Efficacy and safety of imatinib mesylate in advanced gastrointestinal stromal tumors

Chemical approaches to the discovery and development of cancer therapies

The chemical sciences are essential for the process of anticancer-drug discovery, and a range of chemical research techniques is needed to develop clinically effective drugs. Improved understanding of the cellular, molecular and genetic basis of cancer has increased the number of drug targets available. What chemical approaches are used to develop agents that target specific features of cancer cells and make these therapeutics more effective? We outline the roles that chemical synthesis and understanding of drug uptake have had in drug discovery over the past 100 years, as well as the chemical insights derived from knowledge of the three-dimensional structure of targets.

Soft tissue sarcoma: why not treated?

BACKGROUND

Soft tissue sarcomas (STS) are uncommon malignancies and elderly STS patients have been reported to receive less definitive treatment compared to young STS patients. The present study was performed to investigate whether withholding treatment was based on disease specific aspects, patients' general health condition, comorbidity or a combination of these.

METHODS

Patients with primary STS, registered by the Comprehensive Cancer Center North-Netherlands (CCCN) from 1989 to 1999, were analyzed retrospectively with regard to the inclusion-criteria: no primary anti-tumor treatment.

RESULTS

From 1989 to 1999, 620 patients (including 56 Kaposi sarcoma) were registered with primary STS. Seventy-six patients (13%) were registered as untreated. Nineteen patients were excluded. Records of 57 patients, median age 71 years (range 23-92, 40 patients > or =65 years, 17 patients < 65 years) were examined. The reasons for no treatment were irresectability of the sarcoma (65%), metastatic disease (11%), comorbidity (4%), poor general health (5%), death prior to therapy (7%) and refusal of therapy (3%) (motivation not documented in 5%).

CONCLUSIONS

Thirteen percent of all STS patients within the CCCN region were not treated, 70% of these patients were elderly. Withholding treatment was mostly disease-related (76%), e.g. irresectable retroperitoneal STS or metastatic disease; for 19% of the patients, it was related to their poor general health. The decision to refrain from cancer treatment was justifiable in all these STS patients.

The development of imatinib as a therapeutic agent for chronic myeloid leukemia

Imatinib has revolutionized drug therapy of chronic myeloid leukemia (CML). Preclinical studies were promising but the results of clinical trials by far exceeded expectations. Responses in chronic phase are unprecedented, with rates of complete cytogenetic response (CCR) of more than 40% in patients after failure of interferon-α (IFN) and more than 80% in newly diagnosed patients, a level of efficacy that led to regulatory approval in record time. While most of these responses are stable, resistance to treatment after an initial response is common in more advanced phases of the disease. Mutations in the kinase domain (KD) of BCR-ABL that impair imatinib binding have been identified as the leading cause of resistance. Patients with CCR who achieve a profound reduction of BCR-ABL mRNA have a very low risk of disease progression. However, residual disease usually remains detectable with reverse transcription–polymerase chain reaction (RT-PCR), indicating that disease eradication may pose a significant challenge. The mechanisms underlying the persistence of minimal residual disease are unknown. In this manuscript, we review the preclinical and clinical development of imatinib for the therapy of CML, resistance and strategies that may help to eliminate resistant or residual leukemia.

Carney triad: case report and molecular analysis of gastric tumor

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract. Most of them are thought to be sporadic, but some arise in the settings of neurofibromatosis type I (NF-1) and the Carney triad. The Carney triad is a syndrome of unknown etiology, occurring predominantly in young females, comprising gastrointestinal stromal tumors, pulmonary chondromas, and extra-adrenal paragangliomas. GISTs of the Carney triad involve predominantly the body and the antrum of the stomach, are generally multifocal, and have a better prognosis than sporadic GISTs. We describe the clinical and pathological features of a case of Carney triad that featured multiple gastric GISTs, mediastinal paraganglioma, and esophageal leiomyoma. Ten years after gastric resection, the patient developed liver and peritoneal metastasis and was treated with Imatinib mesylate for 6 months with no change in the lesions. The molecular analysis of the GIST, the first reported in a gastric tumor from the triad, showed a wild-type KIT and PDGFRA genes.

Gastrointestinal stromal tumors: the incidence, prevalence, clinical course, and prognostication in the preimatinib mesylate era--a population-based study in western Sweden

BACKGROUND

Recent breakthroughs regarding gastrointestinal stromal tumors (GIST) and their pathogenesis have redefined diagnostic criteria and have led to the development of molecularly targeted drug therapy. New treatment options mandate more accurate information regarding the incidence, prevalence, clinical behavior, and prognostic factors of GIST.

METHODS

All patients (n=1460) who potentially had GIST diagnosed from 1983 to 2000 in western Sweden (population, 1.3-1.6 million) were reviewed, and 288 patients with primary GIST were identified. The incidence and prevalence of GIST were determined, and predictive prognostic factors, including current risk-group stratifications, were analyzed statistically.

RESULTS

Ninety percent of GISTs were detected clinically due to symptoms (69%) or were incidental findings at surgery (21%); the remaining 10% of GISTs were found at autopsy. Forty-four percent of symptomatic, clinically detected GISTs were categorized as high risk (29%) or overtly malignant (15%), with tumor-related deaths occurring in 63% of patients and 83% of patients, respectively (estimated median survival, of 40 months and 16 months, respectively). Tumor-related deaths occurred in only 2 of 170 of patients (1.2%) with very-low-risk, low-risk, or intermediate-risk tumors. The annual incidence of GIST was 14.5 per million. The prevalence of all GIST risk groups was 129 per million (31 per million for the high-risk group and the overtly malignant group).

CONCLUSIONS

GIST has been under recognized: Its incidence, prevalence, and clinical aggressiveness also have been underestimated. Currently existing risk-group stratification systems based on tumor size and mitotic rate delineate GIST patients who have a poor prognosis. Prognostication in patients with GIST can be refined using a proposed risk score based solely on tumor size and proliferative index.

