Dose escalation of imatinib after failure of standard dose in Korean patients with metastatic or unresectable gastrointestinal stromal tumor

Health-Related Quality of Life and Side Effects in Gastrointestinal Stromal Tumor (GIST) Patients Treated with Tyrosine Kinase Inhibitors: A Systematic Review of the Literature

BACKGROUND

The introduction of tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of gastrointestinal stromal tumors (GISTs), resulting in a substantial gain in median overall survival. Subsequently, health-related quality of life (HRQoL) has become more relevant. Here, we systematically review the available literature on HRQoL issues and side effects of different TKIs registered for the treatment of GIST.

METHODS

A search through five databases was performed. Full reports in English describing HRQoL outcomes and/or side effects in GIST patients on TKI therapy were included.

RESULTS

A total of 104 papers were included; 13 studies addressed HRQoL, and 96 studies investigated adverse events. HRQoL in patients treated with imatinib, regorafenib, and ripretinib remained stable, whereas most sunitinib-treated patients reported a decrease in HRQoL. Severe fatigue and fear of recurrence or progression were specifically assessed as HRQoL issues and had a negative impact on overall HRQoL as well as psychological and physical well-being. The majority of studies focused on physician-reported side effects. Nearly all GIST patients treated with a TKI experienced at least one adverse event, mostly mild to moderate.

CONCLUSIONS

Despite the fact that almost all patients treated with a TKI experienced side effects, this did not seem to affect overall HRQoL during TKI therapy. In daily practice, it are the side effects that hamper a patient's HRQoL resulting in treatment adjustments, suggesting that the reported side effects were underestimated by physicians, or the measures used to assess HRQoL do not capture all relevant issues that determine a GIST patient's HRQoL.

Pharmacodynamic and Pharmacokinetic Markers For Anti-angiogenic Cancer Therapy: Implications for Dosing and Selection of Patients

Angiogenesis is integral to tumour growth and invasion, and is a key target for cancer therapeutics. However, for many of the licensed indications, only a modest clinical benefit has been observed for both monoclonal antibody and small-molecule tyrosine kinase inhibitor anti-angiogenic therapy. Pre-clinical and clinical studies have attempted to evaluate circulating, imaging, genomic, pharmacokinetic, and pharmacodynamic markers that may aid both the selection of patients for treatment and define dosing. Correct dosing is likely to be critical in the context of vascular normalization to allow better delivery of concomitant anti-cancer therapy and novel imaging techniques hold much promise in the early evaluation of pharmacodynamic response to improve efficacy.

Antitumor activity of high-dose pulsatile gefitinib in non-small-cell lung cancer with acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have demonstrated efficacy in the treatment of advanced non-small cell lung cancer (NSCLC). However, their clinical efficacy is limited by acquired resistance. Drug resistance may be mediated by EGFR transduction, and a number of clinical trials have demonstrated that high-dose pulsatile TKIs may be effective at treating patients with acquired resistance, though their underlying mechanisms of action remain unknown. The aim of the present study was to investigate the antitumor activity of high-dose pulsatile gefitinib in NSCLC model cell lines, namely the EGFR-TKI-sensitive cell line PC9, as a control group, and the EGFR-TKI-resistant cell lines H1975 and H1650. The cell lines were administered with different doses of gefitinib and cell viability was measured using an MTT assay. Cell apoptosis and cycling were also determined by flow cytometry and the expression of phospho (p)-EGFR, EGFR, p-AKT and AKT were measured by western blot analysis. It was observed that the apoptotic rate of H1975 cells treated with high-dose pulsatile gefitinib significantly increased, while levels of p-EGFR and p-AKT were decreased. However, there was no significant difference in the apoptotic rate or level of p-AKT in gefitinib-treated H1650 cells, while p-EGFR levels decreased. By contrast, the EGFR-TKI-sensitive cell line PC9 exhibited sensitivity to gefitinib. It was demonstrated that the apoptosis rates were markedly increased when treated with high dose pulsatile gefitinib in PC9 cell line, while a decrease was noted in p-EGFR and p-AKT. These data suggest that high-dose pulsatile gefitinib treatment may overcome acquired resistance in NSCLC, though its efficacy is dependent on the type of drug resistance mutation(s) present. Furthermore, high-dose pulsatile gefitinib may inhibit tumor growth and induce cell apoptosis by blocking the EGFR signaling pathway. Therefore, if the signaling pathways involved in drug resistance are not activated by the EGFR gene, high-dose pulsatile gefitinib may have little efficacy in the treatment of NSCLC.

