Early prediction of response to sunitinib after imatinib failure by 18F-fluorodeoxyglucose positron emission tomography in patients with gastrointestinal stromal tumor

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

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

Sunitinib for the treatment of metastatic gastrointestinal stromal tumors: the effect of TDM-guided dose optimization on clinical outcomes

BACKGROUND

Sunitinib is an oral anticancer drug approved for the treatment of among others gastrointestinal stromal tumor (GIST). Previous analyses demonstrated an exposure-response relationship at the standard dose, and minimum target levels of drug exposure have been defined above which better treatment outcomes are observed. Therapeutic drug monitoring (TDM) could be used as a tool to optimize the individual dose, aiming at sunitinib trough concentrations ≥37.5 ng/ml for continuous dosing. Nonetheless, data on the added value of TDM-guided dosing on clinical endpoints are currently lacking. Therefore, we evaluate the effect of TDM in patients with advanced and metastatic GIST treated with sunitinib in terms of efficacy and toxicity.

PATIENTS AND METHODS

A TDM-guided cohort was compared to a non-TDM-guided cohort in terms of median progression-free survival (mPFS) and overall survival (mOS). Also, mPFS between patients with and without dose-limiting toxicities (DLTs) was compared. Patients in the prospective cohort were included in two studies on TDM-guided dosing (the DPOG-TDM study and TUNE study). The retrospective cohort consisted of patients from the Dutch GIST Registry who did not receive TDM-guided dosing.

RESULTS

In total, 51 and 106 patients were included in the TDM-guided cohort and non-TDM-guided cohort, respectively. No statistical difference in mPFS was observed between these two cohorts (39.4 versus 46.9 weeks, respectively; P = 0.52). Patients who experienced sunitinib-induced DLTs had longer mPFS compared to those who did not (51.9 versus 28.9 weeks, respectively; P = 0.002).

CONCLUSIONS

Our results do not support the routine use of TDM-guided dose optimization of sunitinib in patients with advanced/metastatic GIST to improve survival.

[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 Prediction and Monitoring of Treatment Response in Gastrointestinal Stromal Tumors by Means of Imaging: A Systematic Review

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal neoplasms. Tyrosine kinase inhibitor (TKI) therapy is currently part of routine clinical practice for unresectable and metastatic disease. It is important to assess the efficacy of TKI treatment at an early stage to optimize therapy strategies and eliminate futile ineffective treatment, side effects and unnecessary costs. This systematic review provides an overview of the imaging features obtained from contrast-enhanced (CE)-CT and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) PET/CT to predict and monitor TKI treatment response in GIST patients. PubMed, Web of Science, the Cochrane Library and Embase were systematically screened. Articles were considered eligible if quantitative outcome measures (area under the curve (AUC), correlations, sensitivity, specificity, accuracy) were used to evaluate the efficacy of imaging features for predicting and monitoring treatment response to various TKI treatments. The methodological quality of all articles was assessed using the Quality Assessment of Diagnostic Accuracy Studies, v2 (QUADAS-2) tool and modified versions of the Radiomics Quality Score (RQS). A total of 90 articles were included, of which 66 articles used baseline [18F]FDG-PET and CE-CT imaging features for response prediction. Generally, the presence of heterogeneous enhancement on baseline CE-CT imaging was considered predictive for high-risk GISTs, related to underlying neovascularization and necrosis of the tumor. The remaining articles discussed therapy monitoring. Clinically established imaging features, including changes in tumor size and density, were considered unfavorable monitoring criteria, leading to under- and overestimation of response. Furthermore, changes in glucose metabolism, as reflected by [18F]FDG-PET imaging features, preceded changes in tumor size and were more strongly correlated with tumor response. Although CE-CT and [18F]FDG-PET can aid in the prediction and monitoring in GIST patients, further research on cost-effectiveness is recommended.

PET Molecular Imaging: A Holistic Review of Current Practice and Emerging Perspectives for Diagnosis, Therapeutic Evaluation and Prognosis in Clinical Oncology

PET/CT molecular imaging has been imposed in clinical oncological practice over the past 20 years, driven by its two well-grounded foundations: quantification and radiolabeled molecular probe vectorization. From basic visual interpretation to more sophisticated full kinetic modeling, PET technology provides a unique opportunity to characterize various biological processes with different levels of analysis. In clinical practice, many efforts have been made during the last two decades to standardize image analyses at the international level, but advanced metrics are still under use in practice. In parallel, the integration of PET imaging with radionuclide therapy, also known as radiolabeled theranostics, has paved the way towards highly sensitive radionuclide-based precision medicine, with major breakthroughs emerging in neuroendocrine tumors and prostate cancer. PET imaging of tumor immunity and beyond is also emerging, emphasizing the unique capabilities of PET molecular imaging to constantly adapt to emerging oncological challenges. However, these new horizons face the growing complexity of multidimensional data. In the era of precision medicine, statistical and computer sciences are currently revolutionizing image-based decision making, paving the way for more holistic cancer molecular imaging analyses at the whole-body level.

Non-FDG PET/CT

The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.

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.

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.