Treatment and risk factors for recurrence after curative resection of gastrointestinal stromal tumors of the stomach

The current definitive treatment for gastrointestinal stromal tumor (GIST) of the stomach is complete resection. GIST has a highly variable clinical course, and recurrent disease sometimes develops despite curative treatment. Although several known risk factors for recurrence exist, adequate treatment strategies are lacking. This study evaluated factors associated with relapse after curative treatment. Sixty patients with gastric GIST were identified from a hospital disease registry database. Clinicopathologic characteristics of these patients were reviewed and the Cox proportional hazards regression analysis was used to identify recurrent risk factors. With a median follow-up of 60 months (range 5-286 months), recurrence occurred in eight (13%) patients, three of whom underwent resection of the recurrent disease and are alive to date. Univariate analysis demonstrated that invasion of the adjacent organs (p = 0.0005), tumor size (p = 0.0046), and expression of proliferative markers [MIB-1 proliferative index (PI) > or = 10%] (p = 0.0001) were significant risk factors for recurrence. Multivariate analysis with these three factors as variables revealed that only MIB-1 PI was a significant independent risk factor for recurrence (p = 0.0051). In conclusion, surgical resection may be indicated whenever a recurrent GIST is considered resectable. A high MIB-1 PI was identified as an independent indicator of risk for recurrent disease following curative surgery.

Activation mutations of human c-KIT resistant to imatinib mesylate are sensitive to the tyrosine kinase inhibitor PKC412

Constitutively activated forms of the transmembrane receptor tyrosine kinase c-KIT have been associated with systemic mast cell disease, acute myeloid leukemia, and gastrointestinal stromal tumors. Reports of the resistance of the kinase domain mutation D816V to the adenosine triphosphate (ATP)-competitive kinase inhibitor imatinib mesylate prompted us to characterize 14 c-KIT mutations reported in association with human hematologic malignancies for transforming activity in the murine hematopoietic cell line Ba/F3 and for sensitivity to the tyrosine kinase inhibitor PKC412. Ten of 14 c-KIT mutations conferred interleukin 3 (IL-3)-independent growth. c-KIT D816Y and D816V transformed cells were sensitive to PKC412 despite resistance to imatinib mesylate. In these cells, PKC412, but not imatinib mesylate, inhibited autophosphorylation of c-KIT and activation of downstream effectors signal transducer and transcriptional activator 5 (Stat5) and Stat3. Variable sensitivities to PKC412 or imatinib mesylate were observed among other mutants. These findings suggest that PKC412 may be a useful therapeutic agent for c-KIT-positive malignancies harboring the imatinib mesylate-resistant D816V or D816Y activation mutations.

Imatinib and gastrointestinal stromal tumors: Where do we go from here?

Imatinib has tremendously changed the treatment of gastrointestinal stromal tumor (GIST). Research is currently focusing on its optimal use and the mechanisms of resistance that may emerge. A multidisciplinary approach including medical oncologists, surgeons, radiologists, and pathologists is crucial for the optimal management of these patients. Moreover, imatinib treatment in GIST represents an extraordinary model to expand our knowledge on the molecular mechanisms that are basic to the effects of molecularly targeted therapies. This review summarizes the existing knowledge of the imatinib treatment in GIST and describes directions for further development.

Gastrointestinal stromal tumors: CT and MRI findings

The objective of this study was to report the CT and MRI appearances of primary and metastatic gastrointestinal stromal tumor (GIST). The clinical and imaging findings of 31 patients with histological and immunohistochemical diagnosis of GIST were reviewed. The CT and MRI findings were assessed independently for size, location, enhancement characteristics, and pattern of metastatic disease. The tumors were of enteric (n=13), gastric (n=12), duodenal (n=2), and rectal (n=3) origin. In one case the primary site was the mesentery, without involvement of bowel. Primary tumors were typically exophytic (79%), larger than 5 cm (84%), and inhomogeneously enhancing (84%). Central necrosis of all tumors (37%) and aneurysmal dilation of enteric tumors (33%) were less common. Metastases were most commonly to mesentery (26%) or liver (32%). Less common findings were ascites (7%) and omental caking (3%). Liver metastases were hypervascular in 92% of patients and rapidly became cystic following therapy with imatinib mesylate (Gleevec; Novartis, East Hanover, NJ, USA). Lung metastases, bowel obstruction, vascular invasion, and significant lymphadenopathy were not seen in any patient. GISTs have some specific CT findings which could help differentiate them from other gastrointestinal tumors. Liver metastases became cystic following therapy, mimicking simple cysts. MRI was better than single-phase CT for assessing liver metastases, while CT was more sensitive for mesenteric metastases.

Phase II study of ET-743 in advanced soft tissue sarcomas: a European Organisation for the Research and Treatment of Cancer (EORTC) soft tissue and bone sarcoma group trial

PURPOSE

This nonrandomized multicenter phase II study was performed to evaluate the activity and safety of Ecteinascidin (ET-743) administered at a dose of 1.5 mg/m(2) as a 24-hour continuous infusion every 3 weeks in patients with pretreated advanced soft tissue sarcoma.

PATIENTS AND METHODS

Patients with documented progressive advanced soft tissue sarcoma received ET-743 as second- or third-line chemotherapy. Antitumor activity was evaluated every 6 weeks until progression, excessive toxicity, or patient refusal.

RESULTS

One hundred four patients from eight European institutions were included in the study (March 1999 to November 2000). A total of 410 cycles were administered in 99 assessable patients. Toxicity mainly involved reversible grade 3 to 4 asymptomatic elevation of transaminases in 40% of patients, and grade 3 to 4 neutropenia was observed in 52% of patients. There were eight partial responses (PR; objective regression rate, 8%), 45 no change (NC; > 6 months in 26% of patients), and 39 progressive disease. A progression arrest rate (PR + NC) of 56% was observed in leiomyosarcoma and 61% in synovialosarcoma. The median duration of the time to progression was 105 days, and the 6-month progression-free survival was 29%. The median duration of survival was 9.2 months.

CONCLUSION

ET-743 seems to be a promising active agent in advanced soft tissue sarcoma, with no cumulative toxicities. The 6-months progression-free survival observed in advanced soft tissue sarcoma compares favorably with those obtained with other active drugs tested in second-line chemotherapy in previous European Organisation for the Research and Treatment of Cancer trials. The median overall survival was unusually long in these heavily pretreated patients mainly due to the high number of patients who benefit from the drug in terms of tumor control.

Revision of gastrointestinal mesenchymal tumours with CD117

BACKGROUND

Tyrosinekinase inhibitors improve the treatment of gastrointestinal stromal tumours (GISTs) and their diagnosis has been facilitated by recently developed immunohistochemical markers. It is hypothesised that in the past, the true incidence of GISTs has been underestimated.

