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

Discovery and pharmacological characterization of AZD3229, a potent KIT/PDGFRα inhibitor for treatment of gastrointestinal stromal tumors

Gastrointestinal stromal tumor (GIST) is the most common human sarcoma driven by mutations in KIT or platelet-derived growth factor α (PDGFRα). Although first-line treatment, imatinib, has revolutionized GIST treatment, drug resistance due to acquisition of secondary KIT/PDGFRα mutations develops in a majority of patients. Second- and third-line treatments, sunitinib and regorafenib, lack activity against a plethora of mutations in KIT/PDGFRα in GIST, with median time to disease progression of 4 to 6 months and inhibition of vascular endothelial growth factor receptor 2 (VEGFR2) causing high-grade hypertension. Patients with GIST have an unmet need for a well-tolerated drug that robustly inhibits a range of KIT/PDGFRα mutations. Here, we report the discovery and pharmacological characterization of AZD3229, a potent and selective small-molecule inhibitor of KIT and PDGFRα designed to inhibit a broad range of primary and imatinib-resistant secondary mutations seen in GIST. In engineered and GIST-derived cell lines, AZD3229 is 15 to 60 times more potent than imatinib in inhibiting KIT primary mutations and has low nanomolar activity against a wide spectrum of secondary mutations. AZD3229 causes durable inhibition of KIT signaling in patient-derived xenograft (PDX) models of GIST, leading to tumor regressions at doses that showed no changes in arterial blood pressure (BP) in rat telemetry studies. AZD3229 has a superior potency and selectivity profile to standard of care (SoC) agents-imatinib, sunitinib, and regorafenib, as well as investigational agents, avapritinib (BLU-285) and ripretinib (DCC-2618). AZD3229 has the potential to be a best-in-class inhibitor for clinically relevant KIT/PDGFRα mutations in GIST.

The EMA assessment of avapritinib in the treatment of gastrointestinal stromal tumours harbouring the PDGFRA D842V mutation

Avapritinib is a protein kinase inhibitor designed to selectively inhibit oncogenic KIT and platelet-derived growth factor receptor alpha (PDGFRA) mutants by targeting the active conformation of the kinase. On 24 September 2020, a marketing authorisation valid through the European Union was issued for avapritinib as treatment of adult patients with unresectable or metastatic gastrointestinal stromal tumours (GIST) harbouring the PDGFRA D842V mutation. The drug was evaluated in an open-label, phase I, first-in-human, dose-escalation, open-label study to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy of avapritinib in adults with unresectable or metastatic GIST. The benefit of avapritinib was observed in patients with GIST harbouring the PDGFRA D842V mutation. The overall response rate was 95% (95% confidence interval 82.3%-99.4%), with a median duration of response of 22.1 months (95% confidence interval 14.1-not estimable months). The most common adverse events were nausea, fatigue, anaemia, periorbital and face oedema, hyperbilirubinaemia, diarrhoea, vomiting, increased lacrimation, and decreased appetite. Most of the reported cognitive effects were mild memory impairment. Rarer events were cases of severe encephalopathy and intracranial or gastrointestinal bleeding. The aim of this manuscript is to summarise the scientific review of the application leading to regulatory approval in the European Union.

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Avapritinib is a protein kinase inhibitor designed to inhibit oncogenic KIT and PDGFRA mutants.

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A marketing authorisation was issued for avapritinib as treatment of patients with GIST harbouring the PDGFRA D842V mutation.

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The overall response rate was 95% (95% CI 82.3-99.4), with a median duration of response of 22.1 months (95% CI 14.1-NE).

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The most common adverse events were nausea, fatigue, anaemia, periorbital and face oedema, hyperbilirubinaemia and diarrhoea.

An updated review of the treatment landscape for advanced gastrointestinal stromal tumors

Before the introduction of tyrosine kinase inhibitors (TKIs), the overall survival of patients with advanced or metastatic gastrointestinal stromal tumors (GISTs) was 10 to 20 months because of the lack of approved therapies. In the last 20 years, a treatment algorithm for patients with advanced GISTs, which includes imatinib, sunitinib, and regorafenib as first‐, second‐, and third‐line therapies, respectively, has been established. Recently, 2 new TKIs have been approved: ripretinib for fourth‐line therapy and avapritinib as first‐line therapy in patients harboring platelet‐derived growth factor receptor α (PDGFRA) exon 18 D842V mutations. Additionally, there are several experimental therapies under investigation that could advance individualized patient care. All of these therapies have varying efficacies and safety profiles that warrant an updated treatment landscape review. This review article summarizes the efficacy and safety data currently available for conventional TKIs along with recently approved and experimental therapies.

With evolving treatment options and effective toxicity management, patients with advanced gastrointestinal stromal tumors are living longer than ever before. Recently approved targeted therapies and the investigation of experimental treatment options have the potential to alter the current treatment algorithm and encourage personalized patient care.

PDGFRA Immunohistochemistry Predicts PDGFRA Mutations in Gastrointestinal Stromal Tumors

Platelet-derived growth factor receptor A (PDGFRA) is a receptor tyrosine kinase that is activated by mutations in 10% of gastrointestinal stromal tumors (GISTs) and 55% to 70% of inflammatory fibroid polyps. PDGFRA-mutant GISTs are usually epithelioid and occur predominantly in the stomach. Succinate dehydrogenase-deficient GISTs also arise in the stomach and are usually epithelioid, as are some KIT-mutant GISTs. Recently, avapritinib was approved to treat PDGFRA D842V-mutant GISTs, which do not respond to conventional targeted therapy. Here, we evaluate the utility of PDGFRA immunohistochemistry (IHC) to predict PDGFRA mutations to direct targeted therapy. PDGFRA IHC was performed at 1:3000 and 1:10,000 dilutions on a tissue microarray containing 153 GISTs (126 KIT-mutant, 17 PDGFRA-mutant, and 10 succinate dehydrogenase-deficient). The "positive" staining threshold was defined as 50% of neoplastic cells staining at moderate intensity. PDGFRA IHC was 75.0% and 80.9% specific for PDGFRA mutations at 1:3000 and 1:10,000 dilutions, respectively, and it was 100% sensitive at both. On the basis of its higher specificity, a 1:10,000 dilution was used to stain whole-tissue sections of GISTs and other gastric tumor types. Combining tissue microarray and whole-tissue data, PDGFRA IHC was 94.4% sensitive and 81.0% specific for PDGFRA-mutant GIST among all 210 GISTs, and it was 84.1% specific among 149 GISTs with an epithelioid component. PDGFRA was positive in a subset of inflammatory fibroid polyps (15/30; 50%), monophasic synovial sarcomas (5/10; 50%), inflammatory myofibroblastic tumors (5/10; 50%), and plexiform fibromyxomas (2/8; 25%). It was negative in poorly differentiated adenocarcinoma (0/20), diffuse large B-cell lymphoma (0/10), glomus tumor (0/10), gastrointestinal neuroectodermal tumor (0/10), leiomyoma (0/10), gastric schwannoma (0/8), and gastroblastoma (0/3). Among GISTs, PDGFRA IHC is highly sensitive and moderately specific for PDGFRA-mutant tumors; it also can be positive in inflammatory fibroid polyp and some other mesenchymal tumor types. PDGFRA positivity could be used to triage epithelioid GISTs for PDGFRA sequencing to determine optimal therapy.

Optimal Avapritinib Treatment Strategies for Patients with Metastatic or Unresectable Gastrointestinal Stromal Tumors

BACKGROUND

Avapritinib, a novel inhibitor of KIT/PDGFRA, is approved in the U.S. for the treatment of adults with PDGFRA exon 18-mutant unresectable or metastatic gastrointestinal stromal tumors (U/M GISTs). We assessed the safety of avapritinib and provide evidence-based guidance on management of avapritinib-associated adverse events (AEs), including cognitive effects and intracranial bleeding.

