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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., (© 2024 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.)

Background: Safety of minimally invasive surgery (MIS) for gastrointestinal stromal tumours (GISTs) is still under debate since it might increase the risk of tumour rupture, especially in larger tumours. The aim of this study was to investigate trends in treatment and perioperative outcomes of patients undergoing resections of gastric GISTs over time., Methods: This was a multicentre retrospective study of consecutive patients who underwent wedge resection or partial gastrectomy for localized gastric GIST at five GIST reference centres between January 2009 and January 2022. To evaluate changes in treatment and perioperative outcomes over time, patients were divided into four equal periods. Perioperative outcomes were analysed separately and as a novel composite measure textbook outcome (TO)., Results: In total 385 patients were included. Patient and tumour characteristics did not change over time, except for median age (62-65-68-68 years, p = 0.002). The proportion of MIS increased (4.0%-9.8%-37.4%-53.0 %, p < 0.001). Postoperative complications (Clavien Dindo ≥2; 22%-15%-11%-10 %, p = 0.146), duration of admission (6-6-5-4 days, p < 0.001) and operating time (92-94-77-73 min, p = 0.007) decreased over time while TO increased (54.0%- 52.7%-65.9%-76.0 %, p < 0.001). No change was seen in perioperative ruptures (6.0%- 3.6%-1.6%-3.0 %, p = 0.499). MIS was correlated with less CD ≥ 2 complications (p = 0.006), shorter duration of admission (p < 0.001) and more TO (p < 0.001). Similar results were observed in tumours ≤5 cm and >5 cm., Conclusion: A larger percentage of gastric GIST were treated with MIS over time. MIS was correlated with less complications, shorter duration of admission and more TO. Tumour rupture rates remained low over time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)