AIMS

To study the clinicopathological features of previously resected mesenchymal tumours of the gastrointestinal tract and determine the accuracy of previous diagnostic results.

PATIENTS AND METHODS

Patients with mesenchymal tumours of the gastrointestinal tract operated on between 1987 and 2002 were identified using medical and pathologic files. Immunohistochemical staining for CD117, CD34, desmin and S100 was performed, and diagnosis reviewed.

RESULTS

Thirty-six mesenchymal tumours were reanalysed. Before revision, diagnosis of GIST was correctly made in only six cases. Supportive use of immunohistochemical markers for accurate diagnosis of the remaining 30 previously undefined mesenchymal tumours yielded 17 additional GISTs. Therefore, 23 of 36 (63%) gastrointestinal mesenchymal tumours were shown to be GISTs.

CONCLUSIONS

The true incidence of GISTs has been underestimated. There is merit in reviewing the clinical diagnoses of all mesenchymal tumours of the gastrointestinal tract with modern immunohistochemical markers. This may enhance clinical decision making.

In vitro and in vivo activity of ATP-based kinase inhibitors AP23464 and AP23848 against activation-loop mutants of Kit

Oncogenic mutations of the Kit receptor tyrosine kinase occur in several types of malignancy. Juxtamembrane domain mutations are common in gastrointestinal stromal tumors, whereas mutations in the kinase activation loop, most commonly D816V, are seen in systemic mastocytosis and acute myelogenous leukemia. Kit activation-loop mutants are insensitive to imatinib mesylate and have been largely resistant to targeted inhibition. We determined the sensitivities of both Kit mutant classes to the adenosine triphosphate (ATP)-based inhibitors AP23464 and AP23848. In cell lines expressing activation-loop mutants, low-nM concentrations of AP23464 inhibited phosphorylation of Kit and its downstream targets Akt and signal transducer and activator of transcription 3 (STAT3). This was associated with cell-cycle arrest and apoptosis. Wild-type Kit-and juxtamembrane-mutant-expressing cell lines required considerably higher concentrations for equivalent inhibition, suggesting a therapeutic window in which cells harboring D816V Kit could be eliminated without interfering with normal cellular function. Additionally, AP23464 did not disrupt normal hematopoietic progenitor-cell growth at concentrations that inhibited activation-loop mutants of Kit. In a murine model, AP23848 inhibited activation-loop mutant Kit phosphorylation and tumor growth. Thus, AP23464 and AP23848 potently and selectively target activation-loop mutants of Kit in vitro and in vivo and could have therapeutic potential against D816V-expressing malignancies.

Expression of c-kit protooncogene in human hepatocellular carcinoma

The expression of the c-kit protooncogene in human hepatocellular carcinoma (HCC) was investigated. Immunohistochemical staining (IHC) and RT-PCR were employed to examine the protein and mRNA expression of c-kit protooncogene, respectively. IHC results demonstrated that 22 of 86 (25.6%) HCC tissue sections expressed c-kit protein. The c-kit mRNA transcript was further confirmed in all 22 IHC c-kit positive HCC tissue samples by RT-PCR. Moreover, the relationship between c-kit expression in HCC and prognosis of patients was statistically analyzed and a correlation was established. The group of patients whose HCC specimens showed positive c-kit staining exhibited better survival as compared to those patients with negative c-kit expression (p=0.021). These results suggest that c-kit expression may be a good prognostic indicator for HCC.

Novel chemotherapeutic agents for the treatment of glioblastoma multiforme

During the last few decades, the discovery of novel targets for therapeutic intervention led to the development of chemotherapeutic agents that specifically interfere with altered cellular functions of tumour cells. Genetic alterations in glioblastoma affect cell proliferation and cell cycle control, as well as invasive and metastatic growth. Therefore, innovative therapeutic strategies have been based on drugs targeting cellular proliferation, invasion, angiogenesis, metastasis and differentiation of tumour cells. Furthermore, disruption of cell-death pathways also contributes to the pathogenesis of glioblastoma and may result in resistance to chemotherapy and radiation. Therefore, additional treatment strategies that target intracellular survival and/or apoptotic pathways are under current laboratory investigation. The progress in the understanding of glioblastoma tumour biology and the refined diagnosis of individual patients together with the exploration of targeted drugs may allow a risk-adapted, individualised therapeutic strategy and will hopefully improve prognosis of glioblastoma patients in the future.

Novel FLT3 tyrosine kinase inhibitors

Acute myeloid leukaemia (AML) is an aggressive haematological malignancy that is curable in approximately 40% of cases. Activating mutations of the receptor tyrosine kinase FLT3 (FMS-like tyrosine kinase-3) are the single most common molecular abnormalities in AML and are associated with a distinctly worse prognosis. In an effort to target this mutation and improve outcomes in this subgroup of AML patients, several novel small-molecule FLT3 tyrosine kinase inhibitors are currently in development. Some of these FLT3 inhibitors are useful only as laboratory tools, while others clearly have clinical potential. These compounds are derived from a wide variety of chemical classes and differ significantly both in their potency and selectivity. This review summarises these developments and examines these novel agents with regard to both the assays used to characterise them and their clinical potential.

SURGERY FOR GASTROINTESTINAL STROMAL TUMOUR IN THE POST-IMATINIB ERA

Gastrointestinal stromal tumour (GIST) is a rare tumour. Historically, surgery has been the only effective treatment. The prognosis of patients with gastrointestinal stromal tumour is poor. Even after apparently 'curative' surgical resection more than 50% of patients relapse. The development of an effective novel targeted therapy against GIST (imatinib mesylate) is a success story of molecular biology that has dramatically altered the management of patients with these tumours. However, as follow up of patients who have initially responded to imatinib has increased, it has become evident that such hopes of cure were premature because responses to imatinib are of limited duration. Unresolved issues include the role of imatinib as an induction (neo-adjuvant) therapy prior to surgery, or as adjuvant treatment after surgery, the role of surgery in patients with a differential or partial response and the role of surgery in patients with isolated metastatic disease. In the present paper the biology and natural history of GIST are reviewed, and the complexities of surgical management that exist in the context of an effective, but not curative, biological therapy, are addressed.

