CT-based response assessment of advanced gastrointestinal stromal tumor: Dual energy CT provides a more predictive imaging biomarker of clinical benefit than RECIST or Choi criteria

Prospective evaluation of quantitative response parameter in patients with Gastrointestinal Stroma Tumor undergoing tyrosine kinase inhibitor therapy-Impact on clinical outcome

The purpose of this study was to determine if dual-energy CT (DECT) vital iodine tumor burden (ViTB), a direct assessment of tumor vascularity, allows reliable response assessment in patients with GIST compared to established CT criteria such as RECIST1.1 and modified Choi (mChoi). From 03/2014 to 12/2019, 138 patients (64 years [32-94 years]) with biopsy proven GIST were entered in this prospective, multi-center trial. All patients were treated with tyrosine kinase inhibitors (TKI) and underwent pre-treatment and follow-up DECT examinations for a minimum of 24 months. Response assessment was performed according to RECIST1.1, mChoi, vascular tumor burden (VTB) and DECT ViTB. A change in therapy management could be because of imaging (RECIST1.1 or mChoi) and/or clinical progression. The DECT ViTB criteria had the highest discrimination ability for progression-free survival (PFS) of all criteria in both first line and second line and thereafter treatment, and was significantly superior to RECIST1.1 and mChoi (p < .034). Both, the mChoi and DECT ViTB criteria demonstrated a significantly early median time-to-progression (both delta 2.5 months; both p < .036). Multivariable analysis revealed 6 variables associated with shorter overall survival: secondary mutation (HR = 4.62), polymetastatic disease (HR = 3.02), metastatic second line and thereafter treatment (HR = 2.33), shorter PFS determined by the DECT ViTB criteria (HR = 1.72), multiple organ metastases (HR = 1.51) and lower age (HR = 1.04). DECT ViTB is a reliable response criteria and provides additional value for assessing TKI treatment in GIST patients. A significant superior response discrimination ability for median PFS was observed, including non-responders at first follow-up and patients developing resistance while on therapy.

Development of a dual energy CT based model to assess response to treatment in patients with high grade serous ovarian cancer: a pilot cohort study

BACKGROUND

In patients with cancer, the current gold standard for assessing response to treatment involves measuring cancer lesions on computed tomography (CT) imaging. The percentage change in size of specific lesions determines whether patients have had a complete/partial response or progressive disease, according to RECIST criteria. Dual Energy CT (DECT) permits additional measurements of iodine concentration, a surrogate marker of vascularity. Here we explore the role of changes in iodine concentration within cancer tissue on CT scans to assess its suitability for determining treatment response in patients with high grade serous ovarian cancer (HGSOC).

METHODS

Suitable RECIST measurable lesions were identified from the CT images of HGSOC patients, taken at 2 different time points (pre and post treatment). Changes in size and iodine concentration were measured for each lesion. PR/SD were classified as responders, PD was classified as non-responder. Radiological responses were correlated with clinical and CA125 outcomes.

RESULTS

62 patients had appropriate imaging for assessment. 22 were excluded as they only had one DECT scan. 32/40 patients assessed (113 lesions) had received treatment for relapsed HGSOC. RECIST and GCIG (Gynaecologic Cancer Inter Group) CA125 criteria / clinical assessment of response for patients was correlated with changes in iodine concentration, before and after treatment. The prediction of median progression free survival was significantly better associated with changes in iodine concentration (p = 0.0001) and GCIG Ca125 / clinical assessment (p = 0.0028) in comparison to RECIST criteria (p = 0.43).

CONCLUSION

Changes in iodine concentration from dual energy CT imaging may be more suitable than RECIST in assessing response to treatment in patients with HGSOC.

TRIAL REGISTRATION

CICATRIx IRAS number 198179, 14 Dec 2015, https://www.myresearchproject.org.uk/ .

Technical performance of a dual-energy CT system with a novel deep-learning based reconstruction process: Evaluation using an abdomen protocol

BACKGROUND

A new tube voltage-switching dual-energy (DE) CT system using a novel deep-learning based reconstruction process has been introduced. Characterizing the performance of this DE approach can help demonstrate its benefits and potential drawbacks.

PURPOSE

To evaluate the technical performance of a novel DECT system and compare it to that of standard single-kV CT and a rotate/rotate DECT, for abdominal imaging.

METHODS

DE and single-kV images of four different phantoms were acquired on a kV-switching DECT system, and on a rotate/rotate DECT. The dose for the acquisitions of each phantom was set to that selected for the kV-switching DE mode by the automatic tube current modulation (ATCM) at manufacturer-recommended settings. The dose that the ATCM would have selected in single-kV mode was also recorded. Virtual monochromatic images (VMIs) from 40 to 130 keV, as well as iodine maps, were reconstructed from the DE data. Single-kV images, acquired at 120 kV, were reconstructed using body hybrid iterative reconstruction. All reconstructions were made at 0.5 mm section thickness. Task transfer functions (TTFs) were determined for a Teflon and LDPE rod. Noise magnitude (SD), and noise power spectrum (NPS) were calculated using 240 and 320 mm diameter water phantoms. Iodine quantification accuracy and contrast-to-noise ratios (CNRs) relative to water for 2, 5, 10, and 15 mg I/ml were determined using a multi-energy CT (MECT) phantom. Low-contrast visibility was determined and the presence of beam-hardening artifacts and inhomogeneities were evaluated.