MATERIALS AND METHODS

We performed a post hoc analysis of data from a two-part, single-arm dose escalation/expansion phase I study (NAVIGATOR; NCT02508532) in patients with U/M GISTs treated with oral avapritinib 30-600 mg once daily. The primary endpoints were safety and tolerability; the impact of dose modification (interruption and/or reduction) on progression-free survival (PFS) was a secondary endpoint. Efficacy analyses were limited to patients who started avapritinib at 300 mg (approved dose).

RESULTS

Of 250 patients enrolled in the study, 74.0% presented with KIT mutation and 24.8% presented with PDGFRA exon 18-mutation; 66.8% started avapritinib at 300 mg. The most common treatment-related AEs (any grade) were nausea (59.2%), fatigue (50.0%), periorbital edema (42.0%), anemia (39.2%), diarrhea (36.0%), vomiting (36.0%), and increased lacrimation (30.8%). No treatment-related deaths occurred. Among 167 patients starting on 300 mg avapritinib, all-cause cognitive effects rate (grade 1-2) was 37.0% in all patients and 52.0% in patients ≥65 years. Cognitive effects improved to a lower grade more quickly with dose modification (1.3-3.1 weeks) than without (4.9-7.6 weeks). Median PFS was 11.4 months with dose modification and 7.2 months without.

CONCLUSION

Tolerability-guided dose modification of avapritinib is an effective strategy for managing AEs in patients with GISTs.

IMPLICATIONS FOR PRACTICE

Early recognition of adverse events and tailored dose modification appear to be effective approaches for managing treatment-related adverse events and maintaining patients on avapritinib. Dose reduction does not appear to result in reduced efficacy. Patients' cognitive function should be assessed at baseline and monitored carefully throughout treatment with avapritinib for the onset of cognitive adverse events. Dose interruption is recommended at the first sign of any cognitive effect, including grade 1 events.

Clinical efficacy comparison of avapritinib with other tyrosine kinase inhibitors in gastrointestinal stromal tumors with PDGFRA D842V mutation: a retrospective analysis of clinical trial and real-world data

Background

Avapritinib, a potent inhibitor of KIT and platelet-derived growth factor receptor A (PDGFRA) tyrosine kinases, has demonstrated unprecedented clinical activity in PDGFRA D842V-mutant gastrointestinal stromal tumors (GIST).

Methods

This retrospective analysis compared efficacy of avapritinib in patients enrolled in the NAVIGATOR phase 1 trial (NCT02508532) with the efficacy of other tyrosine kinase inhibitors (TKIs) in patients with unresectable/metastatic PDGFRA D842V-mutant GIST enrolled in a retrospective natural history study (Study 1002). The primary endpoint was overall survival (OS) from the start of reference treatment (avapritinib for NAVIGATOR patients or first-line TKI for treatment of unresectable/metastatic GIST for Study 1002 patients); the secondary endpoint was progression-free survival (PFS). Adjusted Kaplan–Meier survival curves were compared by Cox regression.

Results

Fifty-six (NAVIGATOR) and 19 (Study 1002) patients with PDGFRA D842V-mutant GIST were evaluated; of the 56 patients from NAVIGATOR, a subgroup of patients treated with either 300 mg (recommended phase 2 dose) or 400 mg (maximum tolerated dose) avapritinib starting dose (n = 38) were analyzed separately. Patient characteristics were adjusted for imbalances by propensity score between the study groups. Inverse probability of treatment weighting-adjusted Kaplan–Meier analysis of OS showed median OS was not reached for NAVIGATOR patients treated with any of the avapritinib doses tested and was 12.6 months for Study 1002 patients; OS rate at 6/48 months was 100%/63% in NAVIGATOR and 56%/17% in Study 1002 (P = 0.0001). In the 300/400 mg subgroup, adjusted OS rates at 6/36 months were 100%/73 and 68%/20% in Study 1002 (P = 0.0016). Adjusted median PFS was 29.5 months in NAVIGATOR and 3.4 months in Study 1002.

Conclusions

In this indirect, retrospective analysis, avapritinib demonstrated more durable survival outcomes compared with other TKIs in patients with unresectable/metastatic PDGFRA D842V-mutant GIST.

Trial registration

The NAVIGATOR trial was registered at ClinicalTrials.gov as per July 2015, Identifier: NCT02508532.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08013-1.

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.

Avapritinib in unresectable or metastatic PDGFRA D842V-mutant gastrointestinal stromal tumours: Long-term efficacy and safety data from the NAVIGATOR phase I trial

BACKGROUND

PDGFRA D842V mutations occur in 5-10% of gastrointestinal stromal tumours (GISTs), and previously approved tyrosine kinase inhibitors (TKIs) are inactive against this mutation. Consequently, patients have a poor prognosis. We present an updated analysis of avapritinib efficacy and long-term safety in this patient population.

METHODS

NAVIGATOR (NCT02508532), a two-part, open-label, dose-escalation/dose-expansion phase I study, enrolled adult patients with unresectable GISTs. Patients with PDGFRA D842V-mutant GIST were a prespecified subgroup within the overall safety population, which included patients who received ≥1 avapritinib dose. Primary end-points were overall response rate (ORR) and avapritinib safety profile. Secondary end-points were clinical benefit rate (CBR), duration of response (DOR) and progression-free survival (PFS). Overall survival (OS) was an exploratory end-point.

RESULTS

Between 7 October 2015 and 9 March 2020, 250 patients enrolled in the safety population; 56 patients were included in the PDGFRA D842V population, 11 were TKI-naïve. At data cut-off, median follow-up was 27.5 months. Safety profile was comparable between the overall safety and PDGFRA D842V populations. In the PDGFRA D842V population, the most frequent adverse events were nausea (38 [68%] patients) and diarrhoea (37 [66%]), and cognitive effects occurred in 32 (57%) patients. The ORR was 91% (51/56 patients). The CBR was 98% (55/56 patients). The median DOR was 27.6 months (95% confidence interval [CI]: 17.6-not reached [NR]); median PFS was 34.0 months (95% CI: 22.9-NR). Median OS was not reached.

CONCLUSION

Targeting PDGFRA D842V-mutant GIST with avapritinib resulted in an unprecedented, durable clinical benefit, with a manageable safety profile. Avapritinib should be considered as first-line therapy for these patients.

The Identity of PDGFRA D842V-Mutant Gastrointestinal Stromal Tumors (GIST)

Simple Summary

Among the platelet-derived growth factor receptor (PDGFRA) mutations in gastrointestinal stromal tumors (GIST), the most frequent is the substitution at position 842 in the A-loop of an aspartic acid (D) with a valine (V), widely recognized as D842V, a two-sided mutation providing primary resistance to all currently approved agents for GIST treatment. In recent years, new specific inhibitors have been studied in preclinical and clinical settings, and molecular findings have been accumulated, well describing this complex entity. This paper aims at offering a comprehensive picture of the clinical features and the molecular background of this rare subtype of GIST.

Abstract

The majority of gastrointestinal stromal tumors (GIST) carry a sensitive primary KIT mutation, but approximately 5% to 10% of cases harbor activating mutations of platelet-derived growth factor receptor (PDGFRA), mainly involving the A-loop encoded by exon 18 (~5%), or more rarely the JM domain, encoded by exon 12 (~1%), or the ATP binding domain encoded by exon 14 (<1%). The most frequent mutation is the substitution at position 842 in the A-loop of an aspartic acid (D) with a valine (V) in exon 18, widely recognized as D842V. This mutation, as well known, provides primary resistance to imatinib and sunitinib. Thus, until few years ago, no active drugs were available for this subtype of GIST. Conversely, recent years have witnessed the development of a new specific inhibitor—avapritinib—that has been studied in in vitro and clinical setting with promising results. In light of this primary resistance to conventional therapies, the biological background of D842V-mutant GIST has been deeply investigated to better understand what features characterize this peculiar subset of GIST, and some promising insights have emerged. Hereinafter, we present a comprehensive overview on the clinical features and the molecular background of this rare subtype of GIST.

