Diagnosis, prognosis and treatment of patients with gastrointestinal stromal tumour (GIST) and germline mutation of KIT exon 13

Molecular Profiling of KIT/PDGFRA-Mutant and Wild-Type Gastrointestinal Stromal Tumors (GISTs) with Clinicopathological Correlation: An 18-Year Experience at a Tertiary Center in Kuwait

In gastrointestinal stromal tumors (GISTs), identifying prototypical mutations in the KIT/PDGFRA oncogenes, or in rare alternate genes, is essential for prognostication and predicting response to tyrosine kinase inhibitors. Conversely, wild-type GISTs (WT-GIST), which lack known mutations, have limited treatment options. Data on the mutational landscape of GISTs and their impact on disease progression are very limited in Kuwait. Using a targeted next-generation sequencing panel, we investigated the spectrum and frequency of KIT, PDGFRA, and RAS-pathway-related mutations in 95 out of 200 GISTs diagnosed at Kuwait Cancer Center from 2005 to 2023 and assessed their correlation with clinicopathological parameters. Among the 200 tumors (median age 55 years; 15-91), 54% originated in the stomach, 33% in the small bowel, 7% in the colorectum, 1.5% in the peritoneum, and 4.5% had an unknown primary site. Of the 95 molecularly profiled cases, 88% had a mutation: KIT (61%), PDGFRA (25%), NF1 (2%), and one NTRK1 rearrangement. Ten WT-GISTs were identified (stomach = 6, small bowel = 2, and colorectum = 2). WT-GISTs tended to be smaller (median 4.0 cm; 0.5-8.0) (p = 0.018), with mitosis ≤5/5 mm2, and were of lower risk (p = 0.019). KIT mutations were an adverse indicator of disease progression (p = 0.049), while wild-type status did not significantly impact progression (p = 0.934). The genetic landscape in this cohort mirrors that of global studies, but regional collaborations are needed to correlate outcomes with genetic variants.

Molecular characteristics and immune microenvironment of gastrointestinal stromal tumours: targets for therapeutic strategies

Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours, arising mainly from the interstitial cells of Cajal (ICCs) of the gastrointestinal tract. As radiotherapy and chemotherapy are generally ineffective for GISTs, the current primary treatment is surgical resection. However, surgical resection is not choice for most patients. Therefore, new therapeutic strategies are urgently needed. Targeted therapy, represented by tyrosine kinase inhibitors (TKIs), and immunotherapy, represented by immune checkpoint inhibitor therapies and chimeric antigen receptor T-cell immunotherapy (CAR-T), offer new therapeutic options in GISTs and have shown promising treatment responses. In this review, we summarize the molecular classification and immune microenvironment of GISTs and discuss the corresponding targeted therapy and immunotherapy options. This updated knowledge may provide more options for future therapeutic strategies and applications in GISTs.

Case report: detection of multiple sporadic gastrointestinal stromal tumors by dual-time 18 F-FDG PET/CT

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors affecting the gastrointestinal tract. Typically, GISTs are solitary; however, in rare cases, they may be multiple and appear in one or more organs. Multiple GISTs can appear in familial GISTs, children, or certain tumor syndromes such as neurofibromatosis type 1, Carney syndrome, and Carney-Stratakis syndrome. However, the diagnosis of primary multiple sporadic GISTs is often more difficult than that of these diseases. Herein, we report a case of multiple primary sporadic GISTs in a 64-year-old man, affecting the abdominal cavity and retroperitoneum, as identified through dual-time point positron emission tomography (PET) with 18F-labeled fluoro-2-deoxyglucose (18F-FDG) and computed tomography (18F-FDG PET/CT). Notably, the dual-time-point PET/CT revealed the migration of masses near the lower abdomen into the abdominal cavity. Furthermore, a significant increase in radioactive uptake of the mass 3 h after 18F-FDG injection compared with that 1 h after injection may be an important cue for its diagnosis.

