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.

Correlation Between N-Demethyl Imatinib Trough Concentration and Serious Adverse Reactions in Patients with Gastrointestinal Stromal Tumors: A Retrospective Cohort Study.

BACKGROUND: Imatinib is the first-line treatment for gastrointestinal stromal tumors; however, the clinical prognosis and adverse reactions of patients vary owing to individualized discrepancies in plasma exposure. METHODS: To determine the safe interval for steady-state plasma trough concentrations (C min ) of imatinib and its active metabolite, N-demethyl imatinib (NDI), 328 plasma samples from 273 patients treated with imatinib were retrospectively analyzed. Imatinib C min and NDI C min were tested, and adverse reactions were recorded. The association between imatinib C min , NDI C min , and serious adverse reactions was evaluated. RESULTS: The C min range of imatinib was 209.5-4950.0 ng/mL, with the mean value and SD of 1491.8 ± 731.4 ng/mL. The C min range of NDI was 80.0-2390.0 ng/mL with the mean value and SD of 610.8 ± 281.5 ng/mL. NDI C min was positively correlated with imatinib C min , whereas the ratio of NDI C min to imatinib C min (NDI C min /imatinib C min ) was negatively correlated with imatinib C min . Univariate logistic regression analysis demonstrated that the treatment objective, daily dose, imatinib C min , NDI C min , and imatinib C min + NDI C min were significantly associated with serious adverse reactions. Multivariate logistic regression analysis showed that NDI C min was an independent risk factor for serious adverse reactions, with a threshold of 665 ng/mL. CONCLUSIONS: NDI C min was an independent risk factor for serious adverse reactions, with a threshold of 665 ng/mL. Monitoring NDI C min was beneficial for the rational application of imatinib and individualized treatment of patients with gastrointestinal stromal tumors.

Ki-67 labelling index is related to the risk classification and prognosis of gastrointestinal stromal tumours: a retrospective study.

BACKGROUND AND AIMS: Gastrointestinal stromal tumours (GISTs) are the most common mesenchymal tumours of the digestive tract with malignant potential. The current risk classification standard is unable to accurately evaluate the invasiveness and clinical outcomes of GISTs. Ki-67 labelling index (LI) may be an effective indicator in assessing tumour invasiveness and prognosis, however, its exact value in GISTs is still uncertain. The aims of our study were to evaluate the correlation of the Ki-67 LI and clinicopathological features of GISTs and to assess the potential value of the Ki-67 LI in GISTs classification and prognosis. METHODS: The clinical, pathological and prognostic data were collected and analysed to identify the independent influential factors of GISTs risk stratification and the predictors of GISTs prognosis. RESULTS: The Ki-67 LI was significantly associated with the clinicopathological features of tumour progression (P<0.05). It was an independent influential factor of GISTs risk classification (odds ratio: 1.322; 95% confidence interval: 1.031-1.696) (P=0.028), and the area under the curve (AUC) value of the Ki-67 LI on the discrimination ability of GISTs risk stratification was 0.906 (P<0.001). The optimal cutoff value of the Ki-67 LI was 6% (sensitivity of 87.5% and specificity of 76.2%), and patients with Ki-67 LI≥6% exhibited significantly poorer progression-free survival (PFS) than those with Ki-67 LI<6% (P<0.001). The AUC value of the Ki-67 LI for predicting PFS in postoperative patients was 0.813 (P=0.03). CONCLUSIONS: The Ki-67 LI has appreciated value to predict the risk grade and prognosis of GISTs. Patients with Ki-67 LI≥6% are prone to recurrence and metastasis after operation and may need a close follow-up.

Impact of L-carnitine on imatinib-related muscle cramps in patients with gastrointestinal stromal tumor.

