Immunomagnetic purging of Ewing's sarcoma from blood and bone marrow: quantitation by real-time polymerase chain reaction

Exploiting Signaling Pathways and Immune Targets Beyond the Standard of Care for Ewing Sarcoma

Ewing sarcoma (ES) family of tumors includes bone and soft tissue tumors that are often characterized by a specific translocation between chromosome 11 and 22, resulting in the EWS-FLI1 fusion gene. With the advent of multi-modality treatment including cytotoxic chemotherapy, surgery, and radiation therapy, the prognosis for patients with ES has substantially improved. However, a therapeutic plateau is now reached for both localized and metastatic disease over the last two decades. Burdened by the toxicity limits associated with the current frontline systemic therapy, there is an urgent need for novel targeted therapeutic strategies. In this review, we discuss the current treatment paradigm of ES, and explore preclinical evidence and emerging treatments directed at tumor signaling pathways and immune targets.

Adjuvant Immunotherapy to Improve Outcome in High-Risk Pediatric Sarcomas

PURPOSE

Patients with metastatic or relapsed pediatric sarcomas receive cytotoxic regimens that induce high remission rates associated with profound lymphocyte depletion, but ultimately few survive long term. We administered adjuvant immunotherapy to patients with metastatic and recurrent pediatric sarcomas in an effort to improve outcomes.

EXPERIMENTAL DESIGN

Mononuclear cells were collected via apheresis, and tumor lysate was acquired via percutaneous biopsy at enrollment. Participants received standard antineoplastic therapy, followed by autologous lymphocytes, tumor lysate/keyhole limpet hemocyanin-pulsed dendritic cell vaccinations ± recombinant human IL7. Primary outcomes were toxicity and vaccine responses. Secondary outcomes were immune reconstitution, event-free survival, and overall survival (OS).

RESULTS

Forty-three patients enrolled and 29 received immunotherapy. The regimen was well tolerated. Intent-to-treat analysis demonstrated 5-year OS of 51% with significant differences based upon histologic group (63% vs. 0% for Ewing/rhabdomyosarcoma vs. other sarcomas) and response to standard therapy (74% no residual disease vs. 0% residual disease). Five-year intent-to-treat OS of patients with newly diagnosed metastatic Ewing/rhabdomyosarcoma was 77%, higher than previously reported in this population and higher than observed in a similar group treated with an earlier adjuvant immunotherapy regimen (25% 5-year OS). T-cell responses to autologous tumor lysate were identified in 62% of immunotherapy recipients, and survival was higher in those patients (73% 5-year OS with vs. 37% without immune response, P = 0.017). Immune reconstitution, measured by CD4 count recovery, was significantly enhanced in subjects treated with recombinant human IL7.

CONCLUSIONS

Adjuvant immunotherapy may improve survival in patients with metastatic pediatric sarcoma. Clin Cancer Res; 22(13); 3182-91. ©2016 AACR.

Assessment of minimal residual disease in ewing sarcoma

Advances in molecular pathology now allow for identification of rare tumor cells in cancer patients. Identification of this minimal residual disease is particularly relevant for Ewing sarcoma, given the potential for recurrence even after complete remission is achieved. Using RT-PCR to detect specific tumor-associated fusion transcripts, otherwise occult tumor cells are found in blood or bone marrow in 20–30% of Ewing sarcoma patients, and their presence is associated with inferior outcomes. Although RT-PCR has excellent sensitivity and specificity for identifying tumor cells, technical challenges may limit its widespread applicability. The use of flow cytometry to identify tumor-specific antigens is a recently described method that may circumvent these difficulties. In this manuscript, we compare the advantages and drawbacks of these approaches, present data on a third method using fluorescent in situ hybridization, and discuss issues affecting the further development of these strategies.

A pilot study of consolidative immunotherapy in patients with high-risk pediatric sarcomas

PURPOSE

Patients with metastatic or recurrent Ewing's sarcoma family of tumors and alveolar rhabdomyosarcoma have <25% 5-year survival in most studies. This study administered a novel immunotherapy regimen aimed at consolidating remission in these patients.