Monitoring response to treatment in patients utilizing PET

Establishing new surrogate end points for monitoring response to treatment is needed for current therapy modalities and for new therapeutic strategies including molecular targeted cancer therapies. PET as a functional imaging technology provides rapid, reproducible, noninvasive in vivo assessment and quantification of several biologic processes targeted by these therapies. PET is useful in a variety of clinical relevant applications, including distinguishing between radiation necrosis and tumor recurrence, determining the resectability of recurrent tumor, and evaluating response to therapy. FDG-PET has demonstrated efficacy for monitoring therapeutic response in a wide range of cancers, including breast, esophageal, lung, head and neck, and lymphoma. FDG-PET can assess tumor glucose use with high reproducibility. Following therapy, the decrease of glucose use correlates with the reduction of viable tumor cells. FDG-PET allows the prediction of therapy response early in the course of therapy and determining the viability of residual masses after completion of treatment. The molecular basis for the success of FDG-PET is the rapid reduction of tumor glucose metabolism in effective therapies. Of even higher clinical relevance is the accurate identification of nonresponders in patients without a significant change in tumor glucose metabolism after initiation of therapy. PET imaging can easily visualize these changes in metabolic activity and indicate, sometimes within hours of the first treatment, whether or not a patient will respond to a particular therapy. In contrast to CT, MR imaging, or ultrasound, PET imaging allows identification of responding and nonresponding tumors early in the course of therapy. With this information, physicians can rapidly modify ineffective therapies for individual patients and thereby potentially improve patient outcomes and reduce cost. One of the major limitations for the routine application of FDG-PET imaging for therapy monitoring is that no generally accepted cutoff values have been established to differentiate optimally between responders and nonresponders. The patient series are still relatively small and frequently consist of different tumor types and different therapy regimens. Prospective studies including a sufficient number of patients are needed to define cutoff values to differentiate between responder and nonresponder for different tumors and different treatment regimes. In the future, PET imaging can also serve in the evaluation of new therapeutic agents, new experimental treatments, and specifically in monitoring clinical phase II studies.

Esophageal GIST: therapeutic implications of an uncommon presentation of a rare tumor

Gastrointestinal stromal tumors (GISTs) are rarely reported in the esophagus. The authors report a patient with an esophageal GIST, incidentally found after an echocardiogram. CT scan and endoscopic ultrasonography showed the tumor in the dependence of the muscularis propria of the esophageal wall. An Ivor-Lewis esophagectomy was performed. The tumor was well-circumscribed involving the submucosal and the muscular layers of the esophagus, measuring 13.5 x 8.5 x 7.6 cm, without involving the surgical margins. Histologically, the tumor consisted of spindle cells, with low mitotic index (2/50 HPF), that were immunoreactive for KIT (CD117) and CD34, consistent with GIST of high risk of aggressive behavior. No adjuvant therapy was given to the patient, who is alive and without evidence of disease 1 year after surgery. Since esophageal GISTs are rarely reported in the literature and usually have a poor prognosis, the diagnostic differentiation of these tumors from other more common mesenchymal neoplasms is essential, both for therapeutic and prognostic reasons.

C-kit expression in renal oncocytomas and chromophobe renal cell carcinomas

C- kit encodes the membrane-bound tyrosine kinase KIT, whose expression has been identified in several types of human neoplasms. Recently, KIT has been reported to be a marker for chromophobe renal cell carcinoma (RCC) and renal angiomyolipoma. However, expression of this molecule has not been adequately studied in other renal tumors, particularly oncocytoma, which may morphologically resemble chromophobe RCC. In this study, we analyzed c- kit messenger RNA (mRNA) levels in 17 chromophobe RCCs and 20 renal oncocytomas obtained from complementary DNA (cDNA) microarrays. Furthermore, comprehensive immunohistochemical analysis of KIT protein using a monoclonal antibody was performed in 226 renal tumors including chromophobe RCC (n=40), oncocytoma (n=41), clear-cell RCC (n=40), renal angiomyolipoma (n=29), and papillary RCC (n=21) on tissue microarrays (TMAs) and was compared with immunostaining results from 25 chromophobe RCCs and 30 oncocytomas using standard sections. The staining intensity was semiquantitatively graded on a 3-tier scoring system. All chromophobe RCCs and oncocytomas showed significant overexpression of c- kit mRNA. The average increase of mRNA compared with normal kidney tissue was 7.4-fold for chromophobe RCCs and 7.4-fold for oncocytomas. Immunohistochemical expression of KIT was found in most chromophobe RCCs (95% in TMAs and 96% in conventional sections) and oncocytomas (88% in TMAs and 100% in conventional sections) but was infrequently observed in renal angiomyolipomas (17%), papillary RCCs (5%), and clear-cell RCCs (3%). Furthermore, the average KIT immunoreactivity in TMAs was stronger in chromophobe RCC (1.93) and oncocytoma (2.07) than in other subtypes of renal tumors tested, including angiomyolipomas (0.17), papillary RCCs (0.05), and clear-cell RCCs (0.03). In conclusion, we found a significant elevation of c- kit mRNA by cDNA expression microarrays and overexpression of KIT protein by immunohistochemistry not only in chromophobe RCCs but also in oncocytomas. In contrast, immunohistochemical expression of KIT was not detected in most other types of renal cell tumors evaluated. The differential expression of c- kit in these renal tumors may have diagnostic and therapeutic implications.

Primitive mesenteric gastrointestinal stromal tumor with autonomic nerve/ganglionic differentiation presenting as a huge mass with small synchronous nodules

We present a case of a primary mesenteric ectopic gastrointestinal stromal tumor. The pathologic characteristics of this neoplasm, autonomic nerve/ganglionic differentiation and presentation as a huge mass with small synchronous nodules, have not been previously described in the literature.

Genetic alterations and protein expression of KIT and PDGFRA in serous ovarian carcinoma

KIT and PDGFRA are receptor tyrosine kinases that can be specifically inactivated by small-molecule tyrosine kinase inhibitors, notably imatinib mesylate. In ovarian carcinoma, expression of KIT and PDGFRA protein has been documented, but the frequency and the molecular background of expression are poorly known. We analysed the expression of KIT and PDGFRA by immunohistochemistry in 522 serous ovarian carcinomas, and mutations of KIT and PDGFRA by denaturing high-performance liquid chromatographyin 125 and 187 serous ovarian carcinomas, respectively. No mutations of KIT or PDGFRA were detected. KIT expression was detected in 12% of carcinomas: low expression in 10% and high expression in 2% of cases. Using normal serous epithelium as a reference, decreased PDGFRA expression was detected in 12% and increased expression in 13% of carcinomas. Both KIT and PDGFRA expression were associated with high tumour grade, high proliferation index and poor patient outcome. By fluorescence in situ hybridisation, no KIT amplification was found in carcinomas with high KIT expression, but two cases showed a relative gain of chromosome 4. In conclusion, no mutations of KIT or PDGFRA were found, but a subset of serous ovarian carcinoma showed overexpression of the proteins, which was associated with aggressive tumour characteristics.

