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1.
The treatment of pediatric bone malignancies has undergone dramatic change in the past two decades. With the use of adjuvant chemotherapy, survival of patients with osteosarcoma and Ewing's sarcoma has greatly increased and most extremity lesions are now managed with an initial course of chemotherapy followed by limb-sparing surgery rather than amputation. Radiologists are called on not only to help diagnose and stage these tumors, but also to assess their extent, to determine response to preoperative chemotherapy, and to monitor patients for postoperative complications and recurrent disease. This article discusses imaging solutions to clinical issues that arise during the care of these children.  相似文献   

2.
PURPOSE: During recent years, more intensified systemic and local treatment regimens have increased the 5-year survival figures in localized Ewing's sarcoma to more than 60%. There is, however, concern about the risk of second malignancies (SM) in long-term survivors. We have analyzed the second malignancies in patients treated in the German Ewing's Sarcoma Studies CESS 81 and CESS 86. MATERIALS AND METHODS: From January 1981 through June 1991, 674 patients were registered in the two sequential multicentric Ewing's sarcoma trials CESS 81 (recruitment period 1981-1985) and CESS 86 (1986-1991). The systemic treatment in both studies consisted of a four-drug-regimen (VACA = vincristine, actinomycin D, cyclophosphamide, and adriamycin; or VAIA = vincristine, actinomycin D, ifosfamide, and adriamycin) and a total number of four courses, each lasting nine weeks, was recommended by the protocol. Local therapy in curative patients was either complete surgery (n = 162), surgery plus postoperative radiotherapy with 36-46Gy (n = 274), or definitive radiotherapy with 46-60Gy (n = 212). The median follow-up at the time of this analysis was 5.1 years, the maximum follow-up 16.5 years. RESULTS: The overall survival of all patients including metastatic patients was 55% after 5 years, 48% after 10 years, and 37% after 15 years. Eight out of 674 patients (1.2%) developed a SM. Five of these were acute myelogenic leukemias (n = 4) or MDS (n = 1), and three were sarcomas. The interval between diagnosis of Ewing's sarcoma and the diagnosis of the SM was 17-78 months for the four AMLs, 96 months for the MDS and 82-136 months for the three sarcomas. The cumulative risk of an SM was 0.7% after 5 years, 2.9% after 10 years, and 4.7% after 15 years. Out of five patients with AML/MDS, three died of rapid AML-progression, and two are living with disease. Local therapy (surgery vs. surgery plus postoperative irradiation vs. definitive radiotherapy) had no impact on the frequency of AML/MDS, but local therapy did influence the risk of secondary sarcomas. All three patients with secondary sarcomas had received radiotherapy; however, all three sarcomas were salvaged by subsequent treatment and are in clinical remission with a follow-up of 1 month, 4.3 years, and 7.5 years after the diagnosis of the secondary sarcoma. Thus far, SM contributed to less than 1 % (3/328) of all deaths in the CESS-studies. CONCLUSIONS: The risk of leukemia after treatment for Ewing's sarcoma is probably in the range of 2%. The risk of solid tumors also seems to be low within the first 10 years after treatment and remains in the range of 5 % after 15 years. In the CESS-studies, less than 1% of all deaths within the first 10 years after diagnosis were caused by SM. Effective salvage therapy for secondary sarcomas is feasible.  相似文献   

3.
In order to detect skeletal metastases in patients with Ewing's sarcoma, bone scanning is commonly used. However, little information is available about the scintigraphic aspects of the primary Ewing's sarcoma during non-surgical treatment and follow-up. We studied retrospectively the significance of bone scintigraphic findings at the primary tumor site of 58 patients with a Ewing's sarcoma. These patients had chemotherapy and radiotherapy. At presentation 53/58 patients showed an increased tracer uptake at the primary tumor site while 5 patients with a pelvic or sacral bone localization had a normal scan. Bone scans made during treatment and more than 2 years thereafter in the 32 eligible patients demonstrated three patterns. In 16 patients the hot spot disappeared and no local tumor recurrence was encountered. In the other 16 patients the high uptake at the primary tumor site either persisted or diminished first to a normal uptake after a median period of 18 months (range 12-36 months) and returned again to a high uptake within 6-12 months. In these patients local Ewing's sarcoma was still present in 13, while in the other 3 cases a benign disorder (fracture, ectopic bone formation) was the underlying cause. These findings suggest that in non-surgically treated Ewing's sarcoma persisting increased tracer uptake or its recurrence is highly suspicious for the presence of Ewing's sarcoma, while bone scans becoming negative and remaining so for more than 12 months suggest the absence of local tumor.  相似文献   