Predictive value of positron emission tomography for the prognosis of molecularly targeted therapy in solid tumors

Objective

This study aimed at comprehensively exploring the value applying positron emission tomography (PET) to predict the effect of molecularly targeted therapy in solid tumors.

Materials and methods

A systematic search was performed for potentially relevant studies from the time of inception to February 2017. The primary endpoints were progression-free survival (PFS), overall survival (OS), and time to progression (TTP). The results were analyzed by Review Manager version 5.3 (RevMan 5.3) statistical software. Subgroup analyses were implemented based on the type of molecularly targeted agents (monoclonal antibodies arm and small molecular targeted agents arm), mechanism (erlotinib/gefitinib arm and bevacizumab arm), radioactive tracers, type of tumor, and reevaluated PET timing.

Results

Twenty-six studies incorporating 865 individuals were eligible. Compared with PET nonresponse group, PET response group displayed a decrease in maximal standard uptake value (SUVmax), which was associated with a significantly prolonged PFS (HR =0.41, 95% CI [0.29, 0.59]; P<0.00001), OS (HR =0.52, 95% CI [0.40, 0.67]; P<0.00001), and TTP (HR =0.30, 95% CI [0.14, 0.66]; P=0.003). Similar results were obtained in the subgroup analyses of PFS in erlotinib/gefitinib arm and small molecular targeted agents arm; and OS in lung cancer arm, erlotinib/gefitinib arm, bevacizumab arm, small molecular targeted agents arm, monoclonal antibodies arm, 18F-fluorodeoxythymidine (18F-FLT) arm, 18F-fluorodeoxyglucose (18F-FDG) arm, and early PET timing arm.

Conclusion

Our study demonstrated that PET was a favorable approach to predict the prognosis of molecularly targeted therapy for solid tumors. PET assessment within 2 weeks could be useful to predict clinical outcome.

The 18F-FDG PET/CT response to radiotherapy for patients with spinal metastasis correlated with the clinical outcomes

PURPOSE

To evaluate the potential role of 18F-fluorodeoxyglucose-positron emission tomography/computerized tomography (FDG-PET/CT) for predicting treatment response after radiotherapy (RT) in patients with spinal metastases.

MATERIALS AND METHODS

A retrospective analysis was performed of 42 patients with spinal metastases who received RT from January 2010 to December 2014. All patients underwent FDG-PET/CT before and after treatment. Changes in metabolic responses, expressed as the maximum, mean, peak standardized uptake values (SUVmax, SUVmean, SUVpeak), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were analyzed to determine their association with clinical outcomes.

RESULTS

The median age at the time of spinal metastasis diagnosis was 58 years. Median progression-free survival (PFS) and overall survival after RT were 15 months and 22.4 months, respectively. RT produced a significant decrease in SUVmean (2.27 to 1.41), SUVmax (6.87 to 2.99), SUVpeak (5.75 to 2.33) and TLG (52.84 to 24.17) when compared with the baseline values (p<0.001). The mean pain score decreased from 3.86 before RT to 0.79 after RT (p<0.001). There were significant linear relationships between maximum SUV and pain scores at baseline (r = 0.321, p = 0.038) and after treatment (r = 0.369, p = 0.016) as well as TLG at baseline (r = 0.428, p = 0.005) and after treatment (r = 0.403, p = 0.009). Local progression after treatment was identified in 12 patients (28.6%). Univariate analyses showed that >70% reduction in maximum SUV after treatment was independently associated with good PFS (p = 0.036).

CONCLUSIONS

RT is an effective treatment for patients with spinal metastases, and there were significant changes in PET parameters compared with baseline. The metabolic response measured by SUV and TLG changes in FDG-PET/CT correlated with the clinical outcomes, especially with shorter PFS in patients who had higher residual maximum SUV after treatment.

Imaging pediatric gastrointestinal stromal tumor (GIST)

BACKGROUND

Gastrointestinal stromal tumors (GIST) are extremely rare in children. Imaging plays a key role in staging and monitoring therapy (surgical and with tyrosine kinase inhibitors). The vast majority of articles addressing imaging of GIST base on adults and are based on CT. The subtype "pediatric GIST" - if at all - is only mentioned in a dependent clause. Although the imaging features in children and adults are similar, histology, clinical course and thus imaging approach are different.

METHODS

A PubMed search using the search terms "Gastrointestinal stromal tumor, GIST, WT GIST, children, pediatric, carney's triad, imaging, staging, follow-up, MRI, CEUS, ultrasonography, Positron emission tomography" was conducted. Studies that reported on laparoscopy, endoscopy and surgical techniques only were excluded.

RESULTS

Based on our selective literature review, we present alternative radiological imaging strategies using MRI, contrast enhanced ultrasound (CEUS) and PET-CT to stage and follow-up pediatric GIST patients. As pediatric GIST often is a chronic disease, minimizing exposure to ionizing radiation is mandatory.

CONCLUSION

MRI, contrast enhanced ultrasound and PET-CT instead of CT are the imaging modalities to evaluate pediatric GIST.

TYPE OF STUDY

Systematic review LEVEL OF EVIDENCE: III.

