The value of PET, CT and in-line PET/CT in patients with gastrointestinal stromal tumours: long-term outcome of treatment with imatinib mesylate

18F-fluorodeoxyglucose positron emission tomography-computed tomography as a prognostic marker of imatinib-resistant gastrointestinal stromal tumors

PURPOSE

Unresectable or metastatic GISTs often develop resistance to imatinib, but the effectiveness of other drugs is limited. Thus, surgical treatment can be considered, especially for partial resistance. FDG-PET/CT is used for the diagnosis and evaluation of GISTs. We conducted this study to establish whether FDG-PET/CT findings could guide treatment decisions and predict the prognosis of patients with imatinib-resistant GISTs.

METHODS

We analyzed data retrospectively from 45 patients with imatinib-resistant GISTs that were assessed via FDG-PET/CT at our institution between 2003 and 2021. The patients were classified as having low (n = 18) or high (n = 27) SUVmax, with a cutoff value of 5.0.

RESULTS

The overall survival (OS) of the patients with low SUVmax after the diagnosis of imatinib resistance was significantly prolonged. Multivariate analysis identified SUVmax as an independent poor prognostic factor. In 23 patients with resected imatinib-resistant lesions, a close correlation was found between the SUVmax by preoperative FDG-PET/CT and the mitotic rate. A higher SUVmax was associated with a higher mitotic rate. Patients with a low SUVmax (n = 11) had significantly longer postoperative imatinib failure-free survival than those with a high SUVmax (n = 12).

CONCLUSIONS

FDG-PET/CT assessment and diagnosis might reveal the pathological grades of imatinib-resistant GISTs and act as a prognostic marker.

English version of Japanese Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) issued by the Japan Society of Clinical Oncology

The Japan Society of Clinical Oncology Clinical Practice Guidelines 2022 for gastrointestinal stromal tumor (GIST) have been published in accordance with the Minds Manual for Guideline Development 2014 and 2017. A specialized team independent of the working group for the revision performed a systematic review. Since GIST is a rare type of tumor, clinical evidence is not sufficient to answer several clinical and background questions. Thus, in these guidelines, we considered that consensus among the experts who manage GIST, the balance between benefits and harms, patients' wishes, medical economic perspective, etc. are important considerations in addition to the evidence. Although guidelines for the treatment of GIST have also been published by the National Comprehensive Cancer Network (NCCN) and the European Society for Medical Oncology (ESMO), there are some differences between the treatments proposed in those guidelines and the treatments in the present guidelines because of the differences in health insurance systems among countries.

Primary extra-gastrointestinal stromal tumor of retroperitoneum: Clinicopathologic characteristics and prognosis of six cases

Aim

This study investigates the clinicopathological features and prognostic genic biomarker factors of primary retroperitoneal extra-gastrointestinal stromal tumors (EGISTs).

Methods

The clinicopathological data of six patients with primary retroperitoneal EGIST were analyzed, including cell type (epithelioid or spindle), mitoses, and the presence of intratumoral necrosis and hemorrhage. Mitoses were counted and summed from 50 high power fields (HPFs). Mutations of exons 9, 10, 11, 13, 14, and 17 of the C-kit genes and those of exons 12 and 18 of the PDGFRA gene were examined. Follow-up was performed via telephone, and all outpatient records were reviewed. The last follow-up date was February 2022, the median follow-up was 27.5m and the postoperative status, medication, and survival of the patients were recorded.

Result

The patients were treated with radical intent. Four cases (patients 3, 4, 5, and 6) underwent multivisceral resection for encroachment on the adjacent viscera. The postoperative pathological results demonstrated that all biopsy specimens were negative for S-100 and desmin, and positive for DOG1 and CD117. Additionally, four patients (case 1, 2, 4, and 5) were positive for CD34, four (case 1, 3, 5, and 6) were positive for SMA, four (case 1, 4, 5, and 6) had >5/50 HPFs, and three (case 1, 4, and 5) had Ki67 >5%. According to the modified National Institutes of Health (NIH) guidelines, all patients were graded as high-risk cases. By exome sequencing, exon11 mutations were detected in the six patients, while exon10 mutations were detected in two cases (patients 4 and 5). The median follow-up time was 30.5 (11-109) months, with only one fatality at 11 months.

Conclusion

Retroperitoneal EGIST is a rare mesenchymal tumor that is difficult to distinguish from other retroperitoneal tumors. To diagnose this highly malignant tumor, low-threshold suspicion is necessary, and Kit and PDGFRA gene mutations should be routinely tested to confirm the diagnosis and guide subsequent treatment.

[18F]FAPI-42 PET/CT versus [18F]FDG PET/CT for imaging of recurrent or metastatic gastrointestinal stromal tumors

PURPOSE

PET has been important for monitoring recurrence and metastasis of Gastrointestinal Stromal Tumors (GISTs) and the selection of therapeutic strategies. A significant portion of GISTs lesions show negative FDG uptake and therefore calls for more tumor-specific imaging biomarkers. This study compared the imaging performance of [18F]FAPI-42 PET/CT and [18F]FDG PET/CT in recurrent or metastatic gastrointestinal stromal tumors (R/M GISTs).

METHODS

This study retrospectively included 35 patients with R/M GISTs who underwent both FAPI PET/CT and FDG PET/CT. The definite diagnosis was confirmed by pathology or follow-up drug treatment effects. The differences in detection rates and tumor-to-background SUVmax ratio (SUVTBR) of different locations between dual-tracer PET/CT were compared. Factors including tumor size, degree of enhancement, type of gene mutation, and targeted treatment potentially influencing the uptake of both tracers were assessed. The excised lesions (n = 3) underwent immunohistochemical staining to verify FAP expression in the tissue.

RESULTS

A total of 106 lesions in 35 patients were identified, out of which 38/106 (35.8%) lesions (FAPI + /FDG -) were additionally detected by FAPI PET/CT as compared to that by FDG, including 26 liver metastases, ten peritoneal metastases, one gastrointestinal recurrence, and one bone metastasis. The positive detection rate of FAPI PET/CT for recurrent or metastatic GISTs was higher than that of FDG (80.2% vs. 53.8%,  P< 0.001), especially in liver metastases (87.5% vs. 33.3%, P< 0.001). Moreover, the SUVTBR of liver metastases of GISTs in FAPI PET/CT was higher than that in FDG [2.4 (0.3 to 11.2) vs. 0.9 (0.3 to 6.5), P< 0.001]. The longest diameter of tumors in the FDG-positive group was higher than that of the FDG-negative group (P= 0.005); still, it did not differ between the FAPI-positive group and the FAPI-negative group. No difference in the degree of enhancement was observed between both tracers' positive and negative groups. Besides, the SUVTBR of FDG but not FAPI differed significantly among various gene mutations (P< 0.001) as well as the targeted therapy and no targeted therapy groups (P= 0.001). FAP was expressed in R/M GISTs, and the uptake of FAPI corresponded to the level of FAP expression.