Introduction Muscle cramps constitute one of the leading adverse events of imatinib, the standard first-line treatment for advanced gastrointestinal stromal tumor (GIST). This study aims to assess the impact of L-carnitine on relieving cramps in patients with GIST taking imatinib. Materials and methods We reviewed our prospective database for patients with GIST who took L-carnitine (500-mg tablet, 2-3 times daily) for muscle cramps in Asan Medical Center. The assessment tool included severity by the numeric rating scale (NRS), frequency, duration of cramps, and questionnaire for the disturbance in basic activities of daily living (ADL), instrumental ADL (iADL), outdoor activity, or sleeping before and after L-carnitine treatment. Results We examined 42 patients [median age: 60 (range: 17-81) years; males, 52.4%] who received L-carnitine for cramps on NRS ≥ 4 intensity during 2016-2017. In 83.3% of patients (n = 35), the NRS score declined to <4 points, with 8 patients (19.0%) experiencing complete disappearance of symptoms [median response time: 10 (range: 2-30) days]. Moreover, the median duration of each episode and frequency decreased from 5 to 2 min and from 30 to 3 times per month (P < 0.001), respectively. We observed substantial improvement in all quality-of-life aspects after L-carnitine (ADL, 73.2%-14.6%; iADL, 73.2%-17.1%; sleeping, 78.0%-22.0%; outdoor activity, 68.3%-17.1%; P < 0.001). ConclusionL-carnitine could effectively relieve imatinib-related muscle cramps in patients with GIST. Accordingly, a randomized phase 3 study is currently ongoing (NCT03426722).

Clinical value of next generation sequencing of plasma cell-free DNA in gastrointestinal stromal tumors.

BACKGROUND: Gastrointestinal stromal tumor (GIST) initiation and evolution is commonly framed by KIT/PDGFRA oncogenic activation, and in later stages by the polyclonal expansion of resistant subpopulations harboring KIT secondary mutations after the onset of imatinib resistance. Thus, circulating tumor (ct)DNA determination is expected to be an informative non-invasive dynamic biomarker in GIST patients. METHODS: We performed amplicon-based next-generation sequencing (NGS) across 60 clinically relevant genes in 37 plasma samples from 18 GIST patients collected prospectively. ctDNA alterations were compared with NGS of matched tumor tissue samples (obtained either simultaneously or at the time of diagnosis) and cross-validated with droplet digital PCR (ddPCR). RESULTS: We were able to identify cfDNA mutations in five out of 18 patients had detectable in at least one timepoint. Overall, NGS sensitivity for detection of cell-free (cf)DNA mutations in plasma was 28.6%, showing high concordance with ddPCR confirmation. We found that GIST had relatively low ctDNA shedding, and mutations were at low allele frequencies. ctDNA was detected only in GIST patients with advanced disease after imatinib failure, predicting tumor dynamics in serial monitoring. KIT secondary mutations were the only mechanism of resistance found across 10 imatinib-resistant GIST patients progressing to sunitinib or regorafenib. CONCLUSIONS: ctDNA evaluation with amplicon-based NGS detects KIT primary and secondary mutations in metastatic GIST patients, particularly after imatinib progression. GIST exhibits low ctDNA shedding, but ctDNA monitoring, when positive, reflects tumor dynamics.

Elevated preoperative platelet-to-lymphocyte ratio predicts poor prognosis of patients with primary gastrointestinal stromal tumor.

BACKGROUND: The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are considered to reflect the systemic inflammatory response and clinical prognosis. However, the independent prognostic values of the NLR and PLR for patients with gastrointestinal stromal tumor (GIST) remain debatable. This study aims to evaluate the prognostic value of preoperative NLR and PLR in GIST patients. METHODS: We retrospectively reviewed all GIST patients diagnosed and surgically treated at Union Hospital between 2005 and 2018. The preoperative NLR and PLR were calculated to evaluate recurrence-free survival (RFS) and overall survival (OS) by Kaplan-Meier analysis. Univariate and multivariate Cox regression analyses were performed to estimate the independent prognostic values. RESULTS: The median follow-up time was 49 months (interquartile range, 22-74 months). The preoperative PLR was significantly increased in the GIST patients with intermediate and high tumor risks. Increases in the NLR (≥2.34) and PLR (≥185.04) were associated with shorter RFS and OS (P < 0.01). Moreover, the multivariate analysis revealed that elevated PLR was an independent factor for shorter RFS (hazard ratio [HR]: 3.041; 95% confidence interval [CI]: 2.001-4.622; P < 0.001) and OS (HR: 1.899; 95% CI: 1.136-3.173; P = 0.014). CONCLUSIONS: The preoperative PLR is a potential biomarker of GIST and is related to the clinical outcome. An elevated preoperative PLR predicts poor prognosis of patients with primary GIST after complete surgical resection.

Determination of the absolute bioavailability of oral imatinib using a stable isotopically labeled intravenous imatinib-d8 microdose.