EXPERIMENTAL DESIGN

Fifty-two patients with translocation positive, recurrent, or metastatic Ewing's sarcoma family of tumors or alveolar rhabdomyosarcoma underwent prechemotherapy cell harvest via apheresis for potential receipt of immunotherapy. Following completion of standard multimodal therapy, 30 patients ultimately initiated immunotherapy and were sequentially assigned to three cohorts. All cohorts received autologous T cells, influenza vaccinations, and dendritic cells pulsed with peptides derived from tumor-specific translocation breakpoints and E7, a peptide known to bind HLA-A2. Cohort 1 received moderate-dose recombinant human interleukin-2 (rhIL-2), cohort 2 received low-dose rhIL-2, and cohort 3 did not receive rhIL-2.

RESULTS

All immunotherapy recipients generated influenza-specific immune responses, whereas immune responses to the translocation breakpoint peptides occurred in 39%, and only 25% of HLA-A2(+) patients developed E7-specific responses. Toxicity was minimal. Intention-to-treat analysis revealed a 31% 5-year overall survival for all patients apheresed (median potential follow-up 7.3 years) with a 43% 5-year overall survival for patients initiating immunotherapy.

CONCLUSIONS

Consolidative immunotherapy is a scientifically based and clinically practical approach for integrating immunotherapy into a multimodal regimen for chemoresponsive cancer. Patients receiving immunotherapy experienced minimal toxicity and favorable survival. The robust influenza immune responses observed suggest that postchemotherapy immune incompetence will not fundamentally limit this approach. Future studies will seek to increase efficacy by using more immunogenic antigens and more potent dendritic cells.

Preclinical studies of treosulfan demonstrate potent activity in Ewing's sarcoma

OBJECTIVES

High-dose chemotherapy with the alkylating agent busulfan has been widely used in the treatment of patients with high-risk Ewing's sarcoma. Because of risks for toxicity, busulfan and radiotherapy can not be applied together, leading to the omission of one effective therapy component. Treosulfan is a derivative of busulfan which has a lower side effect profile than busulfan and which can be used together with radiotherapy. We investigated the effect of treosulfan in a panel of Ewing's sarcoma cell lines on cell survival, cell cycle and apoptosis in vitro and compared it to busulfan. Furthermore, the anti-tumor effect of treosulfan was studied in an orthotopic Ewing's sarcoma mouse xenograft model.

METHODS

Cell survival was measured by MTT assay and cell cycle analysis by flow cytometry. Apoptosis was analyzed via detection of DNA fragmentation, Hoechst 33258 staining, Annexin V, and cleavage of caspases-3 and 9. The effect of treosulfan and busulfan on primary tumor growth was assessed in Ewing's sarcoma xenografts in NOD/SCID mice (10 mice per group), pharmacokinetics of treosulfan were analyzed in nude mice.

RESULTS

Treosulfan inhibited cell growth to at least 70% in all cell lines at concentrations achievable in vivo. Treosulfan had a greater effect on the inhibition of cell growth at equivalent concentrations compared to busulfan. The growth inhibitory effect of treosulfan at low concentrations was mainly due to a G2 cell cycle arrest, whereas at higher concentrations it was due to apoptosis. Apoptosis was induced at lower concentrations compared to busulfan. In contrast to busulfan, treosulfan induced cell death in an apoptosis-deficient cell line at concentrations achievable in vivo. In mice, treosulfan suppressed tumor growth at dosages of 2,500 and 3,000 mg/kg. Pharmacokinetic exposures of treosulfan in mice were similar to previous reports in human patients. At maximal tolerated dosages treosulfan had a higher anti-tumor activity than busulfan.

CONCLUSIONS

Our results suggest that treosulfan has efficacy against Ewing's sarcoma cells in vitro and in mice. Therefore, controlled trials examining the role of treosulfan in patients with Ewing's sarcoma are warranted.

Does consolidation with autologous stem cell transplantation improve the outcome of children with metastatic or relapsed Ewing sarcoma?

OBJECTIVE

To evaluate the role of high-dose chemotherapy (HDC) and autologous stem cell transplantation (ASCT) as consolidation therapy for children with high-risk Ewing sarcoma (ES) treated at The Hospital for Sick Children (SickKids), Toronto.

