The analysis of status and clinical implication of KIT and PDGFRA mutations in gastrointestinal stromal tumor (GIST)

A rare case of extragastrointestinal stromal tumor of vocal cord - case report

Gastrointestinal stromal tumors (GISTs) are the mesenchymal tumors of the gastrointestinal tract. Extra Gastrointestinal stromal tumors (EGISTs) are rare neoplasms that occur outside the gastrointestinal tract [1]. Miettinen et al. [2] described the first EGIST in 1999. EGIST accounts for 10% of all GISTs [3]. The main distinction between GIST and EGIST is the site of origin of the primary tumor, as GIST occurs throughout the GI tract, from the esophagus to the anus, whereas EGIST is a tumor without any connection with the intestinal wall and are reported in the retroperitoneum, mesentery, and omentum [4]. Hu et al. [5] reported a first case report of EGIST of larynx.We present a second case report of Extra-gastrointestinal stromal tumor of larynx a 47-year-old male reported to ENT Department Command Hospital Central Command Lucknow with complaints of Hoarseness. On examination found to have right vocal cord growth for which he underwent excision of right vocal cord growth. Histopathological examination showed typical of a spindle-cell GIST, showing strong immunoreactivity for CD 117, DOG1, Vimentin and CD 99. 6 months follow up post surgery with no recurrence.

Pancreatic Extragastrointestinal Stromal Tumor: A Case Report

Gastrointestinal stromal tumors (GISTs) are soft tissue sarcomas that originate from the mesenchymal cells of the gastrointestinal tract. Extra-GISTs (EGISTs) are caused by sites outside the gastrointestinal tract. We reported a case of EGIST of the pancreas in a 51-year-old woman. Enhanced CT scan showed a rounded, slightly hypointense focus in the head of the pancreas and the right pars compacta of the descending duodenum. Routine laboratory and endocrine tests were unremarkable. The patient underwent laparoscopic surgery. The diagnosis of EGIST was confirmed through histopathological and immunohistochemical examination. The tumor was found to be CD117+, CD34+, and DOG+ with a high risk of malignancy. No recurrence was observed during the nine-month postoperative follow-up.

Extremely Aggressive Mesenteric Extragastrointestinal Stromal Tumor: A Case Report and Literature Review

Gastrointestinal stromal tumors (GISTs) are rare tumors with increasing incidence. GIST is the most common mesenchymal tumor of the gastrointestinal tract involving the elderly population with a slow progression. It originates from the interstitial cells of Cajal. GISTs that develop outside the gastrointestinal tract and have no connections with the intestinal walls or serosal surfaces of the gastrointestinal tubular organs are referred to as extraintestinal gastrointestinal stromal tumors (EGISTs). They have similar morphological and immunohistological characteristics as GISTs. Here, we describe a unique case of an extremely aggressive mesenteric GIST in a 44-year-old African American male.

The patient presented to the hospital with complaints of generalized abdominal pain associated with 50-pound weight loss, decreased appetite, and constipation. He underwent computed tomography (CT) of the abdomen and pelvis which showed a large mass along the central mesentery measuring about 15 × 11 cm with adjacent metastatic nodal disease. He underwent a CT-guided biopsy of his abdominal mass with histopathology findings positive for c-kit (CD117) and discovered on GIST-1 (DOG-1) consistent with GIST. Based on TNM staging, his tumor was graded T4 with N1 given nodal involvement placing him as a stage IV. He was referred to an oncologist and was started on neoadjuvant therapy with imatinib. Mesenteric EGISTs, while rare, are known to have a worse prognosis compared to other EGISTs; hence, prompt action must be taken in aggressively treating these tumors. Factors such as mitotic index and tumor size affect the prognosis of mesenteric GISTs.

Mutational characteristics of gastrointestinal stromal tumors: A single-center analysis of 302 patients

Gastrointestinal stromal tumors (GISTs) represent a spectrum of tumors characterized by variable behaviors and activating mutations in KIT proto-oncogene, receptor tyrosine kinase (KIT) or platelet derived growth factor receptor α (PDGFRA) genes. However, whether genotype analysis should be regarded as a prognostic indicator remains unclear. In the present study, clinicopathological data and the mutation phenotypes of KIT and PDGFRA genes were assessed in a series of 302 patients with GISTs at a single center. Univariate and multivariate Cox regression analyses were performed to identify the clinicopathological and mutational factors associated with relapse-free survival (RFS) in patients who had undergone complete primary GIST resection. KIT and PDGFRA mutations were identified in 233 (77.2%) and 30 (9.9%) cases, respectively. The following clinicopathological parameters were significantly associated with a shorter RFS: Male, non-gastric tumor origin, larger tumor size (>5 cm), high mitotic activity (>5/50 high-power fields), necrosis and epithelioid morphology. Tumors at non-gastric sites, with high National Institutes of Health risk classification, high World Health Organization (WHO) grade and KIT deletion involving codons 557/558/559 exhibited a significantly higher risk of progression. In the Cox regression model, KIT deletion involving codons 557/558/559, non-gastric origin and high WHO grade were independent indicators of RFS. The adverse prognosis associated with KIT deletions involving codons 557/558/559 was also observed for gastric GISTs. Conversely, spindle morphology, KIT exon 11 substitution and PDGFRA exon 18 mutation were associated with a longer RFS and lower rate of relapse. Furthermore, the coexistence of KIT exon 11 deletion and exon 13 duplication was observed in one tumor, with adverse prognostic features. Heterogeneity affecting morphology, immunostaining and genotype was identified in 4 cases. In addition, the presence of succinate dehydrogenase-deficient GIST was found in 5 cases (3.6%). In conclusion, the tumor genotype with regard to KIT and PDGFRA mutations exhibited prognostic significance for the risk of GIST progression and may be helpful for the optimization of tailored adjuvant therapy.