Diagnosis, Treatment, and Prognosis of Patients with Primary Familial Gastrointestinal Stromal Tumor: A Case Report and Literature Review

Gastrointestinal stromal tumors are the most common mesenchymal tumors of the digestive tract, most of which are sporadic, and familial GISTs with germline mutations are rarely seen. Here, we report a 26-year-old female with a germline p. W557R mutation in exon 11 of the KIT gene. The proband and her father and sister presented with multifocal GIST and pigmented nevi. All 3 patients underwent surgery and imatinib therapy. To date, only 49 kindreds with germline KIT mutations and 6 kindreds with germline PDGFRA mutations have been reported. Summarizing the reported kindreds, the majority of familial GISTs manifest as multiple primary GISTs complicated with special clinical manifestations, including cutaneous hyperpigmentation, dysphagia, mastocytosis, inflammatory fibrous polyps, and large hands. Familial GISTs are generally thought to exhibit TKI sensitivity similar to that of sporadic GISTs with the same mutation.

Management of Advanced Systemic Mastocytosis and Associated Myeloid Neoplasms

Advanced systemic mastocytosis (AdvSM) is a heterogeneous group of disorders characterized by neoplastic mast cell-related organ damage and frequently associated with a myeloid neoplasm. The 3 clinical entities that comprise AdvSM are aggressive SM (ASM), SM-associated hematologic neoplasm, and mast cell leukemia. A gain-of-function KIT D816 V mutation is the primary oncogenic driver found in about 90% of all patients with AdvSM. Midostaurin, an oral multikinase inhibitor with activity against KIT D816V, and avapritinib, an oral selective KIT D816V inhibitor are approved for AdvSM.

Surgical Management of Germline Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma and usually results from a sporadic mutation in KIT or, less frequently, platelet-derived growth factor alpha (PDGFRA). Rarely, a germline mutation in the KIT, PDGFRA, succinate dehydrogenase (SDH), or neurofibromatosis 1 (NF1) gene is responsible for GIST. These tumors are found in the stomach (PDGFRA and SDH), small bowel (NF1), or a combination of both (KIT). There is a need to improve care for these patients regarding genetic testing, screening, and surveillance. Since most GISTs due to a germline mutation do not respond to tyrosine kinase inhibitors, the role of surgery is critical, especially when considering germline gastric GIST. However, in contrast to the established recommendation for prophylactic total gastrectomy in cadherin 1 (CDH1) mutation carriers once they reach adulthood, there are no formal guidelines as to the timing or extent of surgical resection for patients who are either carriers of a germline GIST mutation causing gastric GIST or have already developed gastric GIST(s). Surgeons must balance treating what is often multicentric, yet initially indolent disease with the chance of cure and the complications associated with total gastrectomy. Here, we consider the major issues in performing surgery in patients with germline GIST and illustrate the principles with a previously unreported patient harboring a germline KIT 579 deletion.

KIT-Associated Familial GIST Syndrome: Response to Tyrosine Kinase Inhibitors and Implications for Risk Management

Sporadic gastrointestinal stromal tumors (GIST) are rare tumors, with a median age at diagnosis of 60 years. Familial GISTs are very rare and typically associated with earlier onset, with an average age at diagnosis of 48 years. To date, just over 50 familial cases associated with a germline variant KIT or PDGFRa genes have been published. Therefore, there are many challenges in managing these patients, including the timing of starting systemic treatment, considering that most patients have been asymptomatic for a long period before being diagnosed, as well as the choice of tyrosine kinase inhibitor and the plan for surveillance.

It is uncertain if early diagnosis through screening of asymptomatic individuals improves overall survival. Screening could start from the age of 18 years but may be considered at earlier ages depending on the underlying genotype and family history. The long-term benefit of early diagnosis or palliative/prophylactic treatment with tyrosine kinase inhibitors is unknown as there are no data available. Long-term side effects of treatment with imatinib are rare but well documented and could be damaging in patients who have no or minimal disease.

We present the case of a 53-year-old Caucasian patient who was diagnosed with multifocal GIST and subsequently found to be a carrier of a pathogenic germline KIT variant in exon 11. We discuss the implication of treatment and genetic testing in this case and in familial KIT associated GISTs.

Gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GIST) have an incidence of ~1.2 per 10⁵ individuals per year in most countries. Around 80% of GIST have varying molecular changes, predominantly mutually exclusive activating KIT or PDGFRA mutations, but other, rare subtypes also exist. Localized GIST are curable, and surgery is their standard treatment. Risk factors for relapse are tumour size, mitotic index, non-gastric site and tumour rupture. Patients with GIST with KIT or PDGFRA mutations sensitive to the tyrosine kinase inhibitor (TKI) imatinib that are at high risk of relapse have improved survival with adjuvant imatinib treatment. In advanced disease, median overall survival has improved from 18 months to >70 months since the introduction of TKIs. The role of surgery in the advanced setting remains unclear. Resistance to TKIs arise mainly from subclonal selection of cells with resistance mutations in KIT or PDGFRA when they are the primary drivers. Advanced resistant GIST respond to second-line sunitinib and third-line regorafenib, as well as to the new broad-spectrum TKI ripretinib. Rare molecular forms of GIST with alterations involving NF1, SDH genes, BRAF or NTRK genes generally show primary resistance to standard TKIs, but some respond to specific inhibitors of the activated genes. Despite major advances, many questions in both advanced and localized disease remain unanswered.

Gastrointestinal Stromal Tumor in Monozygotic Twins Shows Distinct Mutational Status: A Case Report

Case series

Patients: Female, 62-year-old • Female, 62-year-old

Final Diagnosis: Gastrointestinal stromal tumor (GIST)

Symptoms: Abdominal pain • fatigue

Medication: —

Clinical Procedure: Genetic analysis

Specialty: Oncology

Preservation of Organ Function in Locally Advanced Non-Metastatic Gastrointestinal Stromal Tumors (GIST) of the Stomach by Neoadjuvant Imatinib Therapy

Simple Summary

This study reports a single-center analysis of 55 patients with primary, locally advanced gastric GIST treated with imatinib mesylate (IM) preoperatively for a median of 10 months. The therapy yielded shrinkage of median tumor size from 113 mm to 62 mm. This facilitated 50 patients to undergo significantly less-extensive surgical procedures and resulted in a stomach preservation rate of 96%. The rate of R0 resections was 94% and was followed by a mean recurrence-free-survival time of 132 months with the median not reached. The approach was successful even for patients starting IM during an episode of upper gastrointestinal bleeding. Neoadjuvant IM therapy for locally advanced, non-metastatic gastrointestinal stromal tumors (GIST) of the stomach may play an important role in preserving organ function which might be important for IM plasma levels in an adjuvant or metastatic setting.

Abstract

Background: Neoadjuvant imatinib mesylate (IM) for advanced, non-metastatic gastrointestinal stromal tumors (GIST) of stomach is recommended to downsize the tumor prompting less-extensive operations and preservation of organ function. Methods: We analyzed the clinical-histopathological profile and oncological outcome of 55 patients (median age 58.2 years; range, 30–86 years) with biopsy-proven, cM0, gastric GIST who underwent IM therapy followed by surgery with a median follow-up of 82 months. Results: Initial median tumor size was 113 mm (range, 65–330 mm) and 10 patients started with acute upper GI bleeding. After a median 10 months (range, 2–21 months) of treatment, tumor size had shrunk to 62 mm (range, 22–200 mm). According to Response Evaluation Criteria In Solid Tumors version 1.0 and version 1.1 (RECIST 1.1), 39 (75%) patients had partial response and 14 patients had stable disease, with no progressive disease. At plateau response, 50 patients underwent surgery with an R0 resection rate of 94% and pathological complete response in 24%. In 12 cases (24%), downstaging allowed laparoscopic resection. The mean recurrence-free survival (RFS) was 123 months (95%CI; 99–147) and the estimated 5-year RFS was 84%. Conclusions: Neoadjuvant IM allowed stomach preservation in 96% of our patients with excellent long-term RFS, even when starting treatment during an episode of upper GI bleeding. Preservation of the stomach provides the physiological basis for the use of oral IM in the adjuvant or metastatic setting.

