Circulating tumor DNA analysis of the phase III VOYAGER trial: KIT mutational landscape and outcomes in patients with advanced gastrointestinal stromal tumor treated with avapritinib or regorafenib

Navigating Ongoing Challenges in GI Stromal Tumors

GI stromal tumors (GISTs) are mesenchymal neoplasms with variable natural histories, originating in the GI tract, most commonly in the stomach. They are frequently characterized by KIT or platelet-derived growth factor receptor alpha (PDGFRA) oncogenic mutations. Surgical resection remains the cornerstone treatment for localized GISTs. Clinical trials have demonstrated the benefits of adjuvant imatinib in patients selected on the basis of recurrence risk and gene mutations, although the optimal duration of therapy is yet to be established. Some data suggest that longer durations of adjuvant imatinib (>3 years) may provide additional benefit, which is being investigated in ongoing trials. Management of imatinib-related adverse effects is essential during treatment, and longitudinal abdominal imaging is mandatory both during and after adjuvant therapy. Once GISTs are more advanced and unresectable, KIT- and PDGFRA-directed tyrosine kinase inhibitors (TKIs) become the key treatment in most patients with KIT mutation. Several TKIs have regulatory approval for advanced GISTs, but in most patients, resistance to TKIs eventually emerges, mainly from secondary resistance mutations in KIT. Each TKI has different coverage of oncogenic KIT mutations, suggested by preclinical and clinical findings, which has given rationale to an ongoing clinical trial that includes molecular selection as eligibility criteria. Furthermore, novel treatment approaches, from TKI combinations to an antibody-drug conjugate, are being investigated. Despite the significant advance in managing GISTs with KIT mutations, those without KIT or PDGFRA mutation, which consists of 10%-15% of patients with GIST, can be a clinical challenge in the advanced setting. These non-KIT/PDGFRA GISTs could be driven by genomic or epigenomic alterations in SDHx, NF1 mutations, and other genomic alterations. Non-KIT/PDGFRA GISTs are less responsive to currently available TKIs than GISTs driven by KIT/PDGFRA mutations, and each subset of non-KIT/PDGFRA GIST has distinctive biology and clinical features. Therefore, individualized, multidisciplinary, biology-based management and consideration for clinical trial enrollment are critical for non-KIT/PDGRFA GISTs.

Emerging Role of Blood-based Biomarkers in Sarcomas

We assess the emerging role of liquid biopsies, particularly circulating tumor DNA (ctDNA), in sarcoma management. Preliminary studies suggest that ctDNA has multiple potential applications including, early detection in patients with cancer predisposition syndromes, diagnosis, prognostication, therapy selection, and monitoring treatment response. Among patients with gastrointestinal stromal tumors, studies have demonstrated the capacity for identification of clinically relevant resistance mutations. In other sarcoma subtypes such as Ewing sarcoma and osteosarcoma, early findings indicate that ctDNA levels might correlate with tumor burden and outcomes, potentially aiding in risk stratification. Clinical utility has not been established for these applications.

Clinical Use of Liquid-Based Comprehensive Genomic Profiling in Gastrointestinal Stromal Tumors

Treatment for gastrointestinal stromal tumor (GIST) focuses on tyrosine kinase inhibitors, the selection of which depends on specific mutations. We sought to determine the clinical use of liquid biopsy in advanced GIST. Liquid (n = 181) (FoundationOne Liquid CDx) and tissue (n = 2198) (FoundationOne and FoundationOne CDx) comprehensive genomic profiling of GIST were evaluated. The presence of circulating tumor DNA in liquid was determined via tumor fraction (TF), with an elevated TF defined as TF ≥ 1%. Liquid comprehensive genomic profiling revealed 30% (54/181) of samples had an elevated TF, among which the prevalence of KIT and PDGFRA alterations were 89% (48/54) and 2% (1/54), respectively. In patient-matched tissue/liquid samples (n = 49), the positive percent agreement of driver alterations in liquid with an elevated TF relative to tissue was 100%. Fifty-five percent (42/77) of liquid samples with a KIT driver mutation had a co-occurring imatinib-resistant alteration; a minority of cases harbored non-KIT mechanisms of resistance such as FGFR2 fusions and BRAF or EGFR alterations. The relative prevalence of imatinib resistance KIT exon 13 and 17 mutations was enriched in liquid compared with tissue. Finally, in the liquid cohort, 2.2%, 1.7%, and 1.1% of patients were predicted to harbor germline KIT, SDHx, or NF1 mutations, respectively. In conclusion, known driver and tyrosine kinase inhibitor--resistant mutations were identified in liquid biopsies of patients with GIST with high concordance to tissue in the presence of an elevated TF. Liquid biopsy may be valuable in the molecular classification and medical management of GIST.