Pretreatment Tumor DNA Sequencing of KIT and PDGFRA in Endosonography-Guided Biopsies Optimizes the Preoperative Management of Gastrointestinal Stromal Tumors

BACKGROUND

Neoadjuvant tyrosine kinase inhibitor (TKI) therapy increases the chance of organ-preserving, radical resection in selected patients with gastrointestinal stromal tumors (GISTs). We aimed to evaluate systematic, immediate DNA sequencing of KIT and PDGFRA in pretreatment GIST tissue to guide neoadjuvant TKI therapy and optimize preoperative tumor response.

METHODS

All patients who were candidates for neoadjuvant therapy of a suspected GIST [the study cohort (SC)] were prospectively included from January 2014 to March 2018. Patients were subjected to pretreatment endosonography-guided fine-needle biopsy (EUS-FNB) or transabdominal ultrasound-guided needle biopsy (TUS-NB), followed by immediate tumor DNA sequencing (< 2 weeks). A historic (2006-2013) reference cohort (RC) underwent work-up without sequencing before neoadjuvant imatinib (n = 42). The rate of optimal neoadjuvant therapy (Therapy_OPTIMAL) was calculated, and the induced tumor size reduction (Tumor Regression_MAX, %) was evaluated by computed tomography (CT) scan.

RESULTS

The success rate of pretreatment tumor DNA sequencing in the SC (n = 81) was 77/81 (95%) [EUS-FNB 71/74 (96%); TUS-NB 6/7 (86%)], with mutations localized in KIT (n = 58), PDGFRA (n = 18), or neither gene, wild type (n = 5). In patients with a final indication for neoadjuvant therapy, the Therapy_OPTIMAL was higher in the SC compared with the RC [61/63 (97%) versus 33/42 (79%), p = 0.006], leading to a significantly higher Tumor Regression_MAX in patients treated with TKI (27% vs. 19%, p = 0.015).

CONCLUSIONS

Pretreatment endosonography-guided biopsy sampling followed by immediate tumor DNA sequencing of KIT and PDGFRA is highly accurate and valuable in guiding neoadjuvant TKI therapy in GIST. This approach minimizes maltreatment with inappropriate regimens and leads to improved tumor size reduction before surgery.

Identification of Wee1 as a target in combination with avapritinib for gastrointestinal stromal tumor treatment

Management of gastrointestinal stromal tumors (GISTs) has been revolutionized by the identification of activating mutations in KIT and PDGFRA and clinical application of RTK inhibitors in advanced disease. Stratification of GISTs into molecularly defined subsets provides insight into clinical behavior and response to approved targeted therapies. Although these RTK inhibitors are effective in most GISTs, resistance remains a significant clinical problem. Development of effective treatment strategies for refractory GISTs requires identification of novel targets to provide additional therapeutic options. Global kinome profiling has the potential to identify critical signaling networks and reveal protein kinases essential in GISTs. Using multiplexed inhibitor beads and mass spectrometry, we explored the majority of the kinome in GIST specimens from the 3 most common molecular subtypes (KIT mutant, PDGFRA mutant, and succinate dehydrogenase deficient) to identify kinase targets. Kinome profiling with loss-of-function assays identified an important role for G₂/M tyrosine kinase, Wee1, in GIST cell survival. In vitro and in vivo studies revealed significant efficacy of MK-1775 (Wee1 inhibitor) in combination with avapritinib in KIT mutant and PDGFRA mutant GIST cell lines as well as notable efficacy of MK-1775 as a monotherapy in the engineered PDGFRA mutant line. These studies provide strong preclinical justification for the use of MK-1775 in GIST.

Gastrointestinal Stromal Tumors (GISTs): Novel Therapeutic Strategies with Immunotherapy and Small Molecules

Gastrointestinal stromal tumors (GISTs) are the most common types of malignant mesenchymal tumors in the gastrointestinal tract, with an estimated incidence of 1.5/100.000 per year and 1–2% of gastrointestinal neoplasms. About 75–80% of patients have mutations in the KIT gene in exons 9, 11, 13, 14, 17, and 5–10% of patients have mutations in the platelet-derived growth factor receptor a (PDGFRA) gene in exons 12, 14, 18. Moreover, 10–15% of patients have no mutations and are classified as wild type GIST. The treatment for metastatic or unresectable GISTs includes imatinib, sunitinib, and regorafenib. So far, GIST therapies have raised great expectations and offered patients a better quality of life, but increased pharmacological resistance to tyrosine kinase inhibitors is often observed. New treatment options have emerged, with ripretinib, avapritinib, and cabozantinib getting approvals for these tumors. Nowadays, immune checkpoint inhibitors form a new landscape in cancer therapeutics and have already shown remarkable responses in various tumors. Studies in melanoma, non-small-cell lung cancer, and renal cell carcinoma are very encouraging as these inhibitors have increased survival rates. The purpose of this review is to present alternative approaches for the treatment of the GIST patients, such as combinations of immunotherapy and novel inhibitors with traditional therapies (tyrosine kinase inhibitors).

The management of metastatic GIST: current standard and investigational therapeutics

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. The majority of GISTs harbor gain of function mutations in either KIT or PDGFRα. Determination of the GIST molecular subtype upon diagnosis is important because this information informs therapeutic decisions in both the adjuvant and metastatic setting. The management of GIST was revolutionized by the introduction of imatinib, a KIT inhibitor, which has become the standard first line treatment for metastatic GIST. However, despite a clinical benefit rate of 80%, the majority of patients with GIST experience disease progression after 2-3 years of imatinib therapy. Second and third line options include sunitinib and regorafenib, respectively, and yield low response rates and limited clinical benefit. There have been recent FDA approvals for GIST including ripretinib in the fourth-line setting and avapritinib for PDGFRA exon 18-mutant GIST. This article aims to review the optimal treatment approach for the management of patients with advanced GIST. It examines the standard treatment options available but also explores the novel treatment approaches in the setting of imatinib refractory GIST.

Resistance to Avapritinib in PDGFRA-Driven GIST Is Caused by Secondary Mutations in the PDGFRA Kinase Domain

Gastrointestinal stromal tumors (GIST) harboring activating mutations of PDGFRA respond to imatinib, with the notable exception of the most common mutation, D842V. Avapritinib is a novel, potent KIT/PDGFRA inhibitor with substantial clinical activity in patients with the D842V genotype. To date, only a minority of PDGFRA-mutant patients treated with avapritinib have developed secondary resistance. Tumor and plasma biopsies in 6 of 7 patients with PDGFRA primary mutations who progressed on avapritinib or imatinib had secondary resistance mutations within PDGFRA exons 13, 14, and 15 that interfere with avapritinib binding. Secondary PDGFRA mutations causing V658A, N659K, Y676C, and G680R substitutions were found in 2 or more patients each, representing recurrent mechanisms of PDGFRA GIST drug resistance. Notably, most PDGFRA-mutant GISTs refractory to avapritinib remain dependent on the PDGFRA oncogenic signal. Inhibitors that target PDGFRA protein stability or inhibition of PDGFRA-dependent signaling pathways may overcome avapritinib resistance. SIGNIFICANCE: Here, we provide the first description of avapritinib resistance mechanisms in PDGFRA-mutant GIST.This article is highlighted in the In This Issue feature, p. 1.

Nationwide evaluation of mutation-tailored treatment of gastrointestinal stromal tumors in daily clinical practice

BACKGROUND

Molecular analysis of KIT and PDGFRA is critical for tyrosine kinase inhibitor treatment selection of gastrointestinal stromal tumors (GISTs) and hence recommended by international guidelines. We performed a nationwide study into the application of predictive mutation testing in GIST patients and its impact on targeted treatment decisions in clinical practice.

