In vivo cytoreduction studies and cell sorting--enhanced tumor-cell detection in high-risk neuroblastoma patients: implications for leukapheresis strategies

28 years of high-dose therapy and SCT for neuroblastoma in Europe: lessons from more than 4000 procedures

Between 1978 and 2006, the European Group for Blood and Marrow Transplantation registered 4098 high-dose therapy (HDT) procedures followed by stem cell rescue (SCR) (3974 autologous/124 allogeneic) in patients with neuroblastoma. The 5-year rates for overall (OS) and event-free survival are 37 and 32%, respectively. The median age at diagnosis is 3.9 years (0.3-62 years) with 76 patients older than 18 years. Patients above 10 years carry a 2.5-fold higher risk. Younger patients cure significantly (<0.001) better with OS rates of 40 and 30% for age groups 2-4 years and 4-10 years, respectively. Their risks are about twofold higher than that of patients below 2 years with OS rates of 60%. The better the quality of remission status before HDT/SCT the better are the observed OS rates: 43% in CR1 (1199 patients) and 42% for CR2 (140 patients), and 36% for those in very good partial or partial remission (1413 patients) and 21% for those with sensitive relapse (134 patients). Patients reported with stable disease in first remission still had an OS rate of 30%. Multivariate analysis shows significantly better OS in the age group of less than 2 years (<0.0001), as well as a better quality of remission status before HDT/SCT (P<0.0001), with the use of peripheral stem cells (P=0.014), autologous SCT (P=0.031) and busulphan/melphalan HDT (P<0.001). Busulphan/melphalan HDT/SCT in first remission achieves an OS of 48%, while it is only 35% with other regimens (P<0.001), including melphalan alone, other melphalan-containing regimens, a variety of other drugs given as a single HDT as well as the addition of TBI or sequential HDT/SCT procedures. Further progress in the field may only be expected from large-scale international randomized trials.

Potential Application of ELAVL4 Real-Time Quantitative Reverse Transcription-PCR for Detection of Disseminated Neuroblastoma Cells

Background: Reliable detection of neuroblastoma cells in bone marrow (BM) is critical because BM involvement influences staging, risk assessment, and evaluation of therapeutic response in neuroblastoma patients. Standard cytomorphologic examination of BM aspirates is sensitive enough to detect single tumor cells. Consequently, more sensitive and specific detection methods are indispensable.

Methods: We used real-time quantitative reverse transcription-PCR (QPCR) of the tyrosine hydroxylase (TH), GD2 synthetase (GALGT), and embryonic lethal, abnormal vision, Drosophila-like 4 (ELAVL4) genes to detect disseminated neuroblastoma cells. We assessed assay sensitivity by addition experiments and then analyzed 97 neuroblastic tumor, BM, peripheral blood (PB), or peripheral blood stem cell (PBSC) samples from 30 patients. The QPCR results were compared with those of a standardized immunocytochemical assay.

Results: The molecular markers were highly expressed in all evaluated tumor samples. In addition, 32%, 11%, and 38% of all BM, PB, and PBSC samples scored positive for TH, GALGT, or ELAVL4, respectively. The TH and ELAVL4 assays could detect 1 neuroblastoma cell in 106 mononuclear cells. By contrast, the GALGT QPCR assay could detect 1 neuroblastoma cell in 104 mononuclear cells. We assessed the potential prognostic value of TH, GALGT, and ELAVL4 QPCR by analyzing subsequent samples from 3 patients with stage 4 disease. Preliminary results indicated that persistence of high ELAVL4 expression has prognostic value.

Conclusions: ELAVL4 QPCR can be used to detect residual neuroblastoma cells in clinical samples. However, combination of several molecular markers and screening techniques should be considered to ensure reliable detection of rare neuroblastoma cells.

Detection of residual neuroblastoma cells in bone marrow: comparison of flow cytometry with immunocytochemistry

BACKGROUND

Because the cytomorphologic examination of bone marrow (BM) aspirates appears not sensitive enough to detect residual neuroblastoma cells, two four-color flow cytometric assays using different combinations of CD9, CD81, CD56, CD45, and anti-GD2 were evaluated.

METHODS

The sensitivity of the flow cytometric assays was assessed by spiking experiments in normal peripheral blood samples. Twenty-eight BM samples, 12 biopsies, and 3 peripheral blood stem cell (PBSC) preparations from 22 patients with neuroblastoma were analyzed. The results were compared with those of an anti-GD2 immunocytochemical reference assay.

