Outcome of patients with platelet-derived growth factor receptor alpha-mutated gastrointestinal stromal tumors in the tyrosine kinase inhibitor era

Targeting kinases with precision

Cancer genomics and mechanistic studies have revealed that heterogeneous mutations within a single kinase can result in a variety of activation mechanisms. The challenge has been to match these insights with tailored drug discovery strategies to yield potent, highly selective drugs. With optimized drugs in hand, physicians could apply the principles of personalized medicine with an increasing number of options to treat patients with improved precision according to their tumor's molecular genotype.

The incidence, mutational status, risk classification and referral pattern of gastro-intestinal stromal tumours in the Netherlands: a nationwide pathology registry (PALGA) study

Symptomatic gastrointestinal stromal tumours (GIST) are infrequent with an incidence of 12.7 per million inhabitants in the western population. We studied whether the incidence of GIST has further increased between 2003 and 2012 and assessed the frequency of mutations, risk groups, histological subtypes and immunohistochemistry results. From PALGA, the nationwide Dutch Pathology Registry, pathology excerpts from all patients with a GIST or GIST-like tumour between 2003 and 2012 were retrieved to calculate incidence rates. Full pathology reports were retrieved of resections in 2011 and 2012 to study the frequency of mutations, risk groups, histological subtypes and immunohistochemistry results. The incidence of GIST increased to 17.7 per million inhabitants in 2012 with a median age of 67 years. Mutational analysis was performed in 33.9% of patients with a resection between 2011 and 2012 (KIT mutation 67.5%, PDGFRA 16.3%, wild-type 11.4%). The percentage of high risk patients in the different risk classifications varied from 19.9% to 38.0% depending on the used classification. Only 35.9% of patients had diagnosis or revision of pathology diagnosis within three months in a designated GIST referral centre. No increase in proportion of central pathology reviews was found. Proportion of patients with mutational analysis increased over the years. The registered incidence of GIST, 17.7 per million inhabitants in 2012 in the Netherlands, is still rising. Despite incorporation in the ESMO GIST guidelines since 2008 for mutational testing and since 2010 for central review of pathology, both are performed in a minority of patients.

Anti-tumor efficacy of oncolytic reovirus against gastrointestinal stromal tumor cells

Imatinib, a multitargeted receptor tyrosine kinase inhibitor, is used as the standard initial therapy against inoperable gastrointestinal stromal tumor (GIST). However, GIST can acquire resistance to imatinib within several years of therapy. The development of oncolytic reovirus as an anticancer agent has expanded to many clinical trials for various tumors. Here, we investigated whether reovirus has antitumor activity against GIST cells in the setting of imatinib sensitivity in vitro and in vivo. Cell proliferation and apoptosis assays were performed using a human GIST cell line, GIST-T1, and imatinib-resistant GIST (GIST-IR) cells that we established. The molecular pathways responsible for cell damage by reovirus were explored using PCR-arrays and Western blots. Reovirus significantly induced apoptotic cell death in GIST-T1 and GIST-IR cells in vitro, despite differences in the activation of receptor tyrosine kinase pathways between GIST-T1 and GIST-IR. Molecular assays indicated the possibility that reovirus induces apoptotic cell death via Fas signaling. Furthermore, in vivo mouse tumor xenograft models demonstrated a significant anti-tumor effect of reovirus on both GIST-T1 and GIST-IR cells. Our results demonstrate the therapeutic potential of reovirus against GIST.

Spotlight on olaratumab in the treatment of soft-tissue sarcoma: design, development, and place in therapy

Soft-tissue sarcoma (STS) is a heterogeneous group of tumors that arise from mesenchymal tissue. The prognosis of metastatic STS is poor with a life expectancy of 12–18 months. The mainstay of treatment is chemotherapy with an anthracycline. The addition of other chemotherapeutic agents to an anthracycline has been studied with limited success in improving outcomes for STS patients. Olaratumab is a fully human IgG1 monoclonal antibody that binds to platelet-derived growth factor receptor α (PDGFR-α) preventing binding of its ligands and receptor activation. This drug recently received the US Food and Drug Administration’s accelerated approval for the treatment of advanced STS when combined with doxorubicin. This approval was based upon an improvement in overall survival of patients receiving the combination of doxorubicin and olaratumab compared to those receiving doxo-rubicin alone. In this review, we have analyzed the available literature on the development of olaratumab, its clinical utility, and its place in therapy. Based on early-phase clinical trials, olaratumab appears to be a promising agent for the treatment of STS.

A phase II study of a human anti-PDGFRα monoclonal antibody (olaratumab, IMC-3G3) in previously treated patients with metastatic gastrointestinal stromal tumors

Background

This study evaluated tumor response to olaratumab (an anti-PDGFRα monoclonal antibody) in previously treated patients with metastatic gastrointestinal stromal tumor (GIST) with or without PDGFRα mutations (cohorts 1 and 2, respectively).

Patients and methods

Patients received olaratumab 20 mg/kg intravenously every 14 days until disease progression, death, or intolerable toxicity occurred. Outcome measures were 12-week tumor response, progression-free survival (PFS), overall survival (OS), and safety.

Results

Of 30 patients enrolled, 21 patients received ≥1 dose of olaratumab. In the evaluable population (cohort 1, n = 6; cohort 2, n = 14), no complete response (CR) or partial response (PR) was observed. Stable disease (SD) was observed in 3 patients (50.0%) in cohort 1 and 2 patients (14.3%) in cohort 2. Progressive disease (PD) was observed in 3 patients (50.0%) in cohort 1 and 12 patients (85.7%) in cohort 2. The 12-week clinical benefit rate (CR + PR + SD) (90% CI) was 50.0% (15.3–84.7%) in cohort 1 and 14.3% (2.6–38.5%) in cohort 2. SD lasted beyond 12 weeks in 5 patients (cohort 1, n = 3; cohort 2, n = 2). Median PFS (90% CI) was 32.1 (5.0–35.9) weeks in cohort 1 and 6.1 (5.7–6.3) weeks in cohort 2. Median OS was not reached in cohort 1 and was 24.9 (14.4–49.1) weeks in cohort 2. All patients in cohort 1 and 9 (64.3%) in cohort 2 experienced an olaratumab-related adverse event (AE), most commonly fatigue (38.1%), nausea (19.0%), and peripheral edema (14.3%). Two grade ≥3 olaratumab-related events were reported (cohort 1, syncope; cohort 2, hypertension).

