Efficacy evaluation of imatinib treatment in patients with gastrointestinal stromal tumors: A meta-analysis

Bioinformatic analysis of KIT juxtamembrane domain mutations in Syrian GIST patients: jigsaw puzzle completed

BACKGROUND

The huge number of detected somatic KIT mutations highlights the necessity of in silico analyses that are almost absent in the relevant medical literature. The aim of this study is to report the mutation spectrum analysis of exon 11 encoding the juxtamembrane (JM) domain of the KIT gene in a group of Syrian GIST patients.

METHODS

Forty-eight formalin-fixed paraffin-embedded GIST tissue samples, collected between 2006 and 2016, were retrieved from the pathological archives and analyzed for KIT exon 11 mutations by DNA sequencing. Structural/functional impact of detected variants was predicted using several bioinformatic tools.

RESULTS

Twenty-one different variants have been detected in intron 10, exon 11, and intron 11 of the KIT gene, eight of which were novel changes. Mutations in exon 11 of the KIT gene were detected in 28 of 48 (58.3%) GIST patients and predicted to be pathogenic and cancer promoting. Specifically, age above 60 was very significantly associated with the negative selection of deletion mutations (p = .007), a phenomenon that points to deletion severity.

CONCLUSIONS

Six bioinformatic tools have proved efficient in predicting the impact of detected KIT variations in view of published structural, experimental, and clinical findings.

Mesenchymal stromal cells promote the drug resistance of gastrointestinal stromal tumors by activating the PI3K-AKT pathway via TGF-β2

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the prevailing sarcomas of the gastrointestinal tract. Tyrosine kinase inhibitors (TKIs) therapy, exemplified by Imatinib mesylate (IM), constitutes the established adjuvant therapy for GISTs. Nevertheless, post-treatment resistance poses a challenge that all patients must confront. The presence of tumor heterogeneity and secondary mutation mechanisms fail to account for some instances of acquired drug resistance. Certain investigations suggest a strong association between tumor drug resistance and mesenchymal stromal cells (MSC) in the tumor microenvironment, but the underlying mechanism remains obscure. Scarce research has explored the connection between GIST drug resistance and the tumor microenvironment, as well as the corresponding mechanism.

METHODS

Immunofluorescence and fluorescence-activated cell sorting (FACS) methodologies were employed to detect the presence of MSC in GIST samples. The investigation encompassed the examination of MSC migration towards tumor tissue and the impact of MSC on the survival of GIST cells under IM treatment. Through ELISA, western blotting, and flow cytometry analyses, it was confirmed that Transforming Growth Factor Beta 2 (TGF-β2) triggers the activation of the PI3K-AKT pathway by MSC, thereby facilitating drug resistance in GIST.

RESULTS

Our findings revealed a positive correlation between a high proportion of MSC and both GIST resistance and a poor prognosis. In vitro studies demonstrated the ability of MSC to migrate towards GIST. Additionally, MSC were observed to secrete TGF-β2, consequently activating the PI3K-AKT pathway and augmenting GIST resistance.

CONCLUSIONS

Our investigation has revealed that MSC within GISTs possess the capacity to augment drug resistance, thereby highlighting their novel mechanism and offering a promising target for intervention in GIST therapy.

Analyses of canine cancer mutations and treatment outcomes using real-world clinico-genomics data of 2119 dogs

Spontaneous tumors in canines share significant genetic and histological similarities with human tumors, positioning them as valuable models to guide drug development. However, current translational studies have limited real world evidence as cancer outcomes are dispersed across veterinary clinics and genomic tests are rarely performed on dogs. In this study, we aim to expand the value of canine models by systematically characterizing genetic mutations in tumors and their response to targeted treatments. In total, we collect and analyze survival outcomes for 2119 tumor-bearing dogs and the prognostic effect of genomic alterations in a subset of 1108 dogs. Our analysis identifies prognostic concordance between canines and humans in several key oncogenes, including TP53 and PIK3CA. We also find that several targeted treatments designed for humans are associated with a positive prognosis when used to treat canine tumors with specific genomic alterations, underscoring the value of canine models in advancing drug discovery for personalized oncology.