Clinical implications of repeated drug monitoring of imatinib in patients with metastatic gastrointestinal stromal tumour

BACKGROUND

Imatinib mesylate (IM) is the preferred treatment for the majority of patients with metastatic gastrointestinal stromal tumour (GIST). Low trough IM concentration (C_min) values have been associated with poor clinical outcomes in GIST patients. However, there are few studies of repeated measurements of IM levels, and therapeutic drug monitoring is not yet a part of routine clinical practice. This study was conducted to reveal clinical scenarios where plasma concentration measurement of IM trough level (C_min) is advantageous.

METHODS

Patients with advanced GIST receiving IM were included from January 2011 to April 2015. Heparin plasma was collected at each follow-up visit. Ninety-six samples from 24 patients were selected for IM concentration measurement. Associations between IM plasma concentration and clinical variables were analyzed by Students' t test, univariate and multivariate linear regression analyses.

RESULTS

The mean IM C_min plasma concentrations for patients taking <400, 400 and >400 mg daily were 782, 1132 and 1665 ng/mL, respectively (p = 0.010). High IM C_min levels were correlated with age, low body surface area, low haemoglobin concentration, low creatinine clearance, absence of liver metastasis and no prior gastric resection in univariate analysis. In multivariate analysis age, gastric resection and liver metastasis were included in the final model. Eight patients had disease progression during the study, and mean IM levels were significantly lower at time of progression compared to the previous measurement for the same patients (770 and 1223 ng/mL, respectively; p = 0.020).

CONCLUSIONS

Our results do not support repeated monitoring of IM levels on a routine basis in all patients. However, we have revealed clinical scenarios where drug measurement could be beneficial, such as for patients who have undergone gastric resection, suspicion of non-compliance, subjectively reported side effects, in elderly patients and at the time of disease progression.

Asian Consensus Guidelines for the Diagnosis and Management of Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors originating in the gastrointestinal tract. With the introduction of molecular-targeted therapy for GISTs which has yielded remarkable outcomes, these tumors have become a model of multidisciplinary oncological treatment. Although Western clinical guidelines are available for GISTs, such as those published by the National Comprehensive Cancer Network (NCCN) and the European Society of Medical Oncology (ESMO), the clinical situations in Asian countries are different from those in Western countries in terms of diagnostic methods, surgical approach, and availability of new targeted agents. Accordingly, we have reviewed current versions of several GIST guidelines published by Asian countries (Japan, Korea, China, and Taiwan) and the NCCN and ESMO and discussed the areas of dissensus. We here present the first version of the Asian GIST consensus guidelines that were prepared through a series of meetings involving multidisciplinary experts in the four countries. These guidelines provide an optimal approach to the diagnosis and management of GIST patients in Asian countries.

Systematic review of the side effects associated with tyrosine kinase inhibitors used in the treatment of gastrointestinal stromal tumours on behalf of the EORTC Quality of Life Group

Tyrosine kinase inhibitors (TKIs) have revolutionised the treatment of advanced gastrointestinal stromal tumours (GISTs). Imatinib is approved as first line therapy and sunitinib is used in cases of imatinib resistance or intolerance. Compared with conventional treatments, TKIs are delivered over longer periods of time and are more specific in their targets (i.e., molecularly targeted), thus presenting different side effect profiles. We review the safety profiles of imatinib and sunitinib, documenting a total of 95 side effects including patient based as well as medically defined outcomes. Gastrointestinal complaints, particularly diarrhoea and nausea, oedema, fatigue and haematological disorders, notably anaemia, are amongst the most prevalent side effects. While there is overlap between the side effect profiles of imatinib and sunitinib, important differences emerge in the frequencies of oedema, hypertension, thyroid functioning, muscle and joint pains, as well as skin and oral conditions. Awareness of potential side effects is informative to both clinician and patient in terms of treatment decision making and can have important implications for treatment adherence and clinical outcome.

Antiproliferative effects of continued mitogen-activated protein kinase pathway inhibition following acquired resistance to BRAF and/or MEK inhibition in melanoma

Inhibitors of the mitogen-activated protein kinases (MAPK), BRAF, and MAP-ERK kinase (MEK) induce tumor regression in the majority of patients with BRAF-mutant metastatic melanoma. The clinical benefit of MAPK inhibitors is restricted by the development of acquired resistance with half of those who benefit having progressed by 6 to 7 months and long-term responders uncommon. There remains no agreed treatment strategy on disease progression in these patients. Without published evidence, fears of accelerated disease progression on inhibitor withdrawal have led to the continuation of drugs beyond formal disease progression. We now show that treatment with MAPK inhibitors beyond disease progression can provide significant clinical benefit, and the withdrawal of these inhibitors led to a marked increase in the rate of disease progression in two patients. We also show that MAPK inhibitors retain partial activity in acquired resistant melanoma by examining drug-resistant clones generated to dabrafenib, trametinib, or the combination of these drugs. All resistant sublines displayed a markedly slower rate of proliferation when exposed to MAPK inhibitors, and this coincided with a reduction in MAPK signaling, decrease in bromodeoxyuridine incorporation, and S-phase inhibition. This cytostatic effect was also associated with diminished levels of cyclin D1 and p-pRb. Two short-term melanoma cultures generated from resistant tumor biopsies also responded to MAPK inhibition, with comparable inhibitory changes in proliferation and MAPK signaling. These data provide a rationale for the continuation of BRAF and MEK inhibitors after disease progression and support the development of clinical trials to examine this strategy.