Pediatric gastrointestinal stromal tumors-a review of diagnostic modalities

Gastrointestinal stromal tumors are exceedingly rare tumors in the pediatric population, as a result many clinicians either may never see this diagnosis or will encounter it only a few times throughout their careers. It is imperative in the pediatric population to follow appropriate steps to ensure a swift diagnosis and referral to specialized centers that are equipped with the multidisciplinary teams accustomed to treating rare diseases. This review aims to discuss the most recent data available on the diagnostic modalities utilized in cases of suspected Pediatric GIST.

Primary Extragastrointestinal Stromal Tumor on FDG PET/CT

Primary extragastrointestinal stromal tumor is very rare. We report a case of cervical paravertebral extragastrointestinal stromal tumor involving adjacent bones revealed by FDG PET/CT in a 66-year-old man without any gastrointestinal involvement.

Pazopanib treatment of a platinum-resistant recurrence of a high-grade Sertoli cell tumor and assessment of the treatment response by FDG-PET/CT: A case report

Ovarian Sertoli cell tumors (SCTs) are rare sex cord tumors (Oliva et al., 2005). The standard treatment for high-grade SCTs is surgery followed by platinum-based chemotherapy. Although platinum-based chemotherapy is also an option for recurrent SCTs (Sigismondi et al., 2012), there is no established chemotherapy regimen for platinum-resistant recurrent SCTs. The effectiveness of pazopanib in treating epithelial ovarian cancer has recently been reported (du Bois et al., 2014; Pignata et al., 2015). In the case described herein, pazopanib was used to treat the platinum-resistant recurrence of a high-grade Sertoli cell tumor, and the response was evaluated by 18F-fluoro-deoxyglucose positron emission tomography (FDG-PET)-computed tomography (CT). Written informed consent to reporting the case was obtained from the patient.

Advances and Challenges on Management of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) originate from interstitial cells of Cajal and account for over 5,000 newly diagnosed cases in the United States. The discovery of activated KIT and PDGFRA mutations and introduction of imatinib revolutionized the treatment strategy and opened up the new era of target therapy for solid tumors. Although surgery remains the primary modality of treatment for curative purpose, almost half of the patients experienced disease recurrence. Tailoring (neo)-adjuvant treatment with imatinib is ongoing to meet the need for an effective therapy. Currently, two drugs (sunitinib and regorafenib) have obtained Food and Drug Administration approval for GISTs after imatinib failure. However, most of the patients eventually progress due to primary or secondary resistance. Deeper understanding of the molecular mechanisms will guide us to develop personalized strategies in the future. Discussion in this review includes current standard management and the most recent advances and multiple ongoing clinical trials with different approaches. This review will provide further steps to be taken to conquer refractory disease.

FDG PET/CT in cancer therapy monitoring

Objectives: We developed and tested a software tool for computer-assisted analysis of FDG-PET/CT in cancer therapy monitoring. The tool provides automatic semi-quantitative analysis of a baseline scan together with up to two follow-up scans (standardized uptake values, glycolytic volume). The tool also supports visual analysis by local spatial registration which allows display of tumor lesions with the same orientation in all scans. The tool’s stability and accuracy was tested at typical everyday image quality. Patients, methods: Ten unselected cancer patients in whom three FDG PET/CT scans had been performed were included. A total of 18 lesions were analyzed. Results: Automatic lesion tracking worked properly in all lesions but one. In this lesion local coregistration had to be adjusted manually tuwhich, however, is easily performed with the tool. Semi-automatic lesion segmentation and fully automatic semi-quantitative analysis worked properly in all cases. Computer-assisted analysis was significantly less time consuming than manual analysis. Conclusions: The novel software tool appears useful for analysis of FDGPET/ CT in cancer therapy monitoring in clinical routine patient care.

Monitoring for Response to Antineoplastic Drugs: The Potential of a Metabolomic Approach

For most cancers, chemotherapeutic options are rapidly expanding, providing the oncologist with substantial choices. Therefore, there is a growing need to select the best systemic therapy, for any individual, that effectively halts tumor progression with minimal toxicity. Having the capability to predict benefit and to anticipate toxicity would be ideal, but remains elusive at this time. An alternative approach is an adaptive approach that involves close observation for treatment response and emergence of resistance. Currently, response to systemic therapy is estimated using radiographic tests. Unfortunately, radiographic estimates of response are imperfect and radiographic signs of response can be delayed. This is particularly problematic for targeted agents, as tumor shrinkage is often not apparent with these drugs. As a result, patients are exposed to prolonged courses of toxic drugs that may ultimately be found to be ineffective. A biomarker-based adaptive strategy that involves the serial analysis of the metabolome is attractive. The metabolome changes rapidly with changes in physiology. Changes in the circulating metabolome associated with various antineoplastic agents have been described, but further work will be required to understand what changes signify clinical benefit. We present an investigative approach for the discovery and validation of metabolomic response biomarkers, which consists of serial analysis of the metabolome and linkage of changes in the metabolome to measurable therapeutic benefit. Potential pitfalls in the development of metabolomic biomarkers of response and loss of response are reviewed.