RESULTS

The TTFs of the kV-switching DE VMIs were higher than that of the single-kV images for Teflon (20% TTF: 6.8 lp/cm at 40 keV, 6.2 lp/cm for single-kV), while for LDPE the DE TTFs at 70 keV and above were equivalent or higher than the single-kV TTF. All TTFs of the kV-switching DECT were higher than for the rotate/rotate DECT. The SD was lowest in the 70 keV VMI (12.0 HU), which was lower than that of single-kV (18.3 HU). The average NPS frequency varied between 2.3 lp/cm and 4.2 lp/cm for the kV-switching VMIs and was 2.2 lp/cm for single-kV. The error in iodine quantification was at maximum 1 mg I/ml (at 5 mg I/ml). The highest CNR for all iodine concentrations was at 60 keV, 2.5 times higher than the CNR for single-kV. At 70-90 keV, the number of visible low contrast objects was comparable to that in single-kV, while other VMIs showed fewer objects. At manufacturer-recommended ATCM settings, the CTDI_vol for the DE acquisitions of the water and MECT phantoms were 12.6 and 15.4 mGy, respectively, and higher than that for single-kV. The 70 keV VMI had less severe beam hardening artifacts than single-kV images. Hyper- and hypo-dense blotches may appear in VMIs when object attenuation exceeds manufacturer recommended limits.

CONCLUSIONS

At manufacturer-recommended ATCM settings for abdominal imaging, this DE implementation results in higher CTDI_vol compared to single-kV acquisitions. However, it can create sharper, lower noise VMIs with up to 2.5 times higher iodine CNR compared to single-kV images acquired at the same dose.

Deep learning image reconstruction to improve accuracy of iodine quantification and image quality in dual-energy CT of the abdomen: a phantom and clinical study

OBJECTIVES

To investigate the effect of deep learning image reconstruction (DLIR) on the accuracy of iodine quantification and image quality of dual-energy CT (DECT) compared to that of other reconstruction algorithms in a phantom experiment and an abdominal clinical study.

METHODS

An elliptical phantom with five different iodine concentrations (1-12 mgI/mL) was imaged five times with fast-kilovoltage-switching DECT for three target volume CT dose indexes. All images were reconstructed using filtered back-projection, iterative reconstruction (two levels), and DLIR algorithms. Measured and nominal iodine concentrations were compared among the algorithms. Contrast-enhanced CT of the abdomen with the same scanner was acquired in clinical patients. In arterial and portal venous phase images, iodine concentration, image noise, and coefficients of variation for four locations were retrospectively compared among the algorithms. One-way repeated-measures analyses of variance were used to evaluate differences in the iodine concentrations, standard deviations, coefficients of variation, and percentages of error among the algorithms.

RESULTS

In the phantom study, the measured iodine concentrations were equivalent among the algorithms: within ± 8% of the nominal values, with root-mean-square deviations of 0.08-0.36 mgI/mL, regardless of radiation dose. In the clinical study (50 patients; 35 men; mean age, 68 ± 11 years), iodine concentrations were equivalent among the algorithms for each location (all p > .99). Image noise and coefficients of variation were lower with DLIR than with the other algorithms (all p < .01).

CONCLUSIONS

The DLIR algorithm reduced image noise and variability of iodine concentration values compared with other reconstruction algorithms in the fast-kilovoltage-switching dual-energy CT.

KEY POINTS

• In the phantom study, standard deviations and coefficients of variation in iodine quantification were lower on images with the deep learning image reconstruction algorithm than on those with other algorithms. • In the clinical study, iodine concentrations of measurement location in the upper abdomen were consistent across four reconstruction algorithms, while image noise and variability of iodine concentrations were lower on images with the deep learning image reconstruction algorithm.

Dual energy CT applications in oncological imaging

Cancer is the second leading cause of death in the United States, killing more than 600.000 people each year.¹ Despite several screening programs available, cancer diagnosis is often made incidentally during imaging studies performed for other reasons. Once the diagnosis is made, treatment assessment and surveillance of these patients heavily rely on radiological tools. Computed tomography (CT) in particular is one of the most commonly ordered modalities due to wide availability even in the most remote locations, and fast results. However, conventional CT often cannot definitively characterize a neoplastic lesion unless it was tailored toward answering a specific question. Furthermore, characterizing small lesions can be difficult with CT. An innovative technique called dual-energy CT (DECT) offers solutions to some of the challenges of conventional CT in oncological imaging.

Exploratory analysis of tumor imaging in a Phase 2 trial with cabozantinib in gastrointestinal stromal tumor: lessons learned from study EORTC STBSG 1317 'CaboGIST'

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are malignant mesenchymal tumors arising in the gastrointestinal tract. Their systemic treatment is based on the use of tyrosine kinase inhibitors (TKIs) with imatinib, sunitinib, and regorafenib being the preferred agents. Assessment of tumor response to TKI treatment in GISTs is traditionally done according the Response Evaluation Criteria in Solid Tumors (RECIST), while Choi criteria have also been proposed as alternative tool assessing both volumetric and density changes on computer tomography (CT) scans. EORTC STBSG 1317 'CaboGIST' was a single-arm prospective Phase 2 trial which met its primary endpoint, as 60% of patients previously treated with imatinib and sunitinib were progression-free at 12 weeks (95% CI 45-74%) based on local RECIST assessment.

MATERIALS AND METHODS

We report here an exploratory analysis of local versus central RECIST version 1.1 assessment and a comparison of RECIST version 1.1 versus Choi criteria.

RESULTS

Comparisons between local and central RECIST version 1.1 at week 12 revealed discrepancies in 17/43 evaluable cases (39.5%). When comparing Choi with local and central RECIST version 1.1, discrepancies were observed in 27/43 (62.8%) and 21/43 (48.8%) cases, respectively. A total of 68% of evaluable patients were progression-free and alive at week 12 based on local RECIST, 84% according to central RECIST analysis and 81% when applying Choi criteria. Central assessment upgraded the treatment response both with RECIST version 1.1 and Choi.