Conclusions

Olaratumab had an acceptable AE profile in patients with GIST. While there was no apparent effect on PFS in patients without PDGFRα mutations, patients with PDGFRα-mutant GIST (all with D842V mutations) treated with olaratumab had longer disease control compared with historical data for this genotype.

ClinicalTrials.gov Identifier

NCT01316263.

Gastrointestinal Stromal Tumors

GI stromal tumors (GISTs) are neoplasms with a varying malignancy potential ranging from virtually indolent tumors to rapidly progressing cancers. GISTs occur throughout the intestinal tract, and most harbor an activating mutation in either KIT or platelet-derived growth factor A ( PDGFRA). Diagnosis is made using immunohistochemistry, but molecular testing with mutation analysis is paramount for selection of appropriate therapy. Most small GISTs are cured with surgery. Tyrosine kinase inhibitor (TKI) therapy has led to substantial improvements in survival, both for patients with localized GIST and those with advanced disease. Adjuvant therapy with imatinib benefits patients with a high risk of recurrence, with studies suggesting most benefit with at least 3 years of therapy. Neoadjuvant imatinib therapy should be considered for patients requiring extensive surgery, aiming at shrinking the tumor to allow organ preservation and less extensive surgery. The following three TKIs have been approved for the management of advanced disease: imatinib, sunitinib, and regorafenib; imatinib is usually the best tolerated of the three and the standard first-line treatment. TKIs benefit the majority of patients with advanced GIST but have no or limited efficacy in patients with the PDGFRA D842V mutation or patients with GIST lacking KIT and PDGFRA mutations. Surgery, the mainstay of primary tumor management, also plays a role in the advanced disease setting for selected patients, as do some other approaches such as palliative radiation therapy. Research continues to identify novel therapies, in particular effective agents to treat TKI-refractory disease.

Olaratumab: a platelet-derived growth factor receptor-α-blocking antibody for the treatment of soft tissue sarcoma

The outcome of patients with unresectable or metastatic soft tissue sarcoma (STS) remains poor with few treatment options. A number of randomized trials in the first-line setting have shown no difference in overall survival between combination anthracycline schedules and single-agent doxorubicin. A Phase Ib/randomized Phase II trial of doxorubicin with or without the platelet-derived growth factor receptor-α (PDGFRα)-blocking antibody, olaratumab, demonstrated a significant difference in median overall survival in favor of the olaratumab arm. The results of this trial led to the approval of olaratumab in combination with doxorubicin in adult anthracycline-naïve unresectable STS. In this review, we discuss the potential role of PDGFRα signaling, early clinical data with olaratumab in sarcomas, the Phase Ib/II trial and ongoing trials with olaratumab in sarcomas.

Tyrosine kinase inhibitor sensitive PDGFRΑ mutations in GIST: Two cases and review of the literature

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal malignancies of the gastrointestinal tract. Most GISTs harbor a c-KIT (80%) or a PDGFRα (10%) mutation that leads to constitutive activation of the tyrosine kinase receptor. Response to treatment with tyrosine kinase inhibitors (TKIs) is dependent on mutational status of the tumor. The most common mutation in PDGFRα, D842V, is known to be imatinib resistant. Almost all other PDGFRα mutations are imatinib sensitive. We describe two patients with a PDGFRα exon 18 mutated GIST responding to treatment with TKIs. One of these patients has a p.M844_S847 deletion, not previously described in relation with TKI treatment response. Mutations in circulating tumor DNA were detectable with digital droplet PCR in serial plasma samples taken during treatment and correlated with treatment response of both patients. Computer 3D-modeling of the PDGFRα kinase domain of these two variants revealed no direct interference in imatinib or sunitinib binding and no effect in its activity in contrast to the reported structure of the imatinib resistant D842V mutation.

An overview is given of the literature regarding the evidence of patients with different PDGFRα mutated GISTs on response to TKIs. The findings emphasize the use of mutational analysis in GIST to provide patients personalized treatment. Detection of mutations in plasma is feasible and can provide real-time information concerning treatment response. We suggest to register GIST patients with these uncommon mutations in a prospective international database to understand the tumor biology and obtain more evidence of such mutations to predict treatment response.

Surgical Pathology of Gastrointestinal Stromal Tumors: Practical Implications of Morphologic and Molecular Heterogeneity for Precision Medicine

Gastrointestinal stromal tumor (GIST), the most common mesenchymal neoplasm of the gastrointestinal tract, exhibits diverse histologic and clinical manifestations. With its putative origin in the gastrointestinal pacemaker cell of Cajal, GIST can arise in association with any portion of the tubular gastrointestinal tract. Morphologically, GISTs are classified as spindled or epithelioid, though each of these subtypes encompasses a broad spectrum of microscopic appearances, many of which mimic other histologic entities. Despite this morphologic ambiguity, the diagnosis of GIST is aided in many cases by immunohistochemical detection of KIT (CD117) or DOG1 expression. The natural history of GIST ranges from that of a tumor cured by surgical resection to that of a locally advanced or even widely metastatic, and ultimately fatal, disease. This clinicopathologic heterogeneity is paralleled by an underlying molecular diversity: the majority of GISTs are associated with spontaneous activating mutations in KIT, PDGFRA, or BRAF, while additional subsets are driven by genetic lesions-often inherited-of NF1 or components of the succinate dehydrogenase enzymatic complex. Specific gene mutations correlate with particular anatomic or morphologic characteristics and, in turn, with distinct clinical behaviors. Therefore, prognostication and treatment are increasingly dictated not only by morphologic clues, but also by accompanying molecular genetic features. In this review, we provide a comprehensive description of the heterogenous molecular underpinnings of GIST, including implications for the practicing pathologist with regard to morphologic identification, immunohistochemical diagnosis, and clinical management.

Latest advances in adult gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common GI tract mesenchymal tumors. GIST patients are optimally managed by a precision medicine approach. Herein, we discuss the latest advances in precision medicine and ongoing clinical trials relevant to GIST. Circulating tumor DNA for detection of mutational changes could replace tissue biopsies and radiographic imaging once validated. Most GISTs are KIT/PDGFRα mutated, and despite the good clinical response to imatinib, treatment is generally not curative, more often due to secondary mutations. New mechanisms to bypass this resistance by inhibiting KIT downstream pathways and by targeting multiple KIT or PDGFRα mutations are being investigated. Immunotherapy for GIST patients is in its infancy. These approaches may lead to more effective, less toxic therapies.

