Molecular and clinical analysis of locally advanced dermatofibrosarcoma protuberans treated with imatinib: Imatinib Target Exploration Consortium Study B2225.

PURPOSE: The cutaneous malignant tumor dermatofibrosarcoma protuberans (DFSP) is typically associated with a translocation between chromosomes 17 and 22 that places the platelet-derived growth factor-B (PDGFB) under the control of the collagen 1A1 promoter. The purpose of this study was to evaluate molecular, cytogenetic, and kinase activation profiles in a series of DFSPs and to determine whether these biologic parameters are correlated with the clinical responses of DFSP to imatinib. PATIENTS AND METHODS: We analyzed the objective radiologic and clinical response to imatinib at 400 mg twice daily in eight patients with locally advanced DFSP and two patients with metastatic disease. RESULTS: Each of eight patients with locally advanced DFSP had evidence of t(17;22) and showed a clinical response to imatinib. Four of these patients had complete clinical responses. The two patients with metastatic disease had fibrosarcomatous histology and karyotypes that were substantially more complex than those typically associated with localized DFSP. One patient with metastatic DFSP and an associated t(17;22) had a partial response to imatinib but experienced disease progression after 7 months of therapy. In contrast, the other patient with metastatic disease had a tumor lacking t(17;22), and there was no clinical response to imatinib. Unexpectedly, there was minimal platelet-derived growth factor receptor-beta phosphorylation in the untreated DFSP, despite the documented presence of a PDGFB autocrine mechanism. CONCLUSION: Imatinib has clinical activity against both localized and metastatic DFSP with t(17;22). However, fibrosarcomatous variants of DFSP lacking t(17;22) may not respond to imatinib.     

Targeted therapy for dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a rare, cutaneous tumor characterized by aggressive local invasion. Local recurrence after excision is common, especially when negative margins are not achieved. DFSP frequently exhibits translocation of chromosomes 17 and 22, t(17;22). This rearrangement fuses the collagen type Ià1 (COL1A1) gene to the platelet-derived growth factor B-chain (PDGFB) gene. The resultant chimeric gene causes unregulated expression of platelet-derived growth factor leading to abnormal activation of the platelet-derived growth factor receptor (PDGFR) a tyrosine kinase through an autocrine loop. This is believed to be the critical event in DFSP tumorigenesis. Imatinib mesylate is a potent inhibitor of several protein tyrosine kinases, including the PDGFRs. Clinical evidence suggests that imatinib mesylate is a safe and effective treatment in DFSP, especially in cases of recurrent or metastatic disease. Three phase II, multicenter clinical trials are open to further investigate the role of imatinib mesylate in DFSP.     

Differential sensitivity to imatinib of 2 patients with metastatic sarcoma arising from dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a rare superficial sarcoma usually affecting the trunk, with significant risk of local recurrence. It is characterized by the presence of ring chromosomes or chromosomal translocations fusing the promoter of the collagen gene COL1A1 to the platelet-derived growth factor beta-chain gene PDGFB, increasing the production of PDGF locally and promoting autocrine or paracrine tumor growth. Fewer than 5% of patients with DFSP develop metastatic sarcoma, with a poor subsequent prognosis. Imatinib (STI-571) was developed as an inhibitor of the PDGF receptor tyrosine kinase and has proven clinical activity against chronic myelogenous leukemia (expressing bcr-abl) and gastrointestinal stromal tumors (expressing c-kit). We describe 2 patients with metastatic and unresectable metastases from DFSP treated with imatinib. After confirmation of negative CD117 status of 2 sarcomas arising from DFSP, patients were given imatinib 400 mg po qd and assessed at regular intervals for their tolerance and response to therapy. One patient had a transient response, then progressed rapidly and died of disease. Another patient showed a partial response to therapy after 2 months, with resolution of superior vena cava syndrome and shrinking of metastatic lung lesions. His response is ongoing after 6 months of therapy. These clinical data confirm findings from models of DFSP and support the use of imatinib in the rare setting of metastatic DFSP. Imatinib may be useful for patients with locally advanced DFSP, when other options for local therapy are limited.     

Phase II, open-label study evaluating the activity of imatinib in treating life-threatening malignancies known to be associated with imatinib-sensitive tyrosine kinases.

