Use of conventional MR imaging and diffusion‐weighted imaging for evaluating the risk grade of gastrointestinal stromal tumors

Predicting the progression-free survival of gastrointestinal stromal tumors after imatinib therapy through multi-sequence magnetic resonance imaging

PURPOSE

Identify radiomics features associated with progression-free survival (PFS) and develop a predictive model for accurate PFS prediction in liver metastatic gastrointestinal stromal tumor patients (GIST).

METHODS

This multi-center retrospective study involved a comprehensive review of clinical and imaging data pertaining to 211 patients with gastrointestinal stromal tumors (GIST) from Center A and B. A total of 147 patients with hepatic metastatic GIST were included, with 102 cases as the training set and 45 cases as the external validation set. Radiomics features were extracted from non-enhanced MR images, specifically T2WI, DWI, and ADC, and relevant features were selected through LASSO-Cox regression. A radiomics nomogram model was then constructed using multivariable Cox regression analysis to effectively predict PFS. The models performance were evaluated with the concordance index (C-index).

RESULTS

The median age of the patients was 53 years, with 82 males and 65 females. A total of 21 radiomics features were selected to generate the radiomics signature. Radiomics signature slightly outperformed the clinical model but without significant difference (P > 0.05). Integrated radiomics signature with clinical features to build a nomogram, which exhibited high predictive performance in both training (C-index 0.757, 95% CI 0.692-0.822) and validation cohorts (C-index 0.718, 95% CI 0.618-0.818). Nomogram significantly outperformed the clinical model (P = 0.002 for training cohort, P < 0.001 for validation cohort). Stable long-term predictions shown by time-dependent ROC analysis (AUC 0.765-0.919 in training, 0.766-0.893 in validation). Multivariable Cox regression confirmed radiomics signature as an independent prognostic factor for preoperative survival prediction in hepatic metastatic GIST patients (HR = 3.973).

CONCLUSION

Radiomics signature is valuable for predicting PFS in metastatic GIST patients. Integrating imaging features and clinical factors into a comprehensive nomogram improves accuracy and effectiveness of survival prognosis, guiding personalized treatment strategies.

Imaging findings of gastrointestinal tract tumors in children and adolescents

Gastrointestinal (GI) tract tumors are rarely seen in children and adolescents, and can easily be misdiagnosed. Lymphoma is the most frequent GI tract tumor, and the common locations are ileum and ileocecal area. GI tract tumors may present as large heterogeneous mass lesions. For gastric and colonic tumors, increased wall thickening usually prompts the diagnosis of GI tract tumors. Computed tomography and magnetic resonance imaging might be used in clinically suspected cases for correct/appropriate diagnosis and management. Awareness as regards the most common tumors and their locations is paramount for radiologists. Likewise, the aim of this article was to define the imaging findings of primary benign and malignant GI tract tumors in children and adolescents.

Mesenchymal Neoplasms of the Prostate and Seminal Vesicles: Spectrum of Disease with Radiologic-Pathologic Correlation

There is a wide spectrum of benign and malignant mesenchymal neoplasms of the prostate, which account for less than 1% of all prostatic tumors. These include distinctive tumors that arise from the specialized prostatic stroma and site-agnostic neoplasms such as smooth muscle tumors, fibrous or myofibroblastic neoplasms, neurogenic tumors, vascular tumors, and a plethora of sarcomas. Select tumors show classic sites of origin within the prostate. While stromal tumors of uncertain malignant potential (STUMPs) commonly involve the peripheral zone at the prostate base, leiomyomas typically originate from the central prostate toward the apex. Some "prostatic" neoplasms such as gastrointestinal stromal tumors, solitary fibrous tumor (SFT), paragangliomas, and neurogenic tumors arise primarily from periprostatic soft tissues. Most mesenchymal tumors of the prostate and seminal vesicles manifest as large tumors that cause nonspecific symptoms; prostate-specific antigen level is not typically elevated. Diverse mesenchymal neoplasms demonstrate characteristic histopathologic and immunocytochemical features and variable cross-sectional imaging findings. While leiomyoma and SFT typically display low signal intensity on T2-weighted images, synovial sarcomas commonly show hemorrhage. Diagnosis is difficult because of the rarity and lack of awareness of the tumors and the significant overlap in histopathologic features. Select tumors show characteristic genetic abnormalities that allow the diagnosis to be established. For example, more than 90% of SFTs are characterized by a unique NAB2-STAT6 gene fusion, and more than 95% of synovial sarcomas are associated with a distinctive SYT-SSX chimeric transcript. Accurate diagnosis is imperative for optimal management owing to markedly different tumor biology as well as attendant therapeutic and prognostic implications. While STUMPs commonly recur, sarcomas typically charter an aggressive course with poor prognosis. Online supplemental material is available for this article. ^©RSNA, 2022.