RESULTS

Flow cytometric and immunocytochemical analyses showed residual neuroblastoma cells in four BM samples. One PBSC preparation and 20 BM samples were negative for both assays. Four BM and two PBSC samples scored positive for the immunocytochemical assay but were negative for the flow cytometric tests. This was due to the limited number of cells that were flow cytometrically analyzed. A strong correlation between the flow cytometric and immunocytochemical tests was found (chi2 = 6.4, P = 0.011).

CONCLUSIONS

When an equal amount of cells is analyzed, the sensitivity of the flow cytometric assays is to be about 10 times lower than that of the immunocytochemical test. However, the flow cytometric assays can be used to screen for residual cells in clinical samples with a sensitivity of one neuroblastoma cell in 10(4) to 10(5) normal mononuclear cells. Flow cytometry is simple, quick, and cost effective compared with immunocytochemistry. In addition, the flow cytometric assays can be used to screen for residual neuroblastoma cells in case of a GD2-negative primary tumor. Therefore we recommend flow cytometry for the detection of residual neuroblastoma cells.

Detection of Neuroblastoma Cells in Bone Marrow and Peripheral Blood by Different Techniques

PURPOSE

Detection of metastatic tumor cells in bone marrow (BM) and peripheral blood (PB) of children with neuroblastoma is crucial for prognosis and planning of therapy. Aims of this large descriptive repeated survey were to evaluate the diagnostic accuracy of different techniques in diagnostic samples obtained at several disease course time points and to correlate positive results with patient clinical features and outcome.

EXPERIMENTAL DESIGN

BM aspirates, trephine biopsies, PB, and peripheral blood stem cell (PBSC) samples from Italian children with neuroblastoma were analyzed by morphological and histologic techniques, as well as by immunocytochemistry (IC) for disialoganglioside GD(2) and reverse transcription-PCRs (RT-PCRs) for tyrosine hydroxylase (TH) and pgp9.5 genes. The diagnostic odd ratio (DOR) was used to measure the accuracy of the different techniques.

RESULTS

A total of 2,247 evaluations were done on 561 BM, 265 PB, and 69 PBSC samples from 247 patients. IC showed the best accuracy. Whereas TH RT-PCR accuracy was satisfactory, that of pgp9.5 was very low. Positive results obtained by IC in BM and PB samples at diagnosis from stage 1, 2, and 3 patients correlated with unfavourable outcome. No correlation was found between positive results obtained by IC or TH RT-PCR in BM, PB, and PBSC samples from stage 4 patients and their outcome.

CONCLUSIONS

Because of its elevated diagnostic accuracy, IC may represent a useful adjunct to conventional morphological techniques, especially in view of its potential prognostic role in patients with localized disease. Longitudinal multicenter studies are warranted to definitely establish the clinical usefulness of TH RT-PCR.

Molecular Detection of Dopamine Decarboxylase Expression by Means of Reverse Transcriptase and Polymerase Chain Reaction in Bone Marrow and Peripheral Blood

A highly sensitive molecular method was used to evaluate the presence of dopamine decarboxylase (DDC) mRNA in the bone marrow and peripheral blood of patients with neuroblastoma (NB). DDC, like tyrosine hydroxylase (TH), is an enzyme involved in the catecholamine synthesis pathway and has recently been proposed as a specific marker of NB among pediatric malignancies. DDC transcript was detected in five of five NB cell lines, 10 of 10 NB primary tumors, 17 of 18 (94%) bone marrow samples, and 12 of 18 (66%) blood samples drawn at diagnosis in 18 patients affected by disseminated NB. In contrast, no PCR signal was found in 20 bone marrow samples obtained from patients with other malignancies or in eight of nine marrow and blood samples drawn from patients with localized NB (two stage 2 and seven stage 3). In addition, all marrow and blood samples obtained from NB patients at relapse revealed DDC mRNA. Furthermore, the percentage of DDC-positive samples was lower among the samples drawn from these patients during treatment. By comparison with conventional methods for disease evaluation, DDC transcript research can increase the sensitivity of NB cell detection in marrow and blood samples at diagnosis and during the treatment and follow-up of NB patients. These results suggest that finding DDC mRNA in NB patients could be a potential marker for minimal residual disease study.