Succinate dehydrogenase deficiency in a PDGFRA mutated GIST

Background

Most gastrointestinal stromal tumors (GISTs) harbor mutually exclusive gain of function mutations in the receptor tyrosine kinase (RTK) KIT (70–80%) or in the related receptor PDGFRA (~10%). These GISTs generally respond well to therapy with the RTK inhibitor imatinib mesylate (IM), although initial response is genotype-dependent. An alternate mechanism leading to GIST oncogenesis is deficiency in the succinate dehydrogenase (SDH) enzyme complex resulting from genetic or epigenetic inactivation of one of the four SDH subunit genes (SDHA, SDHB, SDHC, SDHD, collectively referred to as SDHX). SDH loss of function is generally seen only in GIST lacking RTK mutations, and SDH-deficient GIST respond poorly to imatinib therapy.

Methods

Tumor and normal DNA from a GIST case carrying the IM-resistant PDGFRA D842V mutation was analyzed by whole exome sequencing (WES) to identify additional potential targets for therapy. The tumors analyzed were separate recurrences following progression on imatinib, sunitinib, and the experimental PDGFRA inhibitor crenolanib. Tumor sections from the GIST case and a panel of ~75 additional GISTs were subjected to immunohistochemistry (IHC) for the SDHB subunit.

Results

Surprisingly, a somatic, loss of function mutation in exon 4 of the SDHB subunit gene (c.291_292delCT, p.I97Mfs*21) was identified in both tumors. Sanger sequencing confirmed the presence of this inactivating mutation, and IHC for the SDHB subunit demonstrated that these tumors were SDH-deficient. IHC for the SDHB subunit across a panel of ~75 GIST cases failed to detect SDH deficiency in other GISTs with RTK mutations.

Conclusions

This is the first reported case of a PDGFRA mutant GIST exhibiting SDH-deficiency. A brief discussion of the relevant GIST literature is included.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-017-3499-7) contains supplementary material, which is available to authorized users.

Effect of KIT and PDGFRA Mutations on Survival in Patients With Gastrointestinal Stromal Tumors Treated With Adjuvant Imatinib: An Exploratory Analysis of a Randomized Clinical Trial

Importance

Little is known about whether the duration of adjuvant imatinib influences the prognostic significance of KIT proto-oncogene receptor tyrosine kinase (KIT) and platelet-derived growth factor receptor α (PDGFRA) mutations.

Objective

To investigate the effect of KIT and PDGFRA mutations on recurrence-free survival (RFS) in patients with gastrointestinal stromal tumors (GISTs) treated with surgery and adjuvant imatinib.

Design, Setting, and Participants

This exploratory study is based on the Scandinavian Sarcoma Group VIII/Arbeitsgemeinschaft Internistische Onkologie (SSGXVIII/AIO) multicenter clinical trial. Between February 4, 2004, and September 29, 2008, 400 patients who had undergone surgery for GISTs with a high risk of recurrence were randomized to receive adjuvant imatinib for 1 or 3 years. Of the 397 patients who provided consent, 341 (85.9%) had centrally confirmed, localized GISTs with mutation analysis for KIT and PDGFRA performed centrally using conventional sequencing. During a median follow-up of 88 months (completed December 31, 2013), 142 patients had GIST recurrence. Data of the evaluable population were analyzed February 4, 2004, through December 31, 2013.

Main Outcomes and Measures

The main outcome was RFS. Mutations were grouped by the gene and exon. KIT exon 11 mutations were further grouped as deletion or insertion-deletion mutations, substitution mutations, insertion or duplication mutations, and mutations that involved codons 557 and/or 558.

Results

Of the 341 patients (175 men and 166 women; median age at study entry, 62 years) in the 1-year group and 60 years in the 3-year group), 274 (80.4%) had GISTs with a KIT mutation, 43 (12.6%) had GISTs that harbored a PDGFRA mutation, and 24 (7.0%) had GISTs that were wild type for these genes. PDGFRA mutations and KIT exon 11 insertion or duplication mutations were associated with favorable RFS, whereas KIT exon 9 mutations were associated with unfavorable outcome. Patients with KIT exon 11 deletion or insertion-deletion mutation had better RFS when allocated to the 3-year group compared with the 1-year group (5-year RFS, 71.0% vs 41.3%; P < .001), whereas no significant benefit from the 3-year treatment was found in the other mutational subgroups examined. KIT exon 11 deletion mutations, deletions that involved codons 557 and/or 558, and deletions that led to pTrp557_Lys558del were associated with poor RFS in the 1-year group but not in the 3-year group. Similarly, in the subset with KIT exon 11 deletion mutations, higher-than-the-median mitotic counts were associated with unfavorable RFS in the 1-year group but not in the 3-year group.

Conclusions and Relevance

Patients with KIT exon 11 deletion mutations benefit most from the longer duration of adjuvant imatinib. The duration of adjuvant imatinib modifies the risk of GIST recurrence associated with some KIT mutations, including deletions that affect exon 11 codons 557 and/or 558.

Trial Registration

clinicaltrials.gov Identifier: NCT00116935.

Gastrointestinal stromal tumors (GISTs): point mutations matter in management, a review

The therapeutic implications of the genomic alterations seen within the drivers of gastrointestinal stromal tumors (GIST) are among the best understood in all of solid tumors. Sequencing of cKIT and PDGFRα should be considered standard practice for the treatment of GIST patients. In this article, we will review the common mutations and how they are utilized in clinical management. In addition, we will review the rare D842V PDGFRα mutation and the diverse molecular group that lacks a mutation in either cKIT or PDGFRα (wild-type GIST) which are best treated on clinical trial. Finally, we will look forward at the future therapies that are ever evolving for management of GIST. Taken together, the scientific advances in understanding the molecular basis of GIST validates the importance of knowing and understanding the mutations that are present in any one patient.

Myoepithelial carcinoma with RB1 mutation: remarkable chemosensitivity to carcinoma of unknown origin therapy

Background

Myoepithelial carcinoma of soft tissue is a rare, malignant neoplasm that is morphologically and immunophenotypically similar to its counterpart in salivary gland. It demonstrates myoepithelial differentiation, possessing both epithelial and myogenic characteristics. Thought to be chemotherapy insensitive, the optimal treatment regimen of this tumor has yet to be established and only a select few cases in the literature discuss treatment efficacy in detail.

