Gastrointestinal stromal tumours: an update

A review of imatinib mesilate in the treatment of patients with gastrointestinal stromal tumours and chronic myeloid leukaemia

Context. Imatinib mesylate (GlivecÒ, GleevecÒ, Novartis) has made a dramatic impact on the treatment available for both chronic myeloid leukaemia (CML) and gastrointestinal stromal tumours (GISTs). Both are rare diseases that have possibly been unfamiliar to many pharmacists until now.

Objective. To provide readers with a structured overview of CML and GISTs and the trial data available to support the role imatinib is playing in the treatment of these diseases.

Data sources. Published reviews and primary trial results were sourced via Medline to prepare the review. Articles published up to and including August 2002 were considered. Additionally, pertinent books were used to prepare the text and Novartis kindly supplied information currently only available on file at the company. As imatinib has only been available for a short time, all types and sizes of trials were considered for inclusion. The authors made the final decision as to the relevance and therefore subsequent inclusion of data.

Conclusions. Imatinib is a new molecularly targeted therapy for the treatment of CML and GISTs. It has provided an efficacious alternative therapy choice for physicians managing the care of patients suffering from these diseases. In the future there is the possibility that imatinib may demonstrate activity in other disease states characterized by the genetic changes targeted by imatinib. The results of randomized controlled trials in new and existing indications are awaited.

Role of F-fluoro-2-deoxyglucose Positron Emission Tomography in Gastric GIST: Predicting Malignant Potential Pre-operatively

Purpose

It is difficult to obtain biopsies from gastrointestinal stromal tumors (GISTs) prior to surgery because GISTs are submucoal tumors, despite being the most common nonepithelial neoplasms of the gastrointestinal tract. Unlike anatomic imaging techniques, PET-CT, which is a molecular imaging tool, can be a useful technique for assessing tumor activity and predicting the malignant potential of certain tumors. Thus, we aimed to evaluate the usefulness of PET-CT as a pre-operative prognostic factor for GISTs by analyzing the correlation between the existing post-operative prognostic factors and the maximum SUV uptake (SUVmax) of pre-operative 18F-fluoro-2-deoxyglucose (FDG) PET-CT.

Materials and Methods

The study was conducted on 26 patients who were diagnosed with gastric GISTs and underwent surgery after being examined with pre-operative FDG PET-CT. An analysis of the correlation bewteen (i) NIH risk classfication and the Ki-67 proliferation index, which are post-operative prognostic factors, and (ii) the SUVmax of PET-CT, which is a pre-operative prognostic factor, was performed.

Results

There were significant correlations between (i) SUVmax and (ii) Ki-67 index, tumor size, mitotic count, and NIH risk group (r=0.854, 0.888, 0.791, and 0.756, respectively). The optimal cut-off value for SUVmax was 3.94 between "low-risk malignancy" and "high-risk malignancy" groups. The sensitivity and specificity of SUVmax for predicting the risk of malignancy were 85.7% and 94.7%, respectively.

Conclusions

The SUVmax of PET-CT is associated with Ki-67 index, tumor size, mitotic count, and NIH classification. Therefore, it is believed that PET-CT is a relatively safe, non-invasive diagnostic tool for assessing malignant potential pre-operatively.

Target therapy in gastrointestinal tract sarcoma: What is new?

Soft tissue sarcoma are rare tumors arising mostly from embryonic mesoderm, that can affect almost any part of the human body, including the gastrointestinal tract. The prognosis associated with soft tissue sarcoma is still poor, mainly because of the low efficacy of traditional approaches based on surgery and chemotherapy. As a result of genetic and molecular analysis, several new target therapies have been developed, leading to a significant improvement in the survival of patients affected by advanced disease. In this review we aim to explore the therapeutic potential and benefit of target therapy in the management of gastrointestinal soft tissue sarcoma and the possible complications or pitfalls of such an approach.

Gastrointestinal stromal tumor: a clinical overview

Gastrointestinal stromal tumor (GIST) is a disease that was poorly understood historically. In the last decade, it has undergone a major transformation, sparked by the landmark discovery of the central role of activating KIT mutations in its pathogenesis and recognition of KIT protein expression (CD 117) as a reliable diagnostic marker of disease. The introduction and subsequent US Food and Drug administration approval of imatinib mesylate in the treatment of metastatic or unresectable GIST in February 1, 2002 has thrust this hitherto little known disease into the center stage of oncology, and GIST has served as a model for rationally designed drug trials in the field of cancer therapeutics since.