Update on Molecular Genetics of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. The majority are sporadic, solitary tumors that harbor mutually exclusive KIT or PDGFRA gain-of-function mutations. The type of mutation in addition to risk stratification corresponds to the biological behavior of GIST and response to treatment. Up to 85% of pediatric GISTs and 10–15% of adult GISTs are devoid of these (KIT/PDGFRA) mutations and are referred to as wild-type GISTs (wt-GIST). It has been shown that these wt-GISTs are a heterogeneous tumor group with regard to their clinical behavior and molecular profile. Recent advances in molecular pathology helped to further sub-classify the so-called “wt-GISTs”. Based on their significant clinical and molecular heterogeneity, wt-GISTs are divided into a syndromic and a non-syndromic (sporadic) subgroup. Recently, the use of succinate dehydrogenase B (SDHB) by immunohistochemistry has been used to stratify GIST into an SDHB-retained and an SDHB-deficient group. In this review, we focus on GIST sub-classification based on clinicopathologic, and molecular findings and discuss the known and yet emerging prognostic and predictive genetic alterations. We also give insights into the limitations of targeted therapy and highlight the mechanisms of secondary resistance.

A Novel Kindred with Familial Gastrointestinal Stromal Tumors Caused by a Rare KIT Germline Mutation (N655K): Clinico-Pathological Presentation and TKI Sensitivity

Gastrointestinal stromal tumors (GISTs), the most common mesenchymal tumors of the gastrointestinal tract, are characterized by activating mutations in KIT or PDGFRA genes. The vast majority of GISTs are sporadic, but rare hereditary forms have been reported, often featuring multifocality and younger age of onset. We here report the identification of a novel kindred affected by familial GIST caused by a KIT germline mutation in exon 13 (N655K). No family affected by hereditary GIST due to this KIT variant has been reported in literature so far. We were able to track the mutation in three members of the family (proband, mother, and second-degree cousin), all affected by multiple GISTs. Due to its rarity, the N655K variant is poorly characterized. We conducted in vitro drug sensitivity assays that indicated that most tyrosine kinase inhibitors (TKIs) currently included in the therapeutic armamentarium for GISTs have a limited inhibitory activity toward this mutation. However, when compared to a classical imatinib-resistant KIT mutation (T670I), N655K was slightly more sensitive to imatinib, and encouraging responses were observed with last-generation TKIs.

Gastrointestinal stromal tumours (GISTs): French Intergroup Clinical Practice Guidelines for diagnosis, treatments and follow-up (SNFGE, FFCD, GERCOR, UNICANCER, SFCD, SFED, SFRO)

BACKGROUND

This document is a summary of the French Intergroup guidelines regarding the management of gastrointestinal stromal tumours (GISTs) updated in December 2018.

DESIGN

This collaborative work summarizes clinical practice recommendations (guidelines) on the management of GISTs. It is based on recent literature review, ESMO recommendations and expert opinions.

RESULTS

The diagnosis of GIST is based on histological examination and immunohistochemistry with markers KIT and DOG-1. Each case must be discussed within a multidisciplinary team. Complete surgical resection tumour, avoiding peroperative perforation, is the potentially curative treatment of localized GISTs. The estimation of the recurrence risk is essential, or adjuvant treatment,and follow-up adaptation. Genotyping (KIT and PDGFRA) of all but very low-risk GISTs is recommended. The nature of mutation has a prognostic value and predictive influence on drug efficacy. Imatinib, a tyrosine-kinase inhibitor, is the standard adjuvant treatment after R0 resection of a GIST with a high risk of recurrence, and the first line therapy for advanced GISTs. Suninitib and regorafenib are respectively the second- and third-line standard treatments for advanced GISTs.

CONCLUSION

Guidelines for management of GISTs are continuously evolving and need to be regularly updated. This constant progress is made possible through clinical and translational research.