PURPOSE: The aim of this study was to ascertain whether the absolute bioavailability of oral imatinib (Glivec®) during steady state plasma pharmacokinetics in cancer patients could be determined through a concomitant intravenous administration of a single 100 µg microdose of deuterium labeled imatinib (imatinib-d8). Secondly, the usefulness of liquid chromatography-tandem mass spectrometry (LC-MS/MS) was investigated for simultaneous analysis of orally and intravenously administered imatinib. METHODS: Included patients were on a stable daily dose of 400 mg oral imatinib prior to study participation. On day 1, patients received a 100 µg intravenous imatinib-d8 microdose 2.5 h after intake of the oral dose. Plasma samples were collected for 48 h. Imatinib and imatinib-d8 concentrations were simultaneously quantified using a validated LC-MS/MS assay. The absolute bioavailability was calculated by comparing the dose-normalized exposure with unlabeled and stable isotopically labeled imatinib in plasma. RESULTS: A total of six patients were enrolled. All patients had a history of gastrointestinal stromal tumors (GIST). The median absolute bioavailability of oral imatinib at steady state was 76% (range 44-106%). Imatinib and imatinib-d8 plasma concentrations were quantified in all collected plasma samples, with no samples below the limit of quantification for imatinib-d8. CONCLUSION: The absolute bioavailability of imatinib was successfully estimated at steady state plasma pharmacokinetics using the stable isotopically labeled microdose trial design. This study exhibits the use of a stable isotopically labeled intravenous microdose to determine the absolute bioavailability of an oral anticancer agent in patients with LC-MS/MS as the analytical tool.

Insights into the Proteome of Gastrointestinal Stromal Tumors-Derived Exosomes Reveals New Potential Diagnostic Biomarkers.

Developing tumors continuously release nano-sized vesicles that represent circulating "fingerprints" of the tumor's identity. In gastrointestinal stromal tumor (GIST), we have previously reported that these tumors release "oncosomes" carrying the constitutively activated tyrosine kinase (TK) receptor KIT. Despite the clinical utility of TK inhibitors, such as imatinib mesylate (IM), recurrence and metastasis are clinical problems that urge the need to identify new tumor-derived molecules. To this aim, we performed the first high quality proteomic study of GIST-derived exosomes (GDEs) and identified 1,060 proteins composing the core GDE proteome (cGDEp). The cGDEp was enriched in diagnostic markers (e.g. KIT, CD34, ANO1, PROM1, PRKCQ, and ENG), as well as proteins encoded by genes previously reported expressed in GIST (e.g. DPP4, FHL1, CDH11, and KCTD12). Many of these proteins were validated using cell lines, patient-derived KIT+ exosomes, and GIST tissues. We further show that in vitro and in vivo-derived GDE, carry proteins associated with IM response, such as Sprouty homolog 4 (SPRY4), surfeit 4 (SURF4), ALIX, and the cGMP-dependent 3',5'-cyclic phosphodiesterase 2A (PDE2A). Additionally, we report that the total exosome levels and exosome-associated KIT and SPRY4 protein levels have therapeutic values. In fact, molecular characterization of in vivo-derived KIT+ exosomes indicate significant sorting of p-KITTyr719, total KIT, and SPRY4 after IM-treatment of metastatic patients as compared with the pre-IM levels. Our data suggest that analysis of circulating exosomes levels and molecular markers of IM response in GIST patients with primary and metastatic disease is suitable to develop liquid based biopsies for the diagnosis, prognosis, and monitoring of response to treatment of these tumors. In summary, these findings provide the first insight into the proteome of GIST-derived oncosomes and offers a unique opportunity to further understand their oncogenic elements which contribute to tumorigenesis and drug resistance. Data are available via ProteomeXchange with identifier PXD007997.

Prognostic significance of preoperative plasma fibrinogen levels in primary gastrointestinal stromal tumours: a retrospective cohort study.