Unravelling the pharmacologic opportunities and future directions for targeted therapies in gastro-intestinal cancers part 2: Neuroendocrine tumours, hepatocellular carcinoma, and gastro-intestinal stromal tumours

Until the 1990s, cytotoxic chemotherapy has been the cornerstone of medical therapy for gastrointestinal (GI) cancers. Better understanding of the cancer cell molecular biology has led to the therapeutic revolution of targeted therapies, i.e. monoclonal antibodies or small molecule inhibitors directed against proteins that are specifically overexpressed or mutated in cancer cells. These agents, being more specific to cancer cells, were expected to be less toxic than conventional cytotoxic agents. However, their effects have sometimes been disappointing, due to intrinsic or acquired resistance mechanisms, or to an activity restricted to some tumour settings, illustrating the importance of patient selection and early identification of predictive biomarkers of response to these therapies. Targeted agents have provided clinical benefit in many GI cancer types. Particularly, some GI tumours are considered chemoresistant and targeted therapies have offered a new therapeutic base for their management. Hence, somatostatin receptor-directed strategies, sorafenib, and imatinib have revolutioned the management of neuroendocrine tumours (NET), hepatocellular carcinoma (HCC), and gastrointestinal stromal tumours (GIST), respectively, and are now used as first-line treatment in many patients affected by these tumours. However, these agents face problems of resistances and identification of predictive biomarkers from imaging and/or biology. We propose a comprehensive two-part review providing a panoramic approach of the successes and failures of targeted agents in GI cancers to unravel the pharmacologic opportunities and future directions for these agents in GI oncology. In this second part, we will focus on NET, HCC, and GIST, whose treatment relies primarily on targeted therapies.

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.

Immunomodulatory Activity of VEGF in Cancer

The ability of tumor cells to escape tumor immunosurveillance contributes to cancer development. Factors produced in the tumor microenvironment create "tolerizing" conditions and thereby help the tumor to evade antitumoral immune responses. VEGF-A, already known for its major role in tumor vessel growth (neoangiogenesis), was recently identified as a key factor in tumor-induced immunosuppression. In particular, VEGF-A fosters the proliferation of immunosuppressive cells, limits T-cell recruitment into tumors, and promotes T-cell exhaustion. Antiangiogenic therapies have shown significant efficacy in patients with a variety of solid tumors, preventing tumor progression by limiting tumor-induced angiogenesis. VEGF-targeting therapies have also been shown to modulate the tumor-induced immunosuppressive microenvironment, enhancing Th1-type T-cell responses and increasing tumor infiltration by T cells. The immunomodulatory properties of VEGF-targeting therapies open up new perspectives for cancer treatment, especially through strategies combining antiangiogenic drugs with immunotherapy. Preclinical models and early clinical studies of these combined approaches have given promising results.

Sunitinib in the treatment of gastrointestinal stromal tumor: patient selection and perspectives

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. In advanced setting and after progression to imatinib, the multi-targeted receptor tyrosine kinase inhibitor sunitinib has clearly demonstrated a clinical benefit in terms of response rate and progression-free survival with an acceptable toxicity profile. The recommended schedule for sunitinib administration is 50 mg per day 4 weeks ON and 2 weeks OFF; however, potential alternative schedules are also reviewed in the present article. Several biomarkers have been explored to better select candidates for sunitinib therapy, such as the value of early changes in standardized uptake value assessed by positron emission tomography with ¹⁸F-fluorodeoxyglucose, circulating biomarkers, clinical biomarkers such as the appearance of arterial hypertension during treatment that correlates with better outcomes, and the GIST genotype. GISTs with KIT mutations at exon 9 and the so-called wild-type GISTs seem to better respond to sunitinib. Nonetheless, further investigation is required to confirm these findings as well as to understand the mechanisms of sunitinib resistance such as the development of new KIT mutations or conformational changes in KIT receptor.

Response biomarkers: re-envisioning the approach to tailoring drug therapy for cancer

BACKGROUND

The rapidly expanding arsenal of chemotherapeutic agents approved in the past 5 years represents significant progress in the field. However, this poses a challenge for oncologists to choose which drug or combination of drugs is best for any individual. Because only a fraction of patients respond to any drug, efforts have been made to devise strategies to personalize care. The majority of efforts have involved development of predictive biomarkers. While there are notable successes, there are no predictive biomarkers for most drugs. Moreover, predictive biomarkers enrich the cohort of individuals likely to benefit; they do not guarantee benefit.

MAIN TEXT

There is a need to devise alternate strategies to tailor cancer care. One alternative approach is to enhance the current adaptive approach, which involves administration of a drug and cessation of treatment once progression is documented. This currently involves radiographic tests for the most part, which are expensive, inconvenient and imperfect in their ability to categorize patients who are and are not benefiting from treatment. A biomarker approach to categorizing response may have advantages.

CONCLUSION

Herein, we discuss the state of the art on treatment response assessment. While the most mature technologies for response assessment involve radiographic tests such as CT and PET, reports are emerging on biomarkers used to monitor therapeutic efficacy. Potentially, response biomarkers represent a less expensive and more convenient means of monitoring therapy, although an ideal response biomarker has not yet been described. A framework for future response biomarker discovery is described.

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.