CONCLUSION

In conclusion, FAPI for imaging of R/M GISTs could be superior to FDG, specifically for liver metastases. The uptake of FAPI could reflect the level of FAP expression, and it was independent of tumor size, degree of enhancement, type of gene mutation, and targeted therapy as compared to FDG.

Early response evaluation using 18F-FDG-PET/CT does not influence management of patients with metastatic gastrointestinal stromal tumors (GIST) treated with palliative intent

AIM

The aim of this study was to investigate the impact of ¹⁸F-FDG-PET/CT on treatment decision making in metastatic gastrointestinal stromal tumor (GIST) patients.

METHODS

This study retrospectively evaluated ¹⁸F-FDG-PET/CT scans to monitor response of metastatic GIST patients treated with palliative intent. Data from the Dutch GIST Registry was used. Early scans (<10 weeks after start of treatment) and late scans (>10 weeks after start of treatment) were scored on the impact in change of treatment.

RESULTS

Sixty-one PET/CT scans were performed for treatment evaluation in 39 patients with metastatic GIST of which 36 were early scans and 25 were late scans. Early PET/CT scans led to a change in management in 5.6% of patients and late PET/CT scans led to a change in management in 56% of patients. Change in management was more often seen after scans with lack of metabolic response (48% vs. 11% in scans with metabolic response, p=0.002). Neither metabolic response nor change in treatment were more often seen in patients with KIT mutations compared to patients with non-KIT mutations (metabolic response 65% KIT vs. 46% non-KIT, p=0.33, and change in management 28% KIT vs. 21% non-KIT, p=0.74).

CONCLUSION

¹⁸F-FDG-PET/CT is not recommended for early response evaluation in an unselected patient population with metastatic GIST, since it does not influence treatment decisions. ¹⁸F-FDG-PET/CT, however, can be useful for late response assessment, especially in case of indeterminate CT results.

Dual-Energy CT Vital Iodine Tumor Burden for Response Assessment in Patients With Metastatic GIST Undergoing TKI Therapy: Comparison to Standard CT and FDG PET/CT Criteria

Background: CT-based criteria for assessing gastroinstestinal stromal tumor (GIST) response to tyroskine kinase inhibitor (TKI) therapy are limited partly because tumor attenuation is influenced by treatment-related changes including hemorrhage and calcification. Iodine concentration may be less impacted by such changes. Objective: To determine whether DECT vital iodine tumor burden (TB) provides improved differentiation between responders and non-responders in patients with metastatic GIST undergoing TKI therapy compared to established CT and PET/CT criteria. Methods: An anthropomorphic phantom with spherical inserts mimicking GIST lesions of varying iodine concentrations and having non-enhancing central necrotic cores underwent DECT to determine a threshold iodine concentration. Forty patients (median age 57 years; 25 women, 15 men) treated with TKI for metaststic GIST were retrospectively evaluated. Patients underwent baseline and follow-up DECT and FDG PET/CT. Response assessment was performed using RECIST 1.1, modified Choi (mChoi), vascular tumor burden (VTB), DECT vital iodine TB, and European Organization for Research and Treatment of Cancer (EORTC PET) criteria. DECT vital iodine TB used the same percentage changes as RECIST 1.1 response categories. Progression-free survival (PFS) was compared between responders and non-responders for each response criteria using Cox proportional hazard ratios and Harrell's c-indices. Results: The phantom experiment identified a 0.5 mg/mL threshold to differentiate vital from non-vital tissue. Using DECT vital iodine TB, median PFS was significantly different between non-responders and responders (587 vs 167 days, respectively; p=.02). Hazard ratio for progression for DECT vital iodine TB non-responders versus responders was 6.9, versus 7.6 for EORTC PET, 3.3 for VTB, 2.3 for RECIST 1.1, and 2.1 for mChoi. C-index was 0.74 for EORTC PET, 0.73 for DECT vital iodine TB, 0.67 for VTB, 0.61 for RECIST 1.1, and 0.58 for mChoi. C-index was significantly greater for DECT vital iodine TB than RECIST 1.1 (p=.02) and mChoi (p=.002), but not different than VTB and EORTC PET (p>.05). Conclusion: DECT vital iodine TB criteria showed comparable performance as EORTC PET and outperformed RECIST 1.1 and mChoi for response assessment of metastatic GIST under TKI therapy. Clinical Impact: DECT vital iodine TB could help guide early management decisions in patients on TKI therapy.

Metabolic behavior and prognostic role of pretreatment 18F-FDG PET/CT in gist

AIM

The metabolic behavior and the prognostic value of ¹⁸ F-FDG-PET/CT in gastrointestinal stromal tumor (GIST) is not well investigated. The aim of this study was to analyze the metabolic behavior of GIST and the prognostic role of pretreatment PET/CT features.

METHODS

In this retrospective study, we included 35 patients with a diagnosis of GIST who underwent a pretreatment ¹⁸ F-FDG-PET/CT scan. We analyzed PET images visually and semiquantitatively by measuring several metabolic parameters as the maximum standardized uptake value corrected for body weight (SUVbw), for lean body mass (SUVlbm), for body surface area (SUVbsa), metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The Kaplan-Meier method was used to measure the progression free survival (PFS) and overall survival curves.

RESULTS

Twenty-nine (82%) patients showed a positive ¹⁸ F-FDG-PET/CT, whereas the remaining 6 had no hypermetabolic lesions. ¹⁸ F-FDG-avidity was significantly related with mitotic index, tumor stage and tumor risk group. Instead, semiquantitative PET/CT parameters correlated only with tumor risk group. Disease progression occurred in 16 patients whereas death in seven. ¹⁸ F-FDG-avidity, MTV and TLG were the only variables significantly associated with PFS.

CONCLUSION

An 82% rate of PET avidity in GIST was found and it was correlated with stage, tumor risk group and mitotic index. Only baseline ¹⁸ F-FDG-avidity, MTV and TLG were independently correlated with PFS.

Radiochemistry: A Useful Tool in the Ophthalmic Drug Discovery

Positron Emission Tomography (PET) and Single Photon Emission Computerized Tomography (SPECT) are ultra-sensitive, fully translational and minimally invasive nuclear imaging techniques capable of tracing the spatiotemporal distribution of positron (PET) or gamma (SPECT) emitter-labeled molecules after administration into a living organism. Besides their impact in the clinical diagnostic, PET and SPECT are playing an increasing role in the process of drug development, both during the evaluation of the pharmacokinetic properties of new chemical entities as well as in the proof of concept, proof of mechanism and proof of efficacy studies. However, they have been scarcely applied in the context of ophthalmic drugs. In this paper, the basics of nuclear imaging and radiochemistry are briefly discussed, and the few examples of the use of these imaging modalities in ophthalmic drug development reported in the literature are presented and discussed. Finally, in a purely theoretical exercise, some labeling strategies that could be applied to the preparation of selected ophthalmic drugs are proposed and potential applications of nuclear imaging in ophthalmology are projected.