BACKGROUND: Improved prediction of prognosis for gastrointestinal stromal tumours (GISTs) has become increasingly important since the introduction of targeted therapy. Here, we aimed to evaluate the prognostic significance of preoperative plasma fibrinogen (Fib) levels in patients with primary GISTs and to analyse their correlations with clinicopathological characteristics. METHODS: A total of 201 previously untreated patients with primary GISTs who had undergone radical surgery at our institution between October 2004 and July 2018 were enrolled. The optimal cut-off value for Fib levels was calculated using time-dependent receiver-operating characteristic curve analysis. RFS, the primary endpoint, was calculated by the Kaplan-Meier method and compared by the log-rank test. Univariate and multivariate Cox regression models were calculated. RESULTS: High preoperative plasma Fib levels were detected as an independent adverse prognostic factor (p = 0.008, hazard ratio 3.136, 95% CI 1.356‒7.256). Furthermore, high preoperative plasma Fib levels also indicated a poor prognosis within the modified National Institutes of Health (mNIH) high-risk subgroup (p = 0.041). In addition, preoperative plasma Fib levels showed a positive correlation with several prognostic factors and even a linear relationship with tumour size (Spearman correlation coefficient [r] = 0.411, p < 0.001). CONCLUSIONS: Our results suggest that high preoperative plasma Fib levels may indicate a poor prognosis in patients with primary GISTs. As a cost-effective biomarker, preoperative assessment of plasma Fib levels may help to further risk stratify patients with mNIH high-risk GISTs and instruct the application of targeted therapy.

Diagnosis and Treatment Monitoring of a Patient with Gastrointestinal Stromal Tumor by Next-Generation Sequencing and Droplet Digital Polymerase Chain Reaction Assay of a PDGFRA Mutation in Plasma-Derived Cell-Free Tumor DNA.

In patients with a suspected malignancy, standard-of care management currently includes histopathologic examination and analysis of tumor-specific molecular abnormalities. Herein, we present a 77-year-old patient with an abdominal mass suspected to be a gastrointestinal stromal tumor (GIST) but without the possibility to collect a tumor biopsy. Cell-free DNA extracted from a blood sample was analyzed for the presence of mutations in GIST-specific genes using next generation sequencing. Furthermore, liquid biopsies were used to monitor the levels of mutant DNA copies during treatment with a tumor-specific mutation droplet digital PCR assay that correlated with the clinical and radiological response. Blood-based testing is a good alternative for biopsy-based testing. However, it should only be applied when biopsies are not available or possible to obtain because overall, in only 50%-85% of the cell-free plasma samples is the known tumor mutation detected.

Optimizing the dose in patients treated with imatinib as first line treatment for gastrointestinal stromal tumours: A cost-effectiveness study.

AIMS: Patients with metastatic gastrointestinal stromal tumours (GIST) are treated in first line with the oral tyrosine kinase inhibitor, imatinib, until progressive disease. With this fixed dosing regimen, only approximately 40% of patients reach adequate plasma levels within the therapeutic index. Therapeutic drug monitoring (TDM) is a solution to reach plasma levels within the therapeutic index. However, introducing TDM will also increase costs, due to prolonged imatinib use and laboratory costs. The aim of this study was to evaluate the cost-effectiveness of TDM in patients with metastatic/unresectable GIST treated with imatinib as a first line treatment, compared with fixed dosing. METHODS: A survival model was created to simulate progression, mortality and treatment costs over a 5-year time horizon, comparing fixed dosing vs TDM-guided dosing. The outcomes measured were treatments costs, life-years and quality-adjusted life-years. RESULTS: Total costs over the 5-year time horizon were estimated to be €106 994.85 and €150 477.08 for fixed dosing vs TDM-guided dosing, respectively. A quality-adjusted life year gain of 0.74 (95% confidence interval 0.66-0.90) was estimated with TDM-guided dosing compared to fixed dosing. An average incremental cost-effectiveness ratio of €58 785.70 per quality-adjusted life year gained was found, mainly caused by longer use and higher dosages of imatinib. CONCLUSION: Based on the currently available data, this analysis suggests that TDM-guided dosing may be a cost-effective intervention for patients with metastatic/unresectable GIST treated with imatinib which will be improved when imatinib losses its patency.

Effect of imatinib on plasma glucose concentration in subjects with chronic myeloid leukemia and gastrointestinal stromal tumor.