Efficacy and safety evaluation of two doses of imatinib for the treatment of advanced gastrointestinal stromal tumors (GISTs)

BACKGROUND AND OBJECTIVE

Imatinib is approved worldwide for use in gastrointestinal stromal tumours (GISTs). To evaluate the efficacy and safety of two dose of imatinib treatment for patients with GISTs, a meta-analysis was performed.

METHODS

Electronic search of the PubMed and EMBASE, which have articles published between 1980 and February 2012, was conducted to select studies for this meta-analysis.

RESULTS

Five articles with a total number 1861 of advanced GISTs patients were involved in this meta-analysis. There was a slight but significant 2-year PFS advantage with high-dose group (OR=1.25, 95% CIs=1.03-1.52, P=0.03), but not in the 2-year OS (OR=1.02, 95% CIs=0.84-1.24, P=0.87), CR (OR=1.02, 95% CIs=0.66-1.58, P=0.93), and PR (OR=1.13, 95% CIs=0.94-1.36, P=0.20). In safety, the high-dose group increased the incidence of above grade 3 toxicity (OR=2.05, 95% CIs=1.70-2.48, P<0.00001), particular in the blood toxicity, skin disorders, nausea and so on.

CONCLUSIONS

This analysis confirms a slight 2-year PFS advantage of high-dose imatinib, but imatinib dose escalation could not lead to any other major clinical benefits, and brought more toxic effects for patients.

Systematic review of escalated imatinib doses compared with sunitinib or best supportive care, for the treatment of people with unresectable/metastatic gastrointestinal stromal tumours whose disease has progressed on the standard imatinib dose

Introduction

We conducted a systematic review of evidence on the effectiveness of imatinib at escalated doses of 600 mg/day or 800 mg/day for treatment of adults with unresectable or metastatic gastrointestinal stromal tumours (GIST), following progression on imatinib at the 400 mg/day dose, compared with sunitinib and/or ‘best supportive care’.

Methods

Electronic searches were undertaken to identify relevant randomised controlled trials (RCTs), non-randomised studies, and case series reporting outcome data on survival, quality of life or adverse events. Titles and abstracts were screened by two reviewers and full text reports of potentially relevant studies assessed for inclusion. Included studies were quality assessed by two reviewers and data were extracted. Five studies reported data on the relevant population and were included.

Results and Discussion

Median overall survival for imatinib (800 mg/day) and sunitinib both were less than 2 years. Around 25% of patients required either an imatinib dose delay or reduction. Approximately one-third of patients receiving dose escalated imatinib (either dose) showed either response or stable disease. Amongst those responding to the escalated 800 mg/day dose, median progression-free survival was over 25 months. The statistical likelihood of response may depend on exon mutational status. There were few data and those that were available were potentially biased, due to their non-randomised nature. Further data are needed to justify international guideline recommendations on imatinib dose escalation.

Conclusion

A prospective audit of management and outcomes for unresectable GIST patients treated with dose escalation upon progression at 400 mg/day may be appropriate as an RCT may be unfeasible.

Clinical practice guideline for accurate diagnosis and effective treatment of gastrointestinal stromal tumor in Korea

Despite their rarity in incidence and prevalence, gastrointestinal stromal tumors (GISTs) have emerged as a distinct and noteworthy pathogenetic entity. The clinical management of GISTs has rapidly evolved due to the recent elucidation of their oncogenic signal transduction pathway and the introduction of molecular-targeted therapies. Successful management of GISTs requires a multidisciplinary approach firmly based on an accurate histopathologic diagnosis. In 2007, the Korean GIST study group published the first guideline for optimal diagnosis and treatment of GISTs in Korea. The second version of the guideline was published in 2010. Herein, we provide the results of relevant clinical studies for the purpose of further revision to the guideline. We expect this new guideline will enhance the accuracy of diagnosis, as performed by members of the Korean associate of physicians involved in GIST patient care, thus improving the efficacy of treatment.

Contribution of tumoral and host solute carriers to clinical drug response

Members of the solute carrier family of transporters are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. Several of these solute carriers are known to be expressed in cancer cells or cancer cell lines, and decreased cellular uptake of drugs potentially contributes to the development of resistance. As result, the expression levels of these proteins in humans have important consequences for an individual's susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. In this review article, we provide an update of this rapidly emerging field, with specific emphasis on the direct contribution of solute carriers to anticancer drug uptake in tumors, the role of these carriers in regulation of anticancer drug disposition, and recent advances in attempts to evaluate these proteins as therapeutic targets.