Progress in determining response to treatment in gastrointestinal stromal tumor

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

Role of 18F-FDG PET/CT in restaging and follow-up of patients with GIST

PURPOSE

Gastrointestinal stromal tumor (GIST) is a rare tumor with high risk of recurrence and poor prognosis in case of advanced GIST. The aim of this study was to evaluate the possible role of 18F-FDG PET/CT in restaging GIST.

METHODS

Fifty-four patients (30 male) with histological proven GIST underwent 100 18F-FDG PET/CT for restaging in suspected recurrence or during follow-up. Histopathology results and/or clinical/imaging follow-up for at least 12 months were considered as reference standard. Moreover, the diagnostic accuracy and clinical impact of 18F-FDG PET/CT were calculated.

RESULTS

Twenty-seven (27%) 18F-FDG PET/CT were positive, while the remaining 73 (73%) were negative. Sensitivity, specificity, PPV, NPV, and accuracy of PET/CT were 89% (95% CI 72-98%), 97% (95% CI 90-100%), 93% (95% CI 76-98%), 96% (95% CI 89-98%), and 95% (95% CI 89-98%). 18F-FDG PET/CT had a positive clinical impact in 18/100 studies changing the management, in 8 cases switching from local therapy to systemic therapy due to the detection of disseminate disease at PET/CT, in three cases recognizing relapse not detected by conventional imaging, and in 7 cases demonstrating to be true negative and avoiding unnecessary therapies.

CONCLUSIONS

18F-FDG PET/CT seems to be an accurate method for detection and localization of local and distant recurrence in GIST with good sensitivity and specificity and significant impact on clinical decision-making.

The landscape of tyrosine kinase inhibitors in sarcomas: looking beyond pazopanib

Introduction: Tyrosine kinases are key mediators of intracellular signaling cascades and aberrations in these proteins have been implicated in driving oncogenesis through the dysregulation of fundamental cellular processes including proliferation, migration, and apoptosis. As such, targeting these proteins with small molecule tyrosine kinase inhibitors (TKI) has led to significant advances in the treatment of a number of cancer types.Areas covered: Soft tissue sarcomas (STS) are a heterogeneous and challenging group of rare cancers to treat, but the approval of the TKI pazopanib for the treatment of advanced STS demonstrates that this class of drugs may have broad utility against a range of different sarcoma histological subtypes. Since the approval of pazopanib, a number of other TKIs have entered clinical trials to evaluate whether their activity in STS matches the promising results seen in other solid tumors. In this article, we review the emerging role of TKIs in the evolving landscape of sarcoma treatment.Expert opinion: As our biological understanding of response and resistance of STS to TKIs advances, we anticipate that patient management will move away from a 'one size fits all' paradigm toward personalized, multi-line, and patient-specific treatment regimens where patients are treated according to the underlying biology and genetics of their specific disease.

Mitochondrial Inhibition Augments the Efficacy of Imatinib by Resetting the Metabolic Phenotype of Gastrointestinal Stromal Tumor

Purpose: Imatinib dramatically reduces gastrointestinal stromal tumor (GIST) ¹⁸F-FDG uptake, providing an early indicator of treatment response. Despite decreased glucose internalization, many GIST cells persist, suggesting that alternative metabolic pathways are used for survival. The role of mitochondria in imatinib-treated GIST is largely unknown.Experimental Design: We quantified the metabolic activity of several human GIST cell lines. We treated human GIST xenografts and genetically engineered Kit^V558del/+ mice with the mitochondrial oxidative phosphorylation inhibitor VLX600 in combination with imatinib and analyzed tumor volume, weight, histology, molecular signaling, and cell cycle activity. In vitro assays on human GIST cell lines were also performed.Results: Imatinib therapy decreased glucose uptake and downstream glycolytic activity in GIST-T1 and HG129 cells by approximately half and upregulated mitochondrial enzymes and improved mitochondrial respiratory capacity. Mitochondrial inhibition with VLX600 had a direct antitumor effect in vitro while appearing to promote glycolysis through increased AKT signaling and glucose transporter expression. When combined with imatinib, VLX600 prevented imatinib-induced cell cycle escape and reduced p27 expression, leading to increased apoptosis when compared to imatinib alone. In Kit^V558del/+ mice, VLX600 alone did not induce tumor cell death, but had a profound antitumor effect when combined with imatinib.Conclusions: Our findings show that imatinib alters the metabolic phenotype of GIST, and this may contribute to imatinib resistance. Our work offers preclinical proof of concept of metabolic targeting as an effective strategy for the treatment of GIST. Clin Cancer Res; 24(4); 972-84. ©2017 AACR.

Role of Imaging in Response Assessment and Individualised Treatment for Sarcomas

The first systematic response evaluation criteria were established by WHO, based on the tumor size changes shortly after the computed tomography (CT) technique became available to the daily practice. RECIST, a simplified version of WHO criteria, and its newer version, RECIST1.1 are the currently available international response evaluation criteria in solid tumors and remains based on tumor size changes. While the introduction of molecularly targeted drugs has significantly improved the survival in patient with sarcomas, the evaluation of tumor response has become more complicated. Increasing number of studies have reported the lack of shrinkage in responding tumors and raised concerns of significant underestimation of responses using RECIST. The first such observation was made on gastrointestinal stromal tumor (GIST) treated with imatinib. In GISTs responding to imatinib, the degree of contrast enhancement on CT typically decreases significantly compared with the baseline, and, regardless of whether tumors shrink, heterogeneous hyperattenuating tumors become homogeneous hypoattenuating tumors with a smaller enhancing solid component. In current oncology practice, CT is a widely accepted method of evaluating tumor response. CT images are relatively simple to acquire and can be reasonably reproduced with no significant technical obstacles. FDG-PET is highly sensitive and specific in identifying responding sarcomas. It has mostly been used as a problem solver and for those with marginally resectable GIST. More recently, the utility of whole body MRI is undergoing exploration. This article discusses the traditional size-based response evaluation criteria, and introduces new evidence based response evaluation based on changes in morphology in addition to changes in tumor size on CT images, and whole body imaging is introduced at the end.