BACKGROUND: Type 2 diabetes mellitus has become one of the most important public health concerns worldwide. Due to its high prevalence and morbidity, there is an avid necessity to find new therapies that slow the progression and promote the regression of the disease. Imatinib mesylate is a tyrosine kinase inhibitor that binds to the Abelson tyrosine kinase and related proteins. It enhances ß-cell survival in response to toxins and pro-inflammatory cytokine. The aim of this study is to evaluate the effect of imatinib on fasting plasma glucose in subjects with normal fasting glucose, subjects with impaired fasting glucose and in subjects with type 2 diabetes mellitus. METHODS: We identified 284 subjects diagnosed with chronic myeloid leukemia or gastrointestinal stromal tumors from the Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran database. 106/284 subjects were treated with imatinib. We compared the effect of imatinib on fasting plasma glucose after 1 and 6 months of treatment. We used ANOVA test of repeated samples to determine statistical significance in fasting plasma glucose before imatinib treatment and the follow-up. Statistical analysis was performed with Statistical Package for the Social Sciences v22. RESULTS: We included a total of 106 subjects: 76 with fasting plasma glucose concentrations < 100 mg/dL (normal FG), 19 subjects with fasting plasma glucose concentrations ≥100 mg/dL (impaired fasting glucose), and 11 subjects with ≥126 mg/dL (type 2 diabetes mellitus). We found a significant increase in fasting plasma glucose concentration in the normal fasting glucose group (p = 0.048), and a significant decrease in fasting plasma glucose concentration in the type 2 diabetes mellitus group (p = 0.042). In the impaired fasting glucose group, we also found a tendency towards a decrease in fasting plasma glucose (p = 0.076). We identified 11 subjects with type 2 diabetes mellitus, of whom, 7 (64%) had a reduction in their fasting plasma glucose concentrations after 6 months. A significant glycosylated hemoglobin reduction (p = 0.04) was observed. CONCLUSION: Subjects with chronic myeloid leukemia or gastrointestinal stromal tumor with type 2 diabetes mellitus had a significant reduction in fasting plasma glucose and glycosylated hemoglobin at 1 and 6 months while using imatinib.

Long-Term Imatinib Treatment for Patients with Unresectable or Recurrent Gastrointestinal Stromal Tumors.

BACKGROUND: Only limited data are available concerning the long-term outcomes of imatinib treatment among Japanese or Asian patients with advanced or recurrent gastrointestinal stromal tumors (GIST). Our multicenter study, which was conducted in northern Kanto, Japan, aimed to assess the efficacy of imatinib mesylate against advanced or recurrent GIST. SUMMARY: The clinicopathological data of 234 GIST patients who were treated at one of the 11 participating hospitals from 2001 to 2011 were retrospectively reviewed (GREAT study). Imatinib was administered as a first-line therapy in cases involving unresectable disease or postoperative recurrence (41 cases). The patients treated with imatinib (n = 41) exhibited 1-, 3-, and 5-year overall survival (OS) rates of 92.3, 74.9, and 53.8% respectively. In univariate and multivariate analyses, imatinib continuation with dose reduction and achieving a complete or partial response were found to be associated with increased OS. The results of 2 large-scale, long-term trials demonstrate that the risk of tumor progression decreases with increased treatment duration. Furthermore, the interruption of imatinib treatment in responsive and controlled patients results in a high risk of disease progression. Key Messages: Long-term imatinib treatment is recommended for patients with nonprogressive disease. If patients experience significant toxicities, temporary dose reduction and treatment continuation might be useful.

Effect of Gastrointestinal Bleeding on Gastrointestinal Stromal Tumor Patients: A Retrospective Cohort Study.

BACKGROUND The contemporary risk classification criteria of gastrointestinal stromal tumors (GISTs) may still have room to improve. The aim of our research was to analyze the impact factors for GIST patients' relapse-free survival (RFS). Furthermore, we explore whether gastrointestinal (1) bleeding will be a valuable indicator to predict GIST patients' prognosis. MATERIAL AND METHODS R0 resection GISTs patients were retrospectively enrolled during an 8-year period at West China Hospital of Sichuan University, and all patients' data were from the WCHSU-GIST database. Of a total of 333 GIST patients, 164 patients had GI bleeding. Univariate analysis and Cox regression analysis were used to calculate the survival and recurrence rates. RESULTS Compared with non-GI-bleeding patients, GI-bleeding patients had a shorter relapse-free survival (RFS, P=0.003), but among the different risk groups, GI bleeding only affected the RFS rate of the high-risk group. A Cox regression analysis illustrated that tumor site (P<0.001), tumor size (P=0.009), mitotic index (P<0.001), tumor rupture (P<0.001), and GI-bleeding (P=0.01) were independent indicators for GIST patients' RFS. CONCLUSIONS Our study demonstrates that the RFS of GIST patients with GI bleeding was significantly shorter than that of non-GI-bleeding patients, and GI bleeding was an independent negative factor predicting RFS, while GI bleeding had more influence among high-risk patients.