Case presentation

Here we present a case of a young adult with metastatic myoepithelial carcinoma with an initial excellent response to systemic therapy utilizing carboplatin and paclitaxel with continued complete response after 3 years. The patient also underwent complete surgical excision and received adjuvant radiation to the primary site of disease. Exome sequencing revealed an inactivating mutation in RB1 which we believe to be the first such mutation to be reported in this cancer type.

Conclusions

Given increasing evidence suggesting RB1 loss is associated with responsiveness to conventional chemotherapies, particularly platinum-based regimens, we hypothesize that this genetic feature predisposed chemosensitivity in our patient’s tumor.

Management of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors had the reputation for poor outcomes because of their lack of response to nonsurgical interventions. The discovery of gain-of-function mutations involving receptor tyrosine kinase growth factor receptors altered the biological understanding and management. Beginning in 2000, management of these tumors has changed dramatically because of the availability of tyrosine kinase inhibitors. The role of surgery continues to be refined. This article reviews how surgery and systemic therapy are being used, incorporating definitions of risk. Decisions on how to treat a patient is based on the risk of progression, pathologic characteristics, and tumor location.

Knowns and Known Unknowns of Gastrointestinal Stromal Tumor Adjuvant Therapy

The first 15 years of management of gastrointestinal stromal tumor (GIST) have led to 3 lines of therapy for metastatic disease: imatinib, sunitinib, and regorafenib. In the adjuvant setting, imatinib is usually given for 3 years postoperatively to patients with higher-risk primary tumors that are completely resected. In this review, issues regarding GIST adjuvant therapy are discussed. It is hoped this review will help the reader understand the present standard of care to improve upon it in years to come.

Phosphorylated-insulin growth factor I receptor (p-IGF1R) and metalloproteinase-3 (MMP3) expression in advanced gastrointestinal stromal tumors (GIST). A GEIS 19 study

Background

Most GISTs have mutations in KIT or PDGFRA. Patients with advanced GIST with KIT exon 9, PDGFRA mutation or WT for KIT and PDGFRA have a worse progression-free survival (PFS) compared to patients with KIT exon 11 mutated tumors. We evaluated the immunohistochemical (IHC) expression of p-IGF1R (Y1316) and MMP3 as predictors of PFS or overall survival (OS).

Methods

Ninety-two advanced GIST patients included in GEIS-16 study with KIT and PDGFRA mutational information were examined for p-IGF1R (Y1316) and MMP3 expression in a tissue micro-array. To study activation of the IGF1R system, we have used an antibody (anti-pY1316) that specifically recognizes the active phosphorylated form of the IGF1R. DNA was extracted from paraffin-embedded tissues and intronic PCR primers were used to amplify exons 9, 11, 13 and 17 of KIT, 12 and 18 of PDGFRA. Bidirectional sequencing with specific primers was performed on a ABI3100 sequencer using the Big Dye Terminator v3.1 kit. Multivariate model was built using a stepwise automated variable selection approach with criterion to enter the variable in the model of p < 0.10 and criterion to keep the variable in the model of p < 0.05. PFS was computed as the date of imatinib initiation to progression or death. Overall survival was defined as the time from imatinib initiation to death.

Results

Phospho-IGF1R was expressed only in 9 % (2/22) of cases without KIT mutation. MMP3 expression was detected in 2/5 patients (40 %) with PDGFRA mutation, 1/16 patients (6 %) with WT genotype and 7/71 patients (10 %) of KIT mutant patients. At univariate analysis KIT exon 11/13 mutation had better PFS than patients with exon 9 mutation, PDGFRA mutation or WT genotype (p = 0.021; HR: 0.46; 95 %CI (0.28–0.76). Less than 24 months disease free-interval (HR 24.2, 95 % CI 10.5–55.8), poor performance status (PS) (HR 6.3, 95 % CI 2.5–15.9), extension of disease; >1 organ (HR 1.89; 95 % CI 1.03–3.4) and genotype analysis (HR 0.57, 95 % CI 0.37–0.97) but not immunophenotype analysis (HR 1.53; 95 % CI 0.76–3.06) were the strongest prognostic factors for PFS in the multivariate analysis.

Conclusions

Our results do not support p-IGF-1R and MMP3 evaluation in non-selected GIST patients but evaluation of this immunophenotype in WT and mutant PDGFR mutation in larger group of GIST patients, deserve merits.

Update on clinical research and state of the art management of patients with advanced sarcomas and GIST

Sarcomas constitute a rare group of malignancies. According to histology, different treatment options are effective. For gastrointestinal stromal tumours (GISTs), targeted treatment with imatinib controls about 20% of advanced or metastatic disease, whereas chemotherapy is more effective for the rest of the sarcomas. Currently, new targeted treatments are emerging, showing activity in cases resistant to established primary treatment. On the other hand, the exciting results of immunotherapy for other solid tumours, for example, melanoma and lung cancer, make it a promising option in the fight against sarcomas. In this review, we have collected data of established and promising treatments in trials with a view to facilitating the sequencing of sarcoma treatments and for identifying the future of these therapeutic options.

Giant seminal vesicle cyst: an unusual site for a malignant extragastrointestinal stromal tumour

Mesenchymal tumours with clinicopathological and molecular profiles similar to gastrointestinal stromal tumours (GISTs) are, on occasion, found in extragastrointestinal locations. Extra GIST (EGIST) is a singular occurrence in the genitourinary tract. A 30-year-old man, catheterised following urinary retention, was found to have a complex pelvic retrovesical cyst on imaging. At operation, origin from the right seminal vesicle was evident with histopathology confirming a GIST. The patient received adjuvant therapy with tyrosine kinase inhibitor and is currently disease free at 2 years. This is only the second report of an EGIST at this anatomic locale. The current literature presents significant uncertainty in defining the true origin of EGISTs, particularly those in the pelvis. We propose the designation origin indeterminate stromal tumour (OIST), to facilitate disambiguation and advance accurate profiling of EGIST; a subject in evolution.