Imatinib blocks spontaneous mechanical activities in the adult mouse small intestine: possible inhibition of c-Kit signaling

Interstitial cells of Cajal (ICCs) are postulated to serve as pacemakers that physiologically generate electrical slow waves in the gastrointestinal tract. Imatinib is a novel and potent inhibitor of c-Kit tyrosine kinase and a new therapeutic agent for gastrointestinal stromal tumors (GIST) which presumably arise from ICCs. The effects of imatinib on the basal rhythmic mechanical activities of small intestinal circular muscles were investigated in ring preparations of the gut. The small intestinal rings of BALB/c mice exhibited spontaneous contractile activity at a rate of 40.8 +/- 4.9 contractions/min. Imatinib (1- 81 micromol/l) dose-dependently abolished spontaneous contractile activity in the 9- to 27-micromol/l concentration range. Contraction was restored by washing imatinib out with a fresh buffer. High K(+)-induced contraction was not affected by imatinib, suggesting that the drug does not have nonspecific inhibitory actions on the smooth muscles. The small intestinal rings of adult W/W(v)mice, which lack a functional c-Kit activity,exhibited only small and irregular spontaneous contractions. These results demonstrate that imatinib affects bowel contractions, and suggest that the c-Kit signaling of ICCs plays an essential role in the spontaneous movements in circular muscles of the mouse small intestine.

Spontaneous rupture of giant gastric stromal tumor into gastric lumen

BACKGROUND: Gastrointestinal stromal tumors (GIST) constitute a large majority of mesenchymal tumors of the gastrointestinal (GI) tract, which express the c-kit proto-oncogene protein, a cell membrane receptor with tyrosine kinase activity. GI stromal tumors of the stomach are usually associated with bleeding, abdominal pain or a palpable mass. CASE PRESENTATION: A 75-year-old male presented with upper abdominal pain and palpable mass. Computed tomographic (CT) scan of the abdomen showed a large mass arising in the posterior aspect of fundus, body, and greater curvature of the stomach. Second day after the admission, there was significant reduction in the size of the tumor, clinically as well as radiologically. Endoscopic biopsy showed large bulge in fundus and corpus of the stomach posteriorly with an opening in the posterior part of the corpus, and biopsy from the edge of the opening reveled GIST. Patient underwent curative resection. CONCLUSION: Spontaneous ruptured of giant gastric stromal tumor is very rare presentation of stomach GIST. Thorough clinical examination and timely investigation can diagnose rare complication.

Phase II study of the antiangiogenic agent SU5416 in patients with advanced soft tissue sarcomas

PURPOSE

SU5416 (semaxanib) is a small molecule inhibitor of the vascular endothelial growth factor (VEGF) receptor-2 and KIT receptor tyrosine kinases. This Phase II study was conducted to investigate the safety and efficacy of SU5416 for patients with soft tissue sarcomas.

EXPERIMENTAL DESIGN

Thirteen patients with locally advanced or metastatic soft tissue sarcomas were treated with SU5416 via intravenous infusion at a dose of 145 mg/m(2) twice weekly. In selected cases tumor biopsies were taken before and after 2 months of treatment.

RESULTS

The median progression-free survival was 1.8 months. Median overall survival was 22.8 months. No objective tumor responses were observed. There was evidence of shorter survival among patients with high baseline urine VEGF levels (P = 0.04). No grade 4 toxicities were observed. The most common grade 3 toxicities were headache and thrombosis. Other less serious toxicities included fatigue, nausea, and abdominal pain. The median systolic blood pressure increased from 118 mmHg at baseline to 133 after 1 month of treatment (P = 0.01). Post-treatment tumor biopsies showed no significant decreases in VEGF receptor phosphorylation compared with baseline in 3 evaluable patients. One patient with gastrointestinal stromal tumor who had rapid progression during SU5416 treatment was subsequently treated with another KIT inhibitor, imatinib mesylate, and had a partial response lasting >36 months.

CONCLUSIONS

SU5416 was relatively well tolerated but did not demonstrate significant antitumor activity against advanced soft tissue sarcoma. Correlative studies suggest that VEGF receptor or KIT inhibition was incomplete in at least some cases, providing a possible explanation for the observed lack of activity.

Treatment of Gastrointestinal Stromal Tumors with Imatinib Mesylate:A Major Breakthrough in the Understanding of Tumor-specific Molecular Characteristics

A specific treatment for gastrointestinal stromal tumors (GIST) has been found through improved understanding of the molecular mechanism of carcinogenesis. GIST are radio and chemo-resistant (less than 10 objective responses). Stromal tumors originate from the multiplication of the cells of Cajal, which intervene in intestinal motility and express the c-Kit gene, also called CD117, on their surface. CD117 is a protein with tyrosine kinase activity, and can be demonstrated through immunohistochemical staining techniques. Treatment with Imatinib mesylate (Glivec), a recently discovered selective inhibitor of tyrosine kinases already used in chronic myeloid leukemia (in which an overexpression of tyrosine kinase is observed) was associated with tumor regression of more than 50% in the initial series of patients with GIST treated in 2001. Since then, approximately 2,000 patients have been included in therapeutic trials, with an objective response rate between 60% and 70% 12 to 18 months after inclusion. The clinical benefit has been estimated at 80% to 90% in patients whose chance of survival until now has been less than 30% at one year (median survival 18 months). Nonetheless, imatinib mesylate has not shown any activity in CD117-negative sarcoma (10% of sarcoma). The therapeutic importance of this drug in the treatment of solid GI tumors deemed inoperable is considerable.