Targeting angiogenesis in small cell lung cancer

Small cell lung cancer (SCLC) is a highly aggressive and lethal malignancy. Despite high initial response rates to systemic chemotherapy, the disease eventually relapses; further treatment only modestly improves outcomes and overall survival (OS) for patients with extensive stage disease is less than one year. Little progress has been made during the past decades, with no new drugs approved. Consequently, the development of novel strategies is an unmet need. The inhibition of angiogenesis, a defining characteristic of cancer, has demonstrated modest efficacy in several human malignancies, including non-small cell lung cancer (NSCLC). However, results from clinical trials in SCLC have been disappointing, and no anti-angiogenic agent has received regulatory approval due to lack of clinical efficacy. The elucidation of underlying mechanisms responsible for tumor resistance to angiogenic therapy and the simultaneous blockade of multiple elements that play a role in angiogenesis need to be further explored.

Sunitinib: the antiangiogenic effects and beyond

As a multitargeted kinase inhibitor, sunitinib has carved its way into demonstrating itself as a most effective tyrosine kinase inhibitor in the treatment of metastatic renal cell carcinoma. Mechanistically, sunitinib inhibits multiple receptor tyrosine kinases, especially those involved in angiogenesis, that is, vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and proto-oncogene cKIT. Sunitinib has also been implicated in enhancing cancer invasiveness and metastasis. Mechanisms of resistance are poorly understood, but both intrinsic and acquired mechanisms are thought to be involved. While the side effects are manageable, sunitinib, like many other tyrosine kinase inhibitors, can be associated with serious toxicities that require careful management including frequent dose reductions. Although still in the early stage, emerging evidence points to an immunomodulatory role for sunitinib. It is also likely to contribute to the overall outcomes, especially those seen in metastatic renal cell carcinoma, and such effects are thought to be mediated by the proto-oncogene cKIT receptor. Combination with other modalities such as stereotactic body radiation therapy, therapeutic vaccines, and checkpoint inhibitors is being pursued for improved efficacy.

Thyroglobulin fluctuations in patients with iodine-refractory differentiated thyroid carcinoma on lenvatinib treatment - initial experience

Tyrosine kinase inhibitors (TKI) have shown clinical effectiveness in iodine-refractory differentiated thyroid cancer (DTC). The corresponding role of serum thyroglobulin (Tg) in iodine-refractory DTC has not been investigated yet. 9 patients (3 female, 61 ± 8y) with progressive iodine-refractory DTC starting on lenvatinib were considered. Tumor restaging was performed every 2–3 months including contrast-enhanced computed tomography (CT, RECIST 1.1). Serum Tg was measured and compared to imaging findings. After treatment initiation, serum Tg levels dropped in all patients with a median reduction of 86.2%. During long-term follow-up (median, 25.2 months), fluctuations in Tg could be observed in 8/9 subjects. According to RECIST, 6/9 subjects achieved a partial response or stable disease with the remaining 3/9 experiencing progressive disease (2/3 with Tg levels rising above baseline). All of the patients with disease progression presented with a preceding continuous rise in serum Tg, whereas tumor marker oscillations in the subjects with controlled disease were only intermittent. Initiation of lenvatinib in iodine-refractory DTC patients is associated with a significant reduction in serum Tg levels as a marker of treatment response. In the course of treatment, transient Tg oscillations are a frequent phenomenon that may not necessarily reflect morphologic tumor progression.

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.

Positron emission tomography response evaluation from a randomized phase III trial of weekly nab-paclitaxel plus gemcitabine versus gemcitabine alone for patients with metastatic adenocarcinoma of the pancreas

BACKGROUND

In the phase III MPACT trial, nab-paclitaxel plus gemcitabine (nab-P + Gem) demonstrated superior efficacy versus Gem alone for patients with metastatic pancreatic cancer. We sought to examine the feasibility of positron emission tomography (PET) and to compare metabolic response rates and associated correlations with efficacy in the MPACT trial.

PATIENTS AND METHODS

Patients with previously untreated metastatic adenocarcinoma of the pancreas were randomized 1:1 to receive nab-P + Gem or Gem alone. Treatment continued until disease progression by RECIST or unacceptable toxicity.

RESULTS

PET scans were carried out on the first 257 patients enrolled at PET-equipped centers (PET cohort). Most patients (252 of 257) had ≥2 PET-avid lesions, and median maximum standardized uptake values at baseline were 4.6 and 4.5 in the nab-P + Gem and Gem-alone arms, respectively. In a pooled treatment arm analysis, a metabolic response by PET (best response at any time during study) was associated with longer overall survival (OS) (median 11.3 versus 6.9 months; HR, 0.56; P < 0.001). Efficacy results within each treatment arm appeared better for patients with a metabolic response. The metabolic response rate (best response and week 8 response) was higher for nab-P + Gem (best response: 72% versus 53%, P = 0.002; week 8: 67% versus 51%; P = 0.014). Efficacy in the PET cohort was greater for nab-P + Gem versus Gem alone, including for OS (median 10.5 versus 8.4 months; hazard ratio [HR], 0.71; P = 0.009) and ORR by RECIST (31% versus 11%; P < 0.001).