PURPOSE: To evaluate the activity of imatinib in treating advanced, life-threatening malignancies expressing one or more imatinib-sensitive tyrosine kinases. EXPERIMENTAL DESIGN: This was a phase II, open-label, single arm study. Patients > or = 15 years old with malignancies showing histologic or molecular evidence of expression/activation of imatinib-sensitive tyrosine kinases were enrolled. Patients were treated with 400 or 800 mg/d imatinib for hematologic malignancy and solid tumors, respectively. Treatment was continued until disease progression or unacceptable toxicity. The primary objective was to identify evidence of imatinib activity with tumor response as the primary end point. RESULTS: One hundred eighty-six patients with 40 different malignancies were enrolled (78.5% solid tumors, 21.5% hematologic malignancies). Confirmed response occurred in 8.9% of solid tumor patients (4 complete, 9 partial) and 27.5% of hematologic malignancy patients (8 complete, 3 partial). Notable activity of imatinib was observed in only five tumor types (aggressive fibromatosis, dermatofibrosarcoma protuberans, hypereosinophilic syndrome, myeloproliferative disorders, and systemic mastocytosis). A total of 106 tumors were screened for activating mutations: five KIT mutations and no platelet-derived growth factor receptor mutations were found. One patient with systemic mastocytosis and a partial response to therapy had a novel imatinib-sensitive KIT mutation (D816T). There was no clear relationship between expression or activation of wild-type imatinib-sensitive tyrosine kinases and clinical response. CONCLUSION: Clinical benefit was largely confined to diseases with known genomic mechanisms of activation of imatinib target kinases. Our results indicate an important role for molecular characterization of tumors to identify patients likely to benefit from imatinib treatment.     

甲磺酸伊马替尼治疗晚期隆突性皮肤纤维肉瘤的临床研究

目的 评价晚期隆突性皮肤纤维肉瘤(DFSP)患者应用甲磺酸伊马替尼的疗效和不良反应.方法 2004年11月至2009年10月,应用甲磺酸伊马替尼(400 mg,口服,每日1次)治疗晚期有随访资料的DFSP患者24例,其中二线治疗2例,三线或三线以上治疗22例,对其疗效、不良反应和生存时间进行分析.结果 全组24例患者均可评价疗效,其中完全缓解(CR)8例,占33.3%;部分缓解(PR)10例,占41.7%;稳定(SD)2例,占8.3%;进展(PD)4例,占16.7%.全组患者的疾病控制率为83.3%.获得CR和PR的18例患者的中位缓解时间为5.6个月.疾病控制(CR+PR+SD)者的中位生存时间为30个月,无效(PD)者的中位生存时间为10个月,二者差异有统计学意义(P＜0.001).与甲磺酸伊马替尼治疗相关的不良反应为恶心呕吐(20.8%)、中性粒细胞减少(12.5%)和水肿(8.3%)等,多为轻至中度.结论 甲磺酸伊马替尼治疗中国晚期DFSP患者的有效率高,耐受性好;推荐剂量为400 mg,每日1次.

Abstract：

Objective To evaluate the efficacy, side effects and toxicity of imatinib mesylate in the treatment of patients with locally advanced and/or metastatic dermatofibrosarcoma protuberans (DFSP). Methods Twenty-four cases of advanced DFSP diagnosed by pathology and treated in our hospital from Nov. 2004 to Oct. 2009 were included in this study. The patients were treated with imatinib mesylate (dosage: 400 mg, po, qd) and carefully observed for treatment efficacy, side effects and survival time. There were 2 patients taking the drug as second line therapy, and other 22 patients as third or more than third line therapy. Results The 24 patients were evaluable for the efficacy. There were 8 patients (33.3%) with CR, 10 pts (41.7%) PR, 2 patients (8.3%) SD, and 4 patients (16.7%) PD. The disease control rate (DCR＝CR+PR+SD) was 83.3%. The median response time in 18 cases with CR and PR was 5.6 months. The median survival time in 20 cases with disease control was 30 months, however, that in nonresponse (PD) cases was only 10 months. Side reactions related to imatinib mesylate included nausea and vomiting (20.8%), neutropenia (12.5%), and edema (8.3%). Conclusions Our results are consistent with previous reports in the literature. Imatinib is a safe and effective moleucular target drug used for Chinese. Only mild adverse reactions occur in the treated patients. It is worth using imatinib in the treatment of advanced DFSP patients.     