Imaging therapy response of gastrointestinal stromal tumors (GIST) with FDG PET, CT and MRI: a systematic review

Purpose

Improvement of the therapeutic approaches in gastrointestinal stromal tumors (GIST) by the introduction of targeted therapies requires appropriate diagnostic tools, which allow sufficient assessment of therapeutic response, including differentiation of true progression from pseudoprogression due to myxoid degeneration or intratumoral hemorrhage. In this literature review the impact and limitations of different imaging modalities used in GIST therapy monitoring are discussed.

Methods

PubMed and Cochrane library search were performed using appropriate keywords. Overall, 39 original papers fulfilled the defined criteria and were included in this systematic review.

Results

Morphological imaging modalities like computed tomography (CT) are primarily used for both diagnosis and therapy monitoring. However, therapy with tyrosine kinase inhibitors and other targeted therapies in GIST may lead only to a minor tumor volume reduction even in cases of response. Therefore, the use of Response Evaluation Criteria in Solid Tumors (RECIST) has limitations. To overcome those limitations, modified response criteria have been introduced for the CT-based therapy assessment, like the Choi criteria as well as criteria based on dual energy CT studies. Functional imaging techniques, mostly based on FDG PET-CT are in use, in particular for the assessment of early treatment response.

Conclusions

The impact and the limitations of PET-based therapy monitoring, as well as its comparison with CT, MRI and survival data are discussed in this review. CT is still the standard method for the evaluation of therapy response despite its several limitations. FDG PET-CT is helpful for the assessment of early therapy response; however, more prospective data are needed to define its role as well as the appropriate time intervals for therapy monitoring. A multiparametric evaluation based on changes in both morphological and functional data has to be assessed in further prospective studies.

The clinical utility of FDG PET/CT among solid organ transplant recipients suspected of malignancy or infection

PURPOSE

Solid organ transplant (SOT) recipients are at high risk of developing infections and malignancies. 18F-FDG PET/CT may enable timely detection of these diseases and help to ensure early intervention. We aimed to describe the clinical utility of FDG PET/CT in consecutive, diagnostic unresolved SOT recipients transplanted from January 2004 to May 2015.

METHODS

Recipients with a post-transplant FDG PET/CT performed as part of diagnostic work-up were included. Detailed chart reviews were done to extract relevant clinical information and determine the final diagnosis related to the FDG PET/CT. Based on á priori defined criteria and the final diagnosis, results from each scan were classified as true or false, and diagnostic values determined.

RESULTS

Among the 1,814 recipients in the cohort, 145 had an FDG PET/CT performed; 122 under the indication of diagnostically unresolved symptoms with a suspicion of malignancy or infection. The remaining (N = 23) had an FDG PET/CT to follow-up on a known disease or to stage a known malignancy. The 122 recipients underwent a total of 133 FDG PET/CT scans performed for a suspected malignancy (66 %) or an infection (34 %). Sensitivity, specificity, and positive and negative predictive values of the FDG PET/CT in diagnosing these conditions were 97, 84, 87, and 96 %, respectively.

CONCLUSION

FDG PET/CT is an accurate diagnostic tool for the work-up of diagnostic unresolved SOT recipients suspected of malignancy or infection. The high sensitivity and NPV underlines the potential usefulness of PET/CT for excluding malignancy or focal infections in this often complex clinical situation.

The value of (18) F-fluorodeoxyglucose positron emission tomography for prediction of treatment response in gastrointestinal stromal tumors: a systematic review and meta-analysis

BACKGROUND

Early detection of response to treatment is critically important in gastrointestinal stromal tumors (GIST). Therefore, the present systematic review and meta-analysis assessed the value of (18) f-fluorodeoxyglucose positron emission tomography ((18) FDG-PET) on prediction of therapeutic response of GIST patients to systemic treatments.

METHODS

The literature search was conducted using PubMed, SCOPUS, Cochrane, and Google Scholar databases, and review article references. Eligible articles were defined as studies included confirmed GIST patients who underwent (18) FDG-PET as well as assessing the screening role of it.

RESULTS

Finally, 21 relevant articles were included. The analysis showed the pooled sensitivity and specificity of 18FDG-PET in evaluation of response to treatment of GIST patient were 0.90 (95% CI: 0.85-0.94; I(2)  = 52.59, P = 0.001) and 0.62 (95% CI: 0.49-0.75; I(2)  = 69.7, P = 0.001), respectively. In addition, the pooled prognostic odds ratio of (18) FDG-PET for was 14.99 (95% CI, 6.42-34.99; I(2)  = 100.0, P < 0.001). The Meta regression showed that sensitivity of (18) FDG-PET was higher if the sample size of study was equal or more than 30 cases (sensitivity = 0.93; 95% CI: 0.89-0.97), when using PET/CT (sensitivity = 0.92; 95% CI: 0.89-0.97), and self-design criteria (sensitivity = 0.93; 95% CI: 0.87-1.0).

CONCLUSION

The present meta-analysis showed (18) FDG-PET has a significant value in predicting treatment response in GIST patients.

Personalized Clinical Decision Making in Gastrointestinal Malignancies: The Role of PET

Gastrointestinal malignancies comprise a heterogeneous group of diseases that include both common and rare diseases with very different presentations and prognoses. The mainstay of treatment is surgery in combination with preoperative and adjuvant chemotherapy depending on clinical presentation and initial stages. This article outlines the potential use of fluorodeoxyglucose-PET/CT in clinical decision making with special regard to preoperative evaluation and response assessment in gastric cancer (including the gastroesophageal junction), pancreatic cancer (excluding neuroendocrine tumors), colorectal cancer, and gastrointestinal stromal tumors.

[Gastrointestinal stromal tumors: diagnostics and therapy]

Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. The standard therapy is complete surgical resection with safety margins of 1-2 cm. Intraoperative rupture of the tumor capsule must be avoided because this carries a very high risk of tumor spread. A lymph node dissection is not routinely indicated as lymph node metastases very rarely occur with GIST. Smaller GISTs can normally be removed laparoscopically according to the rules of tumor surgery. Depending on the size of the tumor, the mitosis index and the localization of the primary tumor, the risk of recurrence after potentially curative resection is considerable in many cases. Patients with intermediate and high risks according to Miettinen's classification should receive adjuvant treatment with the tyrosine kinase inhibitor imatinib. Exceptions are those patients whose tumors exhibit the mutation D842V in exon18 of the PDGFRA gene. According to current European Society for Medical Oncology (ESMO) guidelines this therapy should be continued for 3 years. This leads to a significant improvement in progression-free survival compared to a 1-year therapy, and more important to an improvement in overall survival.