Unraveling the spectrum of KIT mutations in gastrointestinal stromal tumors: An Indian Tertiary Cancer Center Experience

Background:

Primary mutations in the KIT gene are the driving force for gastrointestinal stromal tumors (GIST) tumorigenesis. Predictive role of KIT mutation status aids oncologists in patient management. There is a paucity of comprehensive data on the frequency of mutations in the KIT gene in GIST affecting Indian patients. The aims of this study were to determine the frequency and spectrum of molecular alterations affecting the KIT gene and assess their association with clinicopathologic features in a cohort of patients of GIST.

Materials and Methods:

Morphological and immunohistochemically confirmed GIST cases (n = 114) accessioned from August 2014-June 2015 were analyzed for mutations in KIT exons 9, 11, 13, and 17 and subjected to Sanger sequencing onto the ABI 3500 Genetic Analyzer. The sequences were analyzed using sequence analysis software: SeqScape^® and Chromas Lite.

Results:

KIT mutations were seen in 70% of cases and the majority of KIT mutations involved exon 11 (57%), followed by exon 9 (10%), exon 13 (3%), and exon 17 (1%). Most common exon 11 mutations were in-frame deletions (61.4%) followed by substitution mutations (19.3%). Exon 9 mutations showed identical duplication of Ala-Tyr at codons 502–503. Simultaneous mutations affecting exon 11 and 13 were discovered. Novel variations, namely, p.Q556E (c.1666C>G), p.Q556dup (c.1666_1668dupCAG), p.K558_V559delinsS (c.1672_1677delAAGGTTinsAGT), p.Y503_F504insTY (c.1509_1510insACCTAT), and p.K642R (c.1925A>G) involving exons 11, 9, and 13, respectively, were observed.

Interpretation and Conclusions:

First study with complete analysis of all 4 exons of KIT (exons 9, 11, 13, and 17) in Indian GIST patients. Along with well-described KIT mutations, several rare double mutations as well as novel alterations were reported in this series.

Retroperitoneal Extragastrointestinal Stromal Tumors Have a Poor Survival Outcome: A Multicenter Observational Study

Purpose

Gastrointestinal stromal tumors (GISTs) are commonly known to be derived from the gastrointestinal (GI) tract, but recently there have been more and more literature describing lesions with similar pathological and immunohistochemical resembling GISTs but located outside the GI tract, and they have been termed as extra-GISTs (eGISTs). However, due to the rare incidence of eGISTs, its association with survival outcomes is poorly understood, especially in the Chinese population. Here, we aimed to identify the risk factors of eGISTs and to assess their association with overall survival (OS) and disease-free survival (DFS).

Patients and Methods

Data of pathologically confirmed eGISTs cases, without radiological and perioperative evidence of other primary lesions, and with no microscopically identified adhesion between the tumor and the gastrointestinal serosa, which were surgically treated between January 2006 and September 2017 were retrieved from the database of four high-volume hospitals. Immunohistochemical and genetic testing were performed on the postoperative lesions and were staged using the National Institutes of Health (NIH) criteria.

Results

A total of 55 cases were retrieved. eGISTs were identified from the retroperitoneum (36.4%), mesocolon (25.5%), small bowel mesentery (12.7%), abdominopelvic cavity (12.7%), lesser omental sac (5.5%), ovary (3.6%), pancreatic capsule (1.8%), or urinary bladder (1.8%). Based on the NIH risk classification, majority of the lesion were classified as high risk (85.5%). KIT 11 was the most common mutation site (76.5%) and 25.0% of the cases were wild-type eGISTs. Multivariate analyses showed that tumor location and size were independent factors affecting prognoses. Patients with tumors in the retroperitoneum had significantly poorer OS and DFS as compared to those in the non-retroperitoneum (HR [95% CI] for OS and DFS: 2.546 [1.023–6.337] [P = 0.037] and 2.475 [0.975–6.273] [P = 0.049], respectively). Similar findings were found for tumors of size >15 cm, compared to ≤15 cm (HR [95% CI] for OS and DFS: 5.350 [2.022–14.156] [P < 0.001] and 3.861 [1.493–9.988] [P = 0.003], respectively).