The metabolic consequences of imatinib mesylate: Changes on glucose,lypidic and bone metabolism

The therapeutic efficacy of imatinib mesylate is based on its specific inhibition of several tyrosine kinases (TKs) implicated in the disease pathogenesis. These enzymes include BCR/ABL in patients with chronic myeloid leukaemia, PDGF-R alpha and beta in patients with certain myeloproliferative disorders and dermatofibrosarcoma protuberans and c-KIT in patients with gastrointestinal tumors. Most patients tolerate the drug well and apparently no metabolic abnormalities are evidenced during treatment. However, different metabolic effects have been reported as a consequence of imatinib inhibition during treatment of patients with CML. The aim of this review is to report the changes caused by imatinib on glucose, lypidic and bone metabolism.     

Sunitinib as a second-line therapy for imatinib-resistant gastrointestinal stromal tumors

Gastrointestinal stromal tumor(GIST)is one ofthe representative diseases for which molecularly targeted therapy is very effective. Imatinib mesylate, a tyrosine kinase inhibitor of KIT and platelet-derived growth factor receptor(PDGFR), has dramatically improved the prognosis ofpatients with advanced, recurrent, and/or metastatic GISTs. Although the rate of response to imatinib therapy is high, the emergence ofimatinib -resistant tumors and the second-line therapy following imatinib therapy have become new clinical problems. Sunitinib malate, a multi-targeted tyrosine kinase inhibitor that shows activity against KIT and other receptor tyrosine kinases, including PDGFR and vascular endothelial growth factor receptor, is the only treatment for imatinib-resistant GISTs that is covered by national health insurance in Japan as ofthis writing. Several clinical trials that evaluated sunitinib as potential second-line therapy in Western countries and Japan found a clinical benefit rate of2 4 to 39% and a median time to progression of7 months. However, it is necessary to adequately manage the adverse events of sunitinib therapy in order to receive the full benefits of the therapy, because various severe adverse events, particularly thrombocytopenia and hand-foot syndrome in Japanese GIST patients, frequently lead to poor tolerability. Further investigation is required to find an appropriate regimen for Japanese GIST patients.     

Detection of complete response to imatinib mesylate (Glivec/Gleevec) with 18F-FDG PET/CT for low-grade endometrial stromal sarcoma

Malignant mesenchymal tumors consist of approximately 10% of uterine tumors. The majority of uterine sarcomas are leiomyosarcoma and endometrial stromal sarcoma (ESS). Surgery, radiotherapy, chemotherapy, and hormonal therapy are used for the treatment of ESS. Imatinib mesylate is indicated in the management of gastrointestinal stromal tumor and chronic myelogeneus leukemia. There is an interest to use imatinib mesylate in the treatment of c-kit positive ESS. We reported a case of 42-year-old female low-grade ESS progressed on chemotherapy and presented with objective response to imatinib mesylate. The treatment response was evaluated with FDG PET/CT. Complete metabolic response was detected. FDG PET, a sensitive method for tumor response evaluation on the basis of tumor metabolism changes, is useful for the evaluation of imatinib treatment in low-grade ESS. An erratum to this article can be found at     

Immunohistochemical Analysis of Platelet-derived Growth Factor Receptor-α, -β, c-kit, c-abl, and Arg Proteins in Glioblastoma: Possible Implications for Patient Selection for Imatinib Mesylate Therapy