Next questions on gastrointestinal stromal tumors: unresolved challenges and future directions

PURPOSE OF REVIEW

Despite remarkable progress in the management of gastrointestinal stromal tumors (GISTs), critical challenges persist. Key aspects such as risk stratification, the optimal duration of adjuvant therapy, and strategies to enhance the efficacy of first-line treatment remain subjects of ongoing debate. This review explores emerging concepts and innovative approaches aimed at refining patient selection and optimizing therapeutic decision-making to further improve clinical outcomes.

RECENT FINDINGS

Molecular and genomic parameters have the potential to enhance traditional risk models, enabling more precise stratification of high-risk patients. Innovations in artificial intelligence and liquid biopsy are emerging as powerful tools for refining predictions of recurrence and treatment response. Meanwhile, the definition and prognostic significance of tumor rupture remain pivotal challenges that influence both risk assessment and adjuvant therapy decisions. Furthermore, transcriptomic and multiomic analyses have unveiled distinct GIST subtypes with significant prognostic and therapeutic implications, paving the way for more tailored treatment strategies.

SUMMARY

Integrating molecular features into clinical decision making may refine risk assessment and personalize the treatment in patients with GIST. Future research should focus on validating these tools and redefine clinical trial designs to accelerate drug development for this rare disease.

Minimal Residual Disease in Metastatic Soft Tissue Sarcoma

OPINION STATEMENT

Liquid biopsies represent a promising and minimally invasive approach to diagnosing and monitoring cancer. In recent years, studies across a multitude of solid organ malignancies have suggested the clinical utility of biomarkers such as circulating tumor DNA (ctDNA). Particular attention has been given to serial assessment of such biomarkers in an effort to detect minimal residual disease (MRD), in order to predict which patients may be at highest risk of relapse following curative-intent surgical or medical intervention. Such investigations are particularly relevant to sarcomas, which are highly heterogeneous malignancies and commonly develop treatment resistance. While preliminary research described herein is promising, there remain key barriers to widespread adoption of liquid biopsy in sarcoma, including the lack of standardized detection methods, high cost, and the need for large, prospective studies to validate their clinical utility. Given the high level of interest in liquid biopsy in the biomedical community, it is plausible such obstacles may be overcome in the near future. With such advancements, one can anticipate that liquid biopsies may become a key tool in the sarcoma oncologists armamentarium, and offer a path toward improved outcomes for patients with sarcoma.

Establishment and validation of a prognostic nomogram for extra-gastrointestinal stromal tumors

Background

Extra-gastrointestinal stromal tumor (EGIST) is a rare subtype of gastrointestinal stromal tumor, with limited information on its clinical characteristics and prognostic factors. This study aims to identify the risk factors affecting survival in EGIST patients and to develop a prognostic nomogram for predicting EGIST-specific survival (TSS).

Methods

Patients diagnosed with EGIST, aged 18 to 80, were enrolled from the Surveillance, Epidemiology, and End Results (SEER) Research Plus database, covering the years 2000 to 2019. Univariate and multivariate analyses were conducted to identify risk factors for developing a nomogram. The predictive accuracy of the nomogram was evaluated using time-dependent receiver operating characteristic curves, calibration plots, and the concordance index. Decision curve analysis (DCA) was performed to assess the nomogram's clinical utility and net benefit for application in clinical practice. Additionally, the nomogram's performance was compared with the tumor SEER stage.

Results

A total of 389 patients were included in this study. Univariate and multivariate analyses identified age, household income, surgery, tumor grade, tumor size, and tumor SEER stage as significant predictors of TSS (all P<0.05). These factors were incorporated into the prognostic nomogram. The nomogram demonstrated superior prognostic value compared to the tumor SEER stage alone, as evidenced by the area under the curve and concordance index. The calibration plot indicated a high level of accuracy in forecasting survival probabilities. Furthermore, DCA highlighted the nomogram's clinical applicability and positive net benefit. The nomogram also proved more effective than the tumor SEER stage alone in identifying patients with poorer prognoses.