The standard diagnosis, treatment, and follow-up of gastrointestinal stromal tumors based on guidelines

Although gastrointestinal stromal tumors (GISTs) are a rare type of cancer, they are the commonest sarcoma in the gastrointestinal tract. Molecularly targeted therapy, such as imatinib therapy, has revolutionized the treatment of advanced GIST and facilitates scientific research on GIST. Nevertheless, surgery remains a mainstay of treatment to obtain a permanent cure for GIST even in the era of targeted therapy. Many GIST guidelines have been published to guide the diagnosis and treatment of the disease. We review current versions of GIST guidelines published by the National Comprehensive Cancer Network, by the European Society for Medical Oncology, and in Japan. All clinical practice guidelines for GIST include recommendations based on evidence as well as on expert consensus. Most of the content is very similar, as represented by the following examples: GIST is a heterogeneous disease that may have mutations in KIT, PDGFRA, HRAS, NRAS, BRAF, NF1, or the succinate dehydrogenase complex, and these subsets of tumors have several distinctive features. Although there are some minor differences among the guidelines--for example, in the dose of imatinib recommended for exon 9-mutated GIST or the efficacy of antigen retrieval via immunohistochemistry--their common objectives regarding diagnosis and treatment are not only to improve the diagnosis of GIST and the prognosis of patients but also to control medical costs. This review describes the current standard diagnosis, treatment, and follow-up of GISTs based on the recommendations of several guidelines and expert consensus.

Adjuvant Imatinib for High-Risk GI Stromal Tumor: Analysis of a Randomized Trial

PURPOSE

Three years of adjuvant imatinib therapy are recommended for patients with GI stromal tumor (GIST) with high-risk features, according to survival findings in the Scandinavian Sarcoma Group XVIII/AIO (Arbeitsgemeinschaft Internistische Onkologie) trial. To investigate whether the survival benefits have persisted, we performed the second planned analysis of the trial.

PATIENTS AND METHODS

Eligible patients had macroscopically completely excised, KIT-positive GIST with a high risk of recurrence, as determined by using the modified National Institutes of Health criteria. After surgery, the patients were randomly assigned to receive imatinib for either 1 or 3 years. The primary objective was recurrence-free survival (RFS), and the secondary objectives included survival.

RESULTS

A total of 400 patients were entered onto this open-label study between February 4, 2004, and September 29, 2008. During a median follow-up of 90 months, 171 recurrences and 69 deaths were detected. Patients assigned to the 3-year group had longer RFS than those assigned to the 1- year group; 5-year RFS was 71.1% versus 52.3%, respectively (hazard ratio [HR], 0.60; 95% CI 0.44 to 0.81; P < .001), and survival was 91.9% versus 85.3% (HR, 0.60; 95% CI, 0.37 to 0.97; P = .036). Patients in the 3-year group survived longer in the subset with centrally confirmed GIST and without macroscopic metastases at study entry (93.4% v 86.8%; HR, 0.53; 95% CI, 0.30 to 0.93; P = .024). Similar numbers of cardiac events and second cancers were recorded in the groups.

CONCLUSION

Three years of adjuvant imatinib therapy results in longer survival than 1 year of imatinib. High 5-year survival rates are achievable in patient populations with high-risk GIST.

Response to sunitinib of a gastrointestinal stromal tumor with a rare exon 12 PDGFRA mutation

Background

Gastrointestinal stromal tumors (GISTs) are commonly driven by activating mutations in either KIT or PDGFRA. Importantly, different mutations within these two genes can lead to very different levels of sensitivity or resistance to kinase inhibitor therapy. Due to rarity, sensitivity or resistance of exon 12 PDGFRA mutant GIST to kinase inhibitor therapy is not well defined.

Case summary

We report the case of a patient with a PDGFRA exon 12 mutated GIST. The patient experienced a very good response to imatinib in the neoadjuvant setting, but then relapsed while still on adjuvant imatinib. In this patient, we report a dramatic response to second line treatment with sunitinib, with complete resolution of two liver lesions at the time of first restaging.

Conclusions

This is the first report detailing a response to treatment with sunitinib of a gastrointestinal stromal tumor with an uncommon exon 12 PDGFRA mutation. Based on the observed efficacy, GIST patients with this rare molecular subtype should be considered for sunitinib therapy.

Emerging Agents for the Treatment of Advanced, Imatinib-Resistant Gastrointestinal Stromal Tumors: Current Status and Future Directions

Imatinib is strongly positioned as the recommended first-line agent for most patients with advanced gastrointestinal stromal tumor (GIST) due to its good efficacy and tolerability. Imatinib-resistant advanced GIST continues to pose a therapeutic challenge, likely due to the frequent presence of multiple mutations that confer drug resistance. Sunitinib and regorafenib are approved as second- and third-line agents, respectively, for patients whose GIST does not respond to imatinib or who do not tolerate imatinib, and their use is supported by large randomized trials. ATP-mimetic tyrosine kinase inhibitors provide clinical benefit even in heavily pretreated GIST suggesting that oncogenic dependency on KIT frequently persists. Several potentially useful tyrosine kinase inhibitors with distinct inhibitory profiles against both KIT ATP-binding domain and activation loop mutations have not yet been fully evaluated. Agents that have been found promising in preclinical models and early clinical trials include small molecule KIT and PDGFRA mutation-specific inhibitors, heat shock protein inhibitors, histone deacetylase inhibitors, allosteric KIT inhibitors, KIT and PDGFRA signaling pathway inhibitors, and immunological approaches including antibody-drug conjugates. Concomitant or sequential administration of tyrosine kinase inhibitors with KIT signaling pathway inhibitors require further evaluation, as well as rotation of tyrosine kinase inhibitors as a means to suppress drug-resistant cell clones.

The Cancer Genomics Resource List 2014

CONTEXT

Genomic sequencing for cancer is offered by commercial for-profit laboratories, independent laboratory networks, and laboratories in academic medical centers and integrated health networks. The variability among the tests has created a complex, confusing environment.

OBJECTIVE

To address the complexity, the Personalized Health Care (PHC) Committee of the College of American Pathologists proposed the development of a cancer genomics resource list (CGRL). The goal of this resource was to assist the laboratory pathology and clinical oncology communities.

DESIGN

The PHC Committee established a working group in 2012 to address this goal. The group consisted of site-specific experts in cancer genetic sequencing. The group identified current next-generation sequencing (NGS)-based cancer tests and compiled them into a usable resource. The genes were annotated by the working group. The annotation process drew on published knowledge, including public databases and the medical literature.

RESULTS

The compiled list includes NGS panels offered by 19 laboratories or vendors, accompanied by annotations. The list has 611 different genes for which NGS-based mutation testing is offered. Surprisingly, of these 611 genes, 0 genes were listed in every panel, 43 genes were listed in 4 panels, and 54 genes were listed in 3 panels. In addition, tests for 393 genes were offered by only 1 or 2 institutions. Table 1 provides an example of gene mutations offered for breast cancer genomic testing with the annotation as it appears in the CGRL 2014.