Adjuvant therapy with imatinib in gastrointestinal stromal tumors (GISTs)-review and perspectives

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumor of the gastrointestinal (GI) tract. Most of them (>75%) are driven by an oncogenic initiating event involving activating mutations of the genes encoding for tyrosine kinase, KIT or platelet derived growth factor receptor alpha (PDGFRA). Efficacy of the tyrosine kinase Inhibitor imatinib is now well established for advanced disease. For localized GISTs, 3 years treatment is the recommended adjuvant therapy for high risk patients. Whether a longer duration and selection of patients for this adjuvant therapy in localized GISTs remains is not yet established (PERSIST-5 study). Similarly, it will be important to further refine the definition of the population of GIST patients at high risk of relapse including molecular criteria (Annals of Oncology, ESMO guidelines 2018). This review aims to describe current knowledges on the issue of adjuvant therapy of primary GISTs in view of available results.

Remarkable effects of imatinib in a family with young onset gastrointestinal stromal tumors and cutaneous hyperpigmentation associated with a germline KIT-Trp557Arg mutation: case report and literature overview

Gastrointestinal stromal tumors (GISTs) occur mostly sporadically. GISTs associated with a familial syndrome are very rare and are mostly wild type for KIT and platelet-derived growth factor alpha (PDGFRA). To date 35 kindreds and 8 individuals have been described with GISTs associated with germline KIT mutations. This is the third family described with a germline p.Trp557Arg mutation in exon 11 of the KIT gene. The effect of imatinib in patients harboring a germline KIT mutation has been rarely described. Moreover, in some studies imatinib treatment was withheld considering the lack of evidence for efficacy of this treatment in GIST patients harboring a germline KIT mutation. This paper describes a 52-year old patient with a de novo germline p.Trp557Arg mutation with multiple GISTs throughout the gastrointestinal tract and cutaneous hyperpigmentation. Imatinib treatment showed long-term regression of the GISTs and evident pathological response was seen after resection. Remarkably, the hyperpigmentation of the skin also diminished during imatinib treatment. Genetic screening of the family revealed the same mutation in two daughters, both with similar cutaneous hyperpigmentation. One daughter, aged 23, was diagnosed with multiple small intestine GISTs, which were resected. She was treated with adjuvant imatinib which prompted rapid regression of the cutaneous hyperpigmentation. Imatinib treatment in GIST patients harboring a germline KIT mutation shows favorable and long-term responses in both the tumor and the phenotypical hyperpigmentation.

Translating genomic risk into an early detection strategy for sarcoma

Sarcomas have a strong genetic etiology, and the study of families affected by sarcomas has informed much of what we now understand of modern cancer biology. The recent emergence of powerful genetic technologies has led to astonishing reductions in costs and increased throughput. In the clinic, these technologies are revealing a previously unappreciated and rich landscape of genetic cancer risk. In addition to both known and new cancer risk mutations, genomic tools are cataloguing complex and polygenic risk patterns, collectively explaining between 15-25% of apparently sporadic sarcoma cases. The impact on clinical management is exemplified by Li-Fraumeni Syndrome, the most penetrant sarcoma syndrome. Whole body magnetic resonance imaging can identify surgically resectable cancers in up to one in ten individuals with Li-Fraumeni Syndrome. Taken together, parallel developments in genomics, therapeutics and imaging technologies will drive closer engagement between genetics and multidisciplinary care of the sarcoma patient in the 21st century.

Cutaneous hyperpigmentation and familial gastrointestinal stromal tumour associated with KIT mutation

Gastrointestinal stromal tumours (GISTs) are mesenchymal tumours arising in the gastrointestinal tract. Early detection, before metastasis occurs, is important as complete surgical excision achieves cure. Approximately 85% of GISTs are associated with mutations in the KIT gene, and although the majority of GISTs are sporadic, familial GISTs have been identified. Several families with multiple GIST tumours have also been described with various cutaneous findings including hyperpigmentation, multiple lentigines, vitiligo and urticaria pigmentosa. We discuss a 6-year-old boy who presented with an unusual pattern of hyperpigmentation in association with a family history of GIST. A causative KIT mutation was identified in DNA from the pigmented skin and from the resected GIST, and the patient was referred to the Paediatric Gastroenterology department for GIST screening. The term 'GIST cutaneous hyperpigmentation disease' has been suggested previously for the association of familial GIST with cutaneous hyperpigmentation caused by a germline KIT mutation.