Conclusions

Age, household income, surgery, tumor grade, tumor size, and tumor SEER stage were identified as risk factors for TSS in patients with EGIST. We have developed and validated a prognostic nomogram to predict TSS in EGIST patients, which may improve patient management and guide personalized medical treatment for EGIST.

Characteristics and therapeutic strategies for familial gastrointestinal stromal tumors

This editorial discusses Wang et al's article on familial gastrointestinal stromal tumors (GISTs). We read with great interest this article concerning the diagnosis, treatment, and post-treatment management of patients with familial GISTs. The actual incidence of GISTs may be underestimated due to diagnostic limitations and the long-term low-risk behavior of some GISTs. The molecular landscape of GISTs is primarily driven by mutations in the KIT and platelet-derived growth factor receptor alpha (PDGFRA) genes. A subset of GISTs without these mutations known as wild-type GISTs, may harbor other rare mutations, impacting their response to targeted therapies. Clinically, patients with GISTs present with non-specific symptoms, often leading to delayed diagnosis. Genetic predispositions in familial GISTs provide insights into the genetic architecture and extragastrointestinal manifestations of GISTs. Management has evolved from surgical interventions to molecular-based therapies using tyrosine kinase inhibitors. The management of GISTs, especially in familial cases, requires a multidisciplinary approach. Cases of different gene mutations were reported in the same family, suggesting that incorporating genetic testing into routine clinical practice is crucial for the early identification of high-risk individuals and the implementation of tailored surveillance programs.

Emerging treatments for sarcoma: from 2024 onward

INTRODUCTION

Sarcomas are a rare and diverse group of mesenchymal-origin solid tumors, constituting only 1% of adult malignancies and classified into soft tissue and bone sarcomas. For localized diseases, surgery and radiotherapy remain the cornerstone treatments. However, systemic options for advanced stages are limited, with an overall survival of approximately 20 months. There is an urgent need to refine clinical trial designs and evaluate novel therapies to improve patient outcomes.

AREAS COVERED

This review summarizes recent advancements in sarcoma clinical trials, highlighting promising therapies that may reshape treatment paradigms. It also examines insights from comprehensive genomic profiling studies, which are paving the way for next-generation therapeutic approaches.

EXPERT OPINION

The heterogeneity and rarity of sarcomas present substantial challenges to the development and regulatory approval of effective therapies. Recent progress in the field has introduced innovative approaches, including novel chemotherapeutic agents, targeted therapies, and immunotherapeutics. However, despite these advancements, significant hurdles persist. While these strategies have demonstrated some success, the overall improvements in survival have often been modest, irrespective of the therapeutic modality. This underscores critical concerns regarding the true cost-benefit balance and the potential for adverse effects, particularly when evaluated over extended follow-up periods.

Gastrointestinal stromal tumor mimicking perineurioma: A case report

Although gastrointestinal stromal tumor (GIST) can present with various histological characteristics, GIST mimicking perineurioma has not been previously reported. We present the case of a 47-year-old woman diagnosed with GIST after laparoscopic resection of a stomach tumor near the lesser curvature of the gastric body close to the cardia. Morphological features resembled a perineurioma. c.1504_1509 (p.A502_Y503) duplication was found in exon 9 of kinase insert domain receptor (c-KIT). This specific mutation is associated with constitutive activation of the c-KIT, which is crucial in the pathogenesis of GIST. Such unique histological characteristics broaden our understanding of the morphological diversity within GISTs and underscore the importance of considering an extended differential diagnosis when encountering atypical gastrointestinal tumors. This rare presentation may challenge conventional diagnostic criteria and could influence therapeutic strategies, emphasizing the need for comprehensive histological and molecular assessments in patient management.