CONCLUSIONS

The final product, referred to as the Cancer Genomics Resource List 2014, is available as supplemental digital content.

Efficacy of Imatinib in Patients with Platelet-Derived Growth Factor Receptor Alpha-Mutated Gastrointestinal Stromal Tumors

Purpose

The incidence of gastrointestinal stromal tumors (GISTs) harboring platelet-derived growth factor receptor alpha (PDGFRA) mutations is low, therefore further investigation of the efficacy of imatinib in this subgroup was needed.

Materials and Methods

Patients with PDGFRA-mutant GISTs who received imatinib as primary therapy for advanced disease between January 2000 and June 2012 were identified from the GIST registry of Asan Medical Center, Seoul, Korea.

Results

KIT and PDGFRA genotyping in 823 patients identified 18 patients (2%) with PDGFRA mutations who were treated with first-line imatinib. Exon 18 D842V substitution, non-D842V exon 18 mutations, and exon 12 mutations were detected in nine (50%), four (22%), and five (28%) patients, respectively. Objective response rate differed significantly between patients with the D842V mutation and those with non-D842V mutations (0% [0/5] vs. 71% [5/7], p=0.03). In all patients, median progression-free survival (PFS) and overall survival (OS) was 24.8 months (95% confidence interval [CI], 0.0 to 57.2) and 51.2 months (95% CI, 37.1 to 65.3), respectively. Significantly, poorer PFS was observed for patients with D842V-mutant GISTs than those with non-D842V PDGFRA-mutant GISTs: median 3.8 months (95% CI, 1.4 to 6.3) versus 29.5 months (95% CI, 18.3 to 40.7) (p < 0.001). Patients with the D842V mutation had poorer OS than those with non-D842V PDGFRA mutations: median 25.2 months (95% CI, 12.7 to 37.8) versus 59.8 months (95% CI, 43.0 to 76.5) (p=0.02).

Conclusion

Imatinib is active against non-D842V PDGFRA-mutant GISTs, whereas GISTs harboring the D842V mutation are primarily resistant to imatinib.

Effective Downsizing of a Large Oesophageal Gastrointestinal Stromal Tumour with Neoadjuvant Imatinib Enabling an Uncomplicated and without Tumour Rupture Laparoscopic-Assisted Ivor-Lewis Oesophagectomy

Neoadjuvant imatinib for gastrointestinal stromal tumours (GISTs) is increasingly used nowadays. As oesophagectomy is associated with high morbidity and mortality, a preoperative downsizing of an oesophageal GIST to limit the extent of resection would be ideal. Because these tumours are rare and neoadjuvant treatment with imatinib is recent, there is limited literature available regarding neoadjuvant administration of imatinib in patients with oesophageal GISTs. A 50-year-old woman presented with total dysphagia. An upper endoscopy and biopsy revealed a large submucosal KIT-positive GIST obstructing the mid oesophagus. CT confirmed a lesion measuring 99 mm × 50 mm × 104 mm. Because the size and location of the tumour increased the risk of intraoperative rupture, it was decided to administer preoperative imatinib. The patient had an excellent clinical and radiological response. Her dysphagia gradually resolved and the follow-up CT scans of the first 10 months showed a gradually reducing tumour size to 54 mm × 33 mm × 42 mm. The patient underwent an uneventful laparoscopic-assisted Ivor-Lewis oesophagectomy. Postoperatively, the patient continued with adjuvant imatinib. At the last follow-up, 1 year from operation and 38 months from the diagnosis, the patient is disease free.

KIT and PDGFRA mutations and the risk of GI stromal tumor recurrence

PURPOSE

Mutated KIT and platelet-derived growth factor alpha gene (PDGFRA) drive GI stromal tumor (GIST) oncogenesis, but the clinical significance of their single mutations is known incompletely.

PATIENTS AND METHODS

We identified 11 population-based series of patients with GIST through a literature search and pooled individual data from 3,067 patients treated with macroscopically complete tumor excision. Mutation analysis was done from 1,505 tumors. We analyzed associations between KIT and PDGFRA mutations and recurrence-free survival (RFS) in the subsets in which patients were treated with surgery alone.

RESULTS

We identified 301 different single mutations in KIT and 33 in PDGFRA. Patients with PDGFRA mutations had more favorable RFS than those with KIT mutations (hazard ratio, 0.34; P = .004). Only one of the 35 GISTs with KIT exon 11 duplication mutations recurred. Patients with deletions of only one codon of KIT exon 11 had better RFS than those with another deletion type, and some KIT exon 11 substitution mutations (Trp557Arg, Val559Ala, and Leu576Pro) were also associated with favorable RFS. Patients with an identical mutation had greatly variable outcomes depending on the standard prognostic factors, notably, mitotic count. Commonly used risk stratification schemes tended to overestimate the risk for recurrence in subgroups with prognostically favorable mutations.

CONCLUSION

GISTs with an identical KIT or PDGFRA mutation may have widely varying risks for recurrence. Most of the patients with PDGFRA mutations and those with KIT exon 11 duplication mutation or deletion of one codon have favorable RFS with surgery alone and are usually not candidates for adjuvant therapy.

[Molecular biology of sarcoma and therapeutic choices]

Soft tissue sarcomas (STS) are a set of very heterogeneous tumors with numerous histological categories. The development of the molecular biology allowed identifying recurring molecular anomalies in certain subgroups of sarcomas, being able to represent diagnostic, prognosis and therapeutic tools. The molecular classification of STS includes until today 5 main groups of abnormalities: sarcomas with "simple genomic profile" showing reciprocal (1) chromosomal translocations, (2) activating mutation, (3) inhibitive mutation or (4) simple amplification; (5) sarcomas with "complex genomic profile" can include several tens of molecular abnormalities. The development of new-targeted therapies is based on the identification of a target, specific of a tumors subgroup and involved in carcinogenesis mechanisms and/or tumoral growth. Then, the aim of clinical research is to establish the proof of the concept through clinical trials, demonstrating the benefit brought to the patient and ending in the marketing of the drug. This proof of the concept was clearly established for imatinib, sunitinib and regorafenib in gastrointestinal stromal tumors, for imatinib in dermatofibrosarcoma protuberans and pigmented vilo-nodular synovitis, for denosumab in giant cell tumors of the bone, ending in the authorization to use these new therapies in these indications. It is in progress and promising for anti-IGF-1R in Ewing sarcomas, for crizotinib in myofibroblastic inflammatory tumors, for mTOR inhibitor in PEComas... The role of molecular abnormalities identified in the mechanisms of tumoral progress for sarcomas and their potential therapeutic impact will be detailed.