PATIENTS AND METHODS

The charts of children treated for high-risk ES (defined as metastatic at diagnosis or relapsed) between 1990 and 2005 at SickKids were reviewed. Forty-five children were identified. Twenty patients received ASCT after induction with vincristine, doxorubicin, ifosfamide, cyclophosphamide, and etoposide. Patients with resectable tumor or lung metastases underwent surgery and those with non-resectable tumors were treated with irradiation. Twenty-five patients were treated with conventional chemotherapy (CC). Primary metastatic patients were treated with either a local protocol or as per POG 9354. At relapse, patients were treated with topotecan, cyclophosphamide, then ifosfamide, carboplatin, and etoposide (ICE). Local control was attained with surgery and/or irradiation.

RESULTS

Ten of the 20 patients treated with ASCT are alive (median follow-up 6 years), with 8/10 being in remission more than 5 years from diagnosis. The 3-year overall survival (OS) for ASCT was 59%, (95% CI: 36%, 81%) compared to 34% (14%, 53%) for patients treated with CC (P-value = 0.06). The 3-year event-free survival (EFS) for the ASCT was 39% (17%, 60%) compared to 32% (13%, 50%) in the CC group (P = 0.08).

CONCLUSION

ASCT appears to add some benefit to conventional multimodality therapy for children with high-risk ES. Randomized controlled trials are warranted.

Interferon-gamma sensitizes resistant Ewing's sarcoma cells to tumor necrosis factor apoptosis-inducing ligand-induced apoptosis by up-regulation of caspase-8 without altering chemosensitivity

Ewing's sarcoma cells are highly susceptible to apoptosis via tumor necrosis factor apoptosis-inducing ligand (TRAIL). Resistance to TRAIL has been linked to deficient expression of caspase-8 in vitro. Here, we report on the status of caspase-8 expression in tumors from patients with Ewing's sarcoma, the effect of interferon-gamma on caspase-8 expression and apoptosis, and the role of caspase-8 for TRAIL- and chemotherapy-mediated apoptosis in Ewing's sarcoma. Using immunohistochemistry, we show that low expression of caspase-8 is seen in about 24% of tumors. Interferon-gamma induces expression of caspase-8 at concentrations achievable in humans and sensitizes cells to TRAIL. Transfection of wild type but not mutant caspase-8 into caspase-8-deficient Ewing's sarcoma cells restored sensitivity to TRAIL, indicating that up-regulation of caspase-8 is sufficient to restore TRAIL sensitivity. In contrast, no role for caspase-8 in chemotherapy-induced apoptosis was identified, because 1) transfection of caspase-8 or treatment with interferon-gamma did not alter the sensitivity of caspase-8-deficient cells to chemotherapeutics, 2) application of chemotherapy did not select for caspase-8-negative tumor cells in vivo, and 3) the caspase-8 status of tumors did not influence survival after chemotherapy-based protocols. In conclusion, our data provide a rationale for the inclusion of interferon-gamma in upcoming clinical trials with TRAIL.

Ewing Sarcoma tumor cells express CD34: implications for autologous stem cell transplantation

The significance of tumor cell contamination in marrow and peripheral blood stem cell (PBSC) collections of patients with solid tumors remains controversial. Various methods have been developed to purge tumor cells from autologous stem cell products, including CD34+ selection. PBSC harvests from patients with Ewing family of tumors (EFT) were analyzed for contaminating tumor cells prior and after CD34+ selection using reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry (FC) analyzes. The expression of CD34 was studied by RT-PCR and FC in 14 primary tumors and 13 PBSC harvests, respectively. Tumor cells were identified in the harvests by both methods. In two patients, contaminating tumor cells were evident by RT-PCR only after positive selection. FC analysis confirmed a higher level of tumor cells in the CD34+ fraction. In an attempt to explore this finding, expression of CD34 was detected in 93% of primary tumors and 67% of contaminated harvests. As CD34 is expressed on EFT cells, these cells may be enriched following CD34+ selection of harvests, although the total number of tumor cells is reduced. Other methods of purging, rather than CD34+ selection, should be explored in patients with EFT undergoing autologous stem cell transplantation.