Efficacy of imatinib dose escalation in Chinese gastrointestinal stromal tumor patients

AIM: To investigate the efficacy and safety of imatinib dose escalation in Chinese patients with advanced gastrointestinal stromal tumor (GIST).

METHODS: Advanced GIST patients previously failing 400 mg imatinib treatment were enrolled in this study. Patients received imatinib with dose escalation to 600 mg/d, and further dose escalation to 800 mg/d if imatinib 600 mg/d failed. Progression-free survival, overall survival, clinical efficacy, c-kit/PDGFRA genotype and safety were evaluated.

RESULTS: 52 patients were enrolled in this study. For the 47 evaluable patients receiving imatinib (600 mg/d), the disease control rate was 40.4%, and the median progression-free survival for all patients was 17 wk (95% CI: 3.9-30.1). The median overall survival after dose escalation was 81 wk (95% CI: 36.2-125.8). Adverse events, mainly edema, fatigue, granulocytopenia and skin rash were tolerable. However, further dose escalation (800 mg/d) in 14 cases was ineffective, with disease progression and severe adverse events. Among 30 cases examined for gene mutations, patients with exon 9 mutations experienced a better progression-free survival of 47 wk.

CONCLUSION: Imatinib dose escalation to 600 mg/d is more appropriate for Chinese patients and may achieve further survival benefit.

Clinical practice guideline for accurate diagnosis and effective treatment of gastrointestinal stromal tumor in Korea

Despite the rarity in incidence and prevalence, gastrointestinal stromal tumor (GIST) has emerged as a distinct pathogenetic entity. And the clinical management of GIST has been evolving very rapidly due to the recent recognition of its oncogenic signal transduction pathway and the introduction of new molecular-targeted therapy. Successful management of GIST requires a multidisciplinary approach firmly based on accurate histopathologic diagnosis. However, there was no standardized guideline for the management of Korean GIST patients. In 2007, the Korean GIST study group (KGSG) published the first guideline for optimal diagnosis and treatment of GIST in Korea. As the second version of the guideline, we herein have updated recent clinical recommendations and reflected changes in diagnosis, surgical and medical treatments for more optimal clinical practice for GIST in Korea. We hope the guideline can be of help in enhancing the quality of diagnosis by members of the Korean associate of physicians involving in GIST patients's care and subsequently in achieving optimal efficacy of treatment.

Cross-Sectional Study of Imatinib Plasma Trough Levels in Patients With Advanced Gastrointestinal Stromal Tumors: Impact of Gastrointestinal Resection on Exposure to Imatinib

Purpose

Imatinib plasma trough levels (Cmin) have been reported to correlate with treatment outcomes in patients with gastrointestinal stromal tumors (GISTs). We therefore have evaluated the correlation between imatinib Cmin and the clinical characteristics of patients with GIST.

Patients and Methods

Steady-state imatinib Cmin in 107 patients with GIST who were taking imatinib 300 to 800 mg/d was measured.

Results

In patients treated with imatinib 400 (n = 92), 300 (n = 7), 600 (n = 2), or 800 (n = 11) mg/d, imatinib Cmin was 1,305 ± 633 ng/mL, 1,452 ± 830 ng/mL, 1,698 ± 725 ng/mL, and 3,330 ± 1,592 ng/mL, respectively. Of the 92 patients treated with 400 mg/d imatinib, 59 patients (63%) were men; the median age was 55 years (range, 28 to 76 years), and the median duration of imatinib use before sampling was 8.8 months (range, 0.5 to 67.6 months). The mean inter- and intrapatient variability rates were 44.7% and 26.5%, respectively. In univariate analyses, high Cmin was correlated with advanced age (P = .02), low creatinine clearance (P = .001), low hemoglobin (P = .03), and low albumin (P < .001) concentrations. Imatinib Cmin was also significantly lower in patients with (n = 18; 942 ± 330 ng/mL) than without (n = 74; 1,393 ± 659 ng/mL) major (ie, total or subtotal) gastrectomy (P = .002). In multivariate analysis, albumin (P = .001) concentrations, creatinine clearance (P = .002), and major gastrectomy (P = .003) were significantly correlated with Cmin.

Conclusion

In patients with GIST, imatinib Cmin at steady state was significantly associated with albumin concentration, creatinine clearance, and previous major gastrectomy. Although its clinical impact is unclear at present time, monitoring of imatinib Cmin might be particularly important for optimal treatment with imatinib in patients who have undergone major gastrectomy.