Utility of noncontrast MRI in the detection and risk grading of gastrointestinal stromal tumor: a comparison with contrast-enhanced CT

BACKGROUND

Recently developed adjuvant therapies for gastrointestinal stromal tumor (GIST) have been shown to improve patient survival. Guidelines currently recommend contrast-enhanced computed tomography (CECT) for GIST detection and surveillance. Patients with moderate-to-high risk GISTs require more frequent surveillance due to a higher 5-year recurrence rate. Our study aimed to compare noncontrast magnetic resonance imaging (MRI) with CECT for GIST detection, and evaluate volumetric apparent diffusion coefficients (ADCs) for risk stratification of GIST.

METHODS

We retrospectively enrolled 83 patients with histopathologically confirmed GISTs for lesion detection efficiency analysis between noncontrast MRI and matched CECT studies. A 5-point scale was used by two independent reviewers to determine if the lesion was present or absent. Another cohort, comprising 28 patients with pathologically confirmed primary GISTs, was further screened for risk stratification, with a comparison of volumetric ADC parameters between the pathologically very-low-to-low risk and moderate-to-high risk GIST patients.

RESULTS

For identifying GISTs, the sensitivity and specificity of noncontrast MRI were 83.6% and 89.3% for reader 1 respectively, and 81.8% and 92.9% for reader 2 respectively; the sensitivity and specificity of CECT were 76.4% and 89.3% for reader 1 respectively, and 76.4 and 78.6% for reader 2 respectively. Tumor volumetric ADC histogram parameters, including ADCmax, ADCstdev, 90th and 95th percentiles, inhomogeneity, and entropy, were positively correlated with a higher risk grade of GIST (r=0.421-0.758). The receiver operator characteristic curve analysis showed ADCmax achieved the highest area under the curve value of 0.938 for discriminating very-low-to-low risk versus moderate-to-high risk GISTs.

CONCLUSIONS

Noncontrast MRI was an efficient technique for identifying GIST patients. The combination of CECT and noncontrast MRI can improve the reliability of diagnosis. For patients with contraindications to CECT, noncontrast MRI may be a comparable alternative. Volumetric ADC histogram parameters may be useful in differentiating very-low-to-low risk from moderate-to-high risk primary GISTs.

Evaluation of risk classifications for gastrointestinal stromal tumor using multi-parameter Magnetic Resonance analysis

BACKGROUND

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal malignancy of the gastrointestinal tract. At present, it is generally believed that the prognosis of GIST is closely related to its risk classification. It may add value to correctly diagnose and evaluate the risk of invasion using a noninvasive imaging examination prior to surgery. MRI has the advantages of multiple parameters and high soft tissue resolution, which may be the potential method to preoperatively evaluate the risk of GIST.

PURPOSE

To retrospectively evaluate the diagnostic accuracy of multi-parameter MR analysis for preoperative risk classification of GIST.

MATERIALS AND METHODS

In this 6-year retrospective study, full MRI examination was performed on all 60 GIST cases confirmed classified by pathology, including 35 cases of very low-to-low-risk GIST and 25 cases of intermediate-to-high-risk GIST. Dynamic contrast-enhanced T1- and T2-weighted images, and apparent diffusion coefficient (ADC) maps were reviewed independently by two radiologists blinded to pathologic results. Volume, ADC ratio, three wash-in indexes (WII) were calculated and compared using t-test or Kruskal-Wallis nonparametric test. Sensitivity and specificity analyses were performed to calculate diagnostic accuracy using ROC analyses. Differences were considered significant at p < 0.05.

RESULTS

All GISTs were resected. Patient age, sex, tumor location and tumor shape did not differ significantly across the two groups (p = 0.798, 0.767, 0.822 and 0.096, respectively). GIST in the intermediate-to-high-risk group presented significantly greater volume (p = 0.0045), lower ADC ratio (p = 0.0125) and faster enhancement (for WII2, p < 0.0001; for WII3, p = 0.0358) than that of GIST in the very low-to-low-risk group. This combination of the volume, ADC ratio and WII2 provided sensitivity of 88%, specificity of 94.29%, and accuracy of 91.7% for the risk classification of GIST.