CONCLUSIONS

The results of this exploratory analysis support the conclusion that cabozantinib is active in patients with metastatic or recurrent GIST after treatment with imatinib and sunitinib and confirm once again the limitations of RECIST to capture response to TKI in GIST, and the importance to include density changes in the response evaluation in this setting. Clinical trial number: EORTC 1317, NCT02216578.

Comparison of Computed Tomography Features of Gastric and Small Bowel Gastrointestinal Stromal Tumors With Different Risk Grades

OBJECTIVE

This study aimed to compare the computed tomography (CT) features of gastric and small bowel gastrointestinal stromal tumors (GISTs) and further identify the predictors for risk stratification of them, respectively.

METHODS

According to the modified National Institutes of Health criteria, patients were classified into low-malignant potential group and high-malignant potential group. Two experienced radiologists reviewed the CT features including the difference of CT values between arterial phase and portal venous phase (PVPMAP) by consensus. The CT features of gastric and small bowel GISTs were compared, and the association of CT features with risk grades was analyzed, respectively. Determinant CT features were used to construct corresponding models.

RESULTS

Univariate analysis showed that small bowel GISTs tended to present with irregular contour, mixed growth pattern, ill-defined margin, severe necrosis, ulceration, tumor vessels, heterogeneous enhancement, larger size, and marked enhancement compared with gastric GISTs. According to multivariate analysis, tumor size (P < 0.001; odds ratio [OR], 3.279), necrosis (P = 0.008; OR, 2.104) and PVPMAP (P = 0.045; OR, 0.958) were the independent influencing factors for risk stratification of gastric GISTs. In terms of small bowel GISTs, the independent predictors were tumor size (P < 0.001; OR, 3.797) and ulceration (P = 0.031; OR, 4.027). Receiver operating characteristic curve indicated that the CT models for risk stratification of gastric and small bowel GISTs both achieved the best predictive performance.

CONCLUSIONS

Computed tomography features of gastric and small bowel GISTs are different. Furthermore, the qualitative and quantitative CT features of GISTs may be favorable for preoperative risk stratification.

Improving radiation physics, tumor visualisation, and treatment quantification in radiotherapy with spectral or dual-energy CT

Over the past decade, spectral or dual‐energy CT has gained relevancy, especially in oncological radiology. Nonetheless, its use in the radiotherapy (RT) clinic remains limited. This review article aims to give an overview of the current state of spectral CT and to explore opportunities for applications in RT.

In this article, three groups of benefits of spectral CT over conventional CT in RT are recognized. Firstly, spectral CT provides more information of physical properties of the body, which can improve dose calculation. Furthermore, it improves the visibility of tumors, for a wide variety of malignancies as well as organs‐at‐risk OARs, which could reduce treatment uncertainty. And finally, spectral CT provides quantitative physiological information, which can be used to personalize and quantify treatment.

A Method for Reducing Variability Across Dual-Energy CT Manufacturers in Quantification of Low Iodine Content Levels

Background: Clinical use of the dual-energy CT (DECT) iodine quantification technique is hindered by between-platform (i.e., across different manufacturers) variability in iodine concentration (IC), particularly at low iodine levels. Objective: To develop in an anthropomorphic phantom a method for reducing between-platform variability in quantification of low iodine content levels using DECT and to evaluate the method's performance in patients undergoing serial clinical DECT examinations on different platforms. Methods: An anthropomorphic phantom in three body sizes, incorporating varied lesion types and scanning conditions, was imaged with three distinct DECT implementations from different manufacturers at varying radiation exposures. A cross-platform iodine quantification model for correcting between-platform variability at low iodine content was developed using the phantom data. The model was tested in a retrospective series of 30 patients (20 men, 10 women; median age, 62 years) who each underwent three serial contrast-enhanced DECT examinations of the abdomen and pelvis (90 scans total) for routine oncology surveillance, using the same three DECT platforms as in the phantom. Estimated accuracy of phantom IC values was summarized using rootmean-squared error (RMSE) relative to known IC. Between-platform variability in patients was summarized using root-mean-square-deviation (RMSD). RMSE and RMSD were compared between platform-based IC (ICPB) and cross-platform IC (ICCP). ICPB was normalized to aorta and portal vein. Results: In the phantom study, mean RMSE of ICPB across platforms and other experimental conditions was 0.65 ± 0.18 mgI/mL compared with 0.40 ± 0.075 mgI/mL for ICCP (38% decrease in mean RMSE; P<.05). Intra-patient between-platform variability across serial DECT examinations was lower for ICPB than ICCP (RMSD: 97% vs 88%; P<.001). Between-platform variability was not reduced by normalization of ICPB to aorta (RMSD: 97% vs 101%; P=.12) or portal vein (RMSD: 97% vs 97%; P=.81). Conclusion: The developed cross-platform method significantly decreased between-platform variability occurring at low iodine content with platform-based DECT iodine quantification. Clinical Impact: With further validation, the cross-platform method, which has been implemented as a webbased app, may expand clinical use of DECT iodine quantification, yielding meaningful IC values that reflect tissue biologic viability or treatment response in patients who undergo serial examinations on different platforms.

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.

Pediatric Gastrointestinal Stromal Tumors and Neuroendocrine Tumors: Advances in Surgical Management

Gastrointestinal stromal tumors and neuroendocrine tumors in adult and pediatric populations differ immensely. Despite these established differences, the extreme rarity of gastrointestinal stromal tumors and neuroendocrine tumors in the pediatric population has resulted in the lack of consensus management guidelines, making optimal surgical approaches unclear. Comprehensive management principles to guide surgical approaches in adult literature are extensive. However, these are still lacking for pediatric patients. International cooperation to develop standardized pediatric-specific guidelines is urgently warranted in the future. This article highlights the vast differences between adult and pediatric parameters and provides recommendations on optimal and novel surgical approaches in children.