Development of a gene panel for next-generation sequencing of clinically relevant mutations in cell-free DNA from cancer patients.

BACKGROUND: When tumour tissue is unavailable, cell-free DNA (cfDNA)can serve as a surrogate for genetic analyses. Because mutated alleles in cfDNA are usually below 1%, next-generation sequencing (NGS)must be narrowed to target only clinically relevant genes. In this proof-of-concept study, we developed a panel to use in ultra-deep sequencing to identify such mutations in cfDNA. METHODS: Our panel ('SiRe') covers 568 mutations in six genes (EGFR, KRAS, NRAS, BRAF, cKIT and PDGFRα)involved in non-small-cell lung cancer (NSCLC), gastrointestinal stromal tumour, colorectal carcinoma and melanoma. We evaluated the panel performance in three steps. First, we analysed its analytical sensitivity on cell line DNA and by using an artificial reference standard with multiple mutations in different genes. Second, we analysed cfDNA from cancer patients at presentation (n=42), treatment response (n=12) and tumour progression (n=11); all patients had paired tumour tissue and cfDNA previously genotyped with a Taqman-derived assay (TDA). Third, we tested blood samples prospectively collected from NSCLC patients (n=79) to assess the performance of SiRe in clinical practice. RESULTS: SiRe had a high analytical performance and a 0.01% lower limit of detection. In the retrospective series, SiRe detected 40 EGFR, 11 KRAS, 1 NRAS and 5 BRAF mutations (96.8% concordance with TDA). In the baseline samples, SiRe had 100% specificity and 79% sensitivity relative to tumour tissue. Finally, in the prospective series, SiRe detected 8.7% (4/46) of EGFR mutations at baseline and 42.9% (9/21) of EGFR p.T790M in patients at tumour progression. CONCLUSIONS: SiRe is a feasible NGS panel for cfDNA analysis in clinical practice.

Incorporation of NLR into NIH stratification system increases predictive accuracy for surgically resected gastrointestinal stromal tumors.

Previous studies have reported that preoperative neutrophil-to-lymphocyte (NLR) and platelet-to-lymphocyte ratios were prognostic for various types of cancers. The aim of this study was to investigate the predictive utilities of preoperative peripheral blood counts in patients with gastrointestinal stromal tumors (GISTs). We enrolled 510 consecutive, previously untreated patients who underwent surgery for primary, localized GISTs. The relationship between recurrence-free survival and outcome variables was assessed by univariate and multivariate analyses, while the clinicopathologic relevance of NLR was determined using the Chi-square test. A preoperative NLR ≥2 was associated with poor prognosis in patients undergoing surgeries for primary, localized GISTs. It was an independent predictor only in patients classified as National Institutes of Health high risk but not in the entire population. Preoperative NLR is a feasible and reproducible peripheral biomarker that helps identify patients for intensive adjuvant therapy and frequent surveillance.

Detecting Secondary C-KIT Mutations in the Peripheral Blood of Patients with Imatinib-Resistant Gastrointestinal Stromal Tumor.

OBJECTIVE: Imatinib is a standard treatment for metastatic gastrointestinal stromal tumor (GIST). Imatinib resistance is mostly caused by secondary mutations in C-KIT. The antitumor effect of second-line agents is correlated with the type of secondary mutation: indeed, sunitinib is effective against tumors with C-KIT exon 13 or 14 mutations. We investigated whether secondary C-KIT mutations can be detected in circulating tumor DNA (ctDNA) from peripheral blood. METHODS: This study included 4 patients who underwent resection of imatinib-resistant GIST. Tumor-specific mutations in each tumor were determined by Sanger sequencing. ctDNA was extracted from peripheral blood obtained before and after the treatment of imatinib-resistant lesions. Each of the secondary target mutations in ctDNA was investigated, using a next-generation sequencer. RESULTS: Imatinib-resistant lesions had single-nucleotide substitutions in C-KIT exon 13 in 3 patients and exon 18 in 1 patient. Identical secondary C-KIT mutations could be detected in ctDNA with a mutant fraction range of 0.010-9.385%. One patient had growth of an imatinib-resistant tumor containing a C-KIT exon 13 mutation, and the fraction of ctDNA decreased after initiation of sunitinib. CONCLUSION: Detection of secondary C-KIT mutations in ctDNA could be useful for the selection of targeted agents and prediction of antitumor effects.