Conclusion

eGISTs were predominantly found from the retroperitoneum and mostly classified as high risk. Those located in the retroperitoneum and of size >15 cm had the poorer OS and DFS as compared to those in the non-retroperitoneum and of size <15 cm.

Prevalence, diagnosis, and treatment of primary hepatic gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST), which is the most common mesenchymal tumor of the digestive tract, account for 1%-3% of gastrointestinal tumors. Primary stromal tumors outside the gastrointestinal tract are collectively referred to as extra GISTs, and stromal tumors in different regions often have different prognoses. A primary hepatic GIST is a rare tumor with an unknown origin, which may be related to interstitial Cajal-like cells. Although primary hepatic GIST has certain characteristics on imaging, it lacks specific symptoms and signs; thus, the final diagnosis depends on pathological and genetic evidence. This review summarizes all cases of primary hepatic GIST described in the literature and comprehensively analyzes the detailed clinical data of all patients. In terms of treatment, local resection alone or with adjuvant therapy was the prioritized choice to obtain better disease-free survival and longer survival time. For advanced unresectable cases, imatinib mesylate was applied as the first-line chemotherapy agent. Moreover, transcatheter arterial chemoembolization, radiofrequency ablation, and microwave ablation were shown to improve overall survival for selected patients. Liver transplantation was a final treatment option after resistance to chemotherapy developed.

Increased ski expression levels are associated with a higher risk and poor prognosis in patients with gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most commonly diagnosed primary mesenchymal tumors of the gastrointestinal tract and 30% of GISTs are associated with a high recurrence risk or metastasis. The current risk classification criteria of the National Comprehensive Cancer Network are based on tumor size, mitotic activity and localization. Investigating additional biomarkers associated with clinical risk may aid in the diagnosis of GIST and improves prediction of patient prognosis. In the present study, the value of using the expression levels of the oncoprotein ski as a prognostic predictor for GISTs was investigated. The results demonstrated that high ski expression levels were correlated with high risk and recurrence rates and indicated poor prognosis regarding median disease-free survival. Overall, the present study suggests that ski expression levels may serve as a predictor for clinical risk and prognosis of patients with GISTs.

The Impact of Imatinib on Survival and Treatment Trends for Small Bowel and Colorectal Gastrointestinal Stromal Tumors

BACKGROUND

The aim of this study is to assess treatment trends and overall survival (OS) in small bowel (SB) and colorectal (CR) gastrointestinal stromal tumors (GIST) with respect to the introduction of imatinib in 2008.

METHODS

Patients diagnosed with SB and CR GIST were identified from the National Cancer Database (2004-2015). The primary outcome was 5- and 10-year OS. Patients were stratified by tumor site, time period (before and after imatinib), and treatment type. OS was analyzed using Kaplan-Meier survival curves, log-rank test, and Cox proportional hazards models.

RESULTS

A total of 8441 cases were included (SB 81.66%; CR 18.34%). Radical resection was the most common treatment (SB 42.33%; CR 38.69%). The addition of chemotherapy to radical resection for SB GIST increased between the two time periods (31.76 to 40.43%; p < 0.001), and was associated with improved unadjusted and adjusted OS (2009-2015: adjusted HR [AHR] 0.73, 95% CI 0.59-0.89, p = 0.002). Patients with SB GIST had better 5- and 10-year OS compared with CR (SB 69.83% and 47.68%; CR 61.33% and 45.39%; p < 0.001), even after stratifying by treatment type and tumor size and adjusting for other factors (SB 5-year AHR 1.35, 95% CI 1.19-1.53; 10-year AHR 1.23, 95% CI 1.09-1.38; each p < 0.001).

CONCLUSION

CR GIST are associated with lower OS than SB GIST. Radical resection is the most common treatment type for both sites. Chemotherapy with radical resection offers better OS in SB GIST, but not in CR GIST. Further studies are needed to assess the biology of CR GIST to explain the worse OS.

Extragastrointestinal Stromal Tumor (EGIST): A 16-Year Experience of 13 Cases Diagnosed at a Single Center

Background

Gastrointestinal stromal tumor (GISTs) rarely occurs outside the GI tract as extragastrointestinal stromal tumor (EGIST). The aim of this study was to review the clinical presentation, diagnosis, and outcome of EGIST at a single center.

Material/Methods

The study was a retrospective study performed at Istanbul University Hospital in a 16-year period and included patients with a histopathological diagnosis of EGIST confirmed to arise outside the GI tract. The patients’ available medical records included patient demographics, imaging and surgical data, and diagnostic histopathology reports. Cases of EGIST underwent follow-up for several years and the medical files of patients were well maintained.