Imatinib response of gastrointestinal stromal tumor patients with germline mutation on KIT exon 13: A family report

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant disorder associated with mutations in the KIT gene in the majority of cases. Although, exon 11 appears to be the hot spot region for approximately 95% of germline mutations, pathogenic variations have also been identified in exon 8, 13 and 17. Exon 13 germline mutations are extremely rare amongst familial GISTs and seven families with a germline mutation have been reported to date. Moreover, the role of imatinib mesylate in this rare familiar settings is not completely known so far. We describe here clinical, imaging, pathological and genetic findings of a family with four affected members; grandmother, his son and two grand-sons having a germline gain-of-function mutation of KIT in exon 13 and discuss the imatinib mesylate treatment surveillance outcomes towards disease management.

Familial gastrointestinal stromal tumors, lentigines, and café-au-lait macules associated with germline c-kit mutation treated with imatinib

BACKGROUND

Familial lentiginosis syndromes are characterized by a wide array of manifestations resulting from activation of molecular pathways which control growth, proliferation, and differentiation of a broad range of tissues. Familial gastrointestinal stromal tumors (GISTs) are often accompanied by additional features like hyperpigmentation, mastocytosis, and dysphagia. They have been described with mutations in c-kit (most commonly), platelet-derived growth factor receptor A, neurofibromatosis-1, and succinate dehydrogenase genes.

MATERIALS AND METHODS

We report on molecular characterization and tumor histopathology of two siblings in whom lentigines and café-au-lait macules were present along with multifocal GIST. Immuhistochemical analysis of CD34 and CD117 was performed on GIST biopsy samples from both siblings, while c-kit mutational analysis was done by PCR and direct sequencing on DNA from peripheral blood leukocytes of all family members and from paraffin-embedded gastric biopsy specimens of affected siblings.

RESULTS

Histopathology revealed positive expression of CD117 and CD34. Mutational analysis showed the germline c.1676T>C mutation in c-kit exon 11, (p.(Val559Ala)), in the peripheral blood of both siblings and a second exon 11 mutation, c.1669T>A (p.(Trp557Arg)) in the tumor biopsy of one of them. Initiation of imatinib treatment resulted in striking resolution of their hyperpigmentation and a stable gastrointestinal disease in one of them.

CONCLUSIONS

A c-kit mutational test in familial GISTs is indicated before initiation of imatinib therapy, as it can help predict tumor response to treatment.

Germline mutations of KIT in gastrointestinal stromal tumor (GIST) and mastocytosis

Somatic mutations of KIT are frequently found in mastocytosis and gastrointestinal stromal tumor (GIST), while germline mutations of KIT are rare, and only found in few cases of familial GIST and mastocytosis. Although ligand-independent activation is the common feature of KIT mutations, the phenotypes mediated by various germline KIT mutations are different. Germline KIT mutations affect different tissues such as interstitial cells of Cajal (ICC), mast cells or melanocytes, and thereby lead to GIST, mastocytosis, or abnormal pigmentation. In this review, we summarize germline KIT mutations in familial mastocytosis and GIST and discuss the possible cellular context dependent transforming activity of KIT mutations.

Syndromic gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of gastrointestinal tract. They feature heterogeneous triggering mechanisms, implying relevant clinical differences. The vast majority of GISTs are sporadic tumors. Rarely, however, GIST-prone syndromes occur, mostly depending on heritable GIST predisposing molecular defects involving the entire organism. These conditions need to be properly identified in order to plan appropriate diagnostic, prognostic and therapeutic procedures. Clinically, GIST-prone syndromes must be thought of whenever GISTs are multiple and/or associated with accompanying signs peculiar to the background tumorigenic trigger, either in single individuals or in kindreds. Moreover, syndromic GISTs, individually considered, tend to show distinctive features depending on the underlying condition. When applicable, genotyping is usually confirmatory. In GIST-prone conditions, the prognostic features of each GIST, defined according to the criteria routinely applied to sporadic GISTs, combine with the characters proper to the background syndromes, defining peculiar clinical settings which challenge physicians to undertake complex decisions. The latter concern preventive therapy and single tumor therapy, implying possible surgical and molecularly targeted options. In the absence of specific comprehensive guidelines, this review will highlight the traits characteristic of GIST-predisposing syndromes, with particular emphasis on diagnostic, prognostic and therapeutic implications, which can help the clinical management of these rare diseases.