Kinase genotype analysis of gastric gastrointestinal stromal tumor cytology samples using targeted next-generation sequencing

Gastric gastrointestinal stromal tumors (GISTs) usually contain the mast/stem cell growth factor receptor Kit gene (KIT) or platelet-derived growth factor receptor A (PDGFRA) mutations that can be targeted by, or mediate resistance to, imatinib. Diagnostic material often is obtained by endoscopic ultrasound-guided fine-needle aspiration, which often is unsuitable for molecular analysis. We investigated whether targeted next-generation sequencing (NGS) can be used in multiplex genotype analysis of cytology samples collected by endoscopic ultrasound-guided fine-needle aspiration. We used the Ion AmpliSeq V2 Cancer Hotspot NGS Panel (Life Technologies, Carlsbad, CA) to identify mutations in more than 2800 exons from 50 cancer-associated genes in GIST samples from 20 patients. We identified KIT mutations in 58% of samples (91% in exon 11 and 9% in exon 17) and PDGFRA mutations in 26% (60% in exon 18 and 40% in exon 12); 16% of samples had no mutations in KIT or PDGFRA. No pathogenic alterations were found in PIK3CA, BRAF, KRAS, NRAS, or FGFR3. We predicted that 32% of patients would have primary resistance to imatinib, based on mutations in exon 17 of KIT, exon 18 of PDGFRA (D842V), or no mutation in either gene. Targeted NGS of cytology samples from GISTs is feasible and provides clinically relevant data about kinase genotypes that can help guide individualized therapy.

Tyrosine kinase inhibitors in the treatment of unresectable or metastatic gastrointestinal stromal tumors

INTRODUCTION

Gastrointestinal stromal tumor (GIST) is the most common sarcoma of the gastrointestinal tract. Proliferation of GIST is driven by activating mutations in the KIT or PDGFRA genes that found in most sporadic GISTs. Surgery is the main remedial measure for primary GIST, and imatinib is the principal therapeutic of choice for unresectable or metastatic GIST. Imatinib revolutionized treatment for unresectable or metastatic GISTs; however, resistance to imatinib has inevitably developed for most GIST patients.

AREAS COVERED

PubMed was searched to find biological studies of GIST and clinical trials of molecularly targeted agents on unresectable or metastatic GISTs, and the key papers found have been reviewed. In this paper, the standard therapy which includes imatinib, sunitinib and regorafenib for unresectable or metastatic GIST has been reviewed and molecular mechanisms of resistance for tyrosine kinase inhibitors (TKIs) have been postulated and discussed. Treatment measures for resistant GIST and therapeutic choices after the standard therapy have also been described.

EXPERT OPINION

The standard therapy for unresectable or metastatic GISTs is first-line imatinib, second-line sunitinib and third-line regorafenib. After standard therapy, best supportive care or clinical trials is recommended in the guidelines. However, patients may benefit from continuation of TKIs beyond disease progression and from rechallenge of TKIs used previously.

Recent advances in the treatment of gastrointestinal stromal tumors

Constitutively activating mutations in the KIT and platelet-derived growth factor receptor α (PDGFRA) RTKs play a crucial role in the biology of gastrointestinal stromal tumors (GISTs), and this disease has served as an effective model for targeting gain-of-function kinase mutations in cancer. Imatinib has entered the clinical arena in the last decade and substantially improved the outcome in these formerly untreatable cancers. However, most advanced GISTs responding to imatinib progress within 2-3 years due to heterogeneous subclones harboring a range of imatinib-resistant secondary KIT mutations. Sunitinib, and more recently, regorafenib, have obtained US Food and Drug Administration approval for the treatment of GISTs after imatinib failure, and thus expanded the treatment options in resistant disease. Within this framework, we present an evaluation of current GIST management, emphasizing the most recent advances in the field together with a discussion on future steps to be taken in refractory disease.

State of the Art in the Treatment of Gastrointestinal Stromal Tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most frequently diagnosed mesenchymal neoplasms of the gastrointestinal tract. Despite their biological and clinical heterogeneity, the majority of these tumors are positive for the receptor tyrosine kinase KIT and are driven by KIT- or platelet-derived growth factor receptor alpha (PDGFRA)-activating mutations. There are still uncertainties regarding their clinical and molecular characterization and the optimal treatment regimens, making it difficult to establish a universal treatment algorithm for these tumors.

SUMMARY

From a clinical perspective, the main difference between GISTs and other gastrointestinal neoplasms is that the benign or malignant behavior of GISTs cannot be predicted from histopathology, but instead relies on empirically established scoring systems. Clinical data suggest that malignant potential may be an inherent quality of some GISTs rather than a feature acquired by the tumor during disease progression. Thus, some patients may require prolonged anti-tumor treatment even after complete surgical removal of the tumor.

KEY MESSAGE

Although GISTs are the most frequently occurring mesenchymal neoplasms in the gastrointestinal tract, no universal treatment algorithms exist. This paper reviews the current evidence that guides the management of GISTs.

PRACTICAL IMPLICATIONS

The management of localized GISTs involves the use of surgical resection, with the inclusion of preoperative tyrosine kinase inhibitor treatment for locally advanced, primarily unresectable tumors and for resectable cases requiring extensive surgery. Imatinib is also indicated as adjuvant therapy after complete surgical removal of GISTs with a high estimated risk of recurrence unless specific mutations conferring imatinib resistance are present. The optimal duration of adjuvant treatment is still controversial. For patients with metastatic imatinib-sensitive GISTs, imatinib constitutes the first-line standard treatment. Molecular characterization of the tumor (with respect to the PDGFRA and KIT genes) is mandatory prior to imatinib therapy. Sunitinib and regorafenib are established as alternative treatments for patients demonstrating generalized disease progression on imatinib. New tyrosine kinase inhibitors such as ponatinib and crenolanib as well as drugs targeting alternative pathways are currently under investigation. Surgery and locally ablative treatments may be indicated in some metastatic patients.

Pathologic and molecular features correlate with long-term outcome after adjuvant therapy of resected primary GI stromal tumor: the ACOSOG Z9001 trial

PURPOSE

The ACOSOG (American College of Surgeons Oncology Group) Z9001 (Alliance) study, a randomized, placebo-controlled trial, demonstrated that 1 year of adjuvant imatinib prolonged recurrence-free survival (RFS) after resection of primary GI stromal tumor (GIST). We sought to determine the pathologic and molecular factors associated with patient outcome.

