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G D Demetri

Publications and source records attributed to G D Demetri.

At least 19 recordsLinked to original sources
PubMed2001

KIT activation is a ubiquitous feature of gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract, and they are generally resistant to chemotherapy and radiation therapy. Most GISTs express the KIT receptor tyrosine kinase protein, and a subset of GISTs contain activating mutations within the KIT juxtamembrane region. We evaluated 48 GISTs, including 10 benign, 10 borderline, and 28 malignant cases, to determine whether KIT expression and activation are general properties of these tumors. Immunohistochemical KIT expression was demonstrated in each case. Somatic KIT mutations were found in 44 tumors (92%), of which 34 (71%) had juxtamembrane region mutations. Other GISTs had KIT mutations in the extracellular region (n = 6) and in two different regions in the tyrosine kinase domain (n = 4). Contrary to previous reports, KIT mutations were not identified preferentially in higher-grade tumors: indeed, they were found in each of 10 histologically benign GISTs. Notably, mutations in all KIT domains were associated with high-level KIT activation/phosphorylation, and KIT activation was also demonstrated in the four GISTs that lacked detectable KIT genomic and cDNA mutations. These studies underscore the role of KIT activation in GIST pathogenesis, and they suggest that activated KIT might represent a universal therapeutic target in GISTs.

Adult↗
PubMed2001

STI571 inactivation of the gastrointestinal stromal tumor c-KIT oncoprotein: biological and clinical implications.

Mutations in the c-KIT receptor occur somatically in many sporadic Gastrointestinal Stromal Tumors (GIST), and similar mutations have been identified at the germline level in kindreds with multiple GISTs. These mutations activate the tyrosine kinase activity of c-KIT and induce constitutive signaling. To investigate the function of activated c-KIT in GIST, we established a human GIST cell line, GIST882, which expresses an activating KIT mutation (K642E) in the first part of the cytoplasmic split tyrosine kinase domain. Notably, the K642E substitution is encoded by a homozygous exon 13 missense mutation, and, therefore, GIST882 cells do not express native KIT. GIST882 c-KIT protein is constitutively tyrosine phosphorylated, but tyrosine phosphorylation was rapidly and completely abolished after incubating the cells with the selective tyrosine kinase inhibitor STI571. Furthermore, GIST882 cells evidenced decreased proliferation and the onset of apoptotic cell death after prolonged incubation with STI571. Similar results were obtained after administering STI571 to a primary GIST cell culture that expressed a c-KIT exon 11 juxtamembrane mutation (K558NP). These cell-culture-based studies support an important role for c-KIT signaling in GIST and suggest therapeutic potential for STI571 in patients afflicted by this chemoresistant tumor.

Apoptosis↗
PubMed2001

Anaemia and its functional consequences in cancer patients: current challenges in management and prospects for improving therapy.

Anaemia is a common occurrence in patients with cancer and contributes to the clinical symptomatology and reduced quality of life (QOL) seen in cancer patients. Many aspects of reduced QOL, including fatigue, are known to be associated with suboptimally low levels of haemoglobin. Even mild-to-moderate anaemia adversely affects patient-reported QOL parameters. Red blood cell transfusions are associated with many real and perceived risks, inconveniences, costs, and only temporary benefits. Recombinant human erythropoietin (rHuEPO) is an effective therapy to increase haemoglobin values in over half of anaemic cancer patients receiving concurrent chemotherapy. These increased haemoglobin values are closely correlated with improvements in QOL. Despite these objectively defined benefits, less than 50% of anaemic patients undergoing cytotoxic chemotherapy receive rHuEPO, in contrast to patients with chronic renal failure on dialysis, where anaemia is universally and aggressively treated to more optimal haemoglobin values. However, there are several barriers that may limit more widespread use of rHuEPO. These include inconvenience associated with frequent dosing; failure of a large proportion (40 to 50%) of patients to respond; relatively slow time to response; absence of reliable early indicators of response; and current lack of rigorous pharmacoeconomic data demonstrating cost-effectiveness. Darbepoetin alfa is a novel erythropoiesis stimulating protein (NESP) that is biochemically distinct from rHuEPO, and which has been proven to stimulate red blood cell production. The molecule has a 3-fold longer half-life and increased biological activity that will allow less frequent dosing, facilitating improved management of the anaemia of cancer. With this new option for therapy, further avenues of investigation should lead to renewed interest in the clinical benefits of optimal haemoglobin levels for patients with cancer.