Divergent gastrointestinal stromal tumors in syndromic settings

The vast majority of gastrointestinal stromal tumors (GISTs) occur as sporadic tumors. Rarely, however, these neoplasms can arise in syndromic contexts. Under these circumstances, GISTs are often multiple and associated with accompanying signs peculiar of the hosting syndrome. Moreover, syndromic GISTs themselves tend to show heterogeneous features depending on the underlying condition. Multiple inflammatory fibroid polyps (IFPs) and a jejunal spindle-cell GIST were resected in a germline PDGFRA-mutant individual. Although the association of IFP and GIST is typical of this genetic setting (PDGFRA mutations can in fact trigger both these tumor types), PDGFRA-mutant GISTs are usually epithelioid and gastric. This discrepancy was settled evidencing a somatic KIT mutation in the GIST. The awareness of possible somatic mutations can be critical in the management of high-risk/malignant GISTs arising in syndromic settings. GIST features unusual for a given GIST-predisposing syndrome are a valuable tool in the hands of physicians for suspecting these "extra" triggers, which could not be sought for once a diagnosis of GIST-prone syndrome is well established, in a bona fide cost/benefit perspective.

Diagnosis and Management of Hereditary Sarcoma

Sarcomas are rare and heterogeneous diseases that affect a younger population than most epithelial cancers. Epidemiologic studies suggest a strong genetic component to sarcomas, and many familial cancer syndromes have been described, in which sarcomas are a feature. The best known of these are the Li-Fraumeni and retinoblastoma syndromes, study of which has been pivotal to elucidating the molecular basis for the cell response to DNA damage and the cell division. Although much has been learnt about cancer biology from the study of sarcoma families, in general clinical management of increased sarcoma risk has lagged behind other cancer predisposition syndromes. With the advent of genomic tools for genetic testing, it is likely that a substantial fraction of sarcoma patients will be identified as carriers of known risk alleles. The translation of this knowledge into effective risk management programs and cancer treatments will be essential to changes in routine clinical practice.

Copy-neutral loss of heterozygosity and chromosome gains and losses are frequent in gastrointestinal stromal tumors

Background

A KIT gain of function mutation is present in 70% of gastrointestinal stromal tumors (GISTs) and the wild-type (WT) allele is deleted in 5 to 15% of these cases. The WT KIT is probably deleted during GIST progression. We aimed to identify the mechanism of WT KIT loss and to determine whether other genes are involved or affected.

Methods

Whole-genome SNP array analyses were performed in 22 GISTs with KIT exon 11 mutations, including 11 with WT loss, to investigate the mechanisms of WT allele deletion. CGH arrays and FISH were performed in some cases. Common genetic events were identified by SNP data analysis. The 9p21.3 locus was studied by multiplex quantification of genomic DNA.

Results

Chromosome instability involving the whole chromosome/chromosome arm (whole C/CA) was detected in 21/22 cases. The GISTs segregated in two groups based on their chromosome number: polyGISTs had numerous whole C/CA gains (mean 23, range [9 to 43]/3.11 [1 to 5]), whereas biGISTs had fewer aberrations. Whole C/CA losses were also frequent and found in both groups. There were numerous copy-neutral losses of heterozygosity (cnLOH) of whole C/CA in both polyGIST (7/9) and biGIST (9/13) groups. cnLOH were frequent on 4q, 11p, 11q, 1p, 2q, 3p and 10, and never involved 12p, 12q, 20p, 20q or 19q. Other genetic alterations included segmental chromosome abnormalities, complete bi-allelic deletions (homozygous deletions) and, more rarely, amplifications. Nine of 11 GISTs with homozygous KIT exon 11 mutations had cnLOH of chromosome 4.

Conclusion

The cnLOH of whole C/CA is a frequent genetic alteration in GISTs and is closely associated with homozygous mutations of KIT and WT allele deletion.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-246) contains supplementary material, which is available to authorized users.