Clinical Activity of Ripretinib in Patients with Advanced Gastrointestinal Stromal Tumor Harboring Heterogeneous KIT/PDGFRA Mutations in the Phase III INVICTUS Study

PURPOSE

Most patients with gastrointestinal stromal tumor (GIST) have activating mutations in KIT/PDGFRA and are initially responsive to tyrosine kinase inhibitors (TKI). The acquisition of secondary mutations leads to refractory/relapsed disease. This study reports the results of an analysis from the phase III INVICTUS study (NCT03353753) characterizing the genomic heterogeneity of tumors from patients with advanced GIST and evaluating ripretinib efficacy across KIT/PDGFRA mutation subgroups.

PATIENTS AND METHODS

Tumor tissue and liquid biopsy samples that captured circulating tumor DNA were collected prior to study enrollment and sequenced using next-generation sequencing. Subgroups were determined by KIT/PDGFRA mutations and correlation of clinical outcomes and KIT/PDGFRA mutational status was assessed.

RESULTS

Overall, 129 patients enrolled (ripretinib 150 mg once daily, n = 85; placebo, n = 44). The most common primary mutation subgroup detected by combined tissue and liquid biopsies were in KIT exon 11 (ripretinib, 61.2%; placebo, 77.3%) and KIT exon 9 (ripretinib, 18.8%; placebo, 15.9%). Patients receiving ripretinib demonstrated progression-free survival (PFS) benefit versus placebo regardless of mutation status (HR 0.16) and in all assessed subgroups in Kaplan-Meier PFS analysis (exon 11, P < 0.0001; exon 9, P = 0.0023; exon 13, P < 0.0001; exon 17, P < 0.0001). Among patients with wild-type KIT/PDGFRA by tumor tissue, PFS ranged from 2 to 23 months for ripretinib versus 0.9 to 10.1 months for placebo.

CONCLUSIONS

Ripretinib provided clinically meaningful activity across mutation subgroups in patients with advanced GIST, demonstrating that ripretinib inhibits a broad range of KIT/PDGFRA mutations in patients with advanced GIST who were previously treated with three or more TKIs.

Imatinib Regulates miR-483-3p and Mitochondrial Respiratory Complexes in Gastrointestinal Stromal Tumors

Metabolic adaptation to increased oxidative phosphorylation (OXPHOS) has been found in gastrointestinal stromal tumor (GIST) upon imatinib treatment. However, the underlying mechanism of imatinib-induced OXPHOS is unknown. Discovering molecules that mediate imatinib-induced OXPHOS may lead to the development of therapeutic strategies synergizing the efficacy of imatinib. In this study, we explored the role of microRNAs in regulating OXPHOS in GIST upon imatinib treatment. Using a microarray approach, we found that miR-483-3p was one of the most downregulated miRNAs in imatinib-treated tumors compared to untreated tumors. Using an extended series of GIST samples, we further validated the downregulation of miR-483-3p in imatinib-treated GIST samples by RT-qPCR. Using both gain- and loss-of-function experiments, we showed that miR-483-3p could regulate mitochondrial respiratory Complex II expression, suggesting its role in OXPHOS regulation. Functionally, miR-483-3p overexpression could rescue imatinib-induced cell death. These findings provide the molecular link for imatinib-induced OXPHOS expression and the biological role of miR-483-3p in regulating cell viability upon imatinib treatment.

Efficacy evaluation of nilotinib treatment in different genomic subtypes of gastrointestinal stromal tumors: A meta-analysis and systematic review

Nilotinib has been used as a third-line drug for gastrointestinal stromal tumors (GISTs) after a failure of sunitinib. In this study, we aimed to evaluate the efficacy of nilotinib in different genomic subtypes of GISTs. We searched the English articles through EMBASE, Cochrane Library and PubMed Database regarding to the use of nilotinib on GISTs, which published up to February 15, 2019. Inclusion criteria were: GISTs patients received nilotinib in a clinical trial and had detailed genetic subtype records (such as KIT exon 9, KIT exon 11, or PDGFRA mutations, or wild-type). The clinical benefit rate was used to assess the efficacy of nilotinib. A total of 3 studies involving 218 GISTs were included in this meta-analysis. The overall OR (KIT group vs WT group) was 3.26 (95% CI: 1.14-9.28; P = 0.027, P_{heterogeneity} = 0.613). The overall OR in KIT exon 11 group vs WT group was 5.30 (95% CI: 1.79-15.68; P = 0.003, P_{heterogeneity} = 0.409). The overall OR in KIT exon 9 group vs WT group was 0.13 (95% CI: 0.02-0.86; P = 0.035, P_{heterogeneity} = 0.229). The overall OR in KIT exon 11 group vs exon 9 group was 9.96 (95% CI: 0.39-254.66; P < 0.0001, P_{heterogeneity} = 0.024). Different genotypes of GISTs showed different responses to nilotinib, and KIT exon 11-mutant GISTs mostly benefited from nilotinib, followed by KIT exon 9-mutant or WT one.