CONCLUSION

Pancreatic lesions were PET avid at baseline, and the rate of metabolic response was significantly higher for nab-P + Gem versus Gem alone at week 8 and for best response during study. Having a metabolic response was associated with longer survival, and more patients experienced a metabolic response than a RECIST-defined response.

CLINICALTRIALSGOV

NCT00844649.

PK-PD modeling of individual lesion FDG-PET response to predict overall survival in patients with sunitinib-treated gastrointestinal stromal tumor

Pharmacometric models were developed to characterize the relationships between lesion-level tumor metabolic activity, as assessed by the maximum standardized uptake value (SUVmax) obtained on [(18)F]-fluorodeoxyglucose (FDG) positron emission tomography (PET), tumor size, and overall survival (OS) in 66 patients with gastrointestinal stromal tumor (GIST) treated with intermittent sunitinib. An indirect response model in which sunitinib stimulates tumor loss best described the typically rapid decrease in SUVmax during on-treatment periods and the recovery during off-treatment periods. Substantial interindividual and interlesion variability were identified in SUVmax baseline and drug sensitivity. A parametric time-to-event model identified the relative change in SUVmax at one week for the lesion with the most pronounced response as a better predictor of OS than tumor size. Based on the proposed modeling framework, early changes in FDG-PET response may serve as predictor for long-term outcome in sunitinib-treated GIST.

Response to Early Treatment Evaluated with 18F-FDG PET and PERCIST 1.0 Predicts Survival in Patients with Ewing Sarcoma Family of Tumors Treated with a Monoclonal Antibody to the Insulinlike Growth Factor 1 Receptor

The aim of this study was to assess the prognostic and predictive value of early quantitative (18)F-FDG PET to monitor therapy with an antibody to the insulinlike growth factor 1 receptor (IGF-1R antibody) in patients with Ewing sarcoma family of tumors (ESFT).

METHODS

(18)F-FDG PET images at baseline and approximately 9 d after initiation of IGF-1R antibody therapy in 115 patients with refractory or relapsed ESFT were prospectively obtained as part of the Sarcoma Alliance for Research through Collaboration trial. Responses were centrally evaluated by PERCIST 1.0 in 93 patients. The 9-d PET responses were correlated to overall survival (OS), progression-free survival (PFS), and clinical benefit after 6 wk of therapy based on clinical observation and CT response by World Health Organization anatomic criteria.

RESULTS

The median OS was 8.1 mo (95% confidence interval, 6.4-10.0 mo). When PERCIST was used, patients with progressive metabolic disease showed shorter OS (median, 4.7 mo) than patients without progression (median, 10.0 mo; P = 0.001). Progressive metabolic disease on day-9 PET was associated with a significantly higher risk of death (hazard ratio, 2.8; 95% confidence interval, 1.5-5.5). Changes in (18)F-FDG uptake after 9 d of therapy had an area under the curve of receiver-operating characteristic of 0.71 to predict 1-y OS. The area under the curve was 0.63 to predict progression at 3 mo and 0.79 to predict clinical benefit after 6 wk of therapy.

CONCLUSION

Treatment response by quantitative (18)F-FDG PET assessed by PERCIST 1.0 as early as 9 d into IGF-1R antibody therapy in patients with ESFT can predict the OS, PFS, and clinical response to therapy.

Synthesis of [18F]Arenes via the Copper-Mediated [18F]Fluorination of Boronic Acids

A copper-mediated radiofluorination of aryl- and vinylboronic acids with K¹⁸F is described. This method exhibits high functional group tolerance and is effective for the radiofluorination of a range of electron-deficient, -neutral, and -rich aryl-, heteroaryl-, and vinylboronic acids. This method has been applied to the synthesis of [¹⁸F]FPEB, a PET radiotracer for quantifying metabotropic glutamate 5 receptors.

Clinicopathologic Features and Molecular Characteristics of Glucose Metabolism Contributing to ¹⁸F-fluorodeoxyglucose Uptake in Gastrointestinal Stromal Tumors

Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography-computed tomography (PET/CT) is useful in the preoperative diagnosis of gastrointestinal stromal tumors (GISTs); however, the molecular characteristics of glucose metabolism of GIST are unknown. We evaluated 18F-FDG uptake on preoperative PET/CT of 40 patients and analyzed the expression of glycolytic enzymes in resected GIST tissues by qRT-PCR, western blotting, and immunohistochemistry. Results of receiver operating characteristic curve analysis showed that the maximum standardized uptake value (SUVmax) cut-off value of 4.99 had a sensitivity of 89.5%, specificity was 76.2%, and accuracy of 82.5% for identifying tumors with a high risk of malignancy. We found that 18F-FDG uptake correlated positively with tumor size, risk grade, and expression levels of glucose transporter 1 (GLUT1), hexokinase 1 (HK1), and lactate dehydrogenase A (LDHA). Elevated HK and LDH activity was found in high-risk tumors. Among the isoforms of GLUT and HK, GLUT1 and HK1 expression increased with higher tumor risk grade. In addition, overexpression of glycolytic enzymes M2 isoform of pyruvate kinase (PKM2) and LDHA was observed in GISTs, especially in high-risk tumors. These results suggest that upregulation of GLUT1, HK1, PKM2, and LDHA may play an important role in GIST tumorigenesis and may be useful in the preoperative prediction of malignant potential.