4.
The role of ifosfamide as first-line chemotherapy treatment of non metastatic Ewing's sarcoma of the extremity is still under discussion. The purpose of this paper is to report the results achieved in a neoadjuvant protocol (REN-3) in which ifosfamide, added to the conventional VACA regimen, was employed since the induction phase. Induction chemotherapy consisted of vincristine, cyclophosphamide, doxorubicin, actinomycin-D and ifosfamide. After local treatment, patients received the drugs used in the induction phase and etoposide. Between November 1991 and November 1994, 61 patients with non metastatic Ewing's sarcoma of the extremity were treated. Forty-nine patients underwent surgery and 73.5% of them had a good histologic response. At a median follow-up of 60 months (range 32-76), 48 patients (79%) remained continuously disease-free. The 5-year event-free and overall survival were 77% and 87%, respectively. These results were significantly better both in terms of histologic response or event-free and overall survival than those obtained in 58 patients with non metastatic Ewing's sarcoma of the extremity treated in a previous protocol (REN-2) in which the same drugs were used, but ifosfamide was employed only in the maintenance phase. The present study suggests the importance of early use of ifosfamide in the treatment of patients with non metastatic Ewing's sarcoma of the extremity.  相似文献   

5.
Between 1984-1987, 50 patients with Ewing's sarcoma of the bone were entered on combined modality protocol at Tata Memorial Hospital. Protocol treatment involved induction therapy consisting of 6-week therapy with vincristine, Adriamycin (doxorubicin), and cyclophosphamide (VDC) followed by local radiotherapy 50 Gy to the involved bone. This was followed for six more cycles of VDC. Five patients had metastatic disease at presentation. Seventy-six percent (38/50) of patients had disease either at axial or proximal site. With a median follow-up of 48 months (range 14-87) 21 patients remained alive with disease-free survival of 38.0% +/- 2.5% at 5 years and overall survival of 36.0% +/- 2.6% at 5 years. Twenty-five patients relapsed with five patients developing local failure and four local and distant metastasis. Using Lee-Desu statistical methods, only response to therapy was a significant factor for survival. We conclude that more aggressive therapy with proper selection of local treatment modality including surgery and/or radiotherapy is required to produce more long-term survival in high-risk Ewing's sarcoma.  相似文献   

6.
PURPOSE: Treatment results and the pattern of relapse were evaluated in the multimodal treatment of Ewing's sarcomas of the chest wall. METHODS AND MATERIALS: In a retrospective analysis, 114 patients with non-metastatic Ewing's sarcoma of the chest wall were evaluated. They were treated in the CESS 81, CESS 86, or EICESS 92 studies between January 1981 and December 1993. The treatment consisted of polychemotherapy (VACA, VAIA, or EVAIA) and local therapy, either surgery alone (14 patients), radiotherapy alone (28 patients) or a combination of both (71 patients). The median follow-up was 46.6 months (range 5-170). A relapse analysis for all patients with local or combined relapses was performed. RESULTS: Overall survival was 60% after 5 years, event-free survival was 50%. Thirty-seven patients had a systemic relapse (32.4%), 11 patients had a local relapse alone (9.6%), and 3 patients had a combined local and systemic relapse (2.6%). The risk to relapse locally after 5 years was 0% after surgery alone, 19% after radiation alone, and 19% after postoperative irradiation. None of the 8 patients with preoperative irradiation have failed locally so far. With the introduction of central radiotherapy planning in CESS 86, local control of irradiated patients improved. Ten of 14 patients with local failure could be evaluated in the relapse analysis: 3 patients had an in-field relapse, 4 patients had a marginal relapse, 2 patients had a relapse outside the radiation fields, and 1 patient failed with pleural dissemination. Six treatment deviations were observed. CONCLUSION: Local control was best after surgery alone in a positively selected group of patients. Local control after radiation or combined radiation and surgery was good. With diligent performance of radiotherapy, it will be possible to further improve the results in the radiotherapy group.  相似文献   