METHODS

Real-world clinical and pathology information was obtained from GIST patients with initial diagnosis in 2017-2018 through database linkage between the Netherlands Cancer Registry and the nationwide Dutch Pathology Registry.

RESULTS

Predictive mutation analysis was performed in 89% of the patients with high risk or metastatic disease. Molecular testing rates were higher for patients treated in expertise centers (96%) compared to non-expertise centers (75%, P < 0.01). Imatinib therapy was applied in 81% of the patients with high risk or metastatic disease without patient's refusal or adverse characteristics, e.g., comorbidities or resistance mutations. Mutation analysis that was performed in 97% of these imatinib-treated cases, did not guarantee mutation-tailored treatment: 2% of these patients had the PDGFRA p.D842V resistance mutation and 7% initiated imatinib therapy at the normal instead of high dose despite of having a KIT exon 9 mutation.

CONCLUSION

In conclusion, nationwide real-world data show that over 81% of the eligible high risk or metastatic disease patients receive targeted therapy, which was tailored to the mutation status as recommended in guidelines in 88% of cases. Therefore, still 27% of these GIST patients misses out on mutation-tailored treatment. The reasons for suboptimal uptake of testing and treatment require further study.

Recent developments in gastroesophageal mesenchymal tumours

The pathologist's approach to gastroesophageal mesenchymal tumours has changed dramatically during the last 25 years. In particular, gastrointestinal stromal tumour (GIST) has evolved from a wastebasket mesenchymal tumour category to a precisely defined entity with an increasingly detailed genetic subclassification. This subclassification has brought gastrointestinal mesenchymal neoplasia into the realm of precision medicine, with specific treatments optimised for particular genetic subtypes. Molecular genetic data have also greatly improved our understanding of oesophageal mesenchymal tumours, including the discovery that so-called 'giant fibrovascular polyps' in fact represent a clinically distinctive presentation of well-differentiated liposarcoma. Here, we will focus on gastroesophageal mesenchymal tumours for which there have been recent developments in classification, molecular genetics or tumour biology: granular cell tumour, 'giant fibrovascular polyp'/well-differentiated liposarcoma, plexiform fibromyxoma, gastroblastoma and, of course, GIST.

Tyrosine Kinase Receptors in Oncology

Tyrosine kinase receptors (TKR) comprise more than 60 molecules that play an essential role in the molecular pathways, leading to cell survival and differentiation. Consequently, genetic alterations of TKRs may lead to tumorigenesis and, therefore, cancer development. The discovery and improvement of tyrosine kinase inhibitors (TKI) against TKRs have entailed an important step in the knowledge-expansion of tumor physiopathology as well as an improvement in the cancer treatment based on molecular alterations over many tumor types. The purpose of this review is to provide a comprehensive review of the different families of TKRs and their role in the expansion of tumor cells and how TKIs can stop these pathways to tumorigenesis, in combination or not with other therapies. The increasing growth of this landscape is driving us to strengthen the development of precision oncology with clinical trials based on molecular-based therapy over a histology-based one, with promising preliminary results.

Financial Implications of Avapritinib for Treatment of Unresectable Gastrointestinal Stromal Tumors in Patients With a PDGFRA Exon 18 Variant or After 3 Previous Therapies in a Hypothetical US Health Plan

IMPORTANCE

With the approval of avapritinib for adults with unresectable or metastatic gastrointestinal stromal tumors (GISTs) harboring a platelet-derived growth factor receptor alpha (PDGFRA) exon 18 variant, including PDGFRA D842V variants, and National Comprehensive Cancer Network guideline recommendations as an option for patients with GIST after third-line treatment, it is important to estimate the potential financial implications of avapritinib on a payer's budget.

OBJECTIVE

To estimate the budget impact associated with the introduction of avapritinib to a formulary for metastatic or unresectable GISTs in patients with a PDGFRA exon 18 variant or after 3 or more previous treatments from the perspective of a US health plan.

DESIGN, SETTING, AND PARTICIPANTS

For this economic evaluation, a 3-year budget impact model was developed in March 2020, incorporating costs for drug acquisition, testing, monitoring, adverse events, and postprogression treatment. The model assumed that avapritinib introduction would be associated with increased PDGFRA testing rates from the current 49% to 69%. The health plan population was assumed to be mixed 69% commercial, 22% Medicare, and 9% Medicaid. Base case assumptions included a GIST incidence rate of 9.6 diagnoses per million people, a metastatic PDGFRA exon 18 mutation rate of 1.9%, and progression rate from first-line to fourth-line treatment of 17%.

EXPOSURES

The model compared scenarios with and without avapritinib in a formulary.

MAIN OUTCOMES AND MEASURES

Annual, total, and per member per month (PMPM) budget impact.

RESULTS

In a hypothetical 1-million member plan, fewer than 0.1 new patients with a PDGFRA exon 18 variant per year and 1.2 patients receiving fourth-line therapy per year were eligible for treatment. With avapritinib available, the total increase in costs in year 3 for all eligible adult patients with a PDGFRA exon 18 variant was $46 875, or $0.004 PMPM. For patients undergoing fourth-line treatment, the total increase in costs in year 3 was $69 182, or $0.006 PMPM. The combined total budget impact in year 3 was $115 604, or $0.010 PMPM, including an offset of $3607 in postprogression costs avoided or delayed. The higher rates of molecular testing resulted in a minimal incremental testing cost of $453 in year 3.

CONCLUSIONS AND RELEVANCE

These results suggest that adoption of avapritinib as a treatment option would have a minimal budget impact to a hypothetical US health plan. This would be primarily attributable to the small eligible patient population and cost offsets from reduced or delayed postprogression costs.

Gastrointestinal Stromal Tumor – An Overview

Gastrointestinal stromal tumors (GISTs) are rare tumors but are most common mesenchymal tumors of the digestive tract. They are commonly seen in the stomach (60%) and small intestine (30%). GISTs are likely derived from the interstitial cells of Cajal or their stem cell precursors. They are best characterized by computerized tomography and have a specific staining pattern on immunohistochemistry, i.e., C-Kit and DOG-1. The treatment of GIST is based on the risk assessment for relapse, and patients with localized GIST require resection with or without adjuvant imatinib mesylate (IM). Advanced unresectable tumors are usually treated with IM, with a number of further options available for patients post progression on IM. There is an increasing emphasis on identifying C-Kit and platelet-derived growth factor receptor alpha mutations in all patients with GIST, as these are driver mutations with current and future therapeutic implications.

Therapeutic Potential of PI3K/AKT/mTOR Pathway in Gastrointestinal Stromal Tumors: Rationale and Progress

Simple Summary

Most gastrointestinal stromal tumors (GISTs) arise due to gain-of-function mutations of KIT and PDGFRA, encoding the receptor tyrosine kinase (RTK). The introduction of the RTK inhibitor imatinib has significantly improved the management of GISTs; however, drug resistance remains a challenge. Constitutive autophosphorylation of RTKs is associated with the activation of the PI3K/AKT/mTOR pathway. Especially, this pathway plays a pivotal role in mRNA translation initiation, directly regulated by eukaryotic initiation factors (eIFs). This review highlights the progress for targeting PI3K/AKT/mTOR-dependent mechanisms in GISTs and explores the relationship between mTOR downstream eIFs and the development of GISTs, which may be a promising future therapeutic target for this tumor entity.

Abstract

Gastrointestinal stromal tumor (GIST) originates from interstitial cells of Cajal (ICCs) in the myenteric plexus of the gastrointestinal tract. Most GISTs arise due to mutations of KIT and PDGFRA gene activation, encoding the receptor tyrosine kinase (RTK). The clinical use of the RTK inhibitor imatinib has significantly improved the management of GIST patients; however, imatinib resistance remains a challenge. The phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is a critical survival pathway for cell proliferation, apoptosis, autophagy and translation in neoplasms. Constitutive autophosphorylation of RTKs has an impact on the activation of the PI3K/AKT/mTOR pathway. In several preclinical and early-stage clinical trials PI3K/AKT/mTOR signaling inhibition has been considered as a promising targeted therapy strategy for GISTs. Various inhibitory drugs targeting different parts of the PI3K/AKT/mTOR pathway are currently being investigated in phase Ι and phase ΙΙ clinical trials. This review highlights the progress for PI3K/AKT/mTOR-dependent mechanisms in GISTs, and explores the relationship between mTOR downstream signals, in particular, eukaryotic initiation factors (eIFs) and the development of GISTs, which may be instrumental for identifying novel therapeutic targets.