Results

Thirteen cases of EGIST included six women and seven men, with a mean age of 59.6 years (range, 33–83 years). Eleven patients had EGISTs located in the intra-abdominal cavity, one patient’s tumor was in the retroperitoneum, and in the jejunal mesentery in one patient. The mean diameter of the EGISTs was 15.6 cm (range, 4–30 cm). Immunohistochemistry showed that all cases were negative for desmin, with positive immunostaining for CD34 (n=6), smooth muscle actin (SMA) (n=3), and Ki67 (n=6), without specific diagnostic markers. Following surgical resection, tumor recurrence occurred in three patients, and metastasis in two patients. The mean overall survival (OS) was 45.66 months (56.44 months for women; 32.57 months for men); the 5-year survival rate of our patients was 38%.

Conclusions

EGIST presented with a large tumor size at diagnosis, was mainly intra-abdominal, and had a low mean patient survival time with no specific diagnostic tissue immunomarkers.

Comprehensive molecular screening by next generation sequencing reveals a distinctive mutational profile of KIT/PDGFRA genes and novel genomic alterations: results from a 20-year cohort of patients with GIST from north-western Greece

Introduction

Gastrointestinal stromal tumours (GIST) are mesenchymal neoplasms that usually carry an activating mutation in KIT or platelet-derived growth factor receptor alpha (PDGFRA) genes with predictive and prognostic significance. We investigated the extended mutational status of GIST in a patient population of north-western Greece in order to look at geopraphic/genotypic distinctive traits.

Patient and methods

Clinicopathological and molecular data of 38 patients diagnosed from 1996 to 2016 with GIST in the region of Epirus in Greece were retrospectively assessed. Formalin-fixed paraffin-embedded tumours were successfully analysed for mutations in 54 genes with oncogenic potential. Next generation sequencing was conducted by using the Ion AmpliSeqCancer Hotspot Panel V.2 for DNA analysis (Thermofisher Scientific).

Results

Among 38 tumours, 24 (63.16%) and seven (18.42%) of the tumours harboured mutations in the KIT and PDGFRA genes, respectively, while seven (18.42%) tumours were negative for either KIT or PDGFRA mutation. No mutations were detected in five (13.16%) cases. Concomitant mutations of BRAF and fibroblast growth factor receptor 3 (FGFR3) genes were observed in two patients with KIT gene mutation. Two patients with KIT/PDGFRA wild-type GIST had mutations in either KRAS or phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) genes. There was no significant survival difference regarding the exonic site of mutation in either KIT or PDGFRA gene. The presence of a mutation in pathway effectors downstream of KIT or PDGFRA, such as BRAF, KRAS or PIK3CA, was associated with poor prognosis. Adverse prognosticators were also high mitotic index and the advanced disease status at diagnosis.

Conclusions

We report comparable incidence of KIT and PDGFRA mutation in patients with GIST from north-western Greece as compared with cohorts from other regions. Interestingly, we identified rare mutations on RAS, BRAF and PIK3CA genes in patients with poor prognosis.

Rare gastrointestinal stromal tumors (GIST): omentum and retroperitoneum

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms that arise in the gastrointestinal tract and rarely elsewhere in the abdomen. GISTs that develop outside the digestive tract are called extra-GISTs (EGISTs). The incidence of EGISTs is reported to be approximately 10% of all GISTs, and the median age is younger than that of conventional GISTs. EGISTs have similar histology and immunohistochemical features as conventional GISTs, with the majority of them in the omentum and mesentery. Most GISTs harbor a kinase-activating mutation in either KIT or PDGFRA. For EGISTs, the incidence of this type of mutation is 40-50%, which is somewhat lower than for conventional GISTs. EGISTs may have a worse prognosis compared with conventional GISTs with high mitotic indices, large size, and distant metastasis including lymph node involvement. In large abdominal tumors, the visceral origin is almost impossible to discern.

Malignant Retroperitoneal Extra-Gastrointestinal Stromal Tumor: A Unique Entity

Extra-gastrointestinal stromal tumors (EGISTs) are a recently described group of tumors. A handful of less than 70 cases have been reported in English literature, so far, to the best of our knowledge. Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the alimentary canal. EGISTs are a unique entity, which require distinction from GISTs because, even though, they exhibit similar histology and immunohistochemistry to GISTs, they occur outside the gastrointestinal tract, i.e. in omentum, mesentery, retroperitoneum, etc. and have different behavior patterns as far as their prognosis and management are concerned. Retroperitoneal sub-group of EGISTs is extremely rare and we report such a case of primary malignant EGIST of the retroperitoneum which presented as a soft tissue mass on radiological evaluation. The tumor turned out to be a histopathological surprise, and could be distinctively labeled as EGIST only after morphological and immunohistochemical studies. It is imperative for radiologists, pathologists and oncologists, among other clinicians, to be able to recognize and understand the presentation of this group of tumors due to their rapid progression and poor prognosis, so that an early diagnosis and management may be able to improve the final disease outcome.