Prognostic and predictive values of the KIT11-mutated grading system in patients with gastrointestinal stromal tumors: a retrospective study

The KIT11 mutation is the most frequent mutation pattern in gastrointestinal stromal tumors (GISTs). However, few studies have investigated the correlation between the KIT11-mutated grading system and imatinib mesylate (IM) sensitivity (the first choice for adjuvant treatment of GISTs). Here, we elucidated the clinical value of the KIT11-mutated grading system for prognostic prediction in patients with GISTs treated with IM. A total of 106 patients with GIST were treated with IM (8: intermediate-risk, 98: high-risk; 10: KIT9-mutated, 86: KIT11-mutated, 5: wild-type, and 5: other mutations). KIT11-mutated patients were divided into 3 grades based on the KIT11-mutated site and type. Clinical backgrounds and prognostic outcomes were retrospectively compared between the 3 groups. Of 86 KIT11-mutated patients treated with IM, 32 (37.21%) had grade 1 tumors, 37 (43.02%) had grade 2 tumors, and 17 (19.77%) had grade 3 tumors. The 5-year disease-free survival (DFS) was significantly worse in patients with grade 3 KIT11-mutated GISTs (41.96%, p = 0.001) than in those with grade 1 (93%) and grade 2 (70.64%) cases. The multivariable analysis suggested that the KIT11-mutated grading system was an independent risk factor for DFS in patients treated with IM (hazard risk, 2.512; 95% confidence interval, 1.370-4.607; p = 0.003). In conclusion, the KIT11-mutated grading system provides good prognostic stratification for DFS in patients treated with IM. Grade 1 tumors predict a favorable response to IM.

Genomic Subtypes of GISTs for Stratifying Patient Response to Sunitinib following Imatinib Resistance: A Pooled Analysis and Systematic Review

Objectives

Sunitinib (a second-line chemotherapeutic agent that inhibits multiple kinases, including KIT and PDGFR) is widely used in imatinib-resistant patients with gastrointestinal stromal tumors (GISTs). However, diverse responses to sunitinib have been observed in the clinic. We aimed to evaluate whether the different GIST genotypes could be used to stratify patient response to sunitinib.

Methods

We searched the PubMed, Embase, and Cochrane databases and included English-language literature published up to August 31, 2017. Inclusion criteria were GIST patients with KIT exon 9, KIT exon 11, or PDGFRA mutations and those without KIT/PDGFRA mutations (termed the wild-type genotype) who were receiving sunitinib within a clinical trial, and the efficacy evaluation was clinical benefit rate (CBR), median progression-free survival (PFS), and overall survival (OS). Odds ratios (ORs) for CBR and hazard ratios (HRs) for PFS and OS with 95% confidence intervals (CIs) in sunitinib-treated GIST patients with different genotypes were compared.

Results

Seven studies totaling 531 patients were included. Patients with KIT mutations showed an improved CBR to sunitinib compared to those with PDGFRA mutations. In particular, those with the KIT exon 9 or 11 mutation showed improved CBR over those with PDGFRA mutation. Moreover, GIST patients with the KIT exon 9 mutation showed improved CBR over those with the KIT exon 11 mutation. Patients without KIT/PDGFRA mutations (wild-type genotype) showed better CBR than those with PDGFRA mutations.

Conclusion

GIST genotypes may be useful for stratifying patient response to sunitinib after imatinib resistance.