Extra-gastrointestinal stromal tumor arising in the lesser omentum with a platelet-derived growth factor receptor alpha (PDGFRA) mutation: a case report and literature review

BACKGROUND

Gastrointestinal stromal tumors (GIST) arising from sites other than the gastrointestinal (GI) tract, termed extra-gastrointestinal stromal tumors (EGIST), are rare. Among EGIST, those with platelet-derived growth factor receptor alpha (PDGFRA) mutations are even rarer, with only a few cases reported. About 80% of GIST has KIT mutations, and 10% of GIST have PDGFRA mutations, which commonly affect the TK2 domain (exon 18). Among the exon 18 mutations, the D842V substitution is limited to gastric GIST. In EGIST, the degree of KIT and PDGFRA mutations varies on where the location of the tumor is, and it is suggested that omental EGIST is similar to gastric GIST. Adjuvant imatinib therapy is recommended for high-risk GIST; however, it is known that imatinib is less effective against GIST with a PDGFRA D842V mutation.

CASE PRESENTATION

A 75-year-old man was referred to our hospital with an extrinsic tumor of the lesser curvature of the gastric body. Intraoperative findings showed a tumor located outside of the lesser omentum with no connection between the tumor and the gastric wall. The tumor was subsequently resected. Pathological examination indicated a GIST arising in the lesser omentum measuring 70 mm in its longer dimension. Because the tumor had a PDGFRA mutation (D842V substitution), imatinib was suspected to lack efficacy to the tumor. Thus, although the tumor was considered clinically to have a high risk of recurrence, adjuvant imatinib therapy was not indicated. The patient has been free of recurrence for 29 months since the surgery.

CONCLUSION

We described a case of EGIST with a PDGFRA mutation arising in the lesser omentum. And we reviewed 57 cases of omental EGIST and showed that the clinicopathological characteristics and mutation status in omental EGIST were very similar to gastric GIST. In particular, PDGFAR D842V mutation rate in omental EGIST seemed as high as that in gastric GIST. These results suggested that omental EGIST is strongly related to gastric GIST, so the behavior of omental EGIST might be akin to gastric GIST. However, further studies are required to determine the prognosis and the necessity of adjuvant therapy for EGIST with a PDGFRA mutation.

Avapritinib in advanced PDGFRA D842V-mutant gastrointestinal stromal tumour (NAVIGATOR): a multicentre, open-label, phase 1 trial

BACKGROUND

Targeting of KIT and PDGFRA with imatinib revolutionised treatment in gastrointestinal stromal tumour; however, PDGFRA Asp842Val (D842V)-mutated gastrointestinal stromal tumour is highly resistant to tyrosine kinase inhibitors. We aimed to assess the safety, tolerability, and antitumour activity of avapritinib, a novel KIT and PDGFRA inhibitor that potently inhibits PDGFRA D842V, in patients with advanced gastrointestinal stromal tumours, including patients with KIT and PDGFRA D842V-mutant gastrointestinal stromal tumours (NAVIGATOR).

METHODS

NAVIGATOR is a two-part, open-label, dose-escalation and dose-expansion, phase 1 study done at 17 sites across nine countries (Belgium, France, Germany, Poland, Netherlands, South Korea, Spain, the UK, and the USA). Patients aged 18 years or older, with an Eastern Cooperative Oncology Group performance status of 2 or less, and with adequate end-organ function were eligible to participate. The dose-escalation part of the study included patients with unresectable gastrointestinal stromal tumours. The dose-expansion part of the study included patients with an unresectable PDGFRA D842V-mutant gastrointestinal stromal tumour regardless of previous therapy or gastrointestinal stromal tumour with other mutations that either progressed on imatinib and one or more tyrosine kinase inhibitor, or only received imatinib previously. On the basis of enrolment trends, ongoing review of study data, and evolving knowledge regarding the gastrointestinal stromal tumour treatment paradigm, it was decided by the sponsor's medical director together with the investigators that patients with PDGFRA D842V mutations would be analysed separately; the results from this group of patients is reported in this Article. Oral avapritinib was administered once daily in the dose-escalation part (starting dose of 30 mg, with increasing dose levels once daily in continuous 28-day cycles until the maximum tolerated dose or recommended phase 2 dose was determined; in the dose-expansion part, the starting dose was the maximum tolerated dose from the dose-escalation part). Primary endpoints were maximum tolerated dose, recommended phase 2 dose, and safety in the dose-escalation part, and overall response and safety in the dose-expansion part. Safety was assessed in all patients from the dose-escalation part and all patients with PDGFRA D842V-mutant gastrointestinal stromal tumour in the dose-expansion part, and activity was assessed in all patients with PDGFRA D842V-mutant gastrointestinal stromal tumour who received avapritinib and who had at least one target lesion and at least one post-baseline disease assessment by central radiology. This study is registered with ClinicalTrials.gov, NCT02508532.

FINDINGS

Between Oct 26, 2015, and Nov 16, 2018 (data cutoff), 46 patients were enrolled in the dose-escalation part, including 20 patients with a PDGFRA D842V-mutant gastrointestinal stromal tumour, and 36 patients with a PDGFRA D842V-mutant gastrointestinal stromal tumour were enrolled in the dose-expansion part. At data cutoff (Nov 16, 2018), 38 (46%) of 82 patients in the safety population (median follow-up of 19·1 months [IQR 9·2-25·5]) and 37 (66%) of the 56 patients in the PDGFRA D842V population (median follow-up of 15·9 months [IQR 9·2-24·9]) remained on treatment. The maximum tolerated dose was 400 mg, and the recommended phase 2 dose was 300 mg. In the safety population (patients with PDGFRA D842V-mutant gastrointestinal stromal tumour from the dose-escalation and dose-expansion parts, all doses), treatment-related grade 3-4 events occurred in 47 (57%) of 82 patients, the most common being anaemia (14 [17%]); there were no treatment-related deaths. In the PDGFRA D842V-mutant population, 49 (88%; 95% CI 76-95) of 56 patients had an overall response, with five (9%) complete responses and 44 (79%) partial responses. No dose-limiting toxicities were observed at doses of 30-400 mg per day. At 600 mg, two patients had dose-limiting toxicities (grade 2 hypertension, dermatitis acneiform, and memory impairment in patient 1, and grade 2 hyperbilirubinaemia in patient 2).

INTERPRETATION

Avapritinib has a manageable safety profile and has preliminary antitumour activity in patients with advanced PDGFRA D842V-mutant gastrointestinal stromal tumours.

FUNDING

Blueprint Medicines.

Prognostic Indicators for Gastrointestinal Stromal Tumors: A Review

Gastrointestinal stromal tumors (GISTs) are potentially malignancies that can occur anywhere in the digestive tract. Tyrosine kinase inhibitors (TKIs) such as imatinib have proven effective since the discovery of KIT and PDGFRA. The current version of NCNN, ESMO and EURACAN guidelines recognized that the three main prognostic factors are the mitotic rate, tumor size and tumor site. In addition, tumor rupture is also recognized as an independent risk factor. However, recent evidence shows that various types of gene mutations are associated with prognosis, and influencing factors such as gastrointestinal bleeding and high Ki67 index have been associated with poor prognosis. It shows that the current risk classification is still insufficient and controversial. With the emergence of more and more lack mutation in KIT/PDGFRA GISTs (KIT/PDGFRA wild-type GISTs) or drug resistance genes, primary and secondary drug resistance problems are caused, which makes the treatment of late or metastatic GIST face challenges. Therefore, this article will review the clinicopathological characteristics of GIST, the special molecular subtypes and other factors that may affect prognosis. We will also explore reliable prognostic markers for better postoperative management and improve the prognosis of patients with GIST.