Summary Inhibition of tyrosine kinase (TK) receptors by synthetic small molecules has become a promising new therapy option in oncology. The TK inhibitor imatinib mesylate selectively targets PDGFR-α, -β, c-kit, c-abl and arg and has proven successful in the treatment of chronic myeloid leukaemia. In recurrent glioblastoma, phase II therapy trials using imatinib mesylate have been initiated. As only a fraction of patients seems to benefit from imatinib mesylate therapy and due to potential side effects and high costs of imatinib mesylate therapy, selection of the right patients is important. The goal of our study was to assess systematically immunohistochemical expression of the major TKs targeted by imatinib mesylate in glioblastoma, as expression of these factors could be used to select patients for imatinib mesylate therapy. In a cohort of 101 glioblastoma patients, anti-PDGFR-α, -β, c-kit, c-abl and arg protein immunohistochemistry was performed. Expression of these proteins was assessed semi-quantitatively and correlated with patient survival. PDGFR-α and arg expression in tumor cells was widespread in 1/101 cases, respectively. Focal PDGFR-α, -β, c-kit, c-abl and arg immunolabeling was detected in 25/101, 19/101, 4/101, 7/101 and 31/101 cases, respectively. Statistical analysis did not reveal any correlation between expression of the TKs and patient survival. We show here for the first time in a large series of glioblastomas that PDGFR-α, -β, c-kit, c-abl and arg expression is immunohistochemically detectable in a fraction of cases. The value of anti-tyrosine kinase immunolabeling as predictive factor for patient selection remains to be clarified by comparative analysis of tumor tissue of therapy-responders versus non-responders.     

Response of extraabdominal desmoid tumors to therapy with imatinib mesylate

BACKGROUND: Desmoid tumor represents a rare monoclonal neoplasm arising from deep musculoaponeurotic structures and may occur sporadically or in association with the familial adenomatous polyposis and Gardner syndromes. Desmoid tumors do not appear to demonstrate metastatic potential; however, local infiltrative growth results in significant morbidity and potential mortality. Although the delineation of optimal therapy for desmoid tumors has been confounded by several factors, surgical resection with adjuvant radiotherapy for a positive surgical margin remains the standard approach. Responses have been demonstrated to nonsteroidal antiinflammatory agents, antiestrogen compounds, and a variety of other agents in small series. Imatinib mesylate appears to demonstrate inhibitory activity against multiple class 3 receptor tyrosine kinases, including platelet-derived growth factor receptor (PDGFR)-alpha and PDGFR-beta, as well as c-kit. METHODS: The authors performed immunohistochemical and qualitative real-time polymerase chain reaction analysis on nine desmoid tumor specimens that demonstrated consistent positivity for c-kit as well as PDGFR-alpha and PDGFR-beta. At the time of last follow-up, 2 patients had received therapy with imatinib mesylate at a dose of 400 mg twice daily. RESULTS: Both patients demonstrated ongoing radiographic and clinical responses with a duration of 9 months and 11 months, respectively. CONCLUSIONS: Imatinib mesylate has been reported to have activity against desmoid tumor, most likely because of c-kit and PDGFR receptor tyrosine kinase activity inhibition, and warrants further study. The relative novelty of this agent and the lack of long-term toxicity data should prompt its use only in the salvage setting in which established local and systemic approaches fail to control disease. In addition, the use of imatinib mesylate in the treatment of this neoplasm preferably should be in the context of a formal prospective clinical trial.     

Response to imatinib mesylate of a gastrointestinal stromal tumor with very low expression of KIT

More than 90% of gastrointestinal stromal tumors (GISTs) express the receptor tyrosine kinase KIT, and activating mutations of the KIT gene are detectable in the vast majority of these tumors. Imatinib mesylate (formerly STI571) is a potent inhibitor of KIT kinase activity and has been proven to be highly active in patients with unresectable or metastatic GIST expressing immunohistochemically detectable KIT protein. Here we report a patient with metastatic GIST who responded well to imatinib mesylate treatment despite the near absence of KIT expression in two different samples of his tumor. The tumor was morphologically typical for a GIST, stained positively for CD34, and harbored an in-frame deletion (WK 557-558) in KIT exon 11 that is common in GISTs. Our experience with this patient suggests that even GISTs with very low levels of KIT expression may respond to imatinib mesylate therapy.     