Radioimmunotargeting of human rhabdomyosarcoma using monoclonal antibody 8H9

Although metastatic rhabdomyosarcoma (RMS) is chemotherapy and radiotherapy responsive, few patients are cured. 8H9, a murine IgG(1) monoclonal antibody, recognizes a unique cell surface tumor antigen broadly distributed on neuroectodermal, epithelial, and mesenchymal tumors, including RMS. We now report on the in vitro characterization of radiolabeled 8H9 and its in vivo immunotargeting potential in mice with subcutaneous human RMS. Saturation-binding studies carried out to determine (125)I-8H9 affinity to the RMS cell line HTB82 demonstrated that (125)I-8H9 had a K(d) of 10.3nM with an estimated 115,000 binding sites on every HTB82 cell. (125)I-8H9 was retained on the cell surface without significant internalization. Biodistribution of (125)I-8H9 was studied in athymic mice bearing HTB82 xenografts. Following intravenous injection of 4.44MBq of (125)I-8H9, selective tumor uptake was evident 4 to 172 hours after injection. Average tumor uptake was 7.0 +/- 1.8, 11.5 +/- 3.9, 15.1 +/- 3.7, and 5.4 +/- 1.2% injected dose per gram at 4, 24, 48, and 172 hours, respectively. Mean tumor: tissue ratios were maximal at 172 hours (for lung, 4, kidney, 6, liver, 7, spleen, 11, femur, 14, muscle, 18, and brain, 48). Established RMS xenografts treated with a single injection of 18.5 MBq (131)I-8H9 were significantly suppressed compared to controls. Radiolabeled 8H9 effectively targeted RMS xenografts and may have a potential clinical role in radioimmunotherapy.

Current treatment for Ewing's sarcoma

Ewing's sarcoma is the second most common primary bone tumor seen in children and adolescents, and was described by James Ewing in 1921 as a diffuse endothelioma of bone. It is one of the differential diagnoses of pediatric small round blue cell tumors. This is not a single condition, but a group of morphologically and clinically closely related disorders with similar molecular biology -- expression of tumor-specific chimeric oncoproteins through balanced chromosomal translocations involving the EWS gene -- often referred to as the Ewing family of tumors. This includes Ewing's sarcoma of bone, extra-osseous Ewing's sarcoma, Askin tumor and peripheral neuroectodermal tumor. These are aggressive neoplasms with almost 25% of patients having clinically evident metastases at presentation. Ewing's sarcoma has therefore been considered as a systemic disease necessitating local as well as systemic treatment. An aggressive multidisciplinary approach has resulted in significant improvement in prognosis for patients with these tumors. Despite aggressive treatment, 20-40% of patients with localized disease and almost 80% of patients with metastatic disease at presentation succumb to the illness. Advances in understanding the molecular biology of these tumors will hopefully result in the development of novel treatment approaches. The aim of this article is to review the existing treatment methods and to highlight the more recent approaches to the treatment of this condition.

Megachemotherapy followed by autologous stem cell transplantation in children with Ewing's sarcoma

Twenty-one children with high-risk Ewing's tumor received high-dose chemotherapy with a PBSCT. Aim of the study was evaluation of efficiency and safety of this procedure. All but three patients have meta-static disease at presentation. There were 11 females and the median age at diagnosis was 12 yr (range 4.5-18 yr). Megachemotherapy consisted of melphalan 140 mg/m2/busulfan 16 mg/kg in 12 patients, melphalan 140 mg2/treosulfan 10.0 g/m2 in two patients and melphalan with other drugs in seven patients. Eight of 11 patients transplanted in CR survived with a median follow-up 24 month (range 14-60) and probability of 2-year OS is 0.68 and DFS is 0.63. There was no severe regimen-related toxicity in this group. Children transplanted without remission died: Two of them due to transplant related causes and eight had progression of disease in a median time 7 month after PBSCT. Megachemotherapy with PBSCT is a safe procedure in children with Ewing's sarcoma in remission. Autologos transplantation in children with metastatic Ewing's sarcoma seems to improve their outcome. Patients with Ewing's sarcoma, resistant to conventional therapy and with recurrent disease did not benefit from megachemotherapy. New approaches such as anti-tumor vaccination or using of imatinib are reasonable to introduce in patients with relapsed or resistant to therapy Ewing's tumor.

An inter-platform repeatability study investigating real-time amplification of plasmid DNA

Background

The wide variety of real-time amplification platforms currently available has determined that standardisation of DNA measurements is a fundamental aspect involved in the comparability of results.

Statistical analysis of the data arising from three different real-time platforms was conducted in order to assess inter-platform repeatability. On three consecutive days two PCR reaction mixes were used on each of the three amplification platforms – the LightCycler^®, ABI PRISM^® 7700 and Rotor Gene 3000™. Real-time PCR amplification using a fluorogenic 5' exonuclease assay was performed in triplicate on negative controls and DNA plasmid dilutions of 10⁸–10² copies to give a total of 24 reactions per PCR experiment.