FDG and FLT-PET for Early measurement of response to 37.5 mg daily sunitinib therapy in metastatic renal cell carcinoma

BACKGROUND

Metastatic renal cell carcinoma has a poor prognosis and an intrinsic resistance to standard treatment. Sunitinib is an oral receptor tyrosine kinase inhibitor that has been used as a first-line targeted therapy in metastatic renal cell carcinoma. While computed tomography (CT) is currently the gold standard for response assessment in oncological trials, numerous studies have shown that positron emission tomography (PET) imaging can provide information predictive of tumor response to treatment earlier than the typical interval for standard of care follow-up CT imaging. In this exploratory study we sought to characterize early tumor response in patients with metastatic renal cell carcinoma treated with continuous daily 37.5 mg sunitinib therapy.

METHODS

Twenty patients underwent dynamic acquisition positron emission tomography (PET) imaging using (18) F-fluorodeoxyglucose (FDG) and (18) F-fluorothymidine (FLT) at baseline and early in treatment (after 1, 2, 3 or 4 weeks) with 37.5 mg continuous daily dosing of sunitinib. Semi-quantitative analyses were performed to characterize the tumor metabolic (FDG) and proliferative (FLT) responses to treatment.

RESULTS

Proliferative responses were observed in 9/19 patients and occurred in 2 patients at one week (the earliest interval evaluated) after the initiation of therapy. A metabolic response was observed in 5/19 patients, however this was not observed until after two weeks of therapy were completed. Metabolic progression was observed in 2/19 patients and proliferative progression was observed in 1/19 patients. Baseline FDG-PET tumor maximum standardized uptake values correlated inversely with overall survival (p = 0.0036). Conversely, baseline (18) F-fluorothymidine PET imaging did not have prognostic value (p = 0.56) but showed a greater early response rate at 1-2 weeks after initiating therapy.

CONCLUSIONS

While preliminary in nature, these results show an immediate and sustained proliferative response followed by a delayed metabolic response beginning after two weeks in metastatic renal cell carcinoma treated with a continuous daily dose of 37.5 mg sunitinib. The results provide evidence of tumor response to lower-dose sunitinib while also supporting the inclusion of PET imaging as a tool for early assessment in oncological clinical trials.

TRIAL REGISTRATION

ID: NCT00694096.

Contrast-enhanced ultrasound with perflubutane in the assessment of anti-angiogenic effects: early prediction of the anticancer activity of bevacizumab in a mouse xenografted model

To investigate the feasibility of contrast-enhanced ultrasound (CEUS) with perflubutane for evaluating anti-angiogenic effects, we assessed the contrast enhancement of mice xenograft treated with bevacizumab. SJSA-1 implanted mice were imaged before and 2, 6, 9 and 13 d after initiation of bevacizumab or saline treatment. Intra-tumoral perfusion areas were quantified by binarizing the ultrasound images and the micro-vessel density was observed by CD31 immunohistochemistry. As a result, the perfusion area and its ratio in the tumor were smaller in the bevacizumab group than the control group at 9 and 13 d, although tumor size was not significantly different. CD31-positive areas were smaller in the bevacizumab group than the control group and correlated well with the ratio of intra-tumoral perfusion areas. CEUS with perflubutane was found to have potential for early prediction of the anti-cancer activity of bevacizumab, and the perfusion area measured by binarized ultrasound images could be used as an indicator.

Phase 2 study of sunitinib in patients with metastatic mucosal or acral melanoma

BACKGROUND

Patients with mucosal and acral melanomas have limited treatment options and a poor prognosis. Mutations of the KIT oncogene in these melanoma subtypes provide a potential therapeutic target.

METHODS

A multicenter phase 2 trial of sunitinib was conducted in patients with unresectable stage III or IV melanoma of a mucosal or acral primary origin. Patients were treated in 2 cohorts: cohort A received sunitinib at a dose of 50 mg daily for 4 weeks of a 6-week cycle, and cohort B received sunitinib at a dose of 37.5 mg daily on a continuous basis. Dose reductions were permitted for treatment-related toxicities, and tumor assessments were performed every 2 months.

RESULTS

Fifty-two patients were enrolled: 21 in cohort A and 31 in cohort B. Four patients had confirmed partial responses, which lasted 5 to 10 months (1 with a KIT mutation). In both cohorts, the proportion of patients alive and progression-free at 2 months was 52% (95% confidence interval, 38%-66%); this was significantly larger than the hypothesized null of 5%. There was no significant difference in response or overall survival between the 25% of patients with a KIT mutation and those without one (response rate, 7.7% vs 9.7%; overall survival, 6.4 vs 8.6 months). The overall disease control rate was 44%, and a high rate of toxicity was associated with the treatment.

CONCLUSIONS

Sunitinib showed activity in the treatment of mucosal and acral melanoma that was not dependent on the presence of a KIT mutation. However, the medication was poorly tolerated, and there were no prolonged responses. Cancer 2015;121:4007-4015. © 2015 American Cancer Society.