CONCLUSION

Multi-parameter MR analysis provides a preoperative imaging standard for accurately distinguishing very low-to-low-risk GIST from intermediate-to-high-risk GIST.

MRI Texture-Based Models for Predicting Mitotic Index and Risk Classification of Gastrointestinal Stromal Tumors

BACKGROUND

Treatment regimens and prognoses of gastrointestinal stromal tumors (GIST) are quite different for tumors in different risk categories. Accurate preoperative grading of tumors is important for avoiding under- or overtreatment.

PURPOSE

To develop and validate an MRI texture-based model to predict the mitotic index and its risk classification.

STUDY TYPE

Retrospective.

POPULATION

Ninety-one patients with histologically-confirmed GIST; 64 patients in a training cohort, and 27 patients in a test cohort.

FIELD STRENGTH/SEQUENCE

T₂ -weighted imaging (T₂ WI), diffusion-weighted imaging (DWI), and dynamic contrast-enhanced three-dimensional volumetric interpolated breath-hold examination (3D-VIBE) at 1.5T.

ASSESSMENT

GIST images were manually segmented by two independent radiologists using ITK-SNAP software and MRI features were extracted using Pyradiomics. Two pathologists reviewed the tissue specimens of the tumors to identify the mitotic index and risk classification in consensus.

STATISTICAL TESTS

The least absolute shrinkage and selection operator (LASSO) regression method was used to select texture features. A logistic regression model was established based on the radiomic score (radscore), tumor location, and maximum diameter to predict tumor classification and develop a nomogram. Receiver operator characteristic (ROC) curves were used to evaluate the ability of the nomogram to distinguish between two tumors with different risk classifications, and a calibration curve was used to evaluate the consistency between the predicted risk and the actual risk.

RESULTS

The texture signature achieved high efficacy in predicting the mitotic index area under the curve ([AUC], 0.906; 95% confidence interval [CI]: 0.813, 0.961). A nomogram for prediction of the risk classification of GIST, which incorporated this texture signature together with maximum tumor diameter and location, allowed good discrimination in the training cohort (AUC, 0.878; 95% CI: 0.769, 0.960) and the validation cohort (AUC, 0.903; 95% CI: 0.732, 0.922).

DATA CONCLUSION

The texture-based model can be used to predict GIST mitotic index and risk classification preoperatively.

LEVEL OF EVIDENCE

2.

TECHNICAL EFFICACY STAGE

3.

A Systematic Review of Technical Parameters for MR of the Small Bowel in non-IBD Conditions over the Last Ten Years

Technical guidelines for magnetic resonance imaging (MRI) of the small bowel (SB) in the setting of inflammatory bowel diseases (IBDs) were detailed in a 2017 consensus issued by European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and European Society of Pediatric Radiology (ESPR); however, MRI for non-IBD conditions was not addressed. Hence, we performed a systematic review collecting researches on SB MRI for non-IBDs. The literatures were then divided into morphologic group and functional group. Information about the MRI techniques, gastrointestinal preparation, and details of cine-MRI protocols was extracted. We found that a 1.5 T MRI system, prone positioning, and MR enterography were frequently utilized in clinical practice. Gadolinium contrast sequences were routinely implemented, while diffusion-weighted imaging (DWI) was much less performed. The gastrointestinal preparation varied throughout the studies. No uniform protocols for cine imaging could be established. SB MRI examinations for non-IBDs are far from standardized, especially for functional studies. Recommendations for standard parameters in cine-MRI sequences are difficult to make due to lack of evidentiary support. MRI investigations in non-IBD conditions are needed and the standardization of non-IBD imaging in clinical practice is required.

Clinicopathological and morphological spectrum of gastrointestinal stromal tumours on multi-detector computed tomography

PURPOSE

To describe the clinicopathological and morphological features of gastrointestinal stromal tumours (GISTs) on multi-detector computed tomography (MDCT).