Metastatic duodenal GIST: role of surgery combined with imatinib mesylate

BACKGROUND

The best possible treatment of metastatic high grade large duodenal GIST is controversial. Surgery (with or without segmental organ resection) remains the principal treatment for primary and recurrent GIST. However, patients with advanced duodenal GIST have a high risk of early tumour recurrence and short life expectancy.

METHOD

We present a case of a young man treated with a combined modality of surgery and imatinib for an advanced duodenal GIST.

RESULTS

He remains asymptomatic and disease free 42 months following this combined approach.

CONCLUSION

Treatment with imatinib has dramatically improved the outlook for patients with advanced, unresectable and/or metastatic disease.

Gastrointestinal stromal tumors

BACKGROUND

We reviewed radiologic features of gastrointestinal stromal tumors (GISTs) and correlated them with clinical and pathologic findings.

METHODS

We investigated a series of 39 c-Kit-positive GISTs. Clinical and radiologic findings and management of these patients were recorded.

RESULTS

Twenty women and 19 men (mean age 64 years) had histologically proved GIST. Tumor locations were the small bowel (n = 20), stomach (n = 14), rectum (n = 4), and omentum (n = l). Symptoms at presentation were most frequently gastrointestinal bleeding (n = 14) and abdominal pain (n = l1). Tumors were classified as very low risk (n = 2), low risk (n = 10), intermediate risk (n = 12), and high risk (n = 11). Ultrasonography, computed tomography, magnetic resonance, digital subtraction angiography, and barium series were used in the evaluation of these tumors. Most tumors were seen as well-delineated soft tissue masses with heterogeneous contrast enhancement. Necrosis, calcification, and ulceration were most commonly seen in large tumors that presented a more aggressive behavior.

CONCLUSION

GISTs can arise anywhere in the gastrointestinal tract and present a great variety of clinical and radiologic features, depending mostly on size and location.

Gastrointestinal stromal tumours: an update

Recently, there has been intense interest in the study of gastrointestinal stromal tumour (GIST); one might call it a virtual GIST revolution. This is due largely to the realization that most GISTs express KIT and harbour activating c-KIT (KIT) or platelet-derived growth factor receptor-alpha (PDGFRA) receptor tyrosine kinase mutations that can be targeted by small molecule pharmacological inhibitors. Pathologists have benefited greatly from this revolution, mainly in the form of an improved ability to classify GISTs and, even more recently, in understanding the molecular underpinnings that underlie many fascinating clinical and pathological correlations. It is the purpose of this review to summarize recent developments in GIST classification and the molecular pathogenesis of GIST.

The reappraisal of gastrointestinal stromal tumors: from Stout to the KIT revolution

For five decades gastrointestinal stromal tumors (GISTs) truly have represented one of the most confusing as well as neglected areas of both surgical pathology and clinical oncology. The recognition of the central role played by KIT expression in the development of the interstitial cell of Cajal and of the activating KIT mutations in the pathogenesis of GIST have been the keys for a more precise categorization of this long elusive clinicopathological entity. A Consensus Conference held at the National Institutes of Health in 2001 provided both an evidence-based definition and a practical scheme for the assessment of the risk of aggressive clinical behavior. This scheme is based on evaluation of the size and mitotic rate of the tumors, and its use is strongly advocated. On the basis of current data GISTs can be defined as a distinctive group of KIT-expressing mesenchymal neoplasms of the gastrointestinal tract, showing differentiation towards the interstitial cell of Cajal, also known as the gastrointestinal pacemaker cells. Metastatic GISTs have been a virtually incurable disease until the elucidation of the role of KIT mutations. STI-571 (imatinib mesylate) is a molecule that inhibits the function of various receptors with tyrosine kinase activity, such as abl, the bcr-abl chimeric product, platelet-derived growth factor receptor, and KIT. Following its successful use in the treatment of chronic myeloid leukemia, STI-571 has also proved extremely effective in targeting metastatic GIST. Data regarding the duration of the response to this therapy are not yet available, and therefore any overenthusiasm should be avoided. Nonetheless, the GIST story remains paradigmatic of a totally innovative approach to cancer therapy which until now is the most elegant translation of cancer biology experimental knowledge into clinical practice.