Anemia↗
PubMed2001

Malignant epithelioid angiomyolipoma ('sarcoma ex angiomyolipoma') of the kidney: a case report and review of the literature.

Malignant epithelioid angiomyolipoma is a recently described rare tumor of the kidney. Its existence has been questioned, however, on the basis of incomplete evidence of malignant behavior, the absence of an associated classic angiomyolipoma component, or the absence of immunoreactivity for HMB-45 in some cases. We describe a case that was HMB-45-positive and arose in association with a classic angiomyolipoma. The patient was treated with a partial nephrectomy. Three years later, she developed rapidly enlarging liver nodules. A fine-needle aspiration of the liver confirmed the presence of pleomorphic epithelioid cells morphologically and immunohistochemically identical to those comprising the primary renal tumor. After two cycles of treatment with doxorubicin, there was a 50% reduction in the size of the tumors with marked improvement in performance status. We believe this case confirms the existence of a malignant epithelioid angiomyolipoma.

Angiomyolipoma↗
PubMed2001

Response to chemotherapy and predictors of survival in adult rhabdomyosarcoma.

OBJECTIVE: To assess outcome and identify predictors of survival of adults with rhabdomyosarcoma. SUMMARY BACKGROUND DATA: The literature on adult rhabdomyosarcoma is limited. Few studies have identified predictors of long-term survival in this patient population. METHODS: Thirty-nine adults with rhabdomyosarcoma were treated between 1973 and 1996 and prospectively followed. Outcomes were assessed with respect to patient and tumor characteristics, local treatment, and response to chemotherapy. RESULTS: Twenty-six patients had localized/locoregional disease and 13 patients had metastatic disease at presentation. Twenty-one patients underwent attempted curative resection, 27 received radiotherapy, and 37 received chemotherapy. Median follow-up for surviving patients was 152 months. The overall 5- and 10-year survival rates were 31% and 27%, respectively. Five-year survival rates for patients with tumors less than 5 cm, 5 to 10 cm, and more than 10 cm were 60%, 14%, and 0%, respectively. Patients with localized/locoregional disease at presentation had a 44% 5-year survival rate; there were no 5-year survivors among patients with metastatic disease. Patients who had a complete response to chemotherapy had a 5-year survival rate of 57%, compared with a rate of only 7% for poor responders. Metastatic disease at presentation and poor response to chemotherapy were independent predictors of death on multivariate analysis. CONCLUSIONS: Age, location, nodal status, and histologic subtype do not appear be associated with survival in adults with rhabdomyosarcoma treated with multimodal therapy. Metastatic disease at presentation and poor response to chemotherapy are strongly associated with poor prognosis. Future systemic therapies should be targeted to patients with localized/locoregional disease and partial responders to conventional chemotherapy.

Adolescent↗
PubMed2001

Targeted approaches for the treatment of thrombocytopenia.

Molecular targeting of novel therapies has the promise of inducing very specific biologic effects. In clinical hematology and oncology, molecular targeting of specific cell surface receptors with erythropoietin, G-CSF, or GM-CSF has been used to stimulate erythropoiesis and granulopoiesis, respectively. Although anemia and neutropenia can be corrected with targeted therapy, safe and effective treatment of thrombocytopenia remains an unmet medical need. While platelet transfusions still represent the standard of care for severe thrombocytopenia, there are several negative aspects associated with their use, including issues of availability, transient effectiveness, costs, adverse effects, negative perception by patients, and infection considerations. Despite extensive investigations of cytokines which act primarily on primitive levels of hematopoiesis, pharmacologic interventions to date have failed to elevate platelet counts in a reliable, highly effective, and well-tolerated fashion. Recombinant human interleukin-11 has been approved by the U.S. Food and Drug Administration for the treatment of chemotherapy-induced thrombocytopenia but has only modest efficacy and significant side effects. The identification of c-Mpl as the thrombopoietin receptor has opened new avenues for the therapeutic manipulation of thrombopoiesis. The development of specific c-Mpl ligands, including recombinant human thrombopoietin (rHuTPO), has allowed investigators to target this receptor for the treatment of chemotherapy-induced thrombocytopenia and other medical disorders characterized by extremely low platelet counts. As a potent stimulator of platelet production, rHuTPO has the potential to reduce the need for platelet transfusions and their attendant complications.