Detection and Quantification of KIT Mutations in ctDNA by Plasma Safe-SeqS.

We have designed a highly sensitive assay based on the Safe-SeqS technology to detect de novo mutations in the KIT gene and tested its performance. This assay was applied to plasma samples of GIST patients before and after treatment with regorafenib (GRID III trial) and mutations at known and novel sites of potential secondary resistance were identified.

Hypercalcemia in metastatic GIST caused by systemic elevated calcitriol: a case report and review of the literature.

BACKGROUND: Hypercalcemia is the most common oncologic metabolic emergency but very rarely observed in patients with gastrointestinal stromal tumour, which is a rare mesenchymal malignancy of the gastrointestinal tract. We describe a case of hypercalcemia caused by elevated levels of activated vitamin D in a patient with gastrointestinal tumour. Prior to this case report, only one paper has reported an association between hypercalcemia, gastrointestinal stromal tumours and elevated levels of vitamin D. CASE PRESENTATION: An otherwise healthy 70-year-old Caucasian woman, previously treated for duodenal gastrointestinal stromal tumour, was diagnosed with liver metastasis, and relapse of gastrointestinal stromal tumour was confirmed by biopsy. At presentation, the patient suffered from severe symptoms of hypercalcemia. The most common causes of hypercalcemia, hyperparathyrodism, parathyroid hormone-related peptide secretion from tumour cells, and metastatic bone disease, were all dismissed as the etiology. Analysis of vitamin D subtypes revealed normal levels of both 25-OH Vitamin D2 and 25-OH Vitamin D3, whereas the level of activated vitamin D, 1,25 OH Vitamin D3, also referred to as calcitriol, was elevated. CONCLUSION: The fact that plasma calcitriol decreased after initiation of oncological treatment and the finding that hypercalcemia did not recur during treatment support the conclusion that elevated calcitriol was a consequence of the gastrointestinal stromal tumour. We suggest that gastrointestinal stromal tumours should be added to the list of causes of humoral hypercalcemia in malignancy, and propose that gastrointestinal stromal tumour tissue may have high activity of the specific enzyme 1α-hydroxylase, which can lead to increased levels of calcitriol and secondarily hypercalcemia.

Analysis of serum protein biomarkers, circulating tumor DNA, and dovitinib activity in patients with tyrosine kinase inhibitor-refractory gastrointestinal stromal tumors.

BACKGROUND: An exploratory translational analysis was conducted as part of a phase II study of dovitinib to assess the relevance of soluble serum proteins and circulating tumor (ct) DNA (ctDNA) as biomarkers in patients with tyrosine kinase inhibitor (TKI)-refractory gastrointestinal stromal tumors (GISTs). PATIENTS AND METHODS: Predose serum samples were collected from 30 patients on day 1 of cycle 1 and cycle 2. Serum levels of angiogenesis-related proteins were assessed by enzyme-linked immunosorbent assay, and Beads, emulsions, amplification, and magnetics (BEAMing) assays were carried out to detect mutations in serum ctDNA. RESULTS: Dovitinib increased vascular endothelial growth factor (VEGF)165 (1.26-fold, P = 0.006), VEGF-A (1.27-fold, P = 0.004), placental growth factor (6.0-fold, P = 0.002), fibroblast growth factor 23 (1.45-fold, P = 0.02), and interleukin 8 (1.75-fold, P = 0.04) levels, and decreased soluble vascular endothelial growth factor receptor (sVEGFR)-2 levels (0.8-fold, P = 0.001). The changes in sVEGFR-2 were significantly associated with metabolic response determined by positron emission tomography (P = 0.02) and progression-free survival (PFS; P = 0.02). Secondary kinase mutations were identified in the ctDNA of 11 patients (41%), and these patients all had mutations involving KIT exon 17. Patients with secondary KIT mutations had significantly worse overall survival {median, 5.5 months [95% confidence interval (CI) 3.8-7.2 months]} than those with no detectable secondary mutations [9.8 months (95% CI 9.6-10.0 months); hazard ratio = 2.7 (95% CI 1.0-7.3); P = 0.047]. CONCLUSIONS: Changes in sVEGFR-2 levels were associated with dovitinib-mediated antitumor activity. Genotyping of serum ctDNA with BEAMing is useful for the identification of resistant mutations potentially associated with poor prognosis in patients with GISTs.