Diagnosis of gastrointestinal stromal tumors: A consensus approach

As a result of major recent advances in understanding the biology of gastrointestinal stromal tumors (GISTs), specifically recognition of the central role of activating KIT mutations and associated KIT protein expression in these lesions, and the development of novel and effective therapy for GISTs using the receptor tyrosine kinase inhibitor STI-571, these tumors have become the focus of considerable attention by pathologists, clinicians, and patients. Stromal/mesenchymal tumors of the gastrointestinal tract have long been a source of confusion and controversy with regard to classification, line(s) of differentiation, and prognostication. Characterization of the KIT pathway and its phenotypic implications has helped to resolve some but not all of these issues. Given the now critical role of accurate and reproducible pathologic diagnosis in ensuring appropriate treatment for patients with GIST, the National Institutes of Health convened a GIST workshop in April 2001 with the goal of developing a consensus approach to diagnosis and morphologic prognostication. Key elements of the consensus, as described herein, are the defining role of KIT immunopositivity in diagnosis and a proposed scheme for estimating metastatic risk in these lesions, based on tumor size and mitotic count, recognizing that it is probably unwise to use the definitive term "benign" for any GIST, at least at the present time.

Diagnosis of gastrointestinal stromal tumors: a consensus approach

As a result of major recent advances in understanding the biology of gastrointestinal stromal tumors (GIST), specifically recognition of the central role of activating KIT mutations and associated KIT protein expression in these lesions, and the development of novel and effective therapy for GISTs using the receptor tyrosine kinase inhibitor STI-571, these tumors have become the focus of considerable attention among pathologists, clinicians, and patients. Stromal/mesenchymal tumors of the gastrointestinal tract have long been a source of confusion and controversy with regard to classification, line(s) of differentiation, and prognostication. Characterization of the KIT pathway and its phenotypic implications has helped to resolve some but not all of these issues. Given the now critical role of accurate and reproducible pathologic diagnosis in ensuring appropriate treatment for patients with GIST, the National Institutes of Health (NIH) convened a GIST workshop in April 2001 with the goal of developing a consensus approach to diagnosis and morphologic prognostication. Key elements of the consensus, as described herein, are the defining role of KIT immunopositivity in diagnosis and a proposed scheme for estimating metastatic risk in these lesions, based on tumor size and mitotic count, recognizing that it is probably unwise to use the definitive term benign for any GIST, at least at the present time.

Cytologic diagnosis of gastrointestinal stromal tumor with emphasis on the differential diagnosis with leiomyosarcoma

BACKGROUND

Gastrointestinal stromal tumor (GIST) has only recently been distinguished histologically and immunochemically from morphologically similar neoplasms of the abdomen.

METHODS

The authors reviewed 15 cytologic cases of GIST (14 fine-needle aspiration [FNA] specimens and 1 peritoneal fluid specimen) and compared them with 23 cases of leiomyosarcoma (LMS) arising in the abdomen or pelvis (all FNAs). Immunochemistry (IC) was performed on both the cytologic and subsequent tissue specimens if sufficient specimen was available.

RESULTS

Cytologic samples of GISTs typically showed irregularly outlined clusters of uniform spindle cells that were spread easily without crush artifact. The cells had wispy cytoplasm with long, delicate, filamentous extensions (13 cases; 87%). A prominent vascular pattern was common (9 cases; 60%); pleomorphism (1 case; 7%) was uncommon. The LMSs showed three-dimensional, tightly cohesive, sharply marginated syncytia of spindle cells, often with nuclear crush artifact. The cytoplasm/stroma had a distinct wiry, refractile appearance (21 cases; 91%); delicate filamentous cytoplasmic extensions (5 cases; 22%) and prominent vessels (3 cases; 13%) were less common. LMSs more commonly exhibited pleomorphism (14 cases; 61%). Epithelioid cytomorphology, mitoses, and necrosis occasionally were observed in both tumor types. IC for c-kit (on cytologic material) was positive in 10 of 10 cases of GIST (usually diffuse and strong) and 2 of 19 cases of LMS (focal). CD34 positivity favored GIST (4 of 9 cases) over LMS (1 of 19 cases). Smooth muscle actin was positive in 20 of 20 LMSs (strong and diffuse) and 6 of 10 GISTs (usually focal). Desmin was positive in 12 of 20 LMSs and was only focally positive in 1 of 11 GISTs. Correlation of IC results was excellent between cytologic and tissue specimens.