Contrast Media in PET/Computed Tomography Imaging

Is there a need for the contrast-enhanced PET/computed tomography (CT) scan or is the low-dose, non-contrast-enhanced PET/CT scan sufficient? The topic has been debated time and again. Although low-dose noncontrast CT serves the purpose of simple anatomic correlation and attenuation correction of PET images, many times patients have to undergo additional contrast-enhanced diagnostic imaging modalities, which may lead to a delay in decision-making. In this review, the authors have addressed various such issues related to the use of contrast agents and special techniques of clinical interest based on their utility in dual-modality PET/CT.

Gynecologic oncologic imaging with PET/CT

FDG-PET/CT has been evaluated in a variety of gynecologic malignancies in a variety of settings and is approved by the Centers for Medicare & Medicaid Services for the initial and subsequent treatment strategies of these malignancies. Cervical cancer is typically very FDG avid, and FDG-PET/CT appears to be most valuable for initial staging, radiation therapy planning, and detection of recurrent disease. For ovarian cancer, the most value of FDG-PET/CT appears to be for detecting recurrent disease in the setting of rising CA-125 level and negative or equivocal anatomical imaging studies. Initial studies evaluating response to therapy are promising and further work in this area is needed. FDG uptake in both nonmalignant and physiological processes in the pelvis can make interpretation of FDG-PET/CT in this region challenging and knowledge of these entities and patterns can avoid misinterpretation. Some of the most common findings relate to the cyclic changes that occur as part of the menstrual cycle in premenopausal women. Mucinous tumors and low-volume or peritoneal carcinomatosis are causes of false-negative results on FDG-PET/CT studies. As new tracers are developed, comparisons with patient outcomes and standards of care (eg, FDG-PET/CT) will be needed.

Role of fluorine 18 fluorodeoxyglucose positron emission tomography/computed tomography in gastrointestinal cancers

Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) has become a routine imaging modality for many malignancies and its use is currently increasing. In the present review article, we will summarize the evidence for FDG-PET/CT use in digestive cancers (excluding neuroendocrine tumours), and review the existing recommendations. While PET/CT is nowadays considered to be an important tool in the initial workup of oesophageal and anal cancers, new data are emerging regarding its use in assessing therapeutic efficacy, radiotherapy treatment planning, and detection of recurrence in case of isolated tumour marker elevation. Moreover, PET/CT may help decision making by detecting distant metastatic sites especially in potentially resectable metastatic colorectal cancer and, to a lesser extent, in localized gastric and pancreatic cancers. Finally, incidental focal colonic FDG uptakes require exploration by colonoscopy, as they are often associated with premalignant or malignant lesions.

¹⁸F-FDG PET/CT for Therapy Control in Vascular Graft Infections: A First Feasibility Study

The aim of this study was to evaluate the clinical value of PET/CT with (18)F-FDG for therapy control in patients with prosthetic vascular graft infections (PVGIs).

METHODS

In this single-center, observational, prospective cohort study, 25 patients with a median age of 66 y (range, 48-81 y) who had a proven PVGI were included. Follow-up (18)F-FDG PET/CT was performed at a median of 170 d (range, 89-249 d) after baseline examination. Two independent and masked interpreters measured maximum standardized uptake values to quantify metabolic activity and analyzed whole-body datasets for a secondary diagnosis (i.e., infectious foci not near the graft). The metabolic activity of the graft was correlated with clinical information and 2 laboratory markers (C-reactive protein and white blood cell count).

RESULTS

(18)F-FDG PET/CT had an impact on management in all patients. In 19 of 25 patients (76%), antibiotic treatment was continued because of the results of follow-up (18)F-FDG PET/CT. Antibiotic treatment was stopped or changed in 8% and 16% of patients, respectively. In 8 patients (32%), additional incidental findings were detected on follow-up (18)F-FDG PET/CT and had a further impact on patient management. Only in a subgroup of patients with PVGI and no other sites of infection was a significant correlation found between the difference in C-reactive protein at the time of baseline and follow-up (18)F-FDG PET/CT and the difference in maximum standardized uptake value (n = 11; R(2) = 0.67; P = 0.002).

CONCLUSION

(18)F-FDG PET/CT represents a useful tool in therapy monitoring of PVGI and has an impact on patient management.

Value of FDG PET/CT in Patient Management and Outcome of Skeletal and Soft Tissue Sarcomas

Fluorodeoxyglucose (FDG)-PET/computed tomography (CT) has been increasingly used in bone and soft tissue sarcomas and provides advantages in the initial tumor staging, tumor grading, therapy assessment, and recurrence detection. FDG-PET/CT metabolic parameters are reliable predictors of survival in sarcomas and could be implemented in risk stratification models along with other prognostic factors in these patients.

PET/Computed Tomography in the Diagnosis and Staging of Gastric Cancers

Although there has been a reduction of the incidence and mortality of gastric cancer, it remains among the commonest causes of cancer-related death. Accurate staging and evaluation of treatment response are vital for management. PET is used to complement anatomic imaging in cancer management. PET/computed tomography (CT) has demonstrated its potential value for preoperative staging, evaluation of response to therapy, and detection of recurrence. Not all types of gastric cancers have a high affinity for fluorodeoxyglucose. PET/CT in the evaluation and staging of gastric cancer is not established, but studies indicate that there may be an evolving role for this imaging modality.

Assessment of early response to imatinib 800 mg after 400 mg progression by 18F-fluorodeoxyglucose PET in patients with metastatic gastrointestinal stromal tumors

ABSTRACT 

Introduction: Imatinib is the standard first-line therapy for advanced gastrointestinal stromal tumor. 18F-fluorodeoxyglucose PET computed tomography (FDG PET/CT) shows a faster response than computed tomography in nonpretreated patients. Patients & methods: After disease progression on imatinib 400 mg, 16 patients were exposed to 800 mg. Tumor response was evaluated by FDG PET/CT on days 7 and 37. Primary objective was to correlate early metabolic response (EMR) with progression-free survival (PFS). Results: EMR by FDG PET/CT scan was not predictive of PFS. Median PFS in these patients was 3 months. Overall survival was influenced by gastric primary site (p = 0.05). Conclusion: The assessment of EMR by FDG PET/CT in patients with advanced gastrointestinal stromal tumor exposed to imatinib 800 mg was not predictive of PFS or overall survival.