Results

The results of the statistical analyses indicated that the platform with the most precise repeatability was the ABI PRISM^® 7700 when coupled with the FastStart PCR reaction mix. It was also found that there was no obvious relationship between plasmid copy number and repeatability. An ANOVA approach identified the factors that significantly affected the results, in descending order of magnitude, as: plasmid copy number, platform, PCR reaction mix and day (on which the experiment was performed).

Conclusion

In order to deliver useful, informative genetic tests, standardisation of real-time PCR detection platforms to provide repeatable, reliable results is warranted. In addition, a better understanding of inter-assay and intra-assay repeatability is required.

[Cell therapy for cancer treatment in children]

The cure rate for cancer in children is currently almost 75%. This rate has remained fairly constant over the past few years, which suggests that the limits of today's curative treatment potential have been reached. The development of cell therapy techniques opens up new therapeutic possibilities in paediatric oncology. Here, we deal both with a number of cell therapy techniques, which have already proved their efficacy in children, and other more innovative approaches, which require validation. Examples of the use of autologous and allogeneic cells are described. Clinical studies and their results, while often preliminary, are reported. The importance of well run clinical research, a clear and progressive legal framework and the necessary substantial economic support for the development of cell therapy are underlined.

Molecular genetics of pediatric soft tissue tumors: clinical application

The application of molecular genetics to pediatric soft tissue tumors has grown tremendously over the last decade. It has resulted in the identification of novel genes that have provided us with an increased understanding of oncogenesis. Furthermore, these findings have identified diagnostic and potentially prognostic factors for patient management. Molecular diagnostic techniques, such as reverse transcription PCR (RT-PCR) and fluorescence in situ hybridization (FISH), have become important tools for evaluating pediatric soft tissue tumors. By detecting characteristic fusion genes, these techniques have greatly increased the diagnostic accuracy of histopathological classification. One of the exciting promises of the development of these molecular techniques is their ability to detect micrometastasis and minimal residual disease. Monitoring of minimal residual disease in pediatric soft tissue tumors by quantitative RT-PCR may provide important prognostic information. Furthermore, the potential development of targeted therapy based on the understanding of the molecular pathology of a specific soft tissue tumor may complement existing treatments and improve disease outcome.

Increased risk of systemic relapses associated with bone marrow micrometastasis and circulating tumor cells in localized ewing tumor

PURPOSE

The presence of metastasis is a major prognostic factor in Ewing tumor (ET). The relapse pattern of patients with localized tumors has long indicated that cases with disseminated ET cells escape detection at diagnosis. ET cells are characterized by specific gene fusions that can be detected with high sensitivity and specificity by reverse transcriptase polymerase chain reaction (RT-PCR).

PATIENTS AND METHODS

RT-PCR targeting EWS-FLI-1 or EWS-ERG transcripts was used to search for occult tumor cells in peripheral blood (PB) and bone marrow (BM) at diagnosis in 172 patients with ET, and the prognostic significance of this parameter was assessed.

RESULTS

As we suggested previously in a smaller series of patients, RT-PCR positivity of the BM was correlated with a high risk of adverse outcome in the overall study population (P =.007). More interestingly, among patients with otherwise localized tumors, BM micrometastasis also predicted significantly poorer disease-free survival rates (P =.043). The presence of circulating tumor cells (CTC) was more frequently observed in patients with large tumors (P =.006). CTC were associated with a poor outcome among patients with clinically localized disease (P =.045). Patients with clinically localized disease and peripheral occult tumor cells as evidenced by BM and/or PB RT-PCR positivity had axial or proximal tumors and experienced relapses at a systemic rather than at a local level.

CONCLUSION

Patients with localized ET and BM micrometastasis or CTC are comparable to patients with metastases in terms of the localization of the primary tumor, outcome, and relapse pattern.