7.
PURPOSE: To improve response and survival rates in patients with high-risk rhabdomyosarcoma (RMS), extraosseous Ewing's sarcoma, and undifferentiated sarcoma, we used a short course of induction with multi-agent chemotherapy, hyperfractionated radiotherapy, and surgery when possible. Consolidation was with intensive chemotherapy and autologous bone marrow transplantation (ABMT). PATIENTS AND METHODS: Twenty-six patients (21 with RMS, three with undifferentiated sarcoma, and two with extraosseous Ewing's sarcoma) were entered onto the protocol between June 1990 and March 1994. Induction consisted of ifosfamide, etoposide, doxorubicin, dactinomycin, cyclophosphomide, and vincristine, and a split course of hyperfractionated radiotherapy. Patients who attained a complete response (CR) or good partial response (GPR) received consolidation with high-dose melphalan and etoposide followed by ABMT. RESULTS: Of 26 previously untreated patients 19 (73%) achieved a CR (n=13) or GPR (n=6) at the completion of induction and underwent ABMT. Two-year overall survival (OS) was 56% (95% confidence interval [CI], 36% to 76%) and progression-free survival (PFS) was 53% for the whole group (95% CI, 33% to 73%). CONCLUSION: Consolidation of response by myeloablative chemotherapy was well tolerated. Split-course hyperfractionated radiotherapy did not increase the rate of local control. The results of this short-course therapy were comparable to previous therapies of 1 to 2 years' duration. Induction and consolidation chemotherapy, as well as radiation dose, could be further intensified, since no death due to toxicity occurred among these patients.  相似文献   

8.
One hundred and twenty-one consecutive patients with monostotic Ewing's sarcoma (ES) were treated according to three consecutive combined modality programs from 1974 to 1986. Their 3-year progression free survival (PFS) rate from diagnosis of 59% was identical to the event free survival (EFS) rate, since all the 50 events occurring within 3 years from diagnosis were tumor recurrences. Primary tumor was treated with radiotherapy in 75 cases, surgical resection plus radiotherapy in 38, and radical surgery in 8. Chemotherapy was given to all patients and each program included adriamycin, vincristine, and cyclophosphamide +/- dactinomycin. Median follow-up was 12 years, ranging from 6 to 19 years. The PFS rate decreased to 49% at 6 years and plateaued at 46% after the 7th year from diagnosis, even though some relapses were observed as late as 14 years from diagnosis. Second malignancies developed in 7 patients free from progressive ES and were represented by osteogenic sarcoma in previously irradiated bone in 4 cases and by breast carcinoma in 3. No other event but tumor relapse or second malignancy occurred in this series. EFS rate was 47% at 6 years and 39% at 12 years, further decreasing in the following years because of a number of late events. A continuous PFS longer than 7 years may be consistent with cure in the majority of patients with monostotic ES. However, these patients should be followed indefinitely because of risk of second malignancies.  相似文献   

9.
Twenty-four high-risk Ewing's sarcoma patients were treatedf on an intensive combined modality protocol including low-dose fractionated total body irradiation (TBI) and autologous bone marrow infusion (ABMI). Twenty patients (83%) achieved a complete clinical response to the primary and/or metastatic sites following induction therapy. The median disease-free interval was 18 months, and nine patients remain disease-free with a follow-up of 22 to 72 months. Local failure as a manifestation of initial relapse occurred in only three patients (15%), each having synchronous distant failure. Eight patients failed initially with only distant metastases, usually within 1-2 years following a complete clinical response. Two patients with a single metastasis were again rendered disease-free and remain free from second relapse with 18 and 30 months follow-up. No other relapsed patient was able to be rendered disease-free, and most died of progressive disease within 6 to 12 months of relapse. Two patterns of granulocyte recovery following consolidative therapy (include TBI) and ABMI were recognized. Seventeen patients reached a total granulocyte count of >500 cells/mm3 within 4 weeks of ABMI (early graulocyte recovery), while seven patients required >4 weeks from ABMI (late granulocyte recovery). The time of platelet recovery (>50,000/mm3) was different for the groups with early and late granulocyte recovery (25 days vs. 54 days, p <.001). Six of seven patients with late granulocyte recovery received locl high-dose irratiation to >1/2 pelvis prior to bone marrow storage. Patients with late recovery did not tolerate maintenance chemotherapy. However, there was no difference in disease-free and overall survival, when compaing the groups with early and late granulocyte recovery. We conclude that these high-risk Ewing's sarcoma patients remain a poor-prognosis group in spite of intensive combined modality therapy include low-dose TBI. The control of microscopic systemic disease remains the major challenge to improving the cure rate. A new combined modality protocol with high-dose 'therapeutic' TBI (800 rad/2 fractions) is being used and the protocol design is outlined.  相似文献   