Multimodality therapy of rectal gastrointestinal stromal tumors in the era of imatinib-an Indian series

BACKGROUND

Primary objective was to determine if sphincter preservation is possible with the use of neoadjuvant imatinib in cases of rectal gastrointestinal stromal tumor (GIST). Secondary objectives were to determine clinicopathological characteristics and intermediate term oncological outcomes of the cases of rectal GIST.

METHODS

This is a retrospective review of 13 cases of GIST of the rectum diagnosed between January 1, 2010 and June 30, 2015 at Tata Memorial Centre, Mumbai, India. Clinical parameters that were assessed were duration of the neoadjuvant imatinib therapy, type of surgery performed as well as perioperative morbidity. Pathological parameters that were assessed included the size of the tumor, completeness of resection, mitotic count and mutational analysis.

RESULTS

Of the 13 patients included, 11 were nonmetastatic at the time of presentation. All the patients received neoadjuvant imatinib in view of locally advanced nature of the tumors. Median distance from anal verge was 2 cm. Median duration of imatinib was 9 months. Of the 9 patients who underwent surgery, three had sphincter preserving surgery (33%) whereas the rest had abdomino-perineal resection. Two patients had perineal wound infections. All the operated patients received adjuvant imatinib therapy for 3 years. Median follow up period was 34 months. One patient developed distant metastasis; otherwise rest had no local or distant recurrence.

CONCLUSIONS

In cases of rectal GIST, sphincter preservation may not be possible in spite of neoadjuvant therapy with imatinib.

Retrospective analysis of extra-gastrointestinal stromal tumors

AIM: To investigate the clinicopathologic features of patients with extra-gastrointestinal stromal tumors (EGISTs) in South Korea.

METHODS: A total of 51 patients with an EGIST were identified. The clinicopathologic features, including sex, age, location, tumor size, histology, mitotic rate, immunohistochemical features, genetic status and survival data, were analyzed.

RESULTS: The median age was 55 years (range: 29-80 years), and male:female ratio was 1:1.04. The most common site was in the mesentery (n = 15) followed by the retroperitoneum (n = 13) and omentum (n = 8). The median tumor size was 9.0 cm (range: 2.6-30.0 cm) and the median mitotic rate was 5.0/50HPF. (1/50 - 185/50). KIT was analyzed in 16, which revealed 10 cases with wild-type KIT and 6 cases with an exon 11 mutation. Among 51 patients, 31 patients had undergone surgery, and 10 had unresectable disease and had taken palliative imatinib, which resulted in 22.7 mo of progression-free survival. Of the patients who had undergone surgery, 18 did not take adjuvant imatinib, and 8 of these were categorized as “high risk” according to the risk criteria. However, the relapse-free survival was not different (P = 0.157) between two groups.

CONCLUSION: Because the biologic behaviors of GISTs differ according to the location of the tumor, a more stratified strategy is required for managing EGISTs including incorporation of molecular features.

Molecular spectrum of c-KIT and PDGFRA gene mutations in gastro intestinal stromal tumor: determination of frequency, distribution pattern and identification of novel mutations in Indian patients

KIT and PDGFRA gene mutations are the major genetic alterations seen in gastrointestinal stromal tumors (GISTs) and are being used clinically for predicting response to imatinib therapy. In the current study, we set out to explore the frequency and distribution pattern of c-KIT (exons 9, 11 and 13) and PDGFRA (exons 12 and 18) by direct sequencing in a series of 70 Indian GIST cases. Overall, 27 (38.5 %) and 4 (5.7 %) of the cases had c-KIT and PDGFRA mutations, respectively. Majority of KIT mutations involved exon 11 (85.7 %), followed by exon 9 (14.3 %), while none showed exon 13 mutation. Most exon 9 mutations showed Ala503-Tyr504 duplication, while one had novel point mutation at codon 476 (S476G). In contrast to exon 9 mutations, most exon 11 mutations were in-frame deletions (79 %, 19/24), predominantly at codons 550-560, while remaining exon 11 mutant cases were point mutations at codons 559, 560, 568, 573 and 575. Interestingly, P573T, Q556_V560delinsH, Q575H and Q575_P577 were novel variations observed in exon 11. The PDGFRA mutations were seen mostly in exon 18, which showed point mutation at codon 842 (D842V), while exon 12 showed a novel indel variation (V561_H570delinsT). No significant correlation between c-KIT/PDGFRA mutations and clinicopathological data was observed. In conclusion, this study highlights the frequency and distribution pattern of c-KIT/PDGFRA mutation in Indian cohort. The current study identified novel variations that added new insights into the genetic heterogeneity of GIST patients. Furthermore, this is the first study to report the presence of PDGFRA mutation from Indian subcontinent.