Significance of molecular quantification of minimal residual disease in metastatic neuroblastoma

Molecular detection of tumor cells is the most sensitive approach to study residual disease in bone marrow (BM), peripheral blood (PB), and peripheral blood stem cell (PBSC) autografts from children with metastatic neuroblastoma (NB). We have developed a real-time PCR assay that allows the quantification of tyrosine hydroxylase (TH) mRNA, a tissue-specific marker of neuroblasts. We investigated a total of 165 BM, PB, and PBSC samples from 30 children over 1 year of age with stage IV NB and correlated the findings with disease status and patient survival. The levels of TH mRNA agreed well with clinical status and were significantly different across the groups that included samples obtained from patients at diagnosis, after three cycles of chemotherapy, in complete or very good partial remission and at relapse. We found that overall survival was significantly worse for patients with >1000 TH copies in BM after initial chemotherapy (p=0.0075). In 57% of cases, autologous PBSC harvests were found to be contaminated by neuroblasts, the level of TH >500 copies being associated with a decreased survival (p=0.003). In addition, molecular quantification enabled an estimation of tumor depletion in contaminated autografts using CD34 selection (median, 3 logs). In conclusion, quantification of minimal residual disease in metastatic NB using real-time RT-PCR for TH mRNA appears to be of potential clinical value. Further studies are needed to ascertain prognostic implications of molecular analysis of residual disease.

Quantitative analysis of tyrosine hydroxylase mRNA for sensitive detection of neuroblastoma cells in blood and bone marrow

BACKGROUND

Sensitive monitoring of minimal residual disease may improve the treatment of neuroblastoma in children. To detect and monitor neuroblastoma cells in blood and bone marrow, we developed a quantitative method for the analysis of tyrosine hydroxylase mRNA.

METHODS

We used real-time reverse transcription-PCR. The calibrator was constructed from a segment of tyrosine hydroxylase mRNA that included the target. Blood and bone marrow samples from 24 children with neuroblastoma and 1 child with ganglioneuroma were analyzed. Controls were blood samples from the cords of 40 babies, from 58 children 6 months to 15 years of age, and from 34 healthy adults, as well as from 12 children with other diseases.

RESULTS

The detection limit was approximately 70 transcripts/mL. All 144 blood controls were below this limit. At diagnosis, blood tyrosine hydroxylase mRNA was higher in children with widespread disease (stage 4/4S; n = 6; range, 203-46,000 transcripts/mL) than in patients with localized disease (stages 1-3; n = 6; </=83 transcripts/mL; P = 0.002). Bone marrow from all five children with localized disease had concentrations <72 transcripts/mL, whereas five of six stage 4 patients had increased concentrations (6,000-8,000,000 transcripts/mL; P <0.05). In nine children in whom tyrosine hydroxylase mRNA was measured repeatedly, the results corresponded to the clinical course.

CONCLUSION

Quantitative analysis of tyrosine hydroxylase mRNA in blood and bone marrow is reliable and easy to perform and may be used for upfront staging, prognostic assessment, and treatment monitoring of neuroblastoma.

Quantitation of GD2 synthase mRNA by real-time reverse transcription-polymerase chain reaction: utility in bone marrow purging of neuroblastoma by anti-GD2 antibody 3F8

BACKGROUND

Antigen ganglioside GD2 is expressed abundantly on neuroblastoma (NB) cells. Anti-GD2 monoclonal antibody (MoAb) 3F8 kills NB cells by complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity. Its utility in bone marrow (BM) purging is evaluated by a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay to quantify the mRNA of GD2 synthase, the key enzyme in GD2 synthesis.

METHODS

From 1990 to 1993, 10 patients with relapsed/refractory Stage 4 NB participated in a pilot study. In these patients, MoAb 3F8 was used to purge tumor cells from harvested BM that had 5% or less tumor content by immunofluorescence (IF). Subsequently, 31 Stage 4 NB patients who underwent treatment on the N7 protocol (1994-1999) had their BM, which was in remission, purged by 3F8 before (131)I-3F8 myeloablative radioimmunotherapy. GD2-positive tumor cells before and after purging were quantified by real-time quantitative RT-PCR of GD2 synthase.

RESULTS

GD2 positivity by IF was found before purging in six of eight patients in the pilot study. Five of six patients became negative postpurging. Of 31 patients on the N7 protocol, the more sensitive real-time quantitative RT-PCR detected GD2 synthase mRNA in the BM samples of 7 patients even though the prepurge BM samples were negative by histology and IF. Six of the seven BM samples became negative after 3F8 purging. Marker positivity before purging was statistically significant in predicting overall survival (P = 0.04), but not progression-free survival (P = 0.1). In vitro hematopoietic stem cell recovery and the median time to engraftment were acceptable.

CONCLUSION

Tumor cell depletion quantified by real-time RT-PCR demonstrated efficacy of MoAb 3F8 in BM purging.