Radical excision versus local resection for primary rectal gastrointestinal stromal tumors. Cohort Study

BACKGROUND

Rectal gastrointestinal stromal tumor (GIST) is a rare digestive disease that originates in mesenchymal tissues and has malignant tendencies. At present, no standard treatment has been developed, and surgical approaches and the resection scope for rectal GISTs are controversial.

METHODS

The clinical, surgical, pathological and prognosis data of patients with primary rectal GIST in our center from January 2008 to January 2019 were retrospectively collected. The patients were divided into the radical excision (RE) and local resection (LR) groups.

RESULTS

A total of 537 GIST cases were collected, and 64 patients with primary rectal GIST were included in this study, including 25 cases in the RE group and 39 cases in the LR group. Tumor size (p = 0.013), distance from the anus (p = 0.038), National Institutes of Health (NIH) criteria (p = 0.001), preoperative adjuvant therapy (p = 0.016), postoperative adjuvant therapy (p = 0.028), blood loss (p = 0.048), operative time (p = 0.020) and the duration of hospitalization (p = 0.021) were statistically different between these 2 groups. The mean overall follow-up time was 46 months (range, 1-122 months). Disease recurrence was observed in 12 patients. No statistical differences were observed in 5-year disease-free survival (DFS) (93.3% vs 92.6%, p = 0.952) or overall survival (OS) (90.0% vs 91.6%, p = 0.832) between the RE group and the LR group.

CONCLUSION

Our study showed that LR has a similar prognosis to that of RE with respect to DFS and OS. For appropriate cases, LR has the advantages of a short operative time, less bleeding, and a quick recovery. Especially when combined with neoadjuvant therapy, LR can also achieve better perioperative efficacy. Therefore, LR is an effective method for resection of rectal GISTs and warrants clinical endorsement.

Dual-energy CT: theoretical principles and clinical applications

The physical principles of dual-energy computed tomography (DECT) are as old as computed tomography (CT) itself. To understand the strengths and the limits of this technology, a brief overview of theoretical basis of DECT will be provided. Specific attention will be focused on the interaction of X-rays with matter, on the principles of attenuation of X-rays in CT toward the intrinsic limits of conventional CT, on the material decomposition algorithms (two- and three-basis-material decomposition algorithms) and on effective Rho-Z methods. The progresses in material decomposition algorithms, in computational power of computers and in CT hardware, lead to the development of different technological solutions for DECT in clinical practice. The clinical applications of DECT are briefly reviewed in relation to the specific algorithms.

Iodine quantification and detectability thresholds among major dual-energy CT platforms

OBJECTIVES

To estimate the minimum detectable iodine concentration on multiple dual-energy CT (DECT) platforms.

METHODS AND MATERIALS

A phantom containing iodine concentrations ranging from 0 to 10 mg ml^-1 was scanned with five dual-energy platforms (two rapid kilo volt switching (r-kVs), one dual source (DS), one sequential acquisition and one split-filter). Serial dilutions of 300 mg ml^-1 iodinated contrast material were used to generate concentrations below 2 mg ml^-1. Iodine density and virtual monoenergetic images were reviewed by three radiologists to determine the minimum visually detectable iodine concentration. Contrast-to-noise ratios (CNRs) were calculated.

RESULTS

1 mg mL^-1 (~0.8 mg mL^-1 corrected) was the minimum visually detectable concentration among the platforms and could be seen by all readers on the third-generation r-kVs and DS platforms.

CONCLUSIONS

At low concentrations, CNR for monoenergetic images was highest on the DS platform and lowest in the sequential acquisition and split-filter platforms.

ADVANCES IN KNOWLEDGE

The results of this study corroborate previous in vivo estimates of iodine detection limits at DECT and provide a comparison for the performance of different DECT platforms at low iodine concentrations in vitro.

Quantitative Mass Spectrometry Imaging Reveals Mutation Status-independent Lack of Imatinib in Liver Metastases of Gastrointestinal Stromal Tumors

Mass spectrometry imaging (MSI) is an enabling technology for label-free drug disposition studies at high spatial resolution in life science- and pharmaceutical research. We present the first extensive clinical matrix-assisted laser desorption/ionization (MALDI) quantitative mass spectrometry imaging (qMSI) study of drug uptake and distribution in clinical specimen, analyzing 56 specimens of tumor and corresponding non-tumor tissues from 27 imatinib-treated patients with the biopsy-proven rare disease gastrointestinal stromal tumors (GIST). For validation, we compared MALDI-TOF-qMSI with conventional UPLC-ESI-QTOF-MS-based quantification from tissue extracts and with ultra-high resolution MALDI-FTICR-qMSI. We introduced a novel generalized nonlinear calibration model of drug quantities based on computational evaluation of drug-containing areas that enabled better data fitting and assessment of the inherent method nonlinearities. Imatinib tissue spatial maps revealed striking inefficiency in drug penetration into GIST liver metastases even though the corresponding healthy liver tissues in the vicinity showed abundant imatinib levels beyond the limit of quantification (LOQ), thus providing evidence for secondary drug resistance independent of mutation status. Taken together, these findings underscore the important application of MALDI-qMSI in studying the spatial distribution of molecularly targeted therapeutics in oncology, namely to serve as orthogonal post-surgical approach to evaluate the contribution of anticancer drug disposition to resistance against treatment.