非编码RNA在胃肠间质瘤中的研究进展

胃肠间质瘤(gastrointestinal stromal tumor,GIST)是消化道最常见的间叶源性肿瘤,发病原因主要是由于原癌基因受体酪氨酸激酶或血小板衍生生长因子受体基因活化突变。分子靶向治疗药物甲磺酸伊马替尼是抑制KIT、血小板衍生生长因子受体α多肽(platelet-derived growth factor receptor alpha,PDGFRA)基因酪氨酸激酶活性的药物,其能有效治疗进展期GIST。但是,越来越多的研究发现,甲磺酸伊马替尼在治疗GIST过程中存在原发性耐药和继发性耐药。随着近年来对非编码RNA的生理功能和作用机制的深入研究,使人们逐步认识到非编码RNA对基因表达的广泛调控作用,其在肿瘤发生、发展、侵袭、转移和耐药等过程中扮演着重要角色。研究非编码RNA有可能为探讨GIST发病及耐药机制提供新的思路和方向。     

Imatinib mesylate in chordoma

BACKGROUND: To the authors' knowledge, no effective medical therapy currently is available for advanced chordoma. Imatinib mesylate is a tyrosine kinase inhibitor targeting platelet-derived growth factor receptor-beta (PDGFRB), BCR-ABL, and KIT. METHODS: Six patients with advanced chordoma were treated with imatinib mesylate at a dose of 800 mg daily. In all patients, the tumor was found to be positive for PDGFRB, and in four patients PDGFRB was shown to be phosphorylated/expressed. RESULTS: After a treatment period of > or = 1 year, overt tumor liquefaction was evident on computed tomography (CT) scan in the first patient. In previous months, a decrease in contrast enhancement on magnetic resonance imaging (MRI) and a decrease in glucose uptake on positron emission tomography (PET) were detected. Similar signs on MRI and PET were observed in subsequent patients, who had a shorter treatment period. One of these patients initially was removed from therapy and then was readmitted to therapy because of difficulties with regard to tumor response assessment; 1 month after the reinitiation of therapy, an overt decrease in tumor density was visible on CT scan in this patient. In four of five symptomatic patients, a subjective improvement was observed early in the course of treatment. The first patient died after 17 months, with a sizeable, mostly liquefied mass. Another patient died early, apparently of unrelated causes. The remaining patients were on therapy at the time of last follow-up. CONCLUSIONS: Imatinib mesylate has been found to have antitumor activity in patients with chordoma. This activity might be mediated by inactivation of PDGFRB. Tumor response manifests through patterns that are similar to those observed in patients with gastrointestinal stromal tumors who respond to molecular-targeted therapy, but evolves more slowly. The benefit to the patient entailed by this pattern of tumor response in chordoma needs to be elucidated, but may be limited in the presence of significant local disease.     

Imatinib-induced regression of AIDS-related Kaposi's sarcoma.

PURPOSE: Activation of the platelet-derived growth factor (PDGF) and c-kit receptors has been proposed as important in mediating the growth of AIDS-related Kaposi's sarcoma (KS). We investigated the response of KS to the PDGF receptor (PDGFR)/c-kit inhibitor, imatinib mesylate, and investigated the effect of this therapy on critical signal transduction intermediates. PATIENTS AND METHODS: Ten male patients with AIDS-related cutaneous KS, which progressed despite chemotherapy and/or highly active antiretroviral therapy, received imatinib mesylate administered orally, 300 mg twice daily. Clinical response was determined by serial tumor measurements. To determine biologic and histologic response, skin lesion biopsies were obtained at baseline and following 4 weeks of therapy. RESULTS: Five of 10 participants had a partial response by tumor measurements. Biopsies after 4 weeks of therapy demonstrated histologic regression in four of six patients. Four patients' tumor biopsies were assessable for immunohistochemistry end points pre- and post-therapy. These demonstrated inhibition of PDGFR and its downstream effector, extracellular receptor kinase, which is a member of the mitogen-activated protein kinase family. The most common adverse event was diarrhea, which led to dose reduction in six patients. CONCLUSION: Imatinib mesylate administered orally twice daily for AIDS-related KS results in clinical and histologic regression of cutaneous KS lesions within 4 weeks. These promising results demonstrate that inhibition of the c-kit and/or PDGF receptors may represent an effective strategy for treating KS.     