Performance evaluation of endoscopic Cerenkov luminescence imaging system: in vitro and pseudotumor studies

By integrating the clinically used endoscope with the emerging Cerenkov luminescence imaging (CLI) technology, a new endoscopic Cerenkov luminescence imaging (ECLI) system was developed. The aim is to demonstrate the potential of translating CLI to clinical studies of gastrointestinal (GI) tract diseases. We systematically evaluated the feasibility and performance of the developed ECLI system with a series of in vitro and pseudotumor experiments. The ECLI system is comprised of an electron multiplying charge coupled device (EMCCD) camera coupled with a clinically used endoscope via an optical adapter. A 1951-USAF test board was used to measure the white-light lateral resolution, while a homemade test chart filled with (68)Ga was employed to measure the CL lateral resolution. Both in vitro and pseudotumor experiments were conducted to obtain the sensitivity of the ECLI system. The results were validated with that of CLI using EMCCD only, and the relative attenuation ratio of the ECLI system was calculated. Results showed that The white-light lateral resolution of the ECLI system was 198 µm, and the luminescent lateral resolution was better than 1 mm. Sensitivity experiments showed a theoretical sensitivity of [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]) for the in vitro and pseudotumor studies, respectively. The relative attenuation ratio of ECLI to CLI was about 96%. The luminescent lateral resolution of the ECLI system was comparable with that of positron emission tomography (PET). The pseudotumor study illustrated the feasibility and applicability of the ECLI system in living organisms, indicating the potential for translating the CLI technology to the clinic.

Diagnosis and evaluation of gastric cancer by positron emission tomography

Gastric cancer is the second leading cause of cancer mortality worldwide. The diagnosis of gastric cancer has been significantly improved with the broad availability of gastrointestinal endoscopy. Effective technologies for accurate staging and quantitative evaluation are still in demand to merit reasonable treatment and better prognosis for the patients presented with advanced disease. Preoperative staging using conventional imaging tools, such as computed tomography (CT) and endoscopic ultrasonography, is inadequate. Positron emission tomography (PET), using ¹⁸F-fluorodeoxyglucose (FDG) as a tracer and integrating CT for anatomic localization, holds a promise to detect unsuspected metastasis and has been extensively used in a variety of malignancies. However, the value of FDG PET/CT in diagnosis and evaluation of gastric cancer is still controversial. This article reviews the current literature in diagnosis, staging, response evaluation, and relapse monitoring of gastric cancer, and discusses the current understanding, improvement, and future prospects in this area.

Metabolic regulation of cancer cell side population by glucose through activation of the Akt pathway

Side population (SP) cells within tumors are a small fraction of cancer cells with stem-like properties that can be identified by flow cytometry analysis based on their high ability to export certain compounds such as Hoechst 33342 and chemotherapeutic agents. The existence of stem-like SP cells in tumors is considered as a key factor contributing to drug resistance, and presents a major challenge in cancer treatment. Although it has been recognized for some time that tumor tissue niches may significantly affect cancer stem cells (CSCs), the role of key nutrients such as glucose in the microenvironment in affecting stem-like cancer cells and their metabolism largely remains elusive. Here we report that SP cells isolated from human cancer cells exhibit higher glycolytic activity compared to non-SP cells. Glucose in the culture environment exerts a profound effect on SP cells as evidenced by its ability to induce a significant increase in the percentage of SP cells in the overall cancer cell population, and glucose starvation causes a rapid depletion of SP cells. Mechanistically, glucose upregulates the SP fraction through ATP-mediated suppression of AMPK and activation of the Akt pathway, leading to elevated expression of the ATP-dependent efflux pump ABCG2. Importantly, inhibition of glycolysis by 3-BrOP significantly reduces SP cells in vitro and impairs their ability to form tumors in vivo. Our data suggest that glucose is an essential regulator of SP cells mediated by the Akt pathway, and targeting glycolysis may eliminate the drug-resistant SP cells with potentially significant benefits in cancer treatment.

Diffusion-weighted magnetic resonance imaging in metastatic gastrointestinal stromal tumor (GIST): a pilot study on the assessment of treatment response in comparison with 18F-FDG PET/CT

BACKGROUND

Diffusion-weighted magnetic resonance imaging (MRI) is increasingly being used for assessing the treatment succes in oncology, but the real clinical value needs to evaluated by comparison with other, already established, metabolic imaging techniques.

PURPOSE

To prospectively evaluate the clinical potential of diffusion-weighted MRI with apparent diffusion coefficient (ADC) mapping for gastrointestinal stromal tumor (GIST) response to targeted therapy compared with 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT).

MATERIAL AND METHODS

Eight patients (mean age, 56 ± 11 years) known to have metastatic GIST underwent 18F-FDG PET/CT and MRI (T1Gd, DWI [b = 50,300,600], ADC mapping) simultaneously, before and after change in targeted therapy. MR and PET/CT examinations were first analyzed blindly. Second, PET/CT images were co-registered with T1Gd-MR images for lesion detection. Only 18F-FDG avid lesions were considered. Maximum standardized uptake value (SUVmax) and the corresponding minimum ADCmin were measured for the six largest lesions per patient, if any, on baseline and follow-up examinations. The relationship between changes in SUVmax and ADCmin was analyzed (Spearman's correlation).

RESULTS

Twenty-four metastases (12 hepatic, 12 extra-hepatic) were compared on PET/CT and MR images. SUVmax decreased from 7.7 ± 8.1 g/mL to 5.5 ± 5.4 g/mL (P = 0.20), while ADCmin increased from 1.2 ± 0.3 × 10(-3)mm(2)/s to 1.5 ± 0.3 × 10(-3)mm(2)/s (P = 0.0002). There was a significant association between changes in SUVmax and ADCmin (rho = - 0.62, P = 0.0014), but not between changes in lesions size (P = 0.40).

CONCLUSION

Changes in ADCmin correlated with the response of 18F-FDG avid GIST to targeted therapy. Thus, diffusion-weighted MRI may represent a radiation-free alternative for follow-up treatment for metastatic GIST patients.

Role of positron emission tomography-computed tomography in gastrointestinal malignancies

Positron emission tomography (PET) has proved itself to be valuable in the evaluation of patients with a wide array of gastrointestinal (GI) malignancies. Subsequent development of fusion imaging with PET and computed tomography (PET-CT) scanners has significantly advanced the capabilities of imaging by combining the functional data of the(18)F-labeled glucose analogue fluorodeoxyglucose (FDG) with the conventional anatomic data provided by CT. This article reviews the evolving role of FDG PET-CT imaging in the initial assessment and monitoring of GI tumors. Specific applications are discussed, and normal variants and benign findings frequently encountered during PET-CT of the GI tract are reviewed.

Future challenges of multimodality imaging

During the last decade, positron emission tomography/computed tomography (PET/CT) and single-photon emission computed tomography/computed tomography (SPECT/CT) have procured advances in research and clinical application of fusion imaging. The recent introduction of systems that combine PET and MRI opens new horizons for multimodality molecular imaging. These systems offer simultaneous morphologic, functional, and molecular information of a living system. Moreover, other combinations of anatomic and functional imaging modalities (for example CT and MRI or PET and optical imaging) are emerging, holding promise in basic medical research or in clinical medicine. These developments are paralleled by advances in the field of biomolecules and particles, to provide new agents useful for more than one imaging modality and to facilitate the study of the same target by different imaging devices. In the near future PET/MRI may emerge as a new powerful multimodality technique in clinical oncology, offering considerable potential for imaging applications beyond correlation of functional and anatomic images. Future developments should include the simultaneous acquisition of multifunctional data such as PET tracer uptake, MR spectroscopy, or fMRI along with high-resolution anatomic MRI.