Gastrointestinal stromal tumors of the stomach: a clinicopathologic, immunohistochemical, and molecular genetic study of 1765 cases with long-term follow-up

Gastrointestinal (GI) stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are the most common mesenchymal tumors of the GI tract. In this study, we analyzed 1869 cases originally classified as smooth muscle tumors of the stomach and found that 1765 (94%) of these were GISTs. The GISTs had a slight male predominance (55%) with a median age of 63 years. Only 2.7% of tumors occurred before the age of 21 years and 9.1% before the age of 40 years. The tumors varied from 0.5 to 44 cm (median, 6.0 cm) and most commonly presented with GI bleeding; 12% were incidentally detected. Several histologic variants were recognized among the spindle cell tumors (sclerosing, palisaded-vacuolated, hypercellular, and sarcomatous) and of epithelioid tumors (sclerosing, dyscohesive, hypercellular, and sarcomatous). Outcome was strongly dependent on tumor size and mitotic activity. Only 2% to 3% of tumors <10 cm and <5 mitoses/50 HPFs metastasized, whereas 86% of tumors >10 cm and >5 mitoses/50 HPFs metastasized. However, tumors >10 cm with mitotic activity <5/50 HPFs and those <5 cm with mitoses >5/50 HPFs had a relatively low metastatic rate (11% and 15%). A small number of patients survived intra-abdominal metastasis up to over 20 years. Tumor location in fundus or gastroesophageal junction, coagulative necrosis, ulceration, and mucosal invasion were unfavorable factors (P <0.001), whereas tumor location in antrum was favorable (P <0.001). KIT expression was detected in 91% of the cases, CD34 in 82%, smooth muscle actin in 18%, and desmin in 5%; the latter two were favorable (P <0.001). KIT exon 11 mutations were detected in 119 cases; patients with point mutations fared better than those with deletions (P <0.01). PDGFRA exon 18 mutations (total 86 cases) were common in epithelioid GISTs and most commonly represented a D842V point mutation; none of these was prognostically significant. The above results may be helpful for setting the criteria for adjuvant treatment such as Gleevec.

Strategies to overcome resistance to targeted protein kinase inhibitors

Selective inhibition of protein tyrosine kinases is gaining importance as an effective therapeutic approach for the treatment of a wide range of human cancers. However, as extensively documented for the BCR-ABL oncogene in imatinib-treated leukaemia patients, clinical resistance caused by mutations in the targeted oncogene has been observed. Here, we look at how structural and mechanistic insights from imatinib-insensitive Bcr-Abl have been exploited to identify second-generation drugs that override acquired target resistance. These insights have created a rationale for the development of either multi-targeted protein kinase inhibitors or cocktails of selective antagonists as antitumour drugs that combine increased therapeutic potency with a reduced risk of the emergence of molecular resistance.

Characterization of AMN107, a selective inhibitor of native and mutant Bcr-Abl

The Bcr-Abl tyrosine kinase oncogene causes chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL). We describe a novel selective inhibitor of Bcr-Abl, AMN107 (IC50 <30 nM), which is significantly more potent than imatinib, and active against a number of imatinib-resistant Bcr-Abl mutants. Crystallographic analysis of Abl-AMN107 complexes provides a structural explanation for the differential activity of AMN107 and imatinib against imatinib-resistant Bcr-Abl. Consistent with its in vitro and pharmacokinetic profile, AMN107 prolonged survival of mice injected with Bcr-Abl-transformed hematopoietic cell lines or primary marrow cells, and prolonged survival in imatinib-resistant CML mouse models. AMN107 is a promising new inhibitor for the therapy of CML and Ph+ ALL.

Mechanisms of resistance to imatinib mesylate in gastrointestinal stromal tumors and activity of the PKC412 inhibitor against imatinib-resistant mutants

BACKGROUND AND AIMS

Resistance is a major challenge in the treatment of patients with gastrointestinal stromal tumors (GISTs). We investigated the mechanisms of resistance in patients with progressive GISTs with primary KIT mutations and the efficacy of the kinase inhibitor PKC412 for the inhibition of imatinib-resistant mutants.

METHODS

We performed a cytogenetic analysis and screened for mutations of the KIT and PDGFRA kinase domains in 26 resistant GISTs. KIT autophosphorylation status was assessed by Western immunoblotting. Imatinib-resistant GIST cells and Ba/F3 cells expressing these mutant proteins were tested for sensitivity to imatinib and PKC412.

RESULTS

Six distinct secondary mutations in KIT were detected in 12 progressive tumors, with V654A and T670I found to be recurrent. One progressive tumor showed acquired PDGFRA -D842V mutation. Amplification of KIT or KIT / PDGFRA was found in 2 patients. Eight of 10 progressive tumors available for analysis showed phosphorylated KIT. Two remaining progressive tumors lost KIT protein expression. GIST cells carrying KIT -del557-558/T670I or KIT -InsAY502-503/V654A mutations were resistant to imatinib, while PKC412 significantly inhibited autophosporylation of these mutants. Resistance to imatinib and sensitivity to PKC412 of KIT -T670I and PDGFRA -D842V mutants was confirmed using Ba/F3 cells.

CONCLUSIONS

This study shows the high frequency of KIT/PDGFRA kinase domain mutations in patients with secondary resistance and defines genomic amplification of KIT / PDGFRA as an alternative cause of resistance to the drug. In a subset of patients, cancer cells lost their dependence on the targeted tyrosine kinase. Our findings show the sensitivity of the imatinib-resistant KIT -T670I and KIT -V654A and of PDGFRA -D842V mutants to PKC412.

STI571 (Glivec) inhibits the interaction between c-KIT and heat shock protein 90 of the gastrointestinal stromal tumor cell line, GIST-T1

The gastrointestinal stromal tumor cell line, GIST-T1, has a heterogenic 57-base pair deletion in exon 11 of the c-kit mutation, and the c-KIT protein in the GIST-T1 cells constitutively activated. We report that STI571 (Glivec; Novartis, Basel, Switzerland), a specific inhibitor of c-KIT, inhibits the clustering of c-KIT at the cell membrane of the GIST-T1 cells. Furthermore, STI571 prevents the interaction between c-KIT and the molecular chaperone, heat shock protein 90 (Hsp90). Geldanamycin, an inhibitor of Hsp90, also prevents interaction between c-KIT and Hsp90, and inhibits tyrosine phosphorylation of c-KIT. Our results indicate that c-KIT molecules are assembled on the cell surface of the GIST-T1 cells, and that the interaction between c-KIT and Hsp90 plays an important role in c-KIT activation.