Dual-Energy CT-Derived Volumetric Iodine Concentration for the Assessment of Therapeutic Response after Microwave Ablation in a Rabbit Model with Intrahepatic VX2 Tumor

PURPOSE

To evaluate whether changes in volumetric iodine concentration (VIC) could serve as a suitable predictor of therapeutic response to microwave (MW) ablation in a rabbit intrahepatic VX2 tumor model.

MATERIALS AND METHODS

Sixteen intrahepatic VX2 tumors were transplanted in 8 New Zealand White rabbits treated with MW ablation. Contrast-enhanced dual-energy CT scans were obtained at baseline and follow-up. Therapeutic response assessment by modified Response Evaluation Criteria In Solid Tumors (mRECIST), Choi criteria, and VIC changes was performed. An intraclass correlation coefficient (ICC) was used to characterize consistency of assessment results among the criteria used. Technical success was evaluated with explant pathologic findings as a reference. Correlations between technical success and variations in diameter, CT density, and VIC were analyzed.

RESULTS

Disease control was observed in 4, 8, and 10 of the 16 tumors per mRECIST, Choi criteria, and VIC changes, respectively. VIC exhibited strong consistency (ICC = 0.807, P < .0001) with Choi criteria. According to explant pathology, technical success was achieved in 10 of the 16 tumors. There was a moderate correlation between VIC changes and technical success (r = 0.532, P = .034), and no correlation was found between technical success and variations in diameter or CT density.

CONCLUSIONS

Compared with mRECIST and Choi criteria, dual-energy CT-derived VIC allowed for better prediction of therapeutic response after MW ablation and could provide a potential imaging biomarker of tumor response to MW ablation in patients with hepatocellular carcinoma.

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.

The Role of Dual-Energy Computed Tomography in Assessment of Abdominal Oncology and Beyond

The added value and strength of dual energy computed tomography for the evaluation of oncologic patients revolve around the use of lower energy reconstructed images and iodine material density images. Lower keV simulated monoenergetic images optimize soft tissue tumor to nontumoral attenuation differences and increase contrast to noise ratios to improve lesion detection. Iodine material density images or maps are helpful from a qualitative standpoint for image interpretation because they result in improved detection and characterization of tumors and lymph node involvement, and from a quantitative assessment by enabling interrogation of specific properties of tissues to predict and assess therapeutic response.

Role of rapid kV-switching dual-energy CT in assessment of post-surgical local recurrence of pancreatic adenocarcinoma

PURPOSE

The purpose of this study is to evaluate the performance of material-specific iodine (MS-I) images generated by rapid kV-switching single-source dual-energy computed tomography (rsDECT) for distinguishing post-operative changes from local tumor recurrence in patients on follow-up for pancreatic adenocarcinoma after surgical resection.

METHODS

In this IRB-approved HIPPA-compliant study, retrospective review of 51 patients who underwent surgical resection of pancreatic adenocarcinoma was conducted and were followed up using contrast-enhanced rsDECT (Discovery CT 750HD, GE Healthcare, Milwaukee, WI). Independent qualitative assessment for presence of local tumor recurrence was performed by two radiologists who evaluated 65 keV (single-energy CT-equivalent interpretation) and 65 keV with MS-I (rsDECT interpretation) in separate sessions. Quantitative analysis of Hounsfield unit (HU, on 65 keV) and normalized iodine concentration (NIC on MS-I images; iodine concentration ratio in post-operative tissue to aorta) was measured. Follow-up imaging, temporal change of CEA and CA 19-9 or biopsy served as reference standard for presence and absence of local recurrence. Sensitivity and specificity of readers and quantitative parameters was calculated and receiver operating characteristic curves and Fisher's exact test were generated. A p value < 0.05 was considered statistically significant.

RESULTS

A total of 51 patients (27 females, 24 males) with mean age of 64 years built the final cohort. Local recurrence was absent in 23 (Group A) and present in 28 (Group B) patients. The follow-up imaging was performed within 7 months of rsDECT. For both readers, the addition of MS-I increased the specificity for tissue characterization and improved reader confidence as compared to 65 keV (specificity: 80% and 56%, respectively) images alone. Quantitative analysis revealed a significantly lower NIC (0.28 vs. 0.35; p < 0.05) for non-recurrent tissue. However, HU was not significantly different for non-recurrent and recurrent tissue (0.63 vs. 0.70; p > 0.05).

CONCLUSION

In inherently complex cases of post-operative pancreatic adenocarcinoma, MS-I images from rsDECT can be a useful adjunct to conventional scans in characterizing loco-regional soft tissue.

Abdominal Applications of a Novel Detector-Based Spectral CT

Detector-based spectral computed tomography (SDCT) is a recently introduced technology that uses a single x-ray tube and 2 layers of detectors to simultaneously collect low- and high-energy data. In this article, we provide an overview of this novel SDCT technology in abdominal imaging. Several applications of SDCT in abdominal imaging are discussed and illustrated, along with a brief description of current literature on the status of dual-energy computed tomography in these applications. This includes urinary calculus composition, characterization of masses (renal, adrenal, hepatic, and others), tumor perfusion, improving vascular contrast, improving lesion conspicuity, decreasing artifacts, and reducing radiation dose.

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.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

Assessing tumor vascularization as a potential biomarker of imatinib resistance in gastrointestinal stromal tumors by dynamic contrast-enhanced magnetic resonance imaging

BACKGROUND

Most metastatic gastrointestinal stromal tumors (GISTs) develop resistance to the first-line imatinib treatment. Recently, increased vessel density and angiogenic markers were reported in GISTs with a poor prognosis, suggesting that angiogenesis is implicated in GIST tumor progression and resistance. The purpose of this study was to investigate the relationship between tumor vasculature and imatinib resistance in different GIST mouse models using a noninvasive magnetic resonance imaging (MRI) functional approach.