Background: While the effectiveness of tyrosine kinase inhibitors (TKIs) seems similar in older patients with gastrointestinal stromal tumors (GIST) compared with younger patients, toxicities in older patients treated with TKIs more often lead to discontinuation of treatment., Objective: To better understand the age-related pharmacology and pharmacodynamic differences in patients with GIST treated with TKIs, the primary aim of this study was to evaluate TKI dosing patterns in older patients with GIST, while the secondary aims were to evaluate differences in imatinib trough plasma concentrations between age groups and to compare the overall survival (OS) in patients with and without dose reductions in all treatment lines in a palliative setting., Methods: Patients (18 years of age or older) with histologically proven GIST diagnosed between January 2009 and June 2021 and treated with one or more lines of TKIs were selected from the Dutch GIST Registry (DGR) database. Age groups were divided into younger patients (age <70 years) and older patients (age ≥70 years). All imatinib trough plasma concentrations of blood withdrawals taken from initiation of imatinib until a maximum of 1 year of treatment with imatinib were collected. Reasons for first adjustment of treatment were classified as adverse event, dose modification, progressive disease and other reasons. The next treatment steps after first adjustment of treatment were defined as dose escalation, dose reduction, dose interruption, or end of treatment. The association of dose reduction and OS was analyzed using the landmark approach., Results: Overall, 871 patients were included in this study, including 577 younger patients and 294 older patients. Older patients more often had an adverse event as the reason for first adjustment of treatment with both imatinib (45.6%; p < 0.001) and sunitinib (58.6%; p = 0.224) compared with younger patients (19.5% and 42.7%, respectively). Adjustment of imatinib and sunitinib after starting on a standard dose because of an adverse event most often resulted in dose reduction in both age groups. Median trough plasma concentrations of all samples taken within the first year after initiation of imatinib were higher in older patients (1228 ng/mL, interquartile range [IQR] 959-1687) compared with younger patients (1035 ng/mL [IQR 773-1377]; p < 0.001). No significant differences were seen between OS in patients with or without dose reduction in all treatment lines (imatinib: p = 0.270; sunitinib: p = 0.547; and regorafenib: p = 0.784)., Conclusion: Older patients showed higher imatinib trough plasma concentrations compared with younger patients and also had earlier and more often adverse events as the reason for first adjustment of treatment with imatinib followed by dose reduction. However, in a landmark analysis, patients with imatinib dose reductions had no poorer outcomes compared with patients not requiring a dose reduction., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Background: The added value of local treatment in selected metastatic GIST patients is unclear. This study aims to provide insight into the usefulness of local treatment in metastatic GIST by use of a survey study and retrospective analyses in a clinical database., Methods: A survey study was conducted among clinical specialists to select most relevant characteristics of metastatic GIST patients considered for local treatment, defined as elective surgery or ablation. Patients were selected from the Dutch GIST Registry. A multivariate Cox-regression model for overall survival since time of diagnosis of metastatic disease was estimated with local treatment as a time-dependent variable. An additional model was estimated to assess prognostic factors since local treatment., Results: The survey's response rate was 14/16. Performance status, response to TKIs, location of active disease, number of lesions, mutation status, and time between primary diagnosis and metastases, were regarded the 6 most important characteristics. Of 457 included patients, 123 underwent local treatment, which was associated with better survival after diagnosis of metastases (HR = 0.558, 95%CI = 0.336-0.928). Progressive disease during systemic treatment (HR = 3.885, 95%CI = 1.195-12.627) and disease confined to the liver (HR = 0.269, 95%CI = 0.082-0.880) were associated with worse and better survival after local treatment, respectively., Conclusion: Local treatment is associated with better survival in selected patients with metastatic GIST. Locally treated patients with response to TKIs and disease confined to the liver have good clinical outcome. These results might be considered for tailoring treatment, but should be interpreted with care because only specific patients are provided with local treatment in this retrospective study., Competing Interests: Declaration of competing interest The authors have no competing interests to declare., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background and Objectives: Previous literature showed a high risk of recurrence following surgical treatment in patients with gastrointestinal stromal tumours (GISTs). However, little is known about the patient- and treatment characteristics of local recurrences (LRs) in GIST patients. Therefore, this study aimed to better understand patterns of LR in surgically treated localised GIST and to describe treatment options based on our Dutch GIST Registry (DGR)., Methods: Data of primary surgically treated localised GIST between January 2009 until July 2021 were retrospectively retrieved from the DGR., Results: Of 1452 patients registered in the DGR, 912 patients were included in this study. Only 3.8% (35/912) of patients developed LR, including 20 patients with LR only and 15 patients with simultaneous LR and distant metastases (DM). Median time to LR was 30 (interquartile range 8-53) months from date of surgery. Eleven percent (100/912) of patients developed only DM. A total of 2.3% (6/259) of patients treated with adjuvant treatment developed an LR during adjuvant therapy. Seventy percent of patients with LR only (14/20) were treated with surgery (85.7% R0), which was mostly combined with systemic treatment., Conclusions: Patients with primary surgically treated localised GIST have a limited risk of developing recurrence. Fifteen percent developed recurrence, of which one quarter developed an LR. Therefore, less intensified follow-up schedules could be considered, especially during treatment with adjuvant imatinib. In patients with LR only, potentially curative treatment strategies, including surgical (re-)resection, are often possible as treatment for LR., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: This work was supported by a research grant for the Dutch GIST Registry, which was received from Novartis (3017/13), Pfizer (WI189378), Bayer (2013-MED-12005) and Deciphera (4EE9EEC-7F19-484D-86A4-646CFE0950A5). These funding sources did not have any involvement in the conduction of this research., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Patients with unresectable and metastasized gastrointestinal stromal tumor (GIST) experienced a remarkable improvement of progression-free survival (PFS) and overall survival (OS) after the introduction of imatinib. Our hypothesis is that the outcomes of treatment with imatinib are even better nowadays compared with the registration trials that were performed two decades ago. To study this, we used real-life data from a contemporary registry., Methods: A multicenter, retrospective study was performed by exploring clinical data from a prospective real-life clinical database, the Dutch GIST Registry (DGR). Patients with advanced GIST treated with first-line imatinib were included and PFS (primary outcome) and OS (secondary outcome) were analyzed. Results of our study were compared with published results of the European Organisation for Research and Treatment of Cancer (EORTC) 62005 trial, which marked the first era of imatinib in the treatment of GIST., Results: Overall, 420 of the 435 patients treated with imatinib in the DGR had recorded response evaluation and were included in the analysis. During a median follow-up of 35.0 months (range 2.0-136.0), progression of GIST was eventually observed in 217 patients (51.2%). The DGR cohort showed a longer median PFS (33.0 months, 95% confidence interval [CI] 28.4-37.6) compared with the EORTC 62005 trial (an estimated PFS of 19.5 months). Additionally, the median OS of 68.0 months (95% CI 56.1-80.0) was longer than the exposed median OS (46.8 months) published in the long-term follow-up results of the EORTC 62005 trial (median follow-up duration 10.9 years)., Conclusion: This study provides an update on outcomes of imatinib in the treatment of advanced GIST patients and demonstrates improved clinical outcomes since the first randomized studies of imatinib 2 decades ago. Furthermore, these results represent outcomes in real-world clinical practice and can serve as a reference when evaluating effectiveness of imatinib in patients with advanced GIST., (© 2023. The Author(s).)

Background: The prognosis of patients with advanced gastrointestinal stromal tumor (GIST) has improved greatly after the introduction of imatinib. However, primary or secondary resistance to imatinib occurs in the majority of patients. Sunitinib is the standard second line treatment in exon-9 mutated GIST., Objective: We compared the clinical outcomes of sunitinib with imatinib dose escalation in patients with progressive advanced non-KIT exon 9 mutated GIST after failure of first line imatinib., Patients and Methods: A retrospective study was performed, retrieving data from a real-life database (Dutch GIST Registry) including patients with GIST treated with sunitinib or imatinib dose escalation after failure on first line imatinib 400 mg daily. Primary outcome measures were progression free survival (PFS) and overall survival (OS)., Results: In total, 110 patients were included, 72 (65.5%) patients were treated with sunitinib (group A) and 38 (34.5%) received an imatinib dose escalation (group B). Important prognostic features at baseline, such as tumor size, stage at diagnosis, mitotic count and localization were equally distributed in both groups. No significant difference (p = 0.88) between median PFS in group A [8.7 months (95% CI 5.6-11.3)] and group B [5.6 months, (95% CI 2.6-8.7)] was observed. Moreover, the OS was similar between group A and group B; 63.2 months and 63.4 months, respectively., Conclusion: This study represents a proper sample size cohort containing detailed data on mutational status of patients with advanced GIST. We illustrated that imatinib dose escalation could serve as a good alternative for sunitinib as second-line treatment in patients with a non-KIT exon 9 mutation., (© 2022. The Author(s).)