The primary extra-gastrointestinal stromal tumor of pleura: a case report and a literature review

The gastrointestinal stromal tumor is the most common mesenchymal neoplasm of the gastrointestinal tract. The gastrointestinal stromal tumor universally expresses KIT and DOG-1 and frequently harbors oncogenic mutations in the KIT gene. While the gastrointestinal stromal tumor usually arises in the alimentary tract, it is rarely found in the extragastrointestinal area. When it is, it is called an extragastrointestinal stromal tumor. Although the pathogenesis, prognostic factors and outcomes of gastrointestinal stromal tumors are well known, those of extragastrointestinal stromal tumors have not been fully studied. We report, herein, a unique primary extragastrointestinal stromal tumor from the pleura in a 73-year-old woman who presented with pleural mass. The extragastrointestinal stromal tumor was surgically resected and confirmed by means of an immunohistochemical study and a molecular analysis.

Gastrointestinal tumors of the colon and rectum

Gastrointestinal stromal tumors (GISTs) of the colon and rectum are the most common mesenchymal tumors of the gastrointestinal tract. GISTs of the colon and rectum constitute ~5% of all cases. Although colorectal GISTs can be small and found incidentally, the majority appear to be high risk and carry a significant likelihood of recurrent and metastatic disease. Surgery remains the mainstay of treatment for primary disease. There is now considerable interest in GISTs because they can be treated effectively with targeted molecular therapies, specifically tyrosine kinase inhibitors (TKIs), such as imatinib mesylate and sunitinib malate. GISTs are best treated by a multidisciplinary team comprised of the surgeon, medical oncologist, pathologist, and radiologist in the initial evaluation, management, and in continued follow-up. Increasing the number of resectable cases through pharmacologic debulking, optimizing the timing of surgery and organ preservation, reducing recurrence and surgical morbidity, prolonging survival, and possibly enhancing response to imatinib through surgical cytoreduction are all potential benefits of multidisciplinary management.

Frequencies of KIT and PDGFRA mutations in the MolecGIST prospective population-based study differ from those of advanced GISTs

Gastrointestinal stromal tumors (GISTs) are the most common human sarcoma. Most of the data available on GISTs derive from retrospective studies of patients referred to oncology centers. The MolecGIST study sought to determine and correlate clinicopathological and molecular characteristics of GISTs. Tumor samples and clinical records were prospectively obtained and reviewed for patients diagnosed in France during a 24-month period. Five hundred and ninety-six patients were included, of whom 10% had synchronous metastases. GISTs originated from the stomach, small bowel or other site in 56.4, 30.2 and 13.4% of cases, respectively. The main prognostic markers, tumor localization, size and mitotic index were not independent variables (P < 0.0001). Mutational status was determined in 492 (83%) patients, and 138 different mutations were identified. KIT and PDGFRA mutations were detected in 348 (71%) and 74 (15%) patients, respectively, contrasting with 82.8 and 2.1% in patients with advanced GIST (MetaGIST) (P < 0.0001). Further comparison of localized GISTs in the MolecGIST cohort with advanced GISTs from previous clinical trials showed that the mutations of PDGFRA exon18 (D842V and others) as well as KIT exon11 substitutions (W557R and V559D) were more likely to be seen in patients with localized GISTs (odds ratio 7.9, 3.1, 2.7 and 2.5, respectively), while KIT exon 9 502_503dup and KIT exon 11 557_559del were more frequent in metastatic GISTs (odds ratio of 0.3 and 0.5, respectively). These data suggest that KIT and PDGFRA mutations and standardized mitotic count deserve to be investigated to evaluate the relapse risk of GISTs.

C-KIT mutations were closely associated with the response to Imatinib in Chinese advanced gastrointestinal stromal tumor patients

To investigate the correlation between C-KIT/PDGFRα mutations and Imatinib response or survival in Chinese advanced gastrointestinal stromal tumor (GIST) patients. Clinical data and paraffin-embedded tumor specimens were collected from 158 advanced GIST patients receiving first-line Imatinib. Mutation analyses of C-KIT gene (Exons 9, 11, 13, and 17) and PDGFRα gene (exons 12 and 18) were performed by PCR amplification and Sanger sequencing. A total of 135 patients harboring C-KIT mutations (exon 11 mutation: 108; exon 9 mutation: 23; exon 13 mutation: 2; exon 17 mutation: 2) and one patients carrying PDGFRα mutation (exon 18) were found in this study. Twenty-two patients (13.9 %) with neither C-KIT nor PDGFRα mutations were named as wild type. The response rate (64.7 vs. 36.4 %, P = 0.000) and median progression-free survival (28 vs. 8 months, P = 0.000) of mutant patients (n = 136) were significantly higher than those of wild-type patients (n = 22). Moreover, the response rate and median progression-free survival in patients with exon 11 mutations (n = 108), exon 9 mutations (n = 23), and wild-type patients (n = 22) were 68.5, 47.8, and 36.4 % (P = 0.001), and 31 months, 13 months, and 8 months (P = 0.000), respectively. No significant differences of response rate or median progression-free survival were seen in patients with exon 11 deletion mutations, point mutations, and mixed-type mutations. C-KIT mutations were closely associated with Imatinib response and progression-free survival of Chinese advanced GIST patients. Other predictive markers for Imatinib would be further investigated.