Cytokines↗
PubMed2001

Targeting c-kit mutations in solid tumors: scientific rationale and novel therapeutic options.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. These tumors span a wide clinical spectrum from benign to malignant and have long been recognized for their nearly absolute resistance to chemotherapy and radiation treatment. Surgery is the primary treatment modality for GISTs, but GISTs represent an incurable malignancy for patients with metastatic or unresectable disease. Thus, novel approaches to the treatment of GISTs were desperately needed. Gastrointestinal stromal tumors are characterized by expression of the transmembrane receptor tyrosine kinase KIT, which is defined by the CD117 antigen and is the product of the c-kit proto-oncogene. Activating or gain-of-function mutations in the c-kit gene have been identified in the majority of GIST cases. The resulting constitutive KIT tyrosine kinase activity was hypothesized to provide growth and survival signals to GIST cells and to be crucial to the pathogenesis of the disease. This hypothesis became testable with the identification of the signal transduction inhibitor imatinib mesylate (formerly STI571, [Gleevec]; Novartis Pharmaceuticals Corp, East Hanover, NJ), which blocks the tyrosine kinase activity of KIT as well as the kinase activity of the normal c-abl gene product, the oncogenic Bcr-Abl chimeric fusion protein of chronic myeloid leukemia, and the platelet-derived growth factor receptor. Preclinical experiments showed rapid inhibition of ligand-independent KIT phosphorylation, decreased cellular proliferation, and induction of apoptosis after exposure of GIST cells to imatinib mesylate in vitro. These results provided the rationale to move forward with clinical testing of imatinib mesylate as an anticancer therapy for GIST. In early 2000, a dramatic clinical and radiographic response to imatinib mesylate was shown in a single patient with advanced, chemotherapy-resistant GIST. The powerful scientific rationale for this proof-of-concept study, together with the durable and significant response observed in this first GIST patient treated with imatinib mesylate, have provided the driving force for rapid clinical development of this targeted therapy in this solid tumor indication.

Antineoplastic Agents↗
PubMed2000

Pharmacologic treatment options in patients with thrombocytopenia.

Thrombocytopenia that results from chemotherapy has become an increasingly important issue in the treatment of cancer and remains a difficult clinical problem. The identification of a safe and effective platelet growth factor could significantly improve the management of severe chemotherapy-induced thrombocytopenia. Over the past decade, a number of hematopoietic growth factors with thrombopoietic activity have been identified, including stem-cell factor (c-kit ligand), interleukin (IL)-1, IL-3, IL-6, and IL-11, as well as thrombopoietin (TPO) and its derivatives. Only a few of these agents have shown acceptable tolerability and sufficient ability to stimulate thrombopoiesis to justify testing in randomized clinical trials. Currently, IL-11 is the only cytokine licensed in the United States for treatment of chemotherapy-induced thrombocytopenia. However, its thrombopoietic activity is modest and its use is often associated with unfavorable side effects. Identification of TPO, the c-Mpl ligand, as the primary physiologic regulator of megakaryocyte and platelet development offers important promise for treatment of thrombocytopenia. Preliminary clinical studies of recombinant human TPO (rhTPO), a full-length glycosylated molecule, indicate that it is safe and biologically active in reducing severe chemotherapy-induced thrombocytopenia. In addition to rhTPO, the future may see the development of novel genetically engineered, high-affinity cytokine receptor agonists and c-Mpl ligand mimetic peptides.

Cytokines↗
PubMed2000

Management of soft-tissue sarcomas: an overview and update.

Soft-tissue sarcomas (STS) are relatively uncommon, especially when considered as individual histological subtypes (of which there are more than 50). Their incidence increases with age, although they are disproportionately common among children. When diagnosed and managed in a non-specialist environment, outcome is generally significantly poorer than if patients are managed by a multidisciplinary team in a tertiary centre of excellence. Prompt referral of patients with clinically suspicious masses is strongly advocated, before any type of intervention is attempted. This brief, opinion-based overview emphasises the team approach and provides a synopsis of the strategies used at our institution for pre-operative assessment and biopsy, surgical management, and the delivery of radiation therapy when appropriate (focusing on limb preservation and optimisation of function). Predictable variations in the natural history of these tumours, based on accurate histological subclassification, merit wider recognition. The role of systemic chemotherapy for soft-tissue sarcoma is still evolving, but at present the main aims are improved local control, disease-free survival, and quality of life. There are overall survival benefits for specific histological types, but this is a relatively small subgroup. Novel therapies, based on disease mechanisms at the molecular level, show promise for future advances.

Antineoplastic Agents↗
PubMed1999

Uptake of radiolabeled somatostatin analog is detectable in patients with metastatic foci of sarcoma.