PDGFRA and KIT Mutation Status and Its Association With Clinicopathological Properties, Including DOG1

Most of the gastrointestinal stromal tumors (GISTs) have gain-of-function mutations in the KIT gene, which can be used as a prognostic marker for the biological behavior of tumors, predictive marker for the response of tyrosine kinase inhibitors, and diagnostic marker. Researchers have focused on PDGFRA mutations because of both their prognostic and predictive potential and DOG1 positivity for diagnosis on GISTs. The aim of this study is to investigate the effect DOG1, PDGFRA, and KIT mutations on the prediction of the outcome for GIST management. Polymerase chain reaction was performed for KIT gene exons 9, 11, 13, and 17 and PDGFRA gene exons 12 and 18 with the genomic DNA of 46 GIST patients, and amplicons were sequenced in both directions. Immunocytochemical stainings were done by using primary antibodies. Molecular analysis revealed that the KIT mutation was observed in 63% of all cases, while the PDGFRA mutation was observed in 23.9% of cases. Significant relationships were found between age and KIT mutation, tumor location and KIT mutations, and tumor location and PDGFRA mutations (p ≤ 0.05). DOG1 positivity was detected in 65.2% of all GISTs and DOG1-positive cells had a higher KIT mutation ratio than DOG1-negative cells (p ≤ 0.05). KIT gene exon 11 mutations in DOG1-positive cells was higher than DOG1-negative cells (p ≤ 0.05). Conversely, KIT gene exon 13 mutations were higher in DOG1-negative cells than DOG1-positive cells (p ≤ 0.05). In this study, KIT mutation frequency was found similar with the European population; conversely, PDGFRA mutation frequency was similar with an Asian-Chinese-based study. KIT/PDGFRA mutations and tumor location can be used for the prediction of tumor behavior and the management of disease in GISTs. DOG1 positivity might be a candidate marker to support KIT and PDGFRA mutations, due to the higher DOG1 positivity in KIT exon 11 mutant and stomach- and small intestine-localized GISTs.

Clinicopathological significance of c-KIT mutation in gastrointestinal stromal tumors: a systematic review and meta-analysis

Many types of KIT mutations have been observed in gastrointestinal stromal tumors (GISTs), but their prognostic and predictive significance are still unclear. A meta-analysis and literature review were conducted to estimate the contribution of KIT mutations in prognostic parameters and clinic-pathological significance of GISTs. A total of 18 relevant articles from PubMed, EMBASE and Web of Science databases were included in this study. The frequency of KIT mutation was significantly increased in the GIST patients with higher mitosis (≥5/50 high-power fields (HPFs) and larger size (≥5 cm) of tumors than in those with lower MI (≤5/50HPFs) and smaller size (≤5 cm) of GISTs respectively. The rate of KIT mutation was not significantly changed between GISTs in stomachs and in small intestines. KIT mutational status has prognostic significance for patients’ outcome. GIST patients with KIT exon 9 mutations have higher risk of progression than those with exon 11 mutations. 5 year relapse-free survival (RFS) rate was significantly higher in patients with KIT exon 11 deletion than in those with other type of KIT exon 11 mutations. The deletion involving KIT exon 11, particularly codons 557–558, is a valuable predictor of prognosis for patients with GISTs.

Prognostic value of KIT/PDGFRA mutations in gastrointestinal stromal tumors: a meta-analysis

Background

The postulated relationship between KIT/PDGFRA mutations and their prognostic value in gastrointestinal stromal tumors (GISTs) has generated intense attention during the past decade, despite the fact that a great deal of studies have been conducted on this subject. To provide a strong quantitative estimate of this postulated relationship, we carried out a meta-analysis which combined, compared, and summarized the results of existing relevant studies.

Methods

Studies were identified by searching databases and reviewing citations in relevant articles. Of 48 potentially relevant studies, we combined individual patient data from 18 studies which involved 1,487 patients with GISTs, by which we made a comparison between the positive KIT mutation subgroup and the negative KIT mutation subgroup (PDGFRA mutation and wild type). We tabulated and analyzed the patient characteristics from each study, including general information such as age and gender, histopathological parameters, and clinical follow-up outcomes.