Avapritinib in the treatment of PDGFRA exon 18 mutated gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GIST) can be molecularly classified based on different subtypes including mutations in KIT and PDGFRA. Patients with PDGFRA mutations are an important subgroup that commonly arise in the stomach and are associated with a more indolent disease course. Importantly, the most common PDGFRA molecular subtype, the D842V mutation in exon 18 of the gene which alters the activation loop, is imatinib insensitive in in vitro studies. Poor responses to imatinib have been seen clinically compared with PDGFRA exon 18 non-D842V-mutated GIST. Avapritinib (BLU-285) is a potent KIT and PDGFRA-specific tyrosine kinase inhibitor which has shown >90% response rates in patients with PDGFRA exon 18 D842V-mutated GIST. Results from the Phase I trial of avapritinib have indicated that this drug should be the standard of care for patients with PDGFRA exon 18 D842V-mutated GIST.

Gene Expression Profiling of PDGFRA Mutant GIST Reveals Immune Signatures as a Specific Fingerprint of D842V Exon 18 Mutation

Platelet Derived Growth Factor Receptor Alpha (PDGFRA) mutations occur in only about 5-7% of gastrointestinal stromal tumors (GIST), notably with alterations on exons 12/14/18. The most frequent PDGFRA mutation is the exon 18 D842V, which is correlated to specific clinico-pathological features, such as primary imatinib resistance and higher indolence. Here, we present a gene expression profile (GEP) comparison of D842V vs. PDGFRA with mutations other than D842V (non-D842V). GEP was followed by in silico bioinformatic analysis aimed at evaluating differential expression, tumor microenvironment composition and pathway enrichment. We found a large set of oncogenes, transcription factors and nuclear receptors downregulated in the D842V mutant. Conversely, D842V showed a significant enrichment of immune- and interferon- related gene signatures. Differences in tumor microenvironment composition were also highlighted, including a higher abundance of CD8+ T-cells and an overexpression of the T cell-inflamed signature in the D842V mutant subgroup, which is predictive of immunotherapy response. PDGFRA D842V vs. non-D842V GIST display a different expression profile, with a prominent immunological signature, that could represent a proof of principle for testing immunotherapeutic strategies in this drug-orphan subset of GIST.

Progress in determining response to treatment in gastrointestinal stromal tumor

Introduction: Gastrointestinal stromal tumor (GIST) is the most common malignant mesenchymal tumor of the gastrointestinal system. Multiple advances in the management of GIST from the discovery of KIT/PDGRA and other genetic alterations have led to the development of multiple tyrosine kinase inhibitors. Response assessment in GIST is determined with iRECIST (Response Evaluation Criteria in Solid Tumors), PERCIST (PET response criteria in solid tumors), or Choi criteria. Molecular genotyping of the tissue samples is the recent standard for diagnosis, treatment, and response to treatment.Areas covered: In this study, we provide a brief overview of the history of the GIST, molecular sequencing, available treatment options and clinical trials, radiologic response assessment, and the role of ctDNA in response evaluation.Expert opinion: Future GIST management is related to the development of sensitive assays to detect genetic alterations for initial diagnosis, treatment selection, monitoring the response to treatment, resistant mutations, and predicting survival.

New therapeutic agents in gastrointestinal stromal tumours

PURPOSE OF REVIEW

The aim of this study was to provide an update on the most recent developments regarding systemic treatments in the various molecular subtypes of gastrointestinal stromal tumour (GIST).

RECENT FINDINGS

Several novel direct inhibitors of KIT and PDGFRA have entered the advanced clinical development in later treatment lines based on promising early clinical trial experience. Both avapritinib and ripretinib are more potent and more specific against various KIT and PDGFRA mutations. For patients with PDGFRA D842V mutations, the next generation of drugs may become the first active treatment options.Comprehensive molecular testing of KIT/PDGFRA-wildtype GIST may unmask clinically relevant targets, including NTRK fusions.

SUMMARY

The treatment landscape in GIST is expected to undergo a profound transformation with more potent drugs currently in late-stage clinical development.

Genomic-guided precision therapy for soft tissue sarcoma

Soft tissue sarcoma (STS), although heterogeneous in histopathology presentation, has mostly been treated with chemotherapy agents as one entity. Our understanding of crucial genomic alterations in different STS histologies and the advent of molecular-targeted agents have reshaped the treatment paradigm for advanced STS. Small-molecule inhibitors of c-KIT, plate-derived growth factor receptor alpha, c-MET, BRAF, anaplastic lymphoma kinase, ROS1 and colony-stimulating factor-1 receptor have been successfully validated in clinical studies to yield practice-changing results. Inhibitors of other novel genomic targets including mouse double minute 2 homolog, cyclin-dependent kinase 4/6, mitogen-activated protein kinase and epigenetic regulators are expected to be developed in the near future. Furthermore, with the advancement and accessibility of molecular diagnosis and next-generation sequencing, a genomic-based therapeutic approach should be widely applicable to advanced STS patients. This review will focus on the progress of genomic-guided therapy tailored to each molecular alteration of different STS histologies.

Transarterial strategies for the treatment of unresectable hepatocellular carcinoma: A systematic review

Conventional transarterial chemoembolization (cTACE), drug-eluting beads (DEB-TACE) and transarterial radioembolization (TARE) are alternative strategies for unresectable hepatocellular carcinoma (HCC). However, which of these strategies is the best is still controversial. This meta-analysis was performed to evaluate the effects of DEB-TACE, TARE and cTACE in terms of overall survival (OS), tumor response and complications. A literature search was conducted using the EMBASE, PubMed, Google Scholar, and Cochrane databases from inception until July 2019 with no language restrictions. The primary outcome was overall survival, and the secondary outcomes included complete response and local recurrence. The comparison of DEB-TACE with cTACE indicated that DEB-TACE has a better OS at 1 year (RR 0.79, 95% CI 0.67–0.93, p = 0.006), 2 years (RR 0.89; 95% CI 0.81–0.99, p = 0.046), and 3 years (RR 0.89; 95% CI 0.81–0.99, p = 0.035). The comparison of TARE with cTACE indicated that TARE has a better OS than cTACE at 2 years (RR 0.87; 95% CI 0.80–0.95, p = 0.003) and 3 years (RR 0.90; 95% CI 0.85–0.96, p = 0.001). The comparison of DEB-TACE with TARE indicated that DEB-TACE has a better OS than TARE at 2 years (RR 0.40; 95% CI 0.19–0.84, p = 0.016). The current meta-analysis suggests that DEB-TACE is superior to both TARE and cTACE in terms of OS. TARE has significantly lower complications than both DEB-TACE and cTACE for patients with HCC. Further multicenter, well-designed randomized controlled trials are needed, especially for evaluating DEB-TACE versus TARE.

ALK expressed in a gastrointestinal stromal tumor harboring PDGFRA p. D842V mutation:a case report

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common type of adult mesenchymal neoplasms. The events that drive GIST oncogenesis are primarily KIT or PDGFRA mutations, which lead to the susceptibility of these tumors to small-molecule tyrosine kinase inhibitors such as imatinib and sunitinib. However, previous studies have shown that patients with a PDGFRA D842V mutation in GISTs have a very low rate of response to imatinib treatment. Therefore, novel tyrosine kinase inhibitors (TKIs) are currently being evaluated in clinical trials to treat GISTs harboring a PDGFRA D842V mutation. Anaplastic lymphoma kinase (ALK) overexpression was not expected to be present in the GIST, and it has been used as a biomarker to distinguish GISTs from other types of mesenchymal tumors.