Liver surgery in the multidisciplinary management of gastrointestinal stromal tumour

BACKGROUND

After the introduction of tyrosine kinase inhibitors (TKIs), the role of surgical resection in treating liver metastasis from gastrointestinal stromal tumour (GIST) is unclear. In this study, we evaluated the outcome of patients treated with TKIs followed by surgery for metastatic GIST.

METHODS

Eleven patients who underwent liver resection after downsizing TKIs therapy for metastatic GIST from 2006 until 2010 were reviewed.

RESULTS

One and 2-year overall survival (OS) rates were 80.8% and 70.7%. All patients with an initially resectable tumour were still alive without recurrence. Patients operated on clinical response had a better outcome (1-year and 2-year OS rate of 100%) than those operated on disease progression (1-year and 2-year OS rates of 60% and 40%; P = 0.043). No deaths were observed among patients who achieved an R0 resection (R0 versus R1/R2, P = 0.001).

CONCLUSION

R0 resection and clinical response to TKI are predictors of survival. Surgical resection should be performed as soon as feasible in responder patients. In poor responders, surgery may not add any survival benefit, except in localized progressive disease. In resectable metastatic liver disease, preoperative TKIs or upfront surgery followed by adjuvant therapy could be considered. Larger studies are needed to determine the optimum approach in patients with metastatic GIST.

Evaluation of the therapeutic efficacy of a MEK inhibitor (TAK-733) using ¹⁸F-fluorodeoxyglucose-positron emission tomography in the human lung xenograft model A549

Objective

The aim of this study was to evaluate the potential of ¹⁸F-fluorodeoxyglucose-positron emission tomography (¹⁸F-FDG-PET) for monitoring the therapeutic efficacy of TAK-733, an inhibitor of mitogen-activated protein kinase kinase, in nude rats bearing A549 (human lung carcinoma) xenografts.

Methods

TAK-733 was administered orally by gavage to nude xenograft rats for 2 weeks, at dosage levels of 0 (0.5 % w/v methylcellulose solution), 1, 3, and 10 mg/kg/day (n = 8/dose). Tumor size was measured before treatment (day 0), and on days 1, 3, 7, 9, 11, and 14. PET scans were performed pretreatment (day 0), and on days 2, 4, 7, 10, and 14. Tracer accumulations in tumor tissue were quantified as the mean standard uptake value (SUVmean).

Results

No deaths or treatment-related body weight losses occurred during the study period. TAK-733 showed dose-dependent inhibition of tumor growth and ¹⁸F-FDG uptake in tumor tissue. At a dosage of 10 mg/kg, TAK-733 treatment produced a statistically significant reduction in tumor weight from day 11 compared with the vehicle group (P < 0.05). Tumor growth was inhibited in the 10 mg/kg group with a treated/control value of 31 % on day 14. The SUVmean on day 2 in this dosage group was statistically lower than that observed on day 0, and that seen in the vehicle group on day 2 (P < 0.05 for both comparisons). Furthermore, this reduction in SUVmean at 10 mg/kg was maintained over time. In the two lower dosage groups (1 and 3 mg/kg), SUVmean gradually increased over time.

Conclusions

¹⁸F-FDG-PET enabled early determination of late anti-tumor activity in response to TAK-733 treatment.

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.

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.

Imaging intratumor heterogeneity: role in therapy response, resistance, and clinical outcome

Tumors exhibit genomic and phenotypic heterogeneity, which has prognostic significance and may influence response to therapy. Imaging can quantify the spatial variation in architecture and function of individual tumors through quantifying basic biophysical parameters such as CT density or MRI signal relaxation rate; through measurements of blood flow, hypoxia, metabolism, cell death, and other phenotypic features; and through mapping the spatial distribution of biochemical pathways and cell signaling networks using PET, MRI, and other emerging molecular imaging techniques. These methods can establish whether one tumor is more or less heterogeneous than another and can identify subregions with differing biology. In this article, we review the image analysis methods currently used to quantify spatial heterogeneity within tumors. We discuss how analysis of intratumor heterogeneity can provide benefit over more simple biomarkers such as tumor size and average function. We consider how imaging methods can be integrated with genomic and pathology data, instead of being developed in isolation. Finally, we identify the challenges that must be overcome before measurements of intratumoral heterogeneity can be used routinely to guide patient care.

FDG PET/CT imaging as a biomarker in lymphoma

FDG PET/CT has changed the management of FDG-avid lymphoma and is now recommended as the imaging technique of choice for staging and restaging. The need for tailoring therapy to reduce toxicity in patients with a favourable outcome and for improving treatment in those with high-risk factors requires accurate diagnostic methods and a new prognostic algorithm to identify different risk categories. New drugs are used in relapsed/refractory patients. The role of FDG PET/CT as a biomarker in this context is summarized in this review. New trends in FDG metabolic imaging in lymphoma are addressed including metabolic tumour volume measurement at staging and integrative PET which combines PET data with clinical and molecular markers or other imaging techniques. The quantitative approach for response assessment which is under investigation and is used in large ongoing trials is compared with visual criteria. The place of FDG in the era of targeted therapy is discussed.