Differential effects of imatinib mesylate against uveal melanoma in vitro and in vivo

Uveal melanoma is refractory to chemotherapy. The receptor tyrosine kinase inhibitor, imatinib mesylate, has demonstrated antiproliferative effects against uveal melanoma cells in vitro. The effects of imatinib mesylate, alone and combined with the alklyating agent, temozolomide, were examined in vivo as well as in vitro. Proliferation and angiogenic factor production of human uveal melanoma cell lines in response to imatinib mesylate and temozolomide were examined in vitro. Tumor growth, angiogenic factor production, tumor interstitial fluid pressure, and stroma constituents in response to imatinib mesylate and temozolomide were examined in vivo in mice bearing human uveal melanoma xenografts. Imatinib mesylate in vitro antagonized the antiproliferative effects of temozolomide and increased the production of angiogenic factors. In contrast, pretreatment with imatinib mesylate in vivo could improve the antitumor activity of temozolomide. Imatinib mesylate in vivo decreased the production of angiogenic factors in the tumor stroma and tumor interstitial fluid pressure. These effects were transient. Increases in angiogenic factors, interstitial fluid pressure, and tumor infiltrating macrophages were observed with continued imatinib mesylate treatment in vivo. The antitumor effects of imatinib mesylate can vary in vivo when compared with in vitro. Imatinib mesylate can both positively and negatively modify host-tumor interactions in uveal melanoma.     

Dermatofibrosarcoma protuberans: a surgical disease with a molecular savior

PURPOSE OF REVIEW: Dermatofibrosarcoma protuberans is a low-grade malignancy of the skin and subcutaneous tissues with low potential for the development of distant metastases. This tumor is characterized by infiltrative growth, and a chromosomal translocation involving the COL1A1 gene on chromosome 17 and the gene platelet-derived growth factor B gene on chromosome 22. This review will examine recent data confirming the central role of surgery in managing this disease and new findings for the application of molecularly targeted therapy in patients with unresectable disease. RECENT FINDINGS: The largest published series of dermatofibrosarcoma protuberans cases has reported that surgery can lead to excellent local control in dermatofibrosarcoma protuberans in over 95% of cases. In patients with metastatic disease, or with locally advanced disease not suitable for surgical excision, inhibition of platelet-derived growth factor receptors with imatinib (Gleevec) can lead to striking clinical results, including complete responses in some patients. SUMMARY: The identification of platelet-derived growth factor B as a near universal translocation partner in chromosomal rearrangements in dermatofibrosarcoma protuberans has led to the successful application of therapy targeted at platelet-derived growth factor receptors. Although wide surgical excision remains the standard of care, patients with locally advanced disease not suitable for wide surgical excision or with metastatic disease can be managed with the platelet-derived growth factor receptors inhibitor imatinib with high probability of response.     

Chronic myelogenous leukemia in T cell lymphoid blastic phase achieving durable complete cytogenetic and molecular remission with imatinib mesylate (STI571; Gleevec) therapy

BACKGROUND: A T cell lymphoid blastic phase of chronic myelogenous leukemia (CML) is a rare occurrence, with only a few reported cases worldwide. Standard therapy for such patients is undetermined. Imatinib mesylate, a Bcr-Abl tyrosine kinase inhibitor, has shown activity in CML. METHODS: The authors report on a patient with CML and marrow as well as extramedullary nodal T cell lymphoid blastic phase who was treated with imatinib mesylate. RESULTS: The patient achieved complete morphologic and cytogenetic remission within two months of therapy. Competitive quantitative polymerase chain reaction analysis of marrow cells was negative after 15 months. Response had lasted for 26+ months at the time of writing. CONCLUSIONS: The current data suggest that imatinib mesylate may produce long-term event free survival in patients with T-cell lymphoid blastic phase CML. Its potential role alone or in combinations should be further explored in this condition.     