Levels of circulating tumor DNA correlate with tumor volume in gastro-intestinal stromal tumors: an exploratory long-term follow-up study

Patients with gastro-intestinal stromal tumors (GISTs) undergoing tyrosine kinase inhibitor therapy are monitored with regular computed tomography (CT) scans, exposing patients to cumulative radiation. This exploratory study aimed to evaluate circulating tumor DNA (ctDNA) testing to monitor treatment response and compare changes in ctDNA levels with RECIST 1.1 and total tumor volume measurements. Between 2014 and 2021, six patients with KIT proto-oncogene, receptor tyrosine kinase (KIT) exon-11-mutated GIST from whom long-term plasma samples were collected prospectively were included in the study. ctDNA levels of relevant plasma samples were determined using the KIT exon 11 digital droplet PCR drop-off assay. Tumor volume measurements were performed using a semi-automated approach. In total, 94 of 130 clinically relevant ctDNA samples were analyzed. Upon successful treatment response, ctDNA became undetectable in all patients. At progressive disease, ctDNA was detectable in five out of six patients. Higher levels of ctDNA correlated with larger tumor volumes. Undetectable ctDNA at the time of progressive disease on imaging was consistent with lower tumor volumes compared to those with detectable ctDNA. In summary, ctDNA levels seem to correlate with total tumor volume at the time of progressive disease. Our exploratory study shows promise for including ctDNA testing in treatment follow-up.

Monitoring Response Using Circulating Tumor DNA in Undifferentiated Pleomorphic Sarcoma: A Case Report

Circulating tumor DNA (ctDNA) can be used to assess treatment response in patients with undifferentiated pleomorphic sarcoma (UPS). The importance of this is explored in our case of a 75-year-old man who was diagnosed with UPS of the right kidney. After a right nephrectomy and tumor resection, the patient was recovering well with initially undetectable, and then slightly elevated, circulating tumor DNA. Abdominal pain started shortly before a scheduled magnetic resonance imaging (MRI) which revealed a large mass in the resection bed invading the liver. The patient was treated with gemcitabine and docetaxel chemotherapy, and the ctDNA level rose dramatically before gradually decreasing and eventually becoming undetectable. At surgery, pathologic examination of the re-resection specimen revealed a complete pathological response. ctDNA monitoring may be a useful tool for early detection of response to chemotherapy in patients with UPS.

CuET overcomes regorafenib resistance by inhibiting epithelial-mesenchymal transition through suppression of the ERK pathway in hepatocellular carcinoma

BACKGROUND AND PURPOSE

Regorafenib was approved by the US Food and Drug Administration (FDA) for hepatocellular carcinoma (HCC) patients showing progress on sorafenib treatment. However, there is an inevitably high rate of drug resistance associated with regorafenib, which reduces its effectiveness in clinical treatment. Thus, there is an urgent need to find a potential way to solve the problem of regorafenib resistance. The metabolite of disulfiram complexed with copper, the Diethyldithiocarbamate-copper complex (CuET), has been found to be an effective anticancer drug candidate. In the present study, we aimed to evaluate the effect of CuET on regorafenib resistance in HCC and uncover the associated mechanism.

EXPERIMENTAL APPROACH

Regorafenib-resistant HCC strains were constructed by applying an increasing concentration gradient. This study employed a comprehensive range of methodologies, including the cell counting kit-8 (CCK-8) assay, colony formation assay, cell cycle analysis, wound healing assay, Transwell assay, tumor xenograft model, and immunohistochemical analysis. These methods were utilized to investigate the antitumor activity of CuET, assess the combined effect of regorafenib and CuET, and elucidate the molecular mechanism underlying CuET-mediated regorafenib resistance.

KEY RESULTS

The inhibitory effect of regorafenib on cell survival, proliferation and migration was decreased in regorafenib-resistant MHCC-97H (MHCC-97H/REGO) cells compared with parental cells. CuET demonstrated significant inhibitory effects on cell survival, proliferation, and migration of various HCC cell lines. CuET restored the sensitivity of MHCC-97H/REGO HCC cells to regorafenib in vitro and in vivo. Mechanistically, CuET reverses regorafenib resistance in HCC by suppressing epithelial-mesenchymal transition (EMT) through inhibition of the ERK signaling pathway.

CONCLUSION AND IMPLICATIONS

Taken together, the results of this study demonstrated that CuET inhibited the activation of the ERK signaling pathway, leading to the suppression of the epithelial-mesenchymal transition (EMT) and subsequently reversing regorafenib resistance in HCC both in vivo and in vitro. This study provides a new idea and potential strategy to improve the treatment of regorafenib-resistant HCC.