METHODS

Immunodeficient mice (n = 8 for each cell line) were grafted with imatinib-sensitive (GIST882 and GIST-T1) and imatinib-resistant (GIST430) human cell lines. Dynamic contrast-enhanced MRI (DCE-MRI) was performed on GIST xenografts to quantify tumor vessel permeability (K ^trans) and vascular volume fraction (v _p). Microvessel density (MVD), permeability (mean dextran density, MDD), and angiogenic markers were evaluated by immunofluorescence and western blot assays.

RESULTS

Dynamic contrast-enhanced magnetic resonance imaging showed significantly increased vessel density (P < 0.0001) and permeability (P = 0.0002) in imatinib-resistant tumors compared to imatinib-sensitive ones. Strong positive correlations were observed between MRI estimates, K ^trans and v _p, and their related ex vivo values, MVD (r = 0.78 for K ^trans and r = 0.82 for v _p) and MDD (r = 0.77 for K ^trans and r = 0.94 for v _p). In addition, higher expression of vascular endothelial growth factor receptors (VEGFR2 and VEFGR3) was seen in GIST430.

CONCLUSIONS

Dynamic contrast-enhanced magnetic resonance imaging highlighted marked differences in tumor vasculature and microenvironment properties between imatinib-resistant and imatinib-sensitive GISTs, as also confirmed by ex vivo assays. These results provide new insights into the role that DCE-MRI could play in GIST characterization and response to GIST treatment. Validation studies are needed to confirm these findings.

Update on Gastrointestinal Stromal Tumors for Radiologists

The management of gastrointestinal stromal tumors (GISTs) has evolved significantly in the last two decades due to better understanding of their biologic behavior as well as development of molecular targeted therapies. GISTs with exon 11 mutation respond to imatinib whereas GISTs with exon 9 or succinate dehydrogenase subunit mutations do not. Risk stratification models have enabled stratifying GISTs according to risk of recurrence and choosing patients who may benefit from adjuvant therapy. Assessing response to targeted therapies in GIST using conventional response criteria has several potential pitfalls leading to search for alternate response criteria based on changes in tumor attenuation, volume, metabolic and functional parameters. Surveillance of patients with GIST in the adjuvant setting is important for timely detection of recurrences.

Dual energy CT allows for improved characterization of response to antiangiogenic treatment in patients with metastatic renal cell cancer

OBJECTIVES

To evaluate the potential role of dual energy CT (DECT) to visualize antiangiogenic treatment effects in patients with metastatic renal cell cancer (mRCC) while treated with tyrosine-kinase inhibitors (TKI).

METHODS

26 patients with mRCC underwent baseline and follow-up single-phase abdominal contrast enhanced DECT scans. Scans were performed immediately before and 10 weeks after start of treatment with TKI. Virtual non-enhanced (VNE) and colour coded iodine images were generated. 44 metastases were measured at the two time points. Hounsfield unit (HU) values for VNE and iodine density (ID) as well as iodine content (IC) in mg/ml of tissue were derived. These values were compared to the venous phase DECT density (CTD) of the lesions. Values before and after treatment were compared using a paired Student's t test.

RESULTS

Between baseline and follow up, mean CTD and DECT-derived ID both showed a significant reduction (p < 0.005). The relative reduction measured in percent was significantly greater for ID than for CTD (49.8 ± 36,3 % vs. 29.5 ± 20.8 %, p < 0.005). IC was also significantly reduced under antiangiogenic treatment (p < 0.0001).

CONCLUSIONS

Dual energy CT-based quantification of iodine content of mRCC metastases allows for significantly more sensitive and reproducible detection of antiangiogenic treatment effects.

KEY POINTS

• A sign of tumour response to antiangiogenic treatment is reduced tumour perfusion. • DECT allows visualizing iodine uptake, which serves as a marker for vascularization. • More sensitive detection of antiangiogenic treatment effects in mRCC is possible.

A primer on the use of dual-energy CT in the evaluation of commonly encountered neoplasms

Technical improvements in the acquisition and display of dual-energy computed tomography (DECT) have made this technique increasingly applicable to clinical practice, particularly in the setting of oncologic imaging. DECT allows for qualitative and quantitative analysis of tissue composition beyond the standard anatomical evaluation possible with single-energy computed tomography. For example, DECT can be used to interrogate iodine and calcium concentrations and to increase iodine signal, which makes many pathologic processes more conspicuous and provides improved understanding of internal structure within mass lesions. A working understanding of common postprocessing DECT displays will allow radiologists to maximize the additional diagnostic information available in DECT examinations. In this article, we describe common strategies for DECT interrogation by organ system, which may improve the conspicuity and understanding of suspected malignancies.

CT spectral imaging for monitoring the therapeutic efficacy of VEGF receptor kinase inhibitor AG-013736 in rabbit VX2 liver tumours

PURPOSE

The aim of this study was to evaluate the value of computed tomography (CT) spectral imaging in assessing the therapeutic efficacy of a vascular endothelial growth factor (VEGF) receptor inhibitor AG-013736 in rabbit VX2 liver tumours.

METHODS

Twenty-three VX2 liver tumour-bearing rabbits were scanned with CT in spectral imaging mode during the arterial phase (AP) and portal phase (PP). The iodine concentrations(ICs)of tumours normalized to aorta (nICs) at different time points (baseline, 2, 4, 7, 10, and 14 days after treatment) were compared within the treated group (n = 17) as well as between the control (n = 6) and treated groups. Correlations between the tumour size, necrotic fraction (NF), microvessel density (MVD), and nICs were analysed.