BACKGROUND: Somatostatin receptors are present on many types of epithelial tumors, and ligands targeting these receptors are used to treat patients with neuroendocrine malignancies. Preclinical studies have demonstrated the presence of somatostatin receptors on a variety of mesenchymal tumors by in vitro receptor autoradiography. The use of radiolabeled somatostatin analogs to assess the presence of somatostatin receptors in vivo has been established, but use of this technique to evaluate human sarcomas has not been reported previously. METHODS: Seventeen patients (13 females and 4 males) with metastatic sarcoma underwent imaging via somatostatin-receptor scintigraphy. Scans were performed using indium -111 pentetreotide. Planar studies and single photon emission computed tomography imaging were performed at 4 and 24 hours, and results of scintigraphy were correlated with computed tomography findings. RESULTS: Twelve of 17 scans showed increased uptake in regions of known metastatic disease. There was no apparent correlation with scan positivity and patient age, histology, site of disease, or duration of diagnosis. CONCLUSIONS: Seventy-one percent of patients with advanced soft-tissue sarcomas had positive scintigraphy scans demonstrating tumor expression of somatostatin receptors subtype 2 in vivo. Imaging with indium-111 pentetreotide could be studied as an adjunct to conventional imaging modalities for assessment of sarcoma patients. Further research is needed to determine the prognostic implications of somatostatin receptor subtype 2 positivity, including larger studies to evaluate any potential correlation with metastatic behavior and other clinical outcomes.

Abdominal Neoplasms↗
PubMed1999

Induction of solid tumor differentiation by the peroxisome proliferator-activated receptor-gamma ligand troglitazone in patients with liposarcoma.

Agonist ligands for the nuclear receptor peroxisome proliferator-activated receptor-gamma have been shown to induce terminal differentiation of normal preadipocytes and human liposarcoma cells in vitro. Because the differentiation status of liposarcoma is predictive of clinical outcomes, modulation of the differentiation status of a tumor may favorably impact clinical behavior. We have conducted a clinical trial for treatment of patients with advanced liposarcoma by using the peroxisome proliferator-activated receptor-gamma ligand troglitazone, in which extensive correlative laboratory studies of tumor differentiation were performed. We report here the results of three patients with intermediate to high-grade liposarcomas in whom troglitazone administration induced histologic and biochemical differentiation in vivo. Biopsies of tumors from each of these patients while on troglitazone demonstrated histologic evidence of extensive lipid accumulation by tumor cells and substantial increases in NMR-detectable tumor triglycerides compared with pretreatment biopsies. In addition, expression of several mRNA transcripts characteristic of differentiation in the adipocyte lineage was induced. There was also a marked reduction in immunohistochemical expression of Ki-67, a marker of cell proliferation. Together, these data indicate that terminal adipocytic differentiation was induced in these malignant tumors by troglitazone. These results indicate that lineage-appropriate differentiation can be induced pharmacologically in a human solid tumor.

Adult↗
PubMed1999

Adults with Ewing's sarcoma/primitive neuroectodermal tumor: adverse effect of older age and primary extraosseous disease on outcome.

OBJECTIVE: To assess outcome and prognostic factors for survival of adults with Ewing's sarcoma/primitive neuroectodermal tumor (PNET). BACKGROUND: Ewing's sarcoma/PNET is a disease of childhood rarely seen in adults. Accordingly, there is a relative paucity of published literature pertaining to outcome for adults with this disease. METHODS: Between 1979 and 1996, 37 patients with newly diagnosed Ewing's sarcoma/PNET were evaluated and treated at the Adult Sarcoma Program at Dana-Farber Cancer Institute and Brigham & Women's Hospital. Twenty-six patients had localized disease at presentation and 11 had metastatic disease. All but two patients received multiagent chemotherapy. Local treatment consisted of surgery (7 patients), surgery and radiation therapy (19), radiation therapy (6), or no local treatment (5). Median follow-up for living patients was 100 months (range 8 to 199). RESULTS: The 5-year survival rate for the group overall was 37%+/-9%. The 5-year local control rate was 85%+/-7%. Significant favorable predictors for survival on univariate analysis included localized disease at presentation, primary origin in bone, primary size <8 cm, and a favorable objective response to chemotherapy. Patients with localized disease had a 5-year survival rate of 49%+/-11% compared with 0% for those with metastatic disease at presentation. Multivariate analysis showed three significant independent predictors for death: metastatic disease at presentation, primary origin in extraosseous tissue versus bone, and age 26 years or older. CONCLUSION: Adult patients with Ewing's sarcoma/PNET at highest risk for death are those who are older than 26 years and have metastatic disease or an extraosseous primary tumor. The development of novel therapies should target these high-risk groups.