Clinical practice guideline for accurate diagnosis and effective treatment of gastrointestinal stromal tumor in Korea

Despite their rarity in incidence and prevalence, gastrointestinal stromal tumors (GISTs) have emerged as a distinct and noteworthy pathogenetic entity. The clinical management of GISTs has rapidly evolved due to the recent elucidation of their oncogenic signal transduction pathway and the introduction of molecular-targeted therapies. Successful management of GISTs requires a multidisciplinary approach firmly based on an accurate histopathologic diagnosis. In 2007, the Korean GIST study group published the first guideline for optimal diagnosis and treatment of GISTs in Korea. The second version of the guideline was published in 2010. Herein, we provide the results of relevant clinical studies for the purpose of further revision to the guideline. We expect this new guideline will enhance the accuracy of diagnosis, as performed by members of the Korean associate of physicians involved in GIST patient care, thus improving the efficacy of treatment.

Imatinib efficacy by tumor genotype in Korean patients with advanced gastrointestinal stromal tumors (GIST): The Korean GIST Study Group (KGSG) study

PURPOSE

To assess the efficacy of imatinib for different tumor genotypes in Korean patients with advanced gastrointestinal stromal tumors (GIST).

MATERIAL AND METHODS

Clinical data were collected from 370 consecutive patients with locally advanced unresectable, metastatic, or recurrent GIST treated with imatinib 400 mg/day between August 2001 and December 2007 at 20 Korean institutions. Tumor genotypes were determined for 290 patients by direct DNA sequencing of KIT exons 9, 11, 13, and 17, and PDGFRA exons 12, 14, and 18.

RESULTS

Of 290 patients assessed for genotype, 261 (90.0%) had mutations in KIT: 222 (76.6%) in exon 11, 35 (12.1%) in exon 9 and two each (0.7%) for exons 13 and 17. Four patients (1.4%) had mutations in the PDGFRA gene: one in exon 12, and three in exon 18. Twenty-five patients (8.6%) had no detectable mutations. The best responses of the 235 patients with measurable lesions were: 15 complete response (6.4%), 126 partial response (53.5%), 86 stable disease (36.6%), and eight progressive disease (3.4%). Patients with KIT exon 9 mutations, compared with patients with KIT exon 11 mutations, had a lower objective response rate (36.7% vs. 63.6%, p = 0.007) and a shorter progression-free survival (median 28.7 months vs. 49.4 months, p = 0.001). No statistical difference in overall survival was observed between these genotypes.

CONCLUSION

This study confirms that imatinib efficacy is dependent on genotype in Korean GIST patients, consistent with results demonstrated by Western patients with GIST.

MAPKAP kinase 2 overexpression influences prognosis in gastrointestinal stromal tumors and associates with copy number variations on chromosome 1 and expression of p38 MAP kinase and ETV1

PURPOSE

ETV1 has been proposed to be activated by KIT mutations in gastrointestinal stromal tumors (GIST). The aim of the study was to evaluate the clinical role of ETV1 and associated proteins in GIST.

EXPERIMENTAL DESIGN

Expressions of ETV1, MAPKAP kinase 2 (MAPKAPK2), phosphorylated p38 MAP kinase (pp38), phosphorylated MSK1 (pMSK1), phosphorylated RSK1, COP1, and KIT protein were determined immunohistochemically in 139 GISTs. Sequence analysis of KIT, PDGFRA, and MAPKAPK2 and FISHs of ETV1 as well as chromosomes 1 and 7 were done.

RESULTS

Prominent ETV1 expression was seen in 50% of GISTs, but no correlation with clinical outcome was found. Correlation of ETV1 expression and KIT mutation was seen in 60% of cases. MAPKAPK2 overexpression (n = 62/44.6%) correlated with pp38 expression (P = 0.021, χ(2) test) and alterations of chromosome 1 (n = 17, P = 0.024, χ(2) test). In one of 20 sequenced cases with high MAKAPK2 expression, a putative damaging MAPKAPK2 gene mutation was found. All relapsing GISTs with very low/low risk according to Fletcher showed high MAPKAPK2 and KIT expression. MAPKAPK2 overexpression was an independent prognostic factor for disease-free survival (P = 0.006, Cox regression).