Results

KIT mutations, compared with PDGFRA mutations and wild type, showed a marked increased risk not only for tumor size (>5 cm) but also for higher mitotic activity (>5), suggesting that KIT mutations significantly correlated with the National Comprehensive Cancer Network (NCCN) high risk or National Institutes of Health (NIH) high risk (1.74 (95% CI, 1.20 to 2.53) and 2.00 (95% CI, 1.08 to 3.68), respectively). Moreover, higher recurrence and metastasis was observed in GISTs with KIT mutations, revealing its closer correlation with clinical malignant risk (P <0.001 for each, with odds ratio (OR) of 2.06 (95%, 1.37 to 3.11) and 2.77 (95%, 1.64 to 4.67), respectively). High risk or malignant GISTs with KIT mutations had a significantly poorer prognosis, as measured by 3-year overall survival, compared to those with PDGFRA mutations and wild type (0.47 (95% CI, 0.25 to 0.90)).

Conclusions

KIT mutations, compared with PDGFRA mutations and wild type, represent a poorer prognostic marker in high risk or malignant GISTs.

Rare cystic liver lesions: A diagnostic and managing challenge

Cystic formations within the liver are a frequent finding among populations. Besides the common cystic lesions, like simple liver cysts, rare cystic liver lesions like cystadenocarcinoma should also be considered in the differential diagnosis. Thorough knowledge of each entity’s nature and course are key elements to successful treatment. Detailed search in PubMed, Cochrane Database, and international published literature regarding rare cystic liver lesions was carried out. In our research are included not only primary rare lesions like cystadenoma, hydatid cyst, and polycystic liver disease, but also secondary ones like metastasis from gastrointestinal stromal tumors lesions. Up-to date knowledge regarding diagnosis and management of rare cystic liver lesions is provided. A diagnostic and therapeutic algorithm is also proposed. The need for a multidisciplinary approach by a team including radiologists and surgeons familiar with liver cystic entities, diagnostic tools, and treatment modalities is stressed. Patients with cystic liver lesions must be carefully evaluated by a multidisciplinary team, in order to receive the most appropriate treatment, since many cystic liver lesions have a malignant potential and evolution.

What are the current outcomes of advanced gastrointestinal stromal tumors: who are the long-term survivors treated initially with imatinib?

The introduction of imatinib to clinical practice revolutionized therapy of advanced gastrointestinal stromal tumors (GIST), but its long-term results have been only just collected. We have attempted to identify factors related to the long-term survival. We have analyzed the data of 430 inoperable/metastatic/recurrent GIST patients treated with imatinib in reference centers, assessed the factors influencing the long-term overall survival (OS), and compared the outcomes in three periods of initiation of imatinib therapy during one decade (2001–2003, 2004–2006, 2007–2010). During analyzed time periods, we have found decrease in median largest tumor size at the start of imatinib therapy: 90.5 mm (2001–2003) versus 74 mm (2004–2006) versus 58 mm (2007–2010) (p = 0.002). Median progression-free survival (PFS) on 1st line imatinib was 37.5 months, without differences in PFS between three groups. Median OS was 5.8 years, 8-year OS rate was 43 %, and no difference in OS was demonstrated for patients treated in analyzed time periods. Independent good prognostic factors for longer OS were as follows: surgery of residual disease, initial WHO performance status 0/1, normal baseline albumin level, and the presence of exon 11 KIT mutations. Current median OS in advanced GIST reaches 6 years. The long-term survivors were characterized by smaller maximal tumors at imatinib start, better blood tests results, better performance status, and the surgical removal of residual disease. The latter might reduce the impact of tumor size and equalize the long-term results of therapy during last decade from introduction of imatinib. After introduction of subsequent lines of therapy (as sunitinib), the effect of primary mutational status on the long-term OS is also less visible.

Practical role of mutation analysis for imatinib treatment in patients with advanced gastrointestinal stromal tumors: a meta-analysis

BACKGROUND

Imatinib has become the standard first line treatment of gastrointestinal stromal tumors (GIST) in the advanced phase and adjuvant setting. We carried out an up-to-date meta-analysis to determine the practical role of mutation analysis for imatinib treatment in patients with advanced GIST.

METHODS

Eligible studies were limited to imatinib treatment for patients with advanced GIST and reported on mutation analysis. Statistical analyses were conducted to calculate the odds ratio (OR), hazard ratio (HR) and 95% confidence interval (CI) using fixed-effects and random-effects models.