PATIENTS AND METHODS

There were 328 patients assigned to the placebo arm and 317 to the imatinib arm. Median patient follow-up was 74 months. There were 645 tumor specimens available for mitotic rate or mutation analysis.

RESULTS

RFS remained superior in the imatinib arm (hazard ratio, 0.6; 95% CI, 0.43 to 0.75; Cox model-adjusted P < .001). On multivariable analysis of patients in the placebo arm, large tumor size, small bowel location, and high mitotic rate were associated with lower RFS, whereas tumor genotype was not significantly associated with RFS. Multivariable analysis of patients in the imatinib arm yielded similar findings. When comparing the two arms, imatinib therapy was associated with higher RFS in patients with a KIT exon 11 deletion of any type, but not a KIT exon 11 insertion or point mutation, KIT exon 9 mutation, PDGFRA mutation, or wild-type tumor, although some of these patient groups were small. Adjuvant imatinib did not seem to alter overall survival.

CONCLUSION

Our findings show that tumor size, location, and mitotic rate, but not tumor genotype, are associated with the natural history of GIST. Patients with KIT exon 11 deletions assigned to 1 year of adjuvant imatinib had a longer RFS.

Gastrointestinal stromal tumors: what do we know now?

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract, arising from the interstitial cells of Cajal, primarily in the stomach and small intestine. They manifest a wide range of morphologies, from spindle cell to epithelioid, but are immunopositive for KIT (CD117) and/or DOG1 in essentially all cases. Although most tumors are localized at presentation, up to half will recur in the abdomen or spread to the liver. The growth of most GISTs is driven by oncogenic mutations in either of two receptor tyrosine kinases: KIT (75% of cases) or PDGFRA (10%). Treatment with tyrosine kinase inhibitors (TKIs) such as imatinib, sunitinib, and regorafenib is effective in controlling unresectable disease; however, drug resistance caused by secondary KIT or PDGFRA mutations eventually develops in 90% of cases. Adjuvant therapy with imatinib is commonly used to reduce the likelihood of disease recurrence after primary surgery, and for this reason assessing the prognosis of newly resected tumors is one of the most important roles for pathologists. Approximately 15% of GISTs are negative for mutations in KIT and PDGFRA. Recent studies of these so-called wild-type GISTs have uncovered a number of other oncogenic drivers, including mutations in neurofibromatosis type I, RAS genes, BRAF, and subunits of the succinate dehydrogenase complex. Routine genotyping is strongly recommended for optimal management of GISTs, as the type and dose of TKI used for treatment is dependent on the mutation identified.

A current perspective on the role for molecular studies in soft tissue tumor pathology

Soft tissue sarcomas represent an heterogenous group of malignancies. They represent a diagnostic challenge, and their accurate classification impact over treatment options. Sarcomas, similarly to hematologic neoplasm, often harbor relatively specific genetic aberrations, the recognition of which can be used to improved diagnostic accuracy. This review will focus on the clinical relevance of molecular analysis in soft tissue sarcomas, trying to elucidate its role as a diagnostic tool as well as a potential prognostic/predictive marker.

Gastrointestinal stromal tumour

Gastrointestinal stromal tumours (GISTs) are mesenchymal neoplasms that arise in the gastrointestinal tract, usually in the stomach or the small intestine and rarely elsewhere in the abdomen. They can occur at any age, the median age being 60-65 years, and typically cause bleeding, anaemia, and pain. GISTs have variable malignant potential, ranging from small lesions with a benign behaviour to fatal sarcomas. Most tumours stain positively for the mast/stem cell growth factor receptor KIT and anoctamin 1 and harbour a kinase-activating mutation in either KIT or PDGFRA. Tumours without such mutations could have alterations in genes of the succinate dehydrogenase complex or in BRAF, or rarely RAS family genes. About 60% of patients are cured by surgery. Adjuvant treatment with imatinib is recommended for patients with a substantial risk of recurrence, if the tumour has an imatinib-sensitive mutation. Tyrosine kinase inhibitors substantially improve survival in advanced disease, but secondary drug resistance is common.

New fronts in the adjuvant treatment of GIST

PURPOSE

To review the prognostic factors and stratification systems used to determine the need for adjuvant therapy in the treatment of gastrointestinal stromal tumors (GIST), and to review recent clinical advances in investigation of the efficacy and safety of adjuvant imatinib mesylate treatment.

METHODS

Recent data from clinical trials of various durations of adjuvant imatinib in GIST are reviewed, with emphasis on key results from the Phase III American College of Surgeons Oncology Group (ACOSOG) Z9001 trial and the Scandinavian Sarcoma Group XVIII/Arbeitsgemeinschaft Internistische Onkologie (SSGXVIII/AIO) trial.

RESULTS

Complete surgical resection remains the standard of treatment for localized GISTs; however, disease recurrence occurs in up to 50 % of patients who undergo complete resection. The ACOSOG Z9001 trial established that 1 year of adjuvant imatinib reduces the risk of recurrence in patients with resected GIST. The SSGXVIII/AIO trial further demonstrated that 3-year adjuvant imatinib improves both recurrence-free survival and overall survival compared with 1-year therapy in patients at high risk of recurrence after surgery. Considering risk factors associated with tumor recurrence is essential for identifying the patients who are most likely to benefit from adjuvant imatinib.

CONCLUSIONS

Although the optimal duration of adjuvant therapy remains to be determined, results from these pivotal trials provide firm evidence that adjuvant imatinib improves recurrence-free survival and improved overall survival of patients in the SSGXVIII/AIO trial. Ongoing studies may shed further light on the benefits and harms of adjuvant therapy, as well as the most appropriate patient candidates for adjuvant imatinib treatment.

Gastrointestinal stromal tumors: risk assessment and adjuvant therapy

Adjuvant imatinib prolongs recurrence-free survival and probably overall survival of patients who have undergone surgery for gastrointestinal stromal tumor (GIST). Estimation of the risk of recurrence with a prognostication tool and tumor mutation analysis is essential before imatinib initiation, because approximately 60% of patients with GIST with operable tumor are cured by surgery alone and some mutated tyrosine kinases are insensitive to imatinib. Adjuvant imatinib is usually administered for 3 years at the dose of 400 mg once daily. Early detection of tumors that recur despite adjuvant therapy with longitudinal imaging of the abdomen is likely beneficial.