RESULTS

The change of nICs relative to baseline in the treated group was lower compared to the control group. A greater decrease in the nIC of a tumour at 2 days was positively correlated with a smaller increase in tumour size at 14 days (P < 0.05 for both). The tumour nIC values in AP and PP had correlations with MVD (r = 0.71 and 0.52) and NF (r = -0.54 and -0.51) (P < 0.05 for all).

CONCLUSIONS

CT spectral imaging allows for the evaluation and early prediction of tumour response to AG-013736.

KEY POINTS

• AG-013736 treatment response was evaluated by CT in a rabbit tumour model. • CT spectral imaging allows for the early treatment monitoring of targeted anti-tumour therapies. • Spectral CT findings correlated with vascular changes after anti-tumour therapies. • Spectral CT is a promising method for assessing clinical treatment response.

Assessment of Vascularity in Hepatic Alveolar Echinococcosis: Comparison of Quantified Dual-Energy CT with Histopathologic Parameters

Purpose

To investigate whether dual-energy computer tomography(DECT) could determine the angiographic vascularity of alveolar echinococcosis lesions by comparing the quantitative iodine concentration (IC) with the microvascular density (MVD).

Material and Methods

Twenty-five patients (16 men, 9 women; mean age, 40.9 ± 13.8 years) with confirmed hepatic alveolar echinococcosis (HAE) underwent DECT of the abdomen, consisting of arterial phase (AP), portal venous phase (PVP), and delayed phase (DP) scanning, in dual-source mode (100 kV/140 kV). Image data were processed with a DECT software algorithm that was designed for the evaluation of iodine distribution in the different layers (marginal zone, solid and cystic) of the lesions. The CT patterns of HAE lesions were classified into three types: solid type, pseudocystic type and ‘geographic map’ (mixed) type. The IC measurements in different layers and different types of lesions were statistically compared. MVD was examined using CD34 immunohistochemical staining of the resected HAE tissue and scored based on the percentage of positively stained cells and their intensity. Pearson’s correlation analysis was used to evaluate the potential correlation between DECT parameters and MVD.

Results

A total of 27 HAE lesions were evaluated, of which 9 were solid type, 3 were pseudocystic type and 15 were mixed type. The mean lesion size was 100.7 ± 47.3 mm. There was a significant difference in the IC measurements between different layers of HAE lesions during each scan phase (p < 0.001). The IC in the marginal zone was significantly higher than in the solid and cystic components in AP (2.15 mg/mL vs. 0.17 or 0.01 mg/mL), PVP (3.08 mg/mL vs. 0.1 or 0.02 mg/mL), and DP (2.93 mg/mL vs. 0.04 or 0.02 mg/mL). No significant difference was found among the different CT patterns of HAE lesions. Positive expression of CD34 in the marginal zones surrounding HAE lesions was found in 92.5% (25/27) of lesions, of which 18.5% (5/27) were strongly positive, 62.7% (17/27) were moderately positive, and 11.1% (3/27) were weakly positive. In contrast, 7.4% (2/27) of the lesions were negative for CD34. There was a positive correlation between IC measurements and MVD in the marginal zone of HAE lesions (r = 0.73, p < 0.05).

Conclusions

The DECT quantitative iodine concentration was significantly correlated with MVD in the marginal zones surrounding HAE lesions. Dual-energy CT using a quantitative analytic methodology can be used to evaluate the vascularity of AE.

Accuracy of dual-energy computed tomography for the quantification of iodine in a soft tissue-mimicking phantom

The objective of this study was to evaluate the accuracy of dual-energy CT (DECT) for quantifying iodine using a soft tissue-mimicking phantom across various DECT acquisition parameters and dual-source CT (DSCT) scanners. A phantom was constructed with plastic tubes containing soft tissue-mimicking materials with known iodine concentrations (0-20 mg/mL). Experiments were performed on two DSCT scanners, one equipped with an integrated detector and the other with a conventional detector. DECT data were acquired using two DE modes (80 kV/Sn140 kV and 100 kV/Sn140 kV) with four pitch values (0.6, 0.8, 1.0, and 1.2). Images were reconstructed using a soft tissue kernel with and without beam hardening correction (BHC) for iodine. Using the dedicated DE software, iodine concentrations were measured and compared to true concentrations. We also investigated the effect of reducing gantry rotation time on the DECT-based iodine measurement. At iodine concentrations higher than 10 mg/mL, the relative error in measured iodine concentration increased slightly. This error can be decreased by using the kernel with BHC, compared with the kernel without BHC. Both 80 kV/Sn140 kV and 100 kV/Sn140 kV modes could provide accurate quantification of iodine content. Increasing pitch value or reducing gantry rotation time had only a minor impact on the DECT-based iodine measurement. The DSCT scanner, equipped with the new integrated detector, showed more accurate iodine quantification for all iodine concentrations higher than 10 mg/mL. An accurate quantification of iodine can be obtained using the second-generation DSCT scanner in various DE modes with pitch values up to 1.2 and gantry rotation time down to 0.28 s. For iodine concentrations ≥ 10 mg/mL, using the new integrated detector and the kernel with BHC can improve the accuracy of DECT-based iodine measurements.

Quantitative radiology: applications to oncology

Oncologists, clinician-scientists, and basic scientists collect computed tomography, magnetic resonance, and positron emission tomography images in the process of caring for patients, managing clinical trials, and investigating cancer biology. As we have developed more sophisticated means for noninvasively delineating and characterizing neoplasms, these image data have come to play a central role in oncology. In parallel, the increasing complexity and volume of these data have necessitated the development of quantitative methods for assessing tumor burden, and by proxy, disease-free survival.