CASE PRESENTATION

Here, we report a 37-year-old male patient who presented with a large mass in the right upper abdomen and was subsequently diagnosed with a GIST harboring a PDGFRA D842V mutation. We unexpectedly found that the GIST in this patient exhibited simultaneous ALK expression.

CONCLUSIONS

This is the first case reported of a GIST with ALK expression. This rare phenomenon suggests that the diagnosis of a GIST cannot be excluded absolutely if a tumor exhibits ALK expression. In addition, ALK may be a potential therapeutic target for patients with imatinib-resistant stromal tumors.

Intrigue: Phase III study of ripretinib versus sunitinib in advanced gastrointestinal stromal tumor after imatinib

Ripretinib (DCC-2618) is a novel, type II tyrosine switch control inhibitor designed to broadly inhibit activating and drug-resistant mutations in KIT and PDGFRA. Ripretinib has emerged as a promising investigational agent for the treatment of gastrointestinal stromal tumor owing to targeted inhibition of secondary resistance mutations that may develop following treatment with prior line(s) of tyrosine kinase inhibitors. Here we describe the rationale and design of intrigue (NCT03673501), a global, randomized (1:1), open-label, Phase III study comparing the safety and efficacy of ripretinib versus sunitinib in patients with advanced gastrointestinal stromal tumor following imatinib. The primary end point is progression-free survival and key secondary objectives include objective response rate and overall survival. Clinical Trial Registration: NCT03673501.

Oncological Outcome After Diagnostic Biopsies in Gastrointestinal Stromal Tumors: A Retrospective Cohort Study

OBJECTIVE

To analyze whether the route of preoperative biopsy influences oncological outcome in GIST patients.

SUMMARY OF BACKGROUND DATA

Preoperative biopsies are widely used for diagnosing GIST. Little is known about the risk of tumor seeding after different routes of biopsy.

METHODS

Patients who underwent resection of a primary GIST between 1996 and 2014 were identified from 2 databases from 2 tertiary referral centers. Survival data were obtained using the Kaplan-Meier method. Possible confounders were identified using Cox regression analysis. The primary endpoint was local recurrence free survival (RFS) and the secondary endpoint was DSS.

RESULTS

A total of 228 patients were included, with a median age of 62 years (range 17-86) and a median follow-up time of 53 months (range 1-204). From these patients, 42 patients did not have a biopsy (18%), 70 underwent a transcutaneous biopsy (31%), and 116 a transluminal biopsy (51%). A total of 42 patients (19.0%) had a local and/or distant recurrence. From the 70 patients with a transcutaneous biopsy, only 1 patient developed a needle tract recurrence (1.4%). Local RFS and DSS were both significantly shorter in the transcutaneous biopsy group on univariate analysis compared to the other groups; however, in multivariate analysis the route of biopsy did not influence local RFS (P = 0.128) or DSS (P = 0.096).

CONCLUSIONS

Transluminal or transcutaneous biopsies for diagnosing GIST do not significantly alter the risk of local recurrent disease or DSS in multivariate Cox regressions. The risk of needle tract seeding after transcutaneous biopsy was low.

Translational insights into gastrointestinal stromal tumor and current clinical advances

Gastrointestinal stromal tumor (GIST) is the most common soft tissue sarcoma of the gastrointestinal tract and, in the vast majority of cases, is characterized by activating mutations in KIT or, less commonly, PDGFRA. Mutations in these type III receptor tyrosine kinases (RTKs) account for over 85% of GIST cases, and the majority of KIT primary mutations respond to treatment with the tyrosine kinase inhibitor (TKI) imatinib. However, drug resistance develops over time, most commonly due to secondary kinase mutations. Sunitinib and regorafenib are approved for the treatment of imatinib-resistant GIST in the second and third lines, respectively. However, resistance to these agents also develops and new therapeutic options are needed. In addition, a small number of GISTs harbor primary activating mutations that are resistant to currently available TKIs, highlighting an additional unmet medical need. Several novel and selective TKIs that overcome known mechanisms of resistance in GIST have been developed and show promise in early clinical trials. Additional emerging targeted therapies in GIST include modulation of cellular signaling pathways downstream of KIT, antibodies targeting KIT and PDGFRA and immune checkpoint inhibitors. These advancements highlight the rapid evolution in the understanding of this malignancy and provide perspective on the encouraging horizon of current and forthcoming therapeutic strategies for GIST.

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.

Mechanisms of resistance to a PI3K inhibitor in gastrointestinal stromal tumors: an omic approach to identify novel druggable targets

Background: Gastrointestinal stromal tumors (GISTs) represent a worldwide paradigm of target therapy. The introduction of tyrosine kinase inhibitors has deeply changed the prognosis of GIST patients, however, the majority of them acquire secondary mutations and progress. Unfortunately, besides tyrosine-kinase inhibitors, no other therapeutic options are available. Therefore, it is mandatory to identify novel molecules and/or strategies to overcome the inevitable resistance. In this context, after promising preclinical data on the novel PI3K inhibitor BYL719, the NCT01735968 trial in GIST patients who had previously failed treatment with imatinib and sunitinib started. BYL719 has attracted our attention, and we comprehensively characterized genomic and transcriptomic changes taking place during resistance.

Methods: For this purpose, we generated two in vitro GIST models of acquired resistance to BYL719 and performed an omic-based analysis by integrating RNA-sequencing, miRNA, and methylation profiles in sensitive and resistant cells.

Results: We identified novel epigenomic mechanisms of pharmacological resistance in GISTs suggesting the existence of pathways involved in drug resistance and alternatively acquired mutations. Therefore, epigenomics should be taken into account as an alternative adaptive mechanism.

Conclusion: Despite the fact that currently we do not have patients in treatment with BYL719 to verify this hypothesis, the most intriguing result is the involvement of H19 and PSTA1 in GIST resistance, which might represent druggable targets.

Targeted therapy and personalized medicine in gastrointestinal stromal tumors: drug resistance, mechanisms, and treatment strategies

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Since the discovery that the KIT and PDGFRA receptor tyrosine kinases are the primary oncogenic drivers in the vast majority of GISTs, targeted therapy with tyrosine kinase inhibitors has been the mainstay of treatment for this disease. Using molecular profiling of tumor specimens, researchers also discovered that KIT and PDGFRA mutations are non-random and occur in specific regions of the receptors, and furthermore, that particular genotypes predicted response or resistance to targeted therapy. Imatinib, the first tyrosine kinase inhibitor used to treat GIST, remains the first-line therapy in advanced GIST and the only therapy confirmed through clinical trials in the adjuvant or neoadjuvant setting for resectable disease. Resistance to imatinib is well described and is either primary or secondary. Primary resistance is associated with specific tumor genotypes, so genotyping of individual patient tumors helps guide decision-making into whether to offer imatinib and at what dose. Secondary resistance occurs due to the acquisition of secondary mutations during therapy. Currently, the main strategy to combat imatinib resistance is to switch to another tyrosine kinase inhibitor, because imatinib-resistant GIST is usually still oncogenically addicted to KIT/PDGFRA signaling. Surgery can also be used to combat resistant disease in select settings. Unfortunately, progression-free and overall survival remains dismal for patients who develop imatinib-resistant disease, and further research into alternative strategies is still needed.

Using biology to guide the treatment of sarcomas and aggressive connective-tissue tumours

Sarcomas are a heterogeneous group of malignancies that arise from cells of a mesenchymal origin. Surgery forms the mainstay of the treatment of most patients with localized sarcoma and might be followed or preceded by chemotherapy and/or radiotherapy. In the metastatic setting, systemic treatments tend to improve survival and control symptoms. However, the adverse events and sometimes disappointing outcomes associated with these empirical approaches to treatment indicate a need for new approaches. The advent of next-generation sequencing (NGS) has enabled more targeted treatment of many malignancies based on the presence of specific alterations. NGS analyses of sarcomas have revealed the presence of many alterations that can be targeted using therapies that are already used in patients with other forms of cancer. In this Review, we describe the genomic alterations considered to define specific nosological subgroups of sarcoma and whose contribution to oncogenesis provides a biological rationale for the use of a specific targeted therapy. We also report several less successful examples that should guide researchers and clinicians to better define the extent to which the identification of driver molecular alterations should influence the development of novel treatments.