CONCLUSIONS

Delicate cytoplasmic processes; a prominent vascular pattern; a lack of nuclear pleomorphism; and a c-kit-positive, desmin-negative immunoprofile are characteristic features of GIST and help distinguish these tumors from LMS in cytologic specimens.

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.

Signal transduction pathways in sarcoma as targets for therapeutic intervention

Investigations into the molecular alterations in sarcomas have made substantial progress during the past decade. Classical linkage analysis and the direct sequencing of chromosomal translocation fusions have identified candidate genes in many different sarcomas. A large group of these genes participate in signal transduction pathways and represent potential sites of disease intervention with targeted therapies. This review will discuss five types of sarcoma that display aberrant tyrosine kinase pathway signaling: gastrointestinal stromal tumor, inflammatory myofibroblastic tumor, congenital fibrosarcoma and mesoblastic nephroma, dermatofibrosarcoma protuberans, and desmoplastic small round cell tumor; one sarcoma predisposition syndrome with specific dysregulation of the ras pathway--neurofibromatosis--will also be discussed.

Recent progress in the classification of soft tissue tumors: role of genetics and clinical implications

Soft tissue tumors comprise a vast and heterogeneous group of neoplasms. Because different tumors often have different biological behaviors and respond differently to various therapeutic modalities, precise classification is paramount. The majority of soft tissue tumors were first delineated on the basis of morphologic and clinical findings, which in many cases were adequate to accurately separate different tumors into homogeneous groups; however, it has increasingly been appreciated that many entities are actually heterogeneous groups of tumors that have similar histologic and pathologic characteristics but differ in their clinical behavior and underlying pathogenesis. Within the past several years, great strides have been made in the purification of different entities. This accomplishment has largely been because of advances in our understanding of the molecular genetics that underlie the pathogenesis of many sarcomas and the development of new and specific tumor markers. This review highlights some important recent work in two selected soft tissue tumors-gastrointestinal stromal tumor and inflammatory myofibroblastic tumor. These examples illustrate the type of progress that is being made in the classification of soft tissue tumors.

Immunohistochemical detection of cytokeratin and epithelial membrane antigen in leiomyosarcoma: a systematic study of 100 cases

Although 'aberrant' expression of the epithelial markers, cytokeratin (CK) and epithelial membrane antigen (EMA), in leiomyosarcoma has been described previously, there has not been a study of this phenomenon with clinicopathological correlation in a large series of lesions at different anatomical sites. We investigated systematically the immunohistochemical reactivity for CK and EMA in 100 cases of leiomyosarcoma. CK and EMA were positive in 38% and 44% of the cases, respectively. Although staining was usually focal, extensive immunoreactivity was observed in 11% with CK and 6% with EMA. There was no correlation between immunoreactivity for CK and EMA in leiomyosarcomas and non-neoplastic smooth muscle at the same location. Immunoreactivity for CK and EMA was not correlated with the location, age, sex, histological grade, or histological features, except for more frequent EMA positivity in vascular and uterine tumors than in soft tissue cases. These results indicate that CK and/or EMA-positive leiomyosarcomas do not have distinctive clinicopathological features differing from those of negative cases. However, the considerable frequency of immunoreactivity for these epithelial markers in leiomyosarcoma, occasionally with diffuse and strong immunopositivity, should be recognized as a potentially serious diagnostic pitfall in the differential diagnosis of other malignant spindle cell neoplasms.

Molecular Insights into the Histogenesis and Pathogenesis of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) have long been problematic in terms of classification and determination of prognosis. Recent studies have suggested that GISTs differentiate toward a phenotype resembling the interstitial cells of Cajal. This has led to the important discovery that activating mutations in the KIT receptor tyrosine kinase play an important role in the pathogenesis of GISTs. These findings have helped clarify the distinction between GISTs and other mesenchymal neoplasms of the gastrointestinal tract and may translate into an improved ability to predict biologic behavior, as well as suggesting possible avenues for rational drug design for the treatment of GISTs. Int J Surg Pathol 8(1):5-10, 2000