CONCLUSION

ETV1 is not universally overexpressed in GIST and seems to also be induced by pathways other than KIT mutation. Nevertheless, its clinical relevance is low. Overexpression of ETV1 inhibitor MAPKAPK2 is associated with shorter survival in GIST, indicating a clinically relevant role of this gene not reported previously. Patients with low-risk GISTs showing MAPKAPK2 overexpression might profit from early adjuvant tyrosine kinase inhibitor therapy.

Targeted knockdown of canine KIT (stem cell factor receptor) using RNA interference

Canine mast cell tumours often express KIT mutations that result in constitutive activation of the c-kit receptor and which are associated with more aggressive disease. The aim of the current study was to determine whether small inhibitory RNA (SiRNA) molecules could specifically target canine KIT mRNA for knock-down. Canine beta-2 microglobulin (B2M), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and KIT sequences were cloned into the psiCHECK™-2 vector. SiRNA molecules, designed to target gene-specific sequences, were co-transfected with plasmid DNA into Chinese hamster ovary (CHO) cells. Renilla and firefly luciferase activity was measured using the Dual-GLO(®) Luciferase Assay (Promega). Using this reporter system, canine housekeeping gene-specific SiRNA molecules demonstrated knockdown of their targets (72.0% knockdown for B2M and 94.5% knockdown for GAPDH). An SiRNA molecule targeting exon 2 of canine KIT successfully knocked-down reporter gene expression of a KIT(26-407) construct (90.8% knockdown). An SiRNA molecule targeting a 48 base-pair in-tandem duplication mutation in KIT exon 11 selectively knocked down expression of the KIT(1569-1966mutant) construct (93.1% knockdown) but had no effect on the KIT(1569-1918wild-type) construct. The results show that RNA interference can be used to inhibit canine KIT mRNA expression and has the potential to selectively target the mutant version of KIT that is expressed by some malignant mast cells.

Platelet-Derived Growth Factors in Non-GIST Soft-Tissue Sarcomas Identify a Subgroup of Patients with Wide Resection Margins and Poor Disease-Specific Survival

Background. Optimal treatment of nongastrointestinal stromal tumor soft-tissue sarcomas (non-GIST STSs) is resection with wide margins. This study investigates the prognostic impact of the angiogenesis-associated platelet-derived growth factors (PDGFs) and their receptors (PDGFRs) in non-GIST STS patients with wide and nonwide resection margins. Method. Tumor samples and clinical data from 249 patients with non-GIST STS were obtained, and tissue microarrays were constructed for each specimen. Immunohistochemistry was used to evaluate the expression of PDGF-A, -B, -C, and -D and PDGFR-α and -β. Results. In the multivariate analysis of patients with wide resection margins, high expression of PDGF-B (P = .013, HR = 2.954, and 95% CI = 1.255–6.956) and the coexpression of PDGF-B and PDGFR-α (overall; P = .016, high-low/low-high; P = .051, HR = 2.678, 95% CI = 0.996–7.200, high/high; P = .004, HR = 3.930, 95% CI = 1.542–10.015) were independent negative prognostic markers for disease-specific survival. Conclusion. PDGF-B and the coexpression of PDGF-B and PDGFR-α are strong and independent prognostic factors in non-GIST STSs with wide resection margins.

A prospective epidemiological study of new incident GISTs during two consecutive years in Rhône Alpes region: incidence and molecular distribution of GIST in a European region

Background:

Preliminary data indicate that the molecular epidemiology of localised gastrointestinal stromal tumour (GIST) may be different from that of advanced GIST. We sought to investigate the molecular epidemiology of sarcomas, including GIST, in the Rhone-Alpes region in France.

Patients and methods:

A prospective and exhaustive study in the Rhone-Alpes Region in France to assess the precise incidence of primary sarcomas with systematic centralised pathological review and molecular analysis was conducted for 2 consecutive years.

Results:

Among 760 patients with a confirmed diagnosis of sarcoma, 131 (17%) had a GIST. The majority of patients had gastric primaries (61%). Mutational analysis could be performed in 106 tumour samples (74%), and 71 (67%) had exon 11 mutations. PDGFRA mutations were found in 16% of cases, which is twice as high as previously reported for advanced GIST.

Conclusion:

Data indicate that PDGFRA mutations in localised GIST may be twice as high as what was previously reported in patients with advanced disease. This finding may have important consequences for patients offered adjuvant imatinib, although most of these tumours are in the low-risk group.

Catching cancer by the tail: new perspectives on the use of kinase inhibitors

In this issue of Clinical Cancer Research, London and colleagues evaluate a small molecule multiple-targeted tyrosine kinase inhibitor in dogs with c-kit driven skin cancer. The study represents another example of opportunities to include pet dogs in studies that improve our understanding of human cancer biology and therapy.