Gastrointestinal Stromal Tumors (GISTs) in Pediatric Patients: A Case Report and Literature Review

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms that primarily affect adults, with pediatric cases constituting only 0.5-2.7% of the total. Pediatric GISTs present unique clinical, genetic, and pathological features that distinguish them from adult cases. This literature review aims to elucidate these differences, emphasizing diagnostic and therapeutic challenges. We discuss the resistance of pediatric GISTs to conventional chemotherapy and highlight the importance of surgical intervention, especially in emergency situations involving intra-abdominal bleeding. The review also explores the molecular characteristics of pediatric GISTs, including rare mutations such as quadruple-negative wild-type GIST with an FGF3 gene gain mutation. To illustrate these points, we conclude with a case from our clinic involving a 15-year-old female with multiple CD117-positive gastric GISTs and a quadruple-negative wild-type genetic profile who required urgent surgical intervention following a failed tumor embolization. This case underscores the critical need for early diagnosis and individualized therapeutic strategies combining oncologic and surgical care to improve outcomes in pediatric GIST patients.

The potential of lenvatinib in breast cancer therapy

Breast cancer, as a highly prevalent cancer among women, is one of the main causes of female mortality due to cancer. There is a need for more treatment options to improve the survival time of breast cancer patients. Metastasis to distant organs is a standard indicator of advanced breast cancer and a primary cause of breast cancer mortality, making the control of breast cancer metastasis crucial. Targeted therapy, with its advantages of precision, high effectiveness, and minimal side effects, has garnered significant attention as a hot research topic in breast cancer treatment. Among these therapies, anti-angiogenic therapy aim to inhibit tumor angiogenesis, control tumor growth, and reduce metastasis. Additionally, anti-angiogenic therapy can restructure the tumor vasculature, enhancing the effectiveness of other anti-cancer drugs. Lenvatinib, an orally available small molecule multi-targeted tyrosine kinase inhibitor, exerts its anti-tumor effects mainly by inhibiting tumor angiogenesis and tumor cell proliferation. It has been approved for the treatment of thyroid cancer, renal cell carcinoma, and hepatocellular carcinoma. Due to its multi-targeted nature, lenvatinib not only has direct anti-tumor effects but also possesses immunomodulatory activity, which can enhance the tumor immune response. This makes it a promising candidate for a broad range of cancers. Recent studies have explored the role of lenvatinib in breast cancer, including its various mechanisms of action and its use as a monotherapy or in combination to control breast cancer progression. This review will summarize the molecular mechanisms and research progress of lenvatinib in breast cancer treatment, discussing its potential applications and therapeutic prospects in managing breast cancer.

Different efficacy of tyrosine kinase inhibitors by KIT and PGFRA mutations identified in circulating tumor DNA for the treatment of refractory gastrointestinal stromal tumors

BACKGROUND

While advanced gastrointestinal stromal tumors (GISTs) are primarily treated with tyrosine kinase inhibitors (TKIs), acquired resistance from specific mutations in KIT or PDGFRA frequently occurs. We aimed to assess the utility of circulating tumor DNA (ctDNA) as a modality of therapeutic decision-making in advanced GIST.

METHODS

We conducted a pooled analysis of SCRUM-Japan studies for advanced GIST patients. We compared patient characteristics analyzed with tissue and blood samples, assessed gene alteration profiles, and evaluated prognostic implications from ctDNA status.

RESULTS

In 133 patients, tissue and blood samples were analyzed for 89 and 44 patients, respectively. ctDNA was detected in 72.7% of cases; no prior treatment or progressive disease was significantly associated with ctDNA-positivity. ctDNA-positive patients had significantly shorter progression-free survival compared with ctDNA-negative patients (hazard ratio = 3.92; P = 0.007). ctDNA genotyping revealed a complex landscape of gene alterations, characterized by multi-exonic mutations in KIT, compared with tissue-based analysis. Patients who received TKIs matched to the identified KIT mutation in ctDNA demonstrated significantly longer PFS than those with unmatched treatment (median, 8.23 vs. 2.43 months; P < 0.001).

CONCLUSIONS

ctDNA-based analysis facilitates assessment of disease status and genomic profiles, thus potentially assisting in identifying optimal therapeutic strategies for advanced GIST patients.