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.

Molecular modelling evaluation of exon 18 His845_Asn848delinsPro PDGFRα mutation in a metastatic GIST patient responding to imatinib

Platelet-Derived Growth Factor Receptor Alpha (PDGFRA) mutations occur in approximately 5-7% of gastrointestinal stromal tumours (GIST). Over half of all PDGFRA mutations are represented by the substitution at position 842 in the A-loop of an aspartic acid (D) with a valine (V), recognized as D842V, conferring primary resistance to imatinib in vitro and in clinical observations due to the conformation of the kinase domain, which negatively affects imatinib binding. The lack of interaction between imatinib and the D842V PDGFRA mutated model has been established and widely confirmed in vivo. However, for the other PDGFRA mutations, the correlation between pre-clinical and clinical data is still unclear. An in silico evaluation of the p.His845_Asn848delinsPro mutation involving exon 18 of PDGFRA in a metastatic GIST patient responding to first-line imatinib has been provided. Docking analyses were performed, and the ligand-receptor interactions were evaluated with the jCE algorithm for structural alignment. The docking simulation and structural superimposition analysis show that PDGFRA p.His845_Asn848delinsPro stabilizes the imatinib binding site with the residues that are conserved in KIT. The in vivo evidence that PDGFRA p.His845_Asn848delinsPro is sensitive to imatinib was confirmed by the molecular modelling, which may represent a reliable tool for the prediction of clinical outcomes and treatment selection in GIST, especially for rare mutations.

KIT exon 11 and PDGFRA exon 18 gene mutations in gastric GIST: proposal of a short panel for predicting therapeutic response

Background

GIST is the most common mesenchymal tumor of gastrointestinal tract and is more frequent in stomach. Its main mutations affect KIT and PDGFRA genes. Full genetic analysis panels are currently used to study mutations in GIST and other tumors. Considering that in gastric GIST KIT gene mutations in exon 11 are sensitive to IM whereas PDGFRΑ gene mutations in exon 18 (D842V) are resistant to the same drug, the aim of this study is to focus on these two molecular targets as a short alternative panel for predicting therapeutic response in gastric GIST which might optimize resources.

Methods

The genotypes of 38 cases of primary GIST were determined by performing bidirectional DNA sequencing.

Results

Exon 11 of KIT gene showed mutations in 65.3% and the exon 18 of PDGFRA gene showed 9% of cases. So it was possible to determine a subgroup of tumors which presented mutations in KIT exon 11 and PDGFRA exon 18.

Conclusion

Considering all of the foregoing analyzed globally, the application of short panel has impact on the cost and time of release of results to the physician, allowing a rapid approach to patients eligible for treatment with the target therapy.

A precision therapy against cancers driven by KIT/PDGFRA mutations

Targeting oncogenic kinase drivers with small-molecule inhibitors can have marked therapeutic benefit, especially when administered to an appropriate genomically defined patient population. Cancer genomics and mechanistic studies have revealed that heterogeneous mutations within a single kinase can result in various mechanisms of kinase activation. Therapeutic benefit to patients can best be optimized through an in-depth understanding of the disease-driving mutations combined with the ability to match these insights to tailored highly selective drugs. This rationale is presented for BLU-285, a clinical stage inhibitor of oncogenic KIT and PDGFRA alterations, including activation loop mutants that are ineffectively treated by current therapies. BLU-285, designed to preferentially interact with the active conformation of KIT and PDGFRA, potently inhibits activation loop mutants KIT D816V and PDGFRA D842V with subnanomolar potency and also inhibits other well-characterized disease-driving KIT mutants both in vitro and in vivo in preclinical models. Early clinical evaluation of BLU-285 in a phase 1 study has demonstrated marked activity in patients with diseases associated with KIT (aggressive systemic mastocytosis and gastrointestinal stromal tumor) and PDGFRA (gastrointestinal stromal tumor) activation loop mutations.

Which is the best combination of TACE and Sorafenib for advanced hepatocellular carcinoma treatment? A systematic review and network meta-analysis

The aim of this study was to assess the comparative efficacy and safety of combination therapy with transarterial chemoembolization (TACE) and Sorafenib for patients with advanced hepatocellular carcinoma (HCC) through a systematic review and network meta-analysis and identify the best combination of TACE and Sorafenib. We searched databases for publications prior to May 2018. The prespecified efficacy outcomes were the objective response rate, overall survival rate, and time to progression. adverse effects included dermatologic, gastrointestinal, and general disorders. Subgroup analyses, meta-regression, and a network meta-analysis regarding two types of outcomes by different chemotherapy agents in TACE (5-fluorouracil, Adriamycin, Platinum, mitomycin C, hydroxycamptothecin) were included. The study is registered with PROSPERO (CRD42018098541). For efficacy outcomes, subgroups which included 5-fluorouracil and hydroxycamptothecin ranked higher than other chemotherapy agents, while mitomycin C ranked the lowest. For advanced effects, the use of mitomycin C or 5-fluorouracil as the chemotherapy agent ranked higher, while hydroxycamptothecin ranked the lowest. Therefore, we excluded 5-Fu and Mitomycin C in subsequent studies. Additionally, in the evaluation of primary adverse effects by the network meta-analysis, Platinum ranked the highest while hydroxycamptothecin ranked the lowest. Therefore, we excluded Platinum this time. Furthermore, all types of Adriamycin are not same, and some studies included two types of Adriamycin. The network meta-analysis results showed that the TACE (hydroxycamptothecin + pirarubicin) +Sorafenib arm and TACE (hydroxycamptothecin + epirubicin) +Sorafenib arm had significant efficacy differences. In conclusion, for patients with advanced HCC, combination therapy with HCPT plus THP/EPI in TACE and Sorfenib may be used as a first-line treatment.

Nationwide trends in the incidence and outcome of patients with gastrointestinal stromal tumour in the imatinib era

Background

The incidence, treatment and outcome of patients with newly diagnosed gastrointestinal stromal tumour (GIST) were studied in an era known for advances in diagnosis and treatment.

Methods

Nationwide population‐based data were retrieved from the Netherlands Cancer Registry. All patients with GIST diagnosed between 2001 and 2012 were included. Primary treatment, defined as any treatment within the first 6–9 months after diagnosis, was studied. Age‐standardized incidence was calculated according to the European standard population. Changes in incidence were evaluated by calculating the estimated annual percentage change (EAPC). Relative survival was used for survival calculations with follow‐up available to January 2017.

Results

A total of 1749 patients (54·0 per cent male and median age 66 years) were diagnosed with a GIST. The incidence of non‐metastatic GIST increased from 3·1 per million person‐years in 2001 to 7·0 per million person‐years in 2012; the EAPC was 7·1 (95 per cent c.i. 4·1 to 10·2) per cent (P < 0·001). The incidence of primary metastatic GIST was 1·3 per million person‐years, in both 2001 and 2012. The 5‐year relative survival rate increased from 71·0 per cent in 2001–2004 to 81·4 per cent in 2009–2012. Women had a better outcome than men. Overall, patients with primary metastatic GIST had a 5‐year relative survival rate of 48·2 (95 per cent c.i. 42·0 to 54·2) per cent compared with 88·8 (86·0 to 91·4) per cent in those with non‐metastatic GIST.

Conclusion

This population‐based nationwide study found an incidence of GIST in the Netherlands of approximately 8 per million person‐years. One in five patients presented with metastatic disease, but relative survival improved significantly over time for all patients with GIST in the imatinib era.

Surgery improves survival

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.