Benign mesocolon schwannoma in PET/CT and immunohistochemistry assessment: a case report

Schwannoma is a common soft tissue tumour, but it appears to be very rare in the gastrointestinal tract. Benign schwannoma develops extremely rarely in the mesocolon, with only 2 patients reported in the literature. A 75-year-old woman was admitted to our Department of Oncological Surgery with an abdominal mass, which was discovered incidentally during abdominal ultrasound examination. Positron emission tomography/ computed tomography imaging with the use of 18F-fluorodeoxyglucose (FDG PET/CT) showed an abnormal mass in the upper right abdomen with the presence of diffuse FDG uptake. A laparotomy revealed an encapsulated, non-invasive mesocolon tumour in the hepatic flexure region. Definitive diagnosis was confirmed by the histopathological examination of the postoperative preparation. Immunohistochemical staining confirmed benign mesocolon schwannoma. Previous cases indicate that schwannomas in the mesocolon are benign tumours. Our patient had a good prognosis even after enucleation treatment. Although schwannomas are very rare and generally asymptomatic, the differential diagnosis of schwannomas and gastrointestinal stromal tumours is important for practical purposes.

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.

Current and emerging strategies for the management of imatinib-refractory advanced gastrointestinal stromal tumors

Since its approval by the US Food and Drug Administration in February 2002, the tyrosine kinase inhibitor, imatinib, has become the standard of care for patients with metastatic or unresectable KIT-positive gastrointestinal stromal tumors (GISTs). Imatinib functions by blocking the adenosine triphosphate binding site of the constitutively activated mutant KIT or platelet-derived growth factor receptor α, effectively shutting down the oncogenic signal that drives up to 90% of these tumors. In doing so, it has transformed the management of a condition previously refractory to systemic treatments and established GIST as a model for the use of targeted therapies and oncogene addiction in solid tumors. However, while more than 80% of patients will receive clinical benefit from imatinib monotherapy, more than half will develop progressive disease by 2 years. In this article we review the mechanism and patterns of imatinib resistance in GIST; attempt to offer a practical schema for managing imatinib-refractory patients; and lastly, offer some insight as to future directions and emerging therapeutics for the management of this highly interesting and challenging disease.

FDG PET and FDG PET/CT in patients with gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs) are fairly rare neoplasms, constituting less than 3 % of all gastrointestinal malignancies. The integration of molecularly targeted treatment regimes (i.e., tyrosine kinase inhibitors) in clinical oncology has revolutionized the management of patients with irresectable GISTs or metastatic disease. Malignant GISTs usually display increased glucose metabolism and therefore (18)F-fluorodeoxyglucose (FDG) uptake within the scope of positron emission tomography (PET) scans. Nowadays, dual-modality FDG PET/CT (computed tomography) imaging is of considerable value in diagnostic work-up of patients with GISTs acquiring functional and anatomic information simultaneously. The following article sheds light on the impact of FDG PET and combined FDG PET/CT imaging in initial disease evaluation, detection of tumour recurrence and the early assessment of treatment response to molecularly targeted agents such as imatinib mesylate or sunitinib maleate.

[Surgical treatment of gastrointestinal stromal tumours. Analysis of our experience]

INTRODUCTION

Gastrointestinal stromal tumours (GIST) make up 2% of gastrointestinal tumours. Surgery is the only treatment method in localised cases. The laparoscopic approach has increased over the last few years. We present our experience in the treatment of GIST.

MATERIAL AND METHODS

A total of 40 patients with 45 GIST had been subjected to surgical treatment between 1997 and 2010. Data was retrospectively collected on, demographic characteristics, location and tumour biology, diagnosis, type of surgery and the results of that surgery.

RESULTS

A total of 24 males and 16 women, with a mean age of 66.7 years, were treated. The location was gastric in 24 cases (60%), small intestine in 13 (32.5%), colon in 2 (5%) and oesophagus in 1 case (2.5%). Laparotomy was performed in 27 cases, 12 by laparoscopy (1 thoracoscopy), and 1 endoscopic sigmoid tumour resection. Four cases (10%), all after laparotomy, had recurred after a median follow-up of 31 months (2-120), and 2 patients of the laparotomy group died due to their cancer. After a univariate analysis, the prognostic factors for a laparoscopic recurrence were: tumour size (P=.0001), mitosis number (P=.001), being a locally advanced tumour (P=.01) and a ruptured tumour (P=.002). Only size remained as a prognostic factor after the multivariate analysis (P=.029; RR 1.363; 95% CI; 1.033-1.799). The presence of a locally advanced tumour was shown to be significant in the univariate analysis, while there were no significant factors after the multivariate analysis.

CONCLUSIONS

Correct preoperative staging is essential for deciding which surgical approach to employ.

Consensus report on the radiological management of patients with gastrointestinal stromal tumours (GIST): recommendations of the German GIST Imaging Working Group

The aim was to reach consensus in imaging for staging and follow-up as well as for therapy response assessment in patients with gastrointestinal stromal tumours (GIST). The German GIST Imaging Working Group was formed by 9 radiologists engaged in assessing patients with GIST treated with targeted therapy. The following topics were discussed: indication and optimal acquisition techniques of computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET)/CT; tumour response assessment considering response criteria and measurement techniques on CT, MRI and PET/CT; result interpretation; staging interval and pitfalls. Contrast-enhanced CT is the standard method for GIST imaging. MRI is the method of choice in case of liver-specific questions or contraindications to CT. PET/CT should be used for early response assessment or inconclusive results on morphologic imaging. All imaging techniques should be standardized allowing a reliable response assessment. Response has to be assessed with respect to lesion size, lesion density and appearance of new lesions. A critical issue is pseudoprogression due to myxoid degeneration or intratumoural haemorrhage. The management of patients with GIST receiving a targeted therapy requires a standardized algorithm for imaging and an appropriate response assessment with respect to changes in lesion size and density.

Monitoring the effect of targeted therapies in a gastrointestinal stromal tumor xenograft using a clinical PET/CT

Purpose

The purpose of this study is to assess treatment responses induced by the two tyrosine kinase inhibitors, Imatinib and Sunitinib, in a gastrointestinal stromal tumor (GIST) xenograft using a clinical positron emission tomography/computed tomography (PET/CT) scanner.