Endometrium from women with and without endometriosis, and peritoneal, ovarian and bowel endometriosis, show different c-kit protein expression

BACKGROUND

Endometriosis is defined by the presence of endometrium outside the uterus. Changes in the expression of the proto-oncogene c-kit are associated with aggressive behaviour of both benign and malignant tumours, but there are few data on its c-kit expression in endometriosis. Here we examined c-kit expression in endometrium and endometriotic tissue.

METHODS

Immunohistochemistry was used for qualitative and semi-quantitative (mean+/-S.D. positive cells) analysis of c-kit expression in endometrium from women with (n=9) and without endometriosis (n=18), and in peritoneal (n=20), ovarian (n=20) and colorectal endometriosis (n=20).

RESULTS

Semi-quantitative c-kit expression was higher in endometrial glandular cells from women with endometriosis than from women without endometriosis (15.0+/-14.6% versus 3.9+/-7.4%, p=0.01). No difference in c-kit expression was found in qualitative analysis and according to the phase of the menstrual cycle. C-kit expression values in peritoneal, ovarian and colorectal endometriosis were 2.0+/-3.8%, 2.0+/-4.1% and 21.7+/-18.4%, respectively. Qualitative and semi-quantitative c-kit expression was higher in colorectal endometriosis than in peritoneal and ovarian endometriosis (p<0.001); no difference was found between ovarian and peritoneal endometriosis. No c-kit expression was detected in stromal cells of either endometrium or endometriotic tissue.

CONCLUSION

These results suggest that the c-kit/stem cell factor axis is involved in the pathogenesis of endometriosis. Strong c-kit protein expression was associated with invasive endometriotic lesions.

Cystic changes in intraabdominal extrahepatic metastases from gastrointestinal stromal tumors treated with imatinib

Objective

This study was undertaken for the purpose of describing the CT features of intra-abdominal extra-hepatic metastases from gastrointestinal stromal tumors in patients who were treated with imatinib.

Materials and Methods

Eleven patients with intra-abdominal extra-hepatic metastases from gastrointestinal stromal tumors, who were treated with imatinib between May 2001 and December 2003, were included in this study. The clinical findings and CT scans were retrospectively reviewed. The metastatic lesions were assessed according to the location, size (greatest diameter), attenuation, and the enhancing pattern before and after imatinib treatment.

Results

Prior to the treatment, the sizes and attenuation values of the metastatic lesions ranged from 5 to 20 cm and from 63 to 131 H, respectively. The metastatic lesions showed a heterogeneous enhancement pattern on the contrast-enhanced CT scans. After the treatment, the metastatic lesions became smaller in all 11 patients, and the corresponding attenuation value ranged from 15 to 51 H. The metastatic lesions became homogeneous and cystic in appearance on the follow-up CT scans, mimicking ascites.

Conclusion

Intra-abdominal extra-hepatic metastases of patients with gastrointestinal stromal tumors treated with imatinib may appear as well-circumscribed cystic lesions on contrast-enhanced CT. These metastases are likely to become smaller and resemble ascites, but may persist indefinitely on the follow-up CT.

Imatinib Mesylate in Patients With Adenoid Cystic Cancers of the Salivary Glands Expressing c-kit: A Princess Margaret Hospital Phase II Consortium Study

Purpose

This study aimed to assess the antitumor activity of imatinib in adenoid cystic carcinoma (ACC) of the salivary gland expressing c-kit. A high level of c-kit expression has been identified in more than 90% of ACCs. Imatinib specifically inhibits autophosphorylation of the bcr-abl, platelet-derived growth factor receptor beta, and c-kit tyrosine kinases.

Patients and Methods

In a single-arm, two-stage, phase II clinical trial, adult patients with unresectable or metastatic ACC measurable by Response Evaluation Criteria in Solid Tumors Group criteria and expressing c-kit by immunohistochemistry were treated with imatinib 400 mg orally bid. Response was assessed every 8 weeks.

Results

Sixteen patients have been enrolled onto the study; 10 were female. Median age was 47 years (range, 31 to 69 years). Median Eastern Cooperative Oncology Group performance status was 1 (range, 0 to 2). Fourteen patients had lung metastases, 14 had prior radiotherapy, and six had prior chemotherapy. Toxicities occurring in at least 50% of patients included fatigue, nausea, vomiting, diarrhea, anorexia, edema, dyspnea, and/or headache, usually of mild to moderate severity. In 15 patients assessable for response, no objective responses have been observed. Nine patients had stable disease as best response. Six patients had progressive disease after two cycles.

Conclusion

Because of the lack of activity, the study has been stopped after the first stage and additional evaluation of imatinib in this population is not warranted. Overexpression of wild-type c-kit was not sufficient for clinical benefit from imatinib in ACC. Accrual to this study was rapid for a relatively rare cancer, encouraging additional efforts to identify more effective systemic therapy for these patients.

Targeted treatment of hypereosinophilic syndromes and chronic eosinophilic leukemias with imatinib mesylate

Idiopathic hypereosinophilic syndrome (HES) and chronic eosinophilia leukemia (CEL) represent the most recent additions to the list of molecularly defined chronic myeloproliferative disorders. Beginning with the observation that imatinib mesylate (Gleevec) could elicit rapid and complete hematologic remissions in a proportion of patients with HES, a reverse bedside-to-bench translational research effort led to the discovery of FIP1L1-PDGFRA, a novel fusion gene on chromosome 4q12 whose product is an imatinib-sensitive protein tyrosine kinase. FIP1L1-PDGFRA is the first description of a gain-of-function fusion gene derived from an interstitial chromosomal deletion rather than a reciprocal translocation. Empiric use of imatinib in HES and CEL provides a dramatic example of how the development of targeted therapeutics can provide tremendous insight into the molecular etiology of what appear to be a diverse and otherwise indecipherable collection of diseases. In this review, we discuss the role of imatinib in HES/CEL and other malignancies characterized by constitutively activated tyrosine kinases, and examine molecular features of the FIP1L1-PDGFRA fusion.

