondary leukemia. Many authors have related to both the increase in the total cumulative doses and dose intensification of alkylators and topoisomerase-II inhibitors. 8, 9, 17 A report 18 from COG, however, showed in a randomized controlled clinical trial in which one regimen had a higher dose intensity of alkylating agents than the other, that there was no difference in the frequency of secondary leukemia observed. From the COG group is also the experience of higher incidence of secondary leukemia for the highly intensified regimen C in the INT-0091 trial, with a cumulative incidence of secondary leukemia of 11% at 5 years 18. The difference as compared to the intensified regimen in other protocols was the higher dose rate and cumulative dose of doxorubicin. Overall, the COG studies suggest that the main risk factor for secondary leukemia would be the cumulative exposure and/or dose rate of doxorubicin rather than dose intensification of alkylating agents alone.

With the mP6 protocol we reduced the cumulative doses of alkylating agents and topoisomerase-II inhibitors by 28% while maintaining upfront dose intensity. As a result, with a median follow-up time of 4.3 years for surviving patients, only one MDS occurred (cumulative incidence of <1%). Similar results have recently been published for other poor-prognosis pediatric solid tumors. For high-risk neuroblastoma patients, reducing the number of dose-intensive induction cycles significantly decreased the risk of secondary leukemia yielding a cumulative incidence of 2% 19.

In the mP6 protocol, we followed the same local control guidelines as the original P6 protocol including early surgery. One theoretical advantage of dose-intensified chemotherapy upfront is the induction of a more rapid response, allowing for early and effective local control. Previous data indicate that histologic response to induction chemotherapy may play a role in predicting local outcome with surgical therapy 20, 21. In our cohort, >90% of necrosis was observed in 80% of evaluable patients after the first three cycles of chemotherapy, a factor that likely contributed to the high EFS and OS rates observed. Three local relapses occurred (9.6% local failure rate). Of note, these three cases were the only patients who did not receive RT. According to our results, in the setting of this short and intense chemotherapy scheme, early surgery would be insufficient and adding RT is required to achieve good local control.

The presence of metastases at diagnosis is the most significant prognostic factor in patients with ESFT 4. Thus, given that RT-PCR provides a higher sensitivity to detect BM metastases than cytologic examination alone, molecular analysis appears as a potentially relevant strategy to correctly stratify patients. Although the present study analyzes a very reduced cohort that not allows to derive statistically significant conclusions, patients with clinically localized disease and BM micrometastases had a poor outcome. Furthermore, the observation that three of the five patients with BM micrometastases who relapsed had good local response to treatment would indicate that their adverse evolution is linked to the progression of micrometastases rather than to poor local control.

In summary, in this small pilot study, we report a high EFS rate of non-metastatic pediatric ESFT after treatment with the mP6 protocol. There have been no late events in these patients with local-regional disease, and the survival rates, like in the original cohort of P6 patients, seem to be durable. Moreover, none of these patients have developed secondary malignancies, with a median follow-up of 4.3 years for surviving patients. Thus, the mP6 protocol successfully reproduces the favorable disease-free survival rates of the original P6 protocol while reducing the risks associated with exposure to chemotherapy. However, this protocol does not improve the outcome of patients with metastatic disease and novel therapies need to be added for the successful treatment of this subgroup of cases.

Acknowledgements

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

The authors thank all the nurses who take care of the oncology patients at HSJDBCN and the surgical oncology, radiology, pharmacy, pathology, rehabilitation, radiotherapy, support and palliative care teams for their contributions. Statistical support by Raquel Iniesta (Fundació Sant Joan de Déu, ISCIII CA08/00151).

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information
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    Delattre O, Zucman J, Plougastel B, et al. Gene fusion with an ETS DNA-binding domain caused by chromosome translocation in human tumours. Nature 1992; 359: 162165.
  • 3
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Supporting Information

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. Acknowledgements
  8. REFERENCES
  9. Supporting Information

Additional Supporting Information may be found in the online version of this article.

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pbc_22813_sm_SuppTable1.doc28KSupplementary Table 1

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