10.
Between January 1988 and December 1990, 74 patients with localized Ewing's sarcoma of bone were treated with a new protocol that consisted of an initial 6-week period of chemotherapy with vincristine (VCR), adriamycin (ADM) and cyclophosphamide (EDX) followed by local therapy and additional chemotherapy with the same drugs previously indicated plus ifosfamide and VP-16. The rationale for the addition of ifosfamide and VP-16 to the four drugs of the standard chemotherapy of this tumor was that this drug combination was previously very effective in the treatment of metastases from Ewing's sarcoma even in patients who did not respond to cyclophosphamide. As local treatment all patients were offered surgery, when feasible (70 cases). Forty-three patients accepted and 27 refused. These patients, as the 4 patients in whom surgery was not considered feasible, were treated with radiation therapy alone (50-60 Gy). In the remaining patients amputation was performed in 4 cases, rotationplasty in 3 and resection in 36. Where conservative surgery was marginal or intralesional (30 cases), radiotherapy at lower doses (40-45 Gy) was also delivered. At a mean follow-up of 3.5 years (2-7), 43 patients (58%) remained continuously disease-free and 31 relapsed (29 with metastases and 2 with both metastases and local recurrences). These results do not differ from those obtained at our Institution in 98 patients treated between 1983 and 1988 with a neoadjuvant protocol in which only VCR, ADM, EDX and dactinomycin (DAC) were used (3-year continuously disease-free survival (CDFS) respectively of 54% and 55%). Despite the fact that these results came from a nonrandomized study, the Authors conclude that the addition of ifosfamide and VP-16 to the four-drug standard regimen did not improve the outcome of the patients with Ewing's sarcoma of bone which remains a lethal disease in about 50% of the cases. These findings stress the need to find more effective chemotherapeutic regimens for the associated treatment of this tumor.  相似文献   

11.
Twenty-nine patients with Ewing's sarcoma of the lower extremity who survived for two or more years following therapy (5000 rad locally and systemic chemotherapy) were studied to assess functional status of the affected leg. Twenty-two of twenty-nine were alive and were reexamined; the deceased patients were evaluated by record review. Twenty-two of the twenty-nine had serial radiographs, which were reviewed to assess growth change induced by radiation. The living patients were divided on the basis of clinical examination into four functional groups with Group I comprising patients with minor functional limitations and leg length discrepancy 1.5 cm or less. Group II patients had moderate functional limitations with 2.5-cm leg-length discrepancy or less. Group III patients had severe functional limitations with up to 4-cm leg length discrepancy. Group IV patients had severe complications, sufficient enough to warrant amputation. Thirteen of twenty-two patients were classified as functional Group I, five as Group II, three as Group III, and one as Group IV. Radiographic changes in growing bone did not correlate with functional results. Although a femoral fracture and an age less than 16 years at diagnosis were found to be less favorable prognostic factors for the functional treatment result, these results show that neither femoral location nor young age justify primary amputation for Ewing's sarcoma of the lower leg extremity.  相似文献   

12.
The results obtained in 172 cases of non metastatic Ewing's sarcoma of the extremities are reported. The patients were advised to undergo surgical treatment, followed by radiotherapy (40-45 Gy) in case of inadequate surgical margins. 48 patients who refused surgical treatment, were locally treated with radiotherapy alone (50-65 Gy). With a mean follow-up of 8 years (R. 3-15) 101 patients (58.7%) are free of disease and 68 relapsed with metastases and/or local recurrence. A radio-induced bone sarcoma developed in two patients, one patient died of ADM cardiomyopathy. No differences in terms of risk factors were observed between patients who were or were not treated with surgery. A better DFS was observed in the patients treated with surgery (66.9%) in comparison with those treated with radiotherapy alone. The higher percentage of local recurrences observed in patients treated with radiotherapy alone seems to be responsible for the worse prognosis observed in these patients. The authors' conclusion is that the local control in patients with non metastatic Ewing's sarcoma should always be achieved by means of surgery.  相似文献   