RESULTS

A total of 2834 patients from 3 randomized controlled trials and 12 cohort studies were included. The ORs of response rates in KIT exon 11-mutant GISTs were 3.504 (95% CI 2.549-4.816, p<0.001) and 3.521 (95% CI 1.731-7.165, p=0.001) compared with KIT exon 9-mutant and wild type GISTs, respectively. The HRs of progression-free survival in KIT exon 11-mutant GISTs were 0.365 (95% CI 0.301-0.444, p<0.001) and 0.375 (95% CI 0.270-0.519, p<0.001) compared with KIT exon 9-mutant and wild type GISTs. The HRs of overall survival in KIT exon 11-mutant GISTs were 0.388 (95% CI 0.293-0.515, p<0.001) and 0.400 (95% CI 0.297-0.538, p<0.001) compared with KIT exon 9-mutant and wild type GISTs. No statistical significant differences were found between KIT exon 9-mutant and wild type. The overall response rate in KIT-exon 11-mutant GISTs were 70.5% (65%-75.9%) compared with 57.1% (51%-63.2%) in KIT-positive GISTs. No evidence of publication bias was observed.

CONCLUSION

Patients with advanced GIST harboring a KIT exon 11 mutation have the best response rate and long-term survival with imatinib treatment. Mutation analysis would be more helpful than KIT expression analysis to decide appropriate therapy for a specific patient.

Gastrointestinal stromal tumors, somatic mutations and candidate genetic risk variants

Gastrointestinal stromal tumors (GISTs) are rare but treatable soft tissue sarcomas. Nearly all GISTs have somatic mutations in either the KIT or PDGFRA gene, but there are no known inherited genetic risk factors. We assessed the relationship between KIT/PDGFRA mutations and select deletions or single nucleotide polymorphisms (SNPs) in 279 participants from a clinical trial of adjuvant imatinib mesylate. Given previous evidence that certain susceptibility loci and carcinogens are associated with characteristic mutations, or "signatures" in other cancers, we hypothesized that the characteristic somatic mutations in the KIT and PDGFRA genes in GIST tumors may similarly be mutational signatures that are causally linked to specific mutagens or susceptibility loci. As previous epidemiologic studies suggest environmental risk factors such as dioxin and radiation exposure may be linked to sarcomas, we chose 208 variants in 39 candidate genes related to DNA repair and dioxin metabolism or response. We calculated adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the association between each variant and 7 categories of tumor mutation using logistic regression. We also evaluated gene-level effects using the sequence kernel association test (SKAT). Although none of the association p-values were statistically significant after adjustment for multiple comparisons, SNPs in CYP1B1 were strongly associated with KIT exon 11 codon 557-8 deletions (OR = 1.9, 95% CI: 1.3-2.9 for rs2855658 and OR = 1.8, 95% CI: 1.2-2.7 for rs1056836) and wild type GISTs (OR = 2.7, 95% CI: 1.5-4.8 for rs1800440 and OR = 0.5, 95% CI: 0.3-0.9 for rs1056836). CYP1B1 was also associated with these mutations categories in the SKAT analysis (p = 0.002 and p = 0.003, respectively). Other potential risk variants included GSTM1, RAD23B and ERCC2. This preliminary analysis of inherited genetic risk factors for GIST offers some clues about the disease's genetic origins and provides a starting point for future candidate gene or gene-environment research.

Duodenal GIST: a single center experience

PURPOSE

The duodenum as primary site for gastrointestinal stromal tumors (GISTs) is rare and mitotic rate, tumor size, type of mutation and number of chromosomal aberrations have prognostic implications.

METHODS

We analyzed the outcome of 13 patients with duodenal GISTs who underwent surgical tumor resection. Either segmental duodenectomy or pylorus-preserving duodenopancreatectomy was performed. The tumors were histopathologically examined and the risk of progression was assessed based on tumor size and mitotic count. Additionally, mutation analysis of the KIT and PDGFRA receptor tyrosine kinase genes and comparative genomic hybridization (CGH) were performed in all cases.