Dual-energy CT of the abdomen

Although conceived of in the 1970s, practical use of dual-energy CT in the clinical setting did not come to fruition until 2006, and since that time an ever expanding exploration of the technology has been underway. This article will discuss technical aspects of the two commercially available CT scanners, review the recent literature, and provide an organ-based description of abdominal dual-energy CT applications for the practicing radiologist.

Optimization of kiloelectron volt settings in cerebral and cervical dual-energy CT angiography determined with virtual monoenergetic imaging

RATIONALE AND OBJECTIVES

Dual-energy computed tomography (DECT) offers various fields of application, especially in angiography using virtual monoenergetic imaging. The aim of this study was to evaluate objective image quality indices of calculated low-kiloelectron volt monoenergetic DECT angiographic cervical and cerebral data sets compared to virtual 120-kV polyenergetic images.

MATERIALS AND METHODS

Forty-one patients (21 men, mean age 58 ± 14) who underwent DECT angiography of the cervical (n = 7) or cerebral vessels (n = 34) were retrospectively included in this study. Data acquired with the 80 and 140 kVp tube using dual-source CT technology were subsequently used to calculate low-kiloelectron volt monoenergetic image data sets ranging from 120 to 40 keV (at 10-keV intervals per patient). Vessel and soft tissue attenuation and image noise were measured in various regions of interest, and contrast-to-noise ratio (CNR) was subsequently calculated. Differences in image attenuation and CNR were compared between the different monoenergetic data sets and virtual 120-kV polyenergetic images.

RESULTS

For cervical angiography, 60-keV monoenergetic data sets resulted in the greatest improvements in vessel attenuation and CNR compared to virtual 120-kV polyenergetic data sets (+40%, +16%; all P < .01). Also for cerebral vessel assessment, 60-keV monoenergetic data sets provided the greatest improvement in vessel attenuation and CNR (+40%, +9%; all P < .01) compared to virtual 120-kV polyenergetic data sets.

CONCLUSIONS

60-keV monoenergetic image data significantly improve vessel attenuation and CNR of cervical and cerebral DECT angiographic studies. Future studies have to evaluate whether the technique can lead to an increased diagnostic accuracy or should be used for dose reduction of iodinated contrast material.

Objective and subjective image quality of liver parenchyma and hepatic metastases with virtual monoenergetic dual-source dual-energy CT reconstructions: an analysis in patients with gastrointestinal stromal tumor

RATIONALE AND OBJECTIVES

To compare in dual-energy CT (DECT) conventionally reconstructed polyenergetic images (PEI) at 120 kVp to virtual monoenergetic images (MEI) at different kiloelectron volt (keV) levels for evaluation of liver and gastrointestinal stromal tumor (GIST) hepatic metastases with regard to objective (IQob) and subjective image quality (IQsub) assessed by two readers of varying experience. Image quality was correlated to patient size and compared between PEI and MEI.

MATERIALS AND METHODS

From 50 examinations of 17 GIST patients (12 with hepatic metastases) undergoing abdominal dual-source DECT for staging, therapy monitoring or follow-up, PEI and nine MEI in 10-keV intervals from 40 to 120 keV were reconstructed. Liver contrast-to-noise ratios (CNR) and metastasis-to-liver ratios were calculated. MEI reconstructions with the highest IQob were compared to PEI for IQsub by one experienced reader (ER) and one inexperienced reader (IR). Patients' diameters were correlated to IQob and IQsub ratings.

RESULTS

MEI at 70 keV had the highest IQob with equal liver CNR and metastasis-to-liver ratio compared to PEI. The ER rated 70-keV MEI and PEI equally high (median 4), whereas the IR rated IQsub best in 70-keV MEI (median 5). Unlike in PEI, IQsub ratings in 70-keV MEI were not correlated to patient size.

CONCLUSIONS

MEI at 70 keV provided an IQob equivalent to PEI. Regarding the IR, IQsub was improved in 70-keV MEI compared to PEI and less dependent on patient size. Therefore, IRs might improve their diagnostic confidence in the assessment of hepatic GIST metastases by evaluating MEI reconstructions at 70 keV.

Pushing CT and MR imaging to the molecular level for studying the "omics": current challenges and advancements

During the past decade, medical imaging has made the transition from anatomical imaging to functional and even molecular imaging. Such transition provides a great opportunity to begin the integration of imaging data and various levels of biological data. In particular, the integration of imaging data and multiomics data such as genomics, metabolomics, proteomics, and pharmacogenomics may open new avenues for predictive, preventive, and personalized medicine. However, to promote imaging-omics integration, the practical challenge of imaging techniques should be addressed. In this paper, we describe key challenges in two imaging techniques: computed tomography (CT) and magnetic resonance imaging (MRI) and then review existing technological advancements. Despite the fact that CT and MRI have different principles of image formation, both imaging techniques can provide high-resolution anatomical images while playing a more and more important role in providing molecular information. Such imaging techniques that enable single modality to image both the detailed anatomy and function of tissues and organs of the body will be beneficial in the imaging-omics field.

Liver surgery in the multidisciplinary management of gastrointestinal stromal tumour

INTRODUCTION

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

RESULTS

One and two-year overall survival 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- and 2-year overall survival (OS) rate 100%) than those operated on disease progression (1- and 2-year OS rates 60 and 40%; P = 0.043). No deaths were observed among patients who achieved an R0 resection (R0 versus R1/R2, P = 0.001).

DISCUSSION

R0 resection and clinical response to TKI are predictor of survival. Surgical resection should be performed as soon as feasible in responding 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.