13.
Ewing's sarcoma is a highly malignant neoplasm of the bone whose origin is still uncertain. A strong relationship exists between Ewing's sarcoma and tumors of neural origin (Ewing family of tumors). Ewing's sarcoma must be distinguished from other round-cell tumors like lymphoma and neuroblastoma and also must be differentiated from osteogenic sarcomas. On plain radiographs, Ewing's sarcoma appears as a lytic or mixed lytic-sclerotic, rarely as predominantly sclerotic lesion with margins Lodwick grade III. It is located primarily in the diaphyseal and metadiaphyseal regions of the long bones of the lower extremities. A large soft tissue tumor is usually present. Magnetic resonance imaging is the imaging modality of choice to evaluate the extent of the primary lesion, to monitor the response to neoadjuvant chemotherapy and to follow up non-resected Ewing's sarcomas. Bone scintigraphy is necessary to detect skeletal metastasis, and 201thallium scanning has been shown to be sensitive in the monitoring of treatment response. Today, computed tomography is not longer used to image the tumor site; however, spiral CT of the lungs plays a central role as a staging and follow-up tool.  相似文献   

14.
31 patients with primary Ewing's sarcoma of the ribs were treated according to the protocols of CESS 81, CESS 86P and CESS 86. The results of treatment were reviewed and analysed. 24 patients presented with localised disease and 7 with regional disease. 20 of 24 localised cases and 6 of 7 regional cases underwent tumour resection. All but 2 localised cases received irradiation. The cumulative relapse-free survival (RFS) rate of 31 patients was 61% at 12.8 years. Patients with poor prognosis had tumour of the upper ribs (P = 0.0338), the posterior component of the ribs (P = 0.0597), or regional disease (P = 0.0001). Tumour size, existence of pleural effusion, type of the surgical margin and response to chemotherapy were not significant prognostic factors. Most of the localised cases could be controlled by combined treatment, but in regional cases prognosis remained poor.  相似文献   

15.
BACKGROUND: Synovial sarcoma is the third most common pediatric soft tissue tumor. It requires an aggressive approach to achieve a cure. However, optimal treatment modalities adapted to disease extension and histologic variants have not been determined because there is little information about prospectively treated patients. METHODS: A multicenter trial for soft tissue sarcomas (Protocol CWS 81) was conducted in West Germany between 1981-1985, and 31 patients with synovial sarcoma were registered. Treatment included multiagent chemotherapy and irradiation after initial tumor excision or biopsy. The male-female ratio in this group was 1:1.6 with a median age of 14 years (range, 1-19 years). The median follow-up time after diagnosis was 101 months (range, 77-131 months). RESULTS: The overall event-free survival (EFS) for patients with synovial sarcoma was 74.2% at 5 years. Group I-II tumors had a significantly better prognosis than those in Group III-IV (EFS at 5 years 84.4% and 58.3%, respectively; P = 0.024). Small tumors (< 5 cm) responded better than larger tumors (> or = 5 cm; EFS, 93% versus 58%; P = 0.029). Synovial sarcoma involved the extremities in 28 patients who had a better outcome compared with those with extremity rhabdomyosarcoma in this study (EFS for Group I-IV was 82% versus 24%, P = 0.001). CONCLUSIONS: The results appeared superior to previous experience using radical surgery alone and suggested that after initial, nonmutilating surgery, adjuvant chemotherapy, and irradiation contributed to the improved long-term survival.  相似文献   

16.
Except for clear cell carcinomas that metastasize to bone, with renal cell carcinoma being the principal representative of that group, clear cell osseous neoplasms are rare. The only distinct nosologic entity in this category that is primary in the bone is the clear cell chondrosarcoma (CCCS). This lesion, which is most often seen in the proximal femur or humerus, affects males more often than females and has a peak incidence during the third and fourth decades of life. Radiologic images of CCCS show a well-circumscribed, often calcified lytic lesion that may expand the bone, but only uncommonly breaches the cortex. Clear cell elements in CCCS are accompanied by "conventional" foci of chondrosarcoma in less than 50% of cases; noncartilaginous "secondary features," including areas of osteogenesis, osteoclast-like giant cells, and zones resembling aneurysmal bone cyst or giant cell tumor of bone, may be apparent as well. CCCS is a relatively indolent malignancy; roughly 25% of patients experience local recurrences of their tumors or suffer metastasis, but tumor-related death is uncommon, particularly when the lesion has been completely resected en bloc. Sporadic examples of other tumors in bone also may be focally or entirely composed of clear cells. These include osteosarcoma, chondroblastoma, chordoma, adamantinoma, Ewing's sarcoma, and primitive neuroectodermal tumor. The last two of these lesions represent the most common primary clear cell bone tumors in children, whereas metastatic renal clear cell sarcoma is the most frequent metastatic pediatric tumor in this category.  相似文献   