Monitoring advanced gastrointestinal stromal tumor with circulating tumor DNA

PURPOSE OF REVIEW

This review explores the role of circulating tumor (ct)DNA as a biomarker for clinical decision-making and monitoring purposes in metastatic gastrointestinal stromal tumor (GIST) patients. We discuss key insights from recent clinical trials and anticipate the future perspectives of ctDNA profiling within the clinical landscape of GIST.

RECENT FINDINGS

The identification and molecular characterization of KIT/platelet-derived growth factor receptor alpha (PDGFRA) mutations from ctDNA in metastatic GIST is feasible and reliable. Such identification through ctDNA serves as a predictor of clinical outcomes to tyrosine-kinase inhibitors (TKIs) in metastatic patients. Additionally, conjoined ctDNA analysis from clinical trials reveal the evolving mutational landscapes and increase in intratumoral heterogeneity across treatment lines. Together, this data positions ctDNA determination as a valuable tool for monitoring disease progression and guiding therapy in metastatic patients. These collective efforts culminated in the initiation of a ctDNA-based randomized clinical trial in GIST, marking a significant milestone in integrating ctDNA testing into the clinical care of GIST patients.

SUMMARY

The dynamic field of ctDNA technologies is rapidly evolving and holds significant promise for research. Several trials have successfully validated the clinical utility of ctDNA in metastatic GIST, laying the foundations for its prospective integration into the routine clinical management of GIST patients.

Opportunity in Complexity: Harnessing Molecular Biomarkers and Liquid Biopsies for Personalized Sarcoma Care

Due to their rarity and complexity, sarcomas represent a substantial therapeutic challenge. However, the incredible diversity within and across sarcoma subtypes presents an opportunity for personalized care to maximize efficacy and limit toxicity. A deeper understanding of the molecular alterations that drive sarcoma development and treatment response has paved the way for molecular biomarkers to shape sarcoma treatment. Genetic, transcriptomic, and protein biomarkers have become critical tools for diagnosis, prognostication, and treatment selection in patients with sarcomas. In the future, emerging biomarkers like circulating tumor DNA analysis offer the potential to improve early detection, monitoring response to treatment, and identifying mechanisms of resistance to personalize sarcoma treatment. Here, we review the current state of molecular biomarkers for sarcomas and highlight opportunities and challenges for the implementation of new technologies in the future.

Precision Oncology in Soft Tissue Sarcomas and Gastrointestinal Stromal Tumors

Soft tissue sarcomas (STSs), including gastrointestinal stromal tumors (GISTs), are mesenchymal neoplasms with heterogeneous clinical behavior and represent broad categories comprising multiple distinct biologic entities. Multidisciplinary management of these rare tumors is critical. To date, multiple studies have outlined the importance of biological characterization of mesenchymal tumors and have identified key molecular alterations which drive tumor biology. GIST has represented a flagship for targeted therapy in solid tumors with the advent of imatinib which has revolutionized the way we treat this malignancy. Herein, the authors discuss the importance of biological and molecular diagnostics in managing STS and GIST patients.

KIT-SNAP-tag/cell membrane chromatography model coupled with liquid chromatography-mass spectrometry for anti-GIST compound screening from Evodia rutaecarpa

Gastrointestinal mesenchymal tumors, as the most common mesenchymal tumors in the gastrointestinal tract, are adjuvantly treated with multi-targeted tyrosine kinase inhibitors, such as imatinib and sunitinib, but there are problems of drug resistance and complex methods of monitoring therapeutic agents. The pathogenesis of this disease is related to mutations in tyrosine kinase (KIT) or platelet-derived growth factor receptor α, an important target for drug therapy. In recent years, the screening of relevant tyrosine kinase inhibitors from traditional Chinese medicine has become a hotspot in antitumor drug research. In the current study, the KIT-SNAP-tag cell membrane chromatography (KIT-SNAP-tag/CMC) column was prepared with satisfying specificity, selectivity, and reproducibility by chemically bonding high KIT expression cell membranes to the silica gel surface using the SNAP-tag technology. The KIT-SNAP-tag/CMC-HPLC-MS two-dimensional coupling system was investigated using the positive drug imatinib, and the results showed that the system was a reliable model for screening potential antitumor compounds from complex systems. This system screened and identified three potential active compounds of evodiamine (EVO), rutaecarpin (RUT), and dehydroevodiamine (DEVO), which possibly target the KIT receptor, from the alcoholic extract of the traditional Chinese medicine Evodia rutaecarpa. Then, the KD values of the interaction of EVO, RUT, and DEVO with KIT receptors measured using nonlinear chromatography were 7.75 (±4.93) × 10-6, 1.42 (±0.71) × 10-6, and 2.34 (±1.86) × 10-6 mol/L, respectively. In addition, the methyl thiazolyl tetrazolium assay validated the active effects of EVO and RUT in inhibiting the proliferation of high KIT-expressing cells in the ranges of 0.1-10 µmol/L and 0.1-50 µmol/L, respectively. In conclusion, the KIT-SNAP-tag/CMC could be a reliable model for screening antitumor components from complex systems.