Functional deregulation of KIT: link to mast cell proliferative diseases and other neoplasms

In this review, the authors discuss common gain-of-function mutations in the stem cell factor receptor KIT found in mast cell proliferation disorders and summarize the current understanding of the molecular mechanisms by which these transforming mutations may affect KIT structure and function leading to altered downstream signaling and cellular transformation. Drugs targeting KIT have shown mixed success in the treatment of mastocytosis and other hyperproliferative diseases. A brief overview of the most common KIT inhibitors currently used, the reasons for the varied clinical results of such inhibitors and a discussion of potential new strategies are provided.

Realizing the promise of cancer predisposition genes

Genes in which germline mutations confer highly or moderately increased risks of cancer are called cancer predisposition genes. More than 100 of these genes have been identified, providing important scientific insights in many areas, particularly the mechanisms of cancer causation. Moreover, clinical utilization of cancer predisposition genes has had a substantial impact on diagnosis, optimized management and prevention of cancer. The recent transformative advances in DNA sequencing hold the promise of many more cancer predisposition gene discoveries, and greater and broader clinical applications. However, there is also considerable potential for incorrect inferences and inappropriate clinical applications. Realizing the promise of cancer predisposition genes for science and medicine will thus require careful navigation.

Prognostic value of mutational characteristics in gastrointestinal stromal tumors: a single-center experience in 275 cases

The objective of this study was to investigate the impact of KIT/PDGFRA mutations on the prognosis of gastrointestinal stromal tumors (GISTs). In the present study, genotype analyses were performed based on GIST samples from 275 patients. The relationship between mutation and clinicopathological characteristics were explored. All factors were evaluated for their impacts on relapse-free survival (RFS). Briefly, the results of genotype analyses showed that mutations were identified in 258 (93.8 %) patients, and deletion was the most frequent type of mutation accounting for 47.3 % (122/258) of all mutation cases, followed by substitution (87/258, 33.7 %) and duplication (49/258, 19.0 %). Moreover, for KIT exon 11 mutation, the most frequently involved area was from codon 557 to 560. Deep analyses showed that the mutation types were correlated with tumor location (P = 0.005), tumor size (P = 0.022), mitosis rate (P < 0.001), risk grade (P < 0.001), and relapse (P = 0.004). Furthermore, delW557-K558 correlated with mitosis rate (P = 0.042) and relapse (P = 0.036), and delTyr568/570 correlated with tumor origin (P = 0.018). Most importantly, mitotic rate [HR = 2.901 (95 % CI 1.094-7.695), P = 0.032] and risk grade [HR = 9.629 (95 % CI 1.997-46.416), P = 0.005] would be the representative traditional prognostic factors, and deletion with >3 codons would be an novel independent predictor of poor outcome for RFS in GIST patients with deletion mutation of KIT exon 11 [HR = 7.970 (95 % CI 1.774-35.803), P = 0.007]. All results indicated that mutation determined clinicopathological features and prognosis of GISTs, and more than three codons involvement may be a novel adverse indicator.

Multiple gastrointestinal stromal tumors with novel germline c-kit gene mutation, K642T, at exon 13

Multiple gastrointestinal stromal tumors (GISTs) caused by germline c-kit gene mutations are an extremely rare autosomal dominant disorder. A 57-year-old Japanese woman was referred to a hospital for appetite loss and severe weight loss. She had 2 large abdominal masses around the stomach, which were surgically resected. Histological examination revealed that these tumors were GISTs. Multiple microscopic GISTs and diffuse hyperplasia of the interstitial cells of Cajal were also seen in the background gastric and small intestinal walls. Characteristically, the GISTs showed severe hyalinization with calcification and partial heterotopic ossification, which may have caused the patient's severe dysphagia. Mutational analysis of the c-kit gene revealed a substitution at codon 642 in exon 13 (K642T) in the tumor, normal ileal mucosa and peripheral blood leukocytes, indicating that the mutation is in the germline. This is the first case of multiple GISTs with novel germline c-kit gene mutation at exon 13.

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.