Methods

Nude mice bearing human GIST xenografts with mutations in exons 11 and 17 were randomly allocated to treatment with Imatinib, Sunitinib, or placebo daily for seven consecutive days. 2-deoxy-2-[¹⁸F]fluoro-d-glucose PET (¹⁸F-FDG-PET/CT) was performed in a clinical PET/CT scanner at baseline (day 0) and 1 and 7 days after onset of treatment. Treatment response was assessed by measuring tumor volumes and by calculation of tumor-to-liver ¹⁸F-FDG uptake ratios.

Results

Minor reductions in tumor volume were observed in both treatment groups. For the two treatment groups, significantly decreased tumor-to-liver uptake ratios were observed both at day 1 (Imatinib, −41%, p = .002; Sunitinib, −55%, p < .001) and at day 8 (Imatinib, −35%, p < .001; Sunitinib, −50%, p < .001), when compared to individual baseline values. For the control tumors, neither tumor volumes nor tumor-to-liver uptake ratios were altered during the 8 days the experiment lasted.

Conclusions

Significant anti-tumor effects were demonstrated following treatment with both Imatinib and Sunitinib. Decreased tumor-to-liver uptake ratios were more pronounced than tumor volume reductions. Effects of novel targeted therapies can be evaluated in the GIST xenograft model using a clinical PET/CT scanner.

Gastrointestinal stromal tumors

INTRODUCTION

The gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the intestinal tract, known to be refractory to conventional chemotherapy or radiation. Its pathogenesis is defined by mutations within the KIT and PDGFRA gene, which constitutively activate KIT and PDGFRA oncoproteins, and serve as crucial diagnostic and therapeutic targets.

DISCUSSION

Besides surgery, therapy with imatinib mesylate, which inhibits KIT kinase activity, represents the other cornerstone for the treatment of GIST. Still, the only curative option for GIST is given after complete surgical removal even in a metastatic setting, but recurrence is common, and the risk can be defined by surgical factors like incomplete resection, intraperitoneal rupture, or bleeding and tumor associated factors like tumor size, mitotic index, or localization.

CONCLUSION

Consequently, adjuvant therapy with imatinib mesylate or other tyrosine kinase inhibitors is recommended for high-risk patients after complete resection. For unresectable and advanced GIST, a partial response or stable disease can be achieved in about 80% of patients with imatinib mesylate.

CT features, mimics and atypical presentations of gastrointestinal stromal tumor (GIST)

The term stromal tumor was coined in 1983 by Clark and Mazur for smooth muscle neoplasm of the gastrointestinal tract (GIT). Gastrointestinal stromal tumors (GIST) are nonepithelial tumors arising from the interstitial cells of Cajal, which express KIT protein-CD117 on immunohistochemistry. GIST can arise anywhere in the GIT, including the mesentery, omentum, and retroperitoneum.

Early [18F]fluorodeoxyglucose positron emission tomography at two days of gefitinib treatment predicts clinical outcome in patients with adenocarcinoma of the lung

PURPOSE

Positron emission tomography (PET) with [(18)F]fluorodeoxyglucose (FDG) is increasingly used in early assessment of tumor response after chemotherapy. We investigated whether a change in [(18)F]FDG uptake at 2 days of gefitinib treatment predicts outcome in patients with lung adenocarcinoma.

EXPERIMENTAL DESIGN

Twenty patients were enrolled. [(18)F]FDG-PET/computed tomographic (CT) scan was carried out before and 2 days after gefitinib treatment. Maximum standardized uptake values (SUV) were measured, and post-gefitinib percentage changes in SUV were calculated. Early metabolic response (SUV decline < -25%) was compared with morphologic response evaluated by CT scan and with progression-free survival (PFS).

RESULTS

At 2 days of gefitinib treatment, 10 patients (50%) showed metabolic response, 8 had metabolic stable disease, and 2 had progressive metabolic disease. Percentage changes of SUV at 2 days were correlated with those of tumor size in CT at 1 month (R(2) = 0.496; P = 0.0008). EGFR gene was assessable in 15 patients, and of 12 patients with EGFR mutations, 8 showed metabolic response at 2 days and 6 showed morphologic response at 1 month. None of 3 patients with wild-type EGFR showed metabolic or morphologic response. Metabolic response at 2 days was not statistically associated with PFS (P = 0.095), but when a cutoff value of -20% in SUV decline was used, metabolic responders had longer PFS (P < 0.0001).

CONCLUSION

Early assessment of [(18)F]FDG tumor uptake with PET at 2 days of gefitinib treatment could be useful to predict clinical outcome earlier than conventional CT evaluation in patients with lung adenocarcinoma.

F-FDG PET Imaging in the Evaluation of Treatment Response to New Chemotherapies beyond Imatinib for Patients with Gastrointestinal Stromal Tumors

Aim. (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) is a powerful tool for staging and defining "good responders" to chemotherapy in tumor setting. Gastrointestinal stromal tumors (GISTs) are sarcoma involving gastrointestinal tract and may require a chemotherapy including imatinib, a tyrosine kinase inhibitor agent. Some GIST patients become refractory to imatinib; therefore, other tyrosine kinase inhibitors or concomitant chemotherapy may be considered for treatment. The aim of this paper is to assess if (18)F-FDG PET imaging is a useful tool to evaluate treatment response to new chemotherapies beyond imatinib for GIST patients. Methods. We performed a review of the literature about the role of (18)F-FDG PET in the evaluation of treatment response to new chemotherapies beyond imatinib for GIST patients. Results and Conclusions. (18)F-FDG PET seems to be able to assess therapy response earlier than computed tomography (CT) imaging in imatinib refractory GIST patients treated with other agents. However, a dual modality PET-CT imaging is recommendable to achieve a better detection of all lesions.

Treatment of gastrointestinal stromal tumor: focus on imatinib mesylate

Gastrointestinal stromal tumor (GIST) is a rare primary neoplasm of the gastrointestinal tract, mesentery, or omentum. In the past, surgery has been the only effective treatment. The diagnosis and treatment of GIST has been revolutionized over the past decade, since expression of the receptor tyrosine kinase KIT was shown to occur on these tumors. Mutations in this proto-oncogene commonly cause constitutive activation of the KIT tyrosine kinase receptor, an important factor in the pathogenesis of the disease. The development of specific tyrosine kinase inhibitors, such as imatinib mesylate, has led to a breakthrough in the treatment of advanced GIST. Treatment with this drug has led to significant improvements in survival, with overall response rates in excess of 80%. Side effects are common, but usually manageable. The success of this drug has led to further trials investigating its use in the pre- and postoperative situation. This review summarizes the current knowledge of GIST and imatinib treatment and possible future developments.