KIT/PDGFRA inhibitors for the treatment of gastrointestinal stromal tumors: getting to the gist of the problem

INTRODUCTION

Approximately 90% of gastrointestinal stromal tumors (GISTs) are driven by activating mutations in receptor tyrosine-kinases KIT or PDGFRA. Despite the outstanding results of first-line imatinib in advanced GIST, resistance ultimately occurs mainly through secondary mutations in KIT/PDGFRA. Other tyrosine-kinase inhibitors (TKIs) with a broader spectrum of activity against these mutations are approved after imatinib failure. However, response rates and progression-free survival are drastically lower compared to imatinib. Notably, imatinib also triggers early tolerance adaptation mechanisms, which precede the occurrence of secondary mutations.

AREAS COVERED

In this review, we outline the current landscape of KIT inhibitors, discuss the novel agents, and present additional biological pathways that may be therapeutically exploitable.

EXPERT OPINION

The development of broad-spectrum and highly selective TKIs able to induce a sustained KIT/PDGFRA inhibition is the pillar of preclinical and clinical investigation in GIST. However, it is now recognized that the situation is more intricate, with various factors interacting with KIT and PDGFRA, playing a crucial role in the response and resistance to treatments. Future strategies in the management of advanced GIST should integrate driver inhibition with the blockade of other molecules to enhance cell death and establish enduring responses in patients.

Clinical Benefit of Avapritinib in KIT-Mutant Gastrointestinal Stromal Tumors: A Post Hoc Analysis of the Phase I NAVIGATOR and Phase I/II CS3007-001 Studies

PURPOSE

The efficacy of the selective KIT/PDGFRA inhibitor avapritinib (300 mg once daily) was explored in patients with non-PDGFRA-mutant gastrointestinal stromal tumors (GISTs) from the phase I NAVIGATOR and phase I/II CS3007-001 trials.

PATIENTS AND METHODS

Adults with unresectable/metastatic, KIT-only-mutant GISTs and progression following ≥1 tyrosine kinase inhibitors (TKIs) were included in this post hoc analysis. Baseline mutational status was identified in tumor and plasma. Primary endpoints were objective response rate (ORR) and progression-free survival (PFS) by blinded independent radiology review per modified RECIST v1.1 in patients harboring KIT activation-loop mutations (KIT exons 17 or 18) without ATP binding-pocket mutations (KIT exons 13 or 14; ALposABPneg), and other KIT mutations (OTHERS).

RESULTS

Sixty KIT ALposABPneg and 100 KIT OTHERS predominantly heavily pretreated patients (61.3% with ≥3 prior TKIs) were included. ORR was significantly higher in KIT ALposABPneg than KIT OTHERS patients (unadjusted: 26.7% vs. 12.0%; P = 0.0852; adjusted: 31.4% vs. 12.1%; P = 0.0047). Median PFS (mPFS) was significantly longer in KIT ALposABPneg patients compared with KIT OTHERS patients (unadjusted: 9.1 vs. 3.5 months; P = 0.0002; adjusted: 9.1 vs. 3.4 months; P < 0.0001), and longer in second- versus later-line settings (19.3 vs. 5.6-10.6 months). Benefit with avapritinib was observed in patients with KIT exon 9 mutations in the ≥4 line settings (mPFS: 5.6 and 3.7 months for 4 line and >4 line, respectively).

CONCLUSIONS

Avapritinib showed greater antitumor activity in patients with GISTs harboring KIT ALposABPneg mutations versus KIT OTHERS, and may be considered in the former subpopulation. Patients with KIT exon 9 mutations may also benefit in ≥4 line settings.