From cytogenetics to cytogenomics of dermatofibrosarcoma protuberans family of tumors

Dermatofibrosarcoma protuberans (DP) is a rare, slow growing dermal neoplasm of intermediate malignancy. It is made of spindle-shaped tumor cells in a storiform pattern often positive for CD34. The preferred treatment for DP is a surgical wide excision with pathologically sane margins of 3 cm. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes composed of sequences derived from chromosomes 17 and 22 or more rarely of translocations t(17;22). Rings have been mainly observed in adults whereas translocations have been reported in all pediatric cases. These chromosomal rearrangements lead to the formation of a specific fusion gene : COL1A1-PDGFB detected in rings as well as in translocations. DP is therefore a unique example of tumor in which the same molecular event occurs either on rings or linear translocation derivatives and the chromosomal abnormalities display an age-related pattern. So far, the COL1A1-PDGFB fusion gene remains the only fusion gene identified in this tumor. It is also present in variant forms of DP such as giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma and the granular cell variant of DP demonstrating that these tumors are not distinct entities but morphological variants of DP. The breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 of PDGFB under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the alpha-helical coding region (exons 7-47). No correlation between the breakpoint location in COL1A1 and the age of the patient or any clinical or histological particularity has been established. Moreover, no preferential breakpoint appears to be more particularly linked to one or another variant of DP. The COL1A1-PDGFB fusion gene is detectable either by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer for PDGFB exon 2, or by in situ fluorescence hybridization (FISH) on interphase nuclei from frozen or fixed paraffin-embbeded sections. The COL1A1-PDGFB fusion gene is not found in approximately 8% of DP cases, suggesting that genes other than COL1A1 or PDGFB might be involved in a small subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. The PDGF receptor tyrosine kinase antagonist imatinib mesylate has recently been used in clinical trials; its efficiency has been demonstrated in several cases, which allows it to be considered as a novel treatment strategy for metastatic or locally advanced DP.     

A long-term survival case with multiple liver metastases from duodenal gastrointestinal stromal tumor that was drastically reduced by the treatment with imatinib

Constitutive activation of c-kit receptor tyrosine kinase is a critical factor in the pathogenesis of gastrointestinal stromal tumors. Imatinib mesylate (IM), a selective tyrosine kinase inhibitor, has been shown in clinical studies to work against such tumors. But there is little information on whether a combination of IM and surgical treatment can prolong survival in a case of unresectable multiple liver metastases. We report a case of postoperative recurrence of gastrointestinal stromal tumor (GIST) treated by the tyrosine kinase inhibitor IM and surgical treatment. Therefore, we discuss some important implications. This 37-year-old Japanese man underwent a pancreaticoduodenectomy for GIST of the duodenum in January 2003. The postoperative course was good at first, but 3 months after the initial operation, MRI showed multiple liver metastases. The patient was treated with 400 mg of IM once daily with only weak liver dysfunction as a side effect. The initial response to treatment of CR continued for 18 months. Currently, IM is the first-line therapy for non-resectable GISTs. As the mechanisms of recurrence and resistance to imatinib in GIST remain unclear, they should be intensively performed in the sight of both clinical and molecular biological viewpoints. Further examination in more cases of recurrent GIST is also necessary to estimate the effectiveness of treatment with IM.     

Imatinib mesylate treatment of recurrent meningiomas in preselected patients: a retrospective analysis

Some unresectable and symptomatic meningiomas recur after conventional radiation therapy or stereotactic radiosurgery and are a therapeutic challenge. Evidence-based data from medical therapy for patients with recurrent meningioma can be deemed insufficient. Because of the prevalent expression of PDGF receptors in meningiomas, the tyrosine kinase imatinib mesylate has attracted interest as a treatment option for this patient group. In this retrospective study we analyzed 18 patients with recurrent meningiomas who were treated at our institution between 1996 and 2008. Nine patients with positive immunohistochemical staining of at least one of the PDGF receptors were given a daily oral dose of 400?mg imatinib mesylate as first, second, or third-line systemic therapy. Immunohistochemical staining was performed on formalin-fixed and paraffin-embedded tumor tissue with antibodies against PDGFR-α and β, c-Kit, Arg, and c-Abl. Imatinib mesylate at a dose of 400-800?mg/day was well tolerated. Of nine patients treated with imatinib, seven had stable disease and two had progressed at the first scan after three months. We observed no complete or partial responses, although prolonged disease stabilization with progression-free survival of 66.7?% at six months was observed. Overall median progression-free survival was 16?months. We conclude that single-agent imatinib mesylate might be a well-tolerated therapeutic option with high achievement of disease stabilization for preselected patients with recurrent meningiomas. Because of the small cohort, non-randomized design, and highly diverse patient population, we propose future prospective studies to validate our results.