Detection of oncogenic mutations in the EGFR gene in lung adenocarcinoma with differential sensitivity to EGFR tyrosine kinase inhibitors

The complete sequencing of the human genome and the development of molecularly targeted cancer therapy have promoted efforts to identify systematically the genetic alterations in human cancer. By high-throughput sequencing of tyrosine kinase genes in human non-small-cell lung cancer, we identified somatic mutations in the kinase domain of the epidermal growth factor receptor tyrosine kinase gene (EGFR) that are correlated with clinical response to EGFR tyrosine kinase inhibitors (TKIs). We have shown that these mutant forms of EGFR induce oncogenic transformation in different cellular systems. Cells whose growth depends on EGFR with mutations in exons 19 and 21 are sensitive to EGFR-TKIs, whereas cells expressing insertion mutations in exon 20 or the T790M point mutant, found in tumor biopsies from patients that relapsed after an initial response to EGFR-TKIs, are resistant. Furthermore, by applying a novel, massively parallel sequencing technology, we have shown that clinically relevant oncogene mutations can be detected in clinical specimens with very low tumor content, thereby enabling optimal patient selection for mutation-directed therapy. In summary, by applying high-throughput genomic resequencing, we have identified a novel therapeutic target, mutant EGFR, in lung cancer and evaluated its role in predicting response to targeted therapy.

Improving Outcomes in Advanced Malignant Melanoma

Malignant melanoma continues to increase in incidence throughout the developed world. Surgery remains the cornerstone of curative treatment and the use of adjuvant systemic therapy has provoked much debate. Metastatic disease is incurable in most patients. While combination chemotherapy or biochemotherapy may be considered in certain circumstances, it is now clear that single-agent chemotherapy remains the mainstay of treatment for the majority of patients.A number of new agents and novel approaches are under evaluation and show promise. The pro-apoptotic agent oblimersen has shown improved progression-free survival and response rate, although not overall survival, when combined with dacarbazine compared with dacarbazine alone. The BRaf inhibitor sorafenib (BAY 43-9006) has produced encouraging results when administered with chemotherapy and is now being assessed in randomised studies. Thalidomide in combination with chemotherapy is well tolerated and shows a trend towards increased clinical efficacy compared with chemotherapy alone. Other anti-angiogenic drugs, such as bevacizumab, are being investigated in trials. Results with tumour vaccines have been mixed and several large trials are ongoing. This paper discusses recent pivotal studies and promising new agents in systemic therapy for advanced malignant melanoma.

Resection of residual disease in patients with metastatic gastrointestinal stromal tumors responding to treatment with imatinib

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. Long-term survival of patients with metastatic disease has only been observed in patients with completely resected disease. Recently, the tyrosine kinase inhibitor imatinib has been found to yield responses in the majority of patients with metastatic GIST suggesting improved resectability in responding patients. Combined treatment approaches including resective surgery after imatinib treatment in patients with advanced metastatic disease have rarely been explored. We report a series of 90 patients with metastatic GIST in whom treatment with imatinib enabled 12 patients with mostly recurrent and extensive disease to be considered for resection of residual disease. In 11 of these patients, complete resection could be achieved. Viable tumor cells were found in all but one resected specimens suggesting that despite favorable radiological or clinical responses, imatinib is unlikely to induce pathological complete responses. Until more mature data from prospective trials are available, these data suggest that an early aggressive surgical approach should be considered for all patients with metastatic GIST. Further trials investigating a combined surgical and pre/postoperative treatment with imatinib in patients with advanced metastatic GIST are warranted.

A review of the surgical management of metastatic gastrointestinal stromal tumours (GISTs) on imatinib mesylate (Glivec™)

Gastrointestinal stromal tumours (GISTs) are defined as a group of C-KIT positive mesenchymal tumours of the gastrointestinal tract. Although they may arise throughout the gut, the commonest sites are stomach and small intestine. Over 80% of metastases are to the liver and omentum. Targeted therapy (imatinib) can inhibit C-KIT and thereby aberrant tumoural proliferation. Imatinib may induce shrinkage of lesions and cystic change. Such physical changes often correspond with reduced metabolic activity demonstrated by (18-FDG)PET scans. These changes may enable metastatectomy reducing tumour pain and the risk of haemorrhage and rupture in the short term. In the long term, resection may lessen the risk of recurrence by removing potentially resistant clones. The precise role of palliative resection for GIST metastases on imatinib remains unclear. Imatinib has changed the natural history of metastatic GISTs, with increased survival times. Surgery remains an important management strategy in the metastatic setting because complete pathological responses are rare with imatinib. Surgery is likely to provide the best palliation, greatest reduction in tumour burden and eliminate resistant clones. A multidisciplinary team approach with expertise concentrated in a few centres specialising in the management of these rare tumours is vital to the successful outcome. Future issues regarding the management of differential response of the metastases to imatinib are highlighted. With the emergence of techniques enabling identification of the precise mutational status of the C-KIT oncogene, the imatinib/surgery sequence could be tailored to the type of C-KIT mutation.

Dissecting cancer pathways and vulnerabilities with RNAi

The latest generation of molecular-targeted cancer therapeutics has bolstered the notion that a better understanding of the networks governing cancer pathogenesis can be translated into substantial clinical benefits. However, functional annotation exists for only a small proportion of genes in the human genome, raising the likelihood that many cancer-relevant genes and potential drug targets await identification. Unbiased genetic screens in invertebrate organisms have provided substantial insights into signaling networks underlying many cellular and organismal processes. However, such approaches in mammalian cells have been limited by the lack of genetic tools. The emergence of RNA interference (RNAi) as a mechanism to suppress gene expression has revolutionized genetics in mammalian cells and has begun to facilitate decoding of gene functions on a genome scale. Here, we discuss the application of such RNAi-based genetic approaches to elucidating cancer-signaling networks and uncovering cancer vulnerabilities.

Gastric GI stromal tumors (GISTs): The role of surgery in the era of targeted therapy

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasm arising in the stomach. These tumors were previously classified as smooth muscle tumors, but in recent years it has become clear that they are clinically, pathologically, and molecularly distinct from other tumors and are much more common than previously appreciated. Historically, patients with primary localized or advanced GIST have been managed surgically, as there was no proven role of other treatment modalities such as radiation or chemotherapy. However, the field of GIST was revolutionized with the 1998 discovery that the vast majority of these tumors have oncogenic gain-of-function mutations of the KIT receptor tyrosine kinase. Follow-up studies have confirmed that KIT is both a useful diagnostic marker and an excellent therapeutic target. Imatinib, an inhibitor of KIT kinase activity, is now the standard front-line therapy for patients with advanced GIST. In this review, we discuss pathological and molecular features of gastric GISTs and review the historic and current roles of surgery in the treatment of patients with primary or metastatic GIST. The importance of a multi-disciplinary approach using both surgery and imatinib therapy is emphasized.