Sarcoma care in the era of precision medicine

Sarcoma subtype classification is currently mainly based upon histopathological morphology. Molecular analyses have emerged as an efficient addition to the diagnostic workup and sarcoma care. Knowledge about the sarcoma genome increases, and genetic events that can either support a histopathological diagnosis or suggest a differential diagnosis are identified, as well as novel therapeutic targets. In this review, we present diagnostic, therapeutic, and prognostic molecular markers that are, or might soon be, used clinically. For sarcoma diagnostics, there are specific fusions highly supportive or pathognomonic for a diagnostic entity-for instance, SYT::SSX in synovial sarcoma. Complex karyotypes also give diagnostic information-for example, supporting dedifferentiation rather than low-grade central osteosarcoma or well-differentiated liposarcoma when detected in combination with MDM2/CDK4 amplification. Molecular treatment predictive sarcoma markers are available for gastrointestinal stromal tumor (GIST) and locally aggressive benign mesenchymal tumors. The molecular prognostic markers for sarcomas in clinical practice are few. For solitary fibrous tumor, the type of NAB2::STAT6 fusion is associated with the outcome, and the KIT/PDGFRA pathogenic variant in GISTs can give prognostic information. With the exploding availability of sequencing technologies, it becomes increasingly important to understand the strengths and limitations of those methods and their context in sarcoma diagnostics. It is reasonable to believe that most sarcoma treatment centers will increase the use of massive-parallel sequencing soon. We conclude that the context in which the genetic findings are interpreted is of importance, and the interpretation of genomic findings requires considering tumor histomorphology.

Evaluation of Systemic Treatment Options for Gastrointestinal Stromal Tumours

Gastrointestinal stromal tumours (GIST) are the most common mesenchymal tumours of the gastrointestinal tract. Surgical treatment is recommended for the majority of localised GIST, while systemic treatment is the cornerstone of management for metastatic or unresectable disease. While a three-year regimen of imatinib is the standard of care in the adjuvant setting, there is no precise recommendation for the duration of neoadjuvant treatment, where imatinib is usually given between 4 and 12 months. Continuous treatment with imatinib at a dose of 400 mg once per day is recommended for most patients with unresectable or metastatic GIST in the first line. An exception is represented by patients with tumours harbouring the imatinib-insensitive PDGFRA D842V mutation who would be better treated with avapritinib. Targeted therapies are also recommended in the presence of NTRK rearrangements and BRAF mutations, although limited data are available. While an increase in the dose of imatinib to 800 mg is an option for the second line, sunitinib is usually considered the standard of care. Similar outcomes were reported for ripretinib in patients with tumours harbouring KIT exon 11 mutation, with significantly fewer side effects. Regorafenib and ripretinib are the standards of care in the third and fourth lines, respectively. The recent development of various systemic treatment options allows for a more personalised approach based on the molecular profile of the GIST, patient characteristics, and the profile of medications' adverse events. A multidisciplinary approach is paramount since combining systemic treatment with locoregional treatment options and supportive care is vital for long-term survival.

Familial Gastrointestinal Stromal Tumor Associated with Zebra-like Pigmentation

Purpose: According to clinical studies, gastrointestinal stromal tumors (GISTs) are predominantly sporadic. GISTs associated with familial syndromes are very rare, and most patients exhibit wild-type KIT and platelet-derived growth factor alpha (PDGFRA). To date, GISTs associated with germline KIT pathogenic variants have been observed in only 30 kindreds worldwide. The efficacy of imatinib, a multityrosine kinase inhibitor, in patients with GIST presenting germline KIT variants has been poorly reported, and the efficacy in clinical trials of treatments with tyrosine kinase inhibitors remains unclear. Therefore, imatinib is not yet recommended for treating GIST patients with germline KIT variants. Experimental Design: We performed cancer genomic testing on samples from a 32-year-old male patient with advanced GISTs throughout the upper stomach and cutaneous hyperpigmentation to determine diagnosis and treatment strategies. Results: We detected a germline W557R pathogenic variant of KIT. The patient was diagnosed with familial multinodular GIST based on the clinical findings and familial history of malignant tumors. Treatment with imatinib resulted in long-term regression of GISTs. Conclusions: Pathogenic variants detected by cancer genome testing can be used to diagnose malignant tumors and select new therapeutic agents for patients with advanced malignancies.