Disialoganglioside GD2 and a novel tumor antigen: potential targets for immunotherapy of desmoplastic small round cell tumor

BACKGROUND

Desmoplastic small round cell tumor (DSRCT) is an aggressive and often misdiagnosed neoplasm of children and young adults. It is chemotherapy-sensitive, yet patients often relapse off therapy because of residual microscopic disease at distant sites: peritoneum, liver, lymph node, and lung. Strategies directed at minimal residual disease (MRD) may be necessary for cure. Monoclonal antibodies selective for cell surface tumor-associated antigens may have utility for diagnosis and therapy of MRD, as recently demonstrated in advanced-stage neuroblastoma (JCO 16: 3053, 1998). We examined DSRCT samples for the expression of two tumor antigens that could serve as possible targets for antibody-based immunotherapeutic approaches.

PROCEDURES

Using immunohistochemistry, we studied the expression of two antigens: (1) G(D2) using antibody 3F8 and (2) a novel antigen using antibody 8H9 in a panel of 46 freshly frozen DSRCT. G(D2) is a disialoganglioside, which is widely expressed among neuroectodermal tumors as well as adult sarcomas. 8H9 recognizes a 58 kDa surface antigen expressed among neuroectodermal, mesenchymal, and epithelial tumors with restricted expression on normal tissues.

RESULTS

Thirty-two of 46 (70%) tumors were reactive with 3F8, and 44 of 46 (96%) with 8H9. Both G(D2) and the 58 kDa antigen were localized to tumor cell membrane and stroma. In general, immunoreactivity was stronger and more homogeneous with 8H9 than with 3F8. There was no correlation between expression of either antigen or clinical outcome.

CONCLUSIONS

G(D2) and the novel tumor antigen recognized by 8H9 are potential targets for immunodiagnosis and antibody-based therapy of DSRCT. Med Pediatr Oncol 2002;39:547-551.

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.

How effective is dose-intensive/myeloablative therapy against Ewing's sarcoma/primitive neuroectodermal tumor metastatic to bone or bone marrow? The Memorial Sloan-Kettering experience and a literature review

PURPOSE

Attempts to improve outcomes of patients with Ewing's sarcoma/primitive neuroectodermal tumor (ES/PNET) metastatic to bone/bone marrow (BM) have focused on chemotherapy dose intensification strategies. We now present results achieved with that approach, as carried out at Memorial Sloan-Kettering Cancer Center (MSKCC) and as reported in the literature.

PATIENTS AND METHODS

Twenty-one unselected MSKCC patients with newly diagnosed ES/PNET metastatic to bone/BM received the "P6" protocol which includes cycles of cyclophosphamide (4.2 g/m(2))/doxorubicin (75 mg/m(2))/vincristine and cycles of ifosfamide (9 g/m(2))/etoposide (500 mg/m(2)). Patients in complete/very good partial remission (CR/VGPR) after P6 received myeloablative therapy with either total-body irradiation (TBI) (hyperfractionated 15 Gy)/melphalan (180 mg/m(2)) or thiotepa (900 mg/m(2))/carboplatin (1,500 mg/m(2)). We reviewed the literature.

RESULTS

Only one MSKCC patient became a long-term event-free survivor; all but one relapse was in a distant site. Initial responses to P6 were CR/VGPR in 19 patients, but eight of them plus two others developed PD while receiving or shortly after completing P6. Eight patients were treated with TBI/melphalan: four relapsed 2 to 7 months after transplantation; two died early of toxicity; one died of pulmonary failure 17 months after transplantation (no evidence of ES/PNET); and one remains in CR at more than 7 years. The three patients treated with thiotepa/carboplatin relapsed 3 to 4 months after transplantation. All reports on large series of unselected patients with ES/PNET metastatic to bone/BM showed similarly unsatisfactory results. Poor outcome was seen with use of active agents for ES/PNET-cyclophosphamide, ifosfamide, doxorubicin, dactinomycin, vincristine, etoposide - at standard dosages for prolonged periods of time and at higher dosages in intensive regimens for short or prolonged periods of time. No improvements in event-free survival rates occurred with successive cooperative group or large single-institutional studies that used increasingly aggressive chemotherapeutic approaches. Inclusion of ifosfamide with or without etoposide made no difference nor did consolidation of remission with myeloablative chemoradiotherapy. Secondary leukemia emerged as a major risk with dose-intensive regimens.

CONCLUSION

The MSKCC experience and findings reported in the literature suggest that dose-intensive use of the chemotherapy agents with established activity against ES/PNET is reaching its efficacy and toxicity limits. A major impact on prognosis awaits the development of entirely novel therapies.