Adolescent↗
PubMed1999

Long-term outcomes after function-sparing surgery without radiotherapy for soft tissue sarcoma of the extremities and trunk.

PURPOSE: To define the rate of local recurrence (LR) and identify prognostic factors for LR for patients with soft tissue sarcoma (STS) treated with function-sparing surgery (FSS) without radiotherapy (RT). PATIENTS AND METHODS: Between 1970 and 1994, 242 patients with STS of the trunk and extremity presented with primary localized disease, 74 of whom were treated with FSS without RT (31%). The median tumor size was 4 cm (range, 0.5 to 31 cm). There were 40 patients with grade 1 tumors and 34 with grade 2 and 3 tumors. Median follow-up was 126 months. RESULTS: The 10-year actuarial local control rate was 93% +/- 4%. Resection margin status was a significant predictor for LR. Patients with closest histologic resection margins of less than 1 cm had a 10-year local control rate of 87% +/- 6% compared with 100% for patients with closest histologic resection margins of >/= 1 cm (P =.04). There was no significant association between LR and tumor grade, size, site (truncal v extremity), or depth (superficial v deep). For all patients, the 10-year actuarial survival rate was 73% +/- 6%. CONCLUSION: The 7% LR rate after treatment of STS with FSS without RT reported herein is comparable to published rates following treatment where adjuvant RT is used. These results suggest there may be a select subset of patients with STS in whom carefully performed FSS may serve as definitive therapy and in whom adjuvant RT may not be necessary. However, further study is needed to carefully define this subset of patients and to identify the optimal surgical approach and technique for patients treated without RT.

Adult↗
PubMed1998

Major developments in the understanding and treatment of soft-tissue sarcomas in adults.

Soft-tissue sarcomas in adults comprise less than 1% of human malignancies by incidence, yet this class of tumors is highly visible in the oncology research literature. Great strides are being made in the understanding of this heterogeneous class of cancers of mesenchymal origin. A better understanding of the benefits and limitations of current therapeutic strategies for sarcomas accompanies this improved understanding of the diseases. In this review, key developments from 1997 are presented and discussed, including the most recent data analyzing the use of adjuvant chemotherapy. Other relevant topics include new prognostic factors for sarcomas, research in new drugs, the chemotherapy dose-response relationship, and novel biological insights into sarcomas, which are spurring research regarding nontoxic differentiation therapy for this disease.

Adult↗
PubMed1998

Quality-of-life benefit in chemotherapy patients treated with epoetin alfa is independent of disease response or tumor type: results from a prospective community oncology study. Procrit Study Group.

PURPOSE: To evaluate prospectively the effectiveness of epoetin alfa as an adjunct to chemotherapy in patients with cancer based on changes in quality-of-life parameters and hemoglobin levels, and to correlate these changes with antitumor response. PATIENTS AND METHODS: Two thousand three hundred seventy patients with nonmyeloid malignancies who received chemotherapy were enrolled onto this study from 621 US community-based practices. Patients received epoetin alfa 10,000 U three times weekly, which could be increased to 20,000 U three times weekly depending on the hemoglobin response at 4 weeks. Treatment continued for a maximum of 16 weeks in patients who showed evidence of hematologic response. RESULTS: Two thousand two hundred eighty-nine patients (97%) were eligible for efficacy analyses. Epoetin alfa therapy was associated with improved quality-of-life parameters; these improvements correlated significantly with hemoglobin levels and were independent of tumor response. Provider-reported Karnofsky performance scores did not correlate with the improved quality-of-life changes. Epoetin alfa therapy was also associated with a significant increase in hemoglobin levels and decrease in transfusion use. Tumor type, chemotherapy agent/regimen, prior chemotherapy, baseline hemoglobin level, and baseline erythropoietin level were not predictive of a positive response to treatment. Epoetin alfa was well tolerated. CONCLUSION: Epoetin alfa appears to have a beneficial impact on patient-reported functional capacity and quality of life in patients with cancer who received chemotherapy independent of tumor response. Concordantly, epoetin alfa appeared to increase hemoglobin levels and decrease transfusion use. Patients responded across all tumor types. The results suggest that epoetin alfa effectively improves functional outcomes in patients with cancer who receive chemotherapy.

Aged↗