RESULTS

Eight patients underwent segmental duodenectomy and five patients were treated with pylorus-preserving duodenopancreatectomy. None of the five GISTs with low or no risk for malignancy according to the Miettinen classification developed tumor progress. In contrast, five of eight cases (62.5%) with high-risk tumors revealed tumor progress, and four of these patients died (50%). The median overall survival for all patients was 66 months, and the median disease-free survival 41 months. The operative procedure and type of mutation did not correlate with long-term survival. CGH analysis displayed -15q in 12/13 tumors, and -1p in 11/13 cases as characteristic chromosomal aberrations for intestinal origin. Notably, -22q was present in three of four cases with tumor progress.

CONCLUSIONS

Both segmental duodenectomy and pylorus-preserving duodenopancreatectomy are appropriate options to treat duodenal GIST and should be implemented depending on resectability and the patient's performing state. The Miettinen classification and CGH findings correlate with the clinical course.

Optimized dose of imatinib for treatment of gastrointestinal stromal tumors: a meta-analysis

OBJECTIVE

To investigate the efficacy and safety of standard-dose versus high-dose imatinib.

METHODS

After a systematic review of English language articles, five studies including 2008 patients were eligible for the meta-analysis. Data extracted from each study were synthesized into overall odds ratios (OR).

RESULTS

The overall OR for the high dose vs standard dose was 1.19 (95% CI 1.00-1.42) and the Z-score for the overall effect was 1.93 (P = 0.054), suggesting that high-dose imatinib added no survival benefits. The dose-related toxicity was also assessed in the same way. The rates of rash, hemorrhage, nausea, vomiting and taste disturbance increased as dose increased (P < 0.05), whereas the incidence of headache, abdominal pain, edema, fatigue, anemia, infection, muscle cramp and constipation was nearly identical and showed no significant difference.

CONCLUSIONS

Imatinib at a standard dose produces a similar effect to that at a high dose. The severity of the toxicity is associated with the dose of imatinib. However, larger and randomized studies are needed to draw definitive conclusions.

Giant solitary fibrous tumor arising from greater omentum

Extrathoracic solitary fibrous tumors (SFTs) have been described at almost every anatomic location of human body, but reports of SFT in the abdominal cavity are rare. We herein present a rare case of SFT originating from greater omentum. Computed tomography revealed a 15.8 cm × 21.0 cm solid mass located at superior aspect of stomach. Open laparotomy confirmed its mesenchymal origin. Microscopically, its tissue was composed of non-organized and spindle-shaped cells exhibiting atypical nuclei, which were divided up by branching vessel and collagen bundles. Immunohistochemical staining showed that this tumor was negative for CD117, CD99, CD68, cytokeratin, calretinin, desmin, epithelial membrane antigen, F8 and S-100, but positive for CD34, bcl-2, α-smooth muscle actin and vimentin. The patient presented no evidence of recurrence during follow-up. SFT arising from abdominal cavity can be diagnosed by histological findings and immunohistochemical markers, especially for CD34 and bcl-2 positive cases.

Predictive value of p53 expression in the risk of malignant gastrointestinal stromal tumors: Evidence from 19 studies

The current published data on p53 expression and its predictive value in the risk of malignant gastrointestinal stromal tumors (GIST) has are inconclusive. To derive a more precise estimation of the correlation between p53 and the biological behavior of GIST, a meta-analysis was performed. Studies were identified by searching PubMed and Embase. Inclusion criteria were GIST patients, and the evaluation of p53 expression and risk of malignancy. The odds ratio (OR) for a positive rate of p53 in the benign group vs. that in the malignant group and the ORs for the positive rate of p53 in the National Institutes of Health (NIH) very low risk + low risk group (VL+L) vs. the NIH intermediate risk + high risk (I+H) group were calculated with a 95% confidence interval (CI) for each study as an estimation of the predictive value of p53. A total of 19 studies including 1163 patients were involved in this meta-analysis. The overall OR for the positive rate of p53 in the malignant group vs. the benign group revealed that significantly elevated risks of positive p53 in the malignant group were achieved (OR 0.14, 95% CI: 0.06-0.31, P<0.00001, P(heterogeneity)=0.86). Moreover, significantly elevated risks of correlation between p53 expression and the NIH I+H group were achieved in the comparison of the NIH VL+L group vs. the NIH I+H group (OR, 0.25; 95% CI, 0.17-0.38; P<0.00001, P(heterogeneity)=0.04). The results indicate that p53 expression correlates with poor prognosis in GIST and has a close relationship within the NIH I+H group.