17.
From 1975 to 1990, eighty-nine primary tumors of the thoracic skeleton; ribs, sternum, scapula, clavicle, and thoracic spine, were treated. Forty-four tumors (49%) were benign lesions. Forty-five tumors were malignant and were proportionately distributed amongst the five sites. The most common malignancies were Ewing's sarcomas, chondrosarcomas, plasmacytomas, osteogenic sarcomas, and lymphomas. All patients with Ewing's sarcomas were treated with combination chemotherapy, surgical resection, and radiation therapy for those with residual disease after surgery. Only one patient has died of disease. Patients with primary chondrosarcomas were treated by surgery alone and all are free of disease or have died without disease. Patients with solitary plasmacytomas or primary lymphomas of bone were treated with radiation therapy initially. Half the patients developed systemic disease. The patients with osteogenic sarcomas included several with radiation induced lesions and Paget's osteosarcoma and all but one died of disease.  相似文献   

18.
Two cases of biliary duct carcinoma occurring in patients who had received prophylactic abdominal irradiation 17 years previously are described. Although external beam radiation has been implicated in the aetiology of many malignancies, there is only one previous report of it being associated with carcinoma of the bile duct. All patients receiving external beam irradiation for curable malignancies require long term follow-up so that treatment induced malignancies may be detected.  相似文献   

19.
Postradiation sarcoma of bone is an uncommon but serious sequela of radiation therapy. Seventy-eight Mayo Clinic patients have been treated for sarcomas arising in irradiated bones. They received their initial radiotherapy for a wide variety of nonneoplastic and neoplastic conditions, both benign and malignant. Thirty-five sarcomas arose in bone that was normal at the time of radiotherapy, and 43 arose in irradiated preexisting osseous lesions. The latent period between radiotherapy and diagnosis of sarcoma averaged 14.3 years. Ninety percent of the postradiation sarcomas were either osteosarcomas or fibrosarcomas; chondrosarcoma, malignant (fibrous) histiocytoma, malignant lymphoma, Ewing's tumor, and metastasizing chondroblastoma also occurred. Prompt radical surgery, when feasible, is usually the treatment of choice for the sarcoma. About 30% of patients with sarcomas of the extremities or craniofacial bones survived 5 years without recurrence; there were no disease-free survivors among patients with tumors of the vertebral column, pelvis, or shoulder girdle. The low risk of sarcoma following radiotherapy for the treatment of cancer should not be a contraindication to its use in these patients; however, radiation therapy for benign bone tumors should be reserved for lesions that are not amenable to surgical treatment. An unusual case is also reported herein in which a fibrosarcoma was discovered in the humerus of a patient who had received radiotherapy 55 years previously for a verified osteosarcoma in the same site.  相似文献   

20.
The high chemosensitivity of pediatric tumors along with their natural propensity for an early distant dissemination have stimulated the interest for chemo-radiation combinations in children since the mid 50s. Following the early experiments in nephroblastomas on the interaction of Actinomycin-D and radiotherapy, multiple national and international studies have been conducted since the mid 70s with considerable success: nowadays most pediatric tumors enjoy a long term survival in excess of 70%. Like their adult counterparts, these associations aim to induce an early control of the primary tumor and distant spreading (spatial cooperation) but also, more specifically in children, to limit the toxicity on normal tissues when treatment intensity can be further reduced. The association of an initial chemotherapy followed by local radiation at a dose and in a volume adapted to the response to chemotherapy along with associated prognostic factors has become widely tested in national and international studies conducted in Hodgkin's disease, Ewing's sarcoma, medulloblastomas, and brain tumors in the very young. Conversely, concomitant associations have remained limited to high-risk subgroups (parameningeal rhabdomyosarcomas for example) due to their potential hazards.  相似文献   

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