MATERIAL AND METHODS

MDCT (plain and post contrast) images of 25 confirmed cases of GISTs were retrospectively evaluated from our hospital database. The images were analysed for the location, size, growth pattern, attenuation pattern, relation to adjacent structures, presence or absence of ulceration, calcification, metastases, lymphadenopathy, and for any complications such as haemorrhage, intestinal obstruction, etc. Institutional Ethics Committee clearance was obtained prior to the commencement of the study. Statistics used included percentage frequency.

RESULTS

Our study group comprised 14 males and 11 females. The mean age of our study population was 60 years (age range: 40 to 82 years). The mean tumour size was 11.7 cm. The stomach and small bowel accounted for 76% of the primary tumour site. The commonest imaging appearance of GIST observed in our study was that of an exophytic mass (76%) with a heterogenous pattern of enhancement (96%) with intratumoural necrosis (76%). MDCT demonstrated complications in three patients (12%). Six patients presented with metastatic foci (five to the liver and one to the lung), while lymphadenopathy was observed in five patients (20%). Associated complications included intestinal obstruction (8%) and retrogastric haematoma (4%). Incidental findings included uterine fibroid (n = 1), ovarian dermoid (n = 1), and chronic pancreatitis (n = 1).

CONCLUSIONS

GISTs are predominantly large tumours with a well circumscribed and exophytic pattern on MDCT, with or without cystic/necrotic areas, and they mostly show a heterogenous pattern of enhancement on post-contrast administration.

MRI features of gastrointestinal stromal tumors

OBJECTIVE

The purpose of this study was to investigate the MRI features of gastrointestinal stromal tumors (GISTs) with special emphasis on the dynamic enhancement pattern and findings of diffusion restriction.

MATERIALS AND METHODS

Forty-two patients with pathologically proven GISTs who underwent MRI that included dynamic contrast-enhanced and diffusion-weighted imaging (DWI) were included in this study. Two abdominal radiologists analyzed the MR images in consensus regarding the morphologic features, enhancement degree and pattern, and findings of diffusion restriction. The mean apparent diffusion coefficient (ADC) values of the tumors were measured by one of the radiologists. The MRI features and mean ADC values were analyzed with respect to tumor size and malignancy risk.

RESULTS

Small GISTs (≤ 5 cm, n = 25) appeared as round tumors with strong and homogeneous arterial enhancement and a persistent enhancement pattern. Large GISTs (> 5 cm, n = 17) appeared as lobulated tumors with mild heterogeneous gradual enhancement, and they frequently exhibited intratumoral cystic change (n = 13). The prevalence of intratumoral cystic change was higher in the moderate to high risk group than in very low to low risk group (p < 0.05). There was negative linear correlation between the mean ADC values and the malignancy risk of GISTs (r = -0.670, p < 0.05).

CONCLUSION

Small GISTs had MRI features different from the well-known imaging features of large GISTs. The presence of intratumoral cystic change and a low mean ADC value may be helpful for predicting the high malignancy potential of GISTs.

Gastrointestinal stromal tumours: correlation of modified NIH risk stratification with diffusion-weighted MR imaging as an imaging biomarker

PURPOSE

To evaluate the correlation of risk grade of gastrointestinal stromal tumours (GISTs) based on modified National Institutes of Health (NIH) criteria with conventional magnetic resonance (MR) imaging and diffusion-weighted (DW) imaging.

METHODS

We included 22 patients with histopathologically proven GISTs in the stomach or small bowel who underwent pre-operative gadoxetic acid-enhanced MR imaging and DW imaging. We retrospectively assessed correlations between morphologic findings, qualitative (signal intensity, consensus from two observers) and quantitative (degree of dynamic enhancement using signal intensity of tumour/muscle ratio and apparent diffusion coefficient [ADC]) values, and the modified NIH criteria for risk stratification. Spearman partial correlation analysis was used to control for tumour size as a confounding factor. The optimal cut-off level of ADC values for intermediate or high risk GISTs was analyzed using a receiver operating characteristic analysis.

RESULTS

Except tumour size and necrosis, conventional MR imaging findings, including the degree of dynamic enhancement, were not significantly different according to the modified NIH criteria (p>0.05). Tumour ADC values were negatively correlated with the modified NIH criteria, before and after adjustment of tumour size (ρ=-0.754; p<0.001 and ρ=-0.513; p=0.017, respectively). The optimal cut-off value for the determination of intermediate or high-risk GISTs was 1.279 × 10(-3)mm(2)/s (100% sensitivity, 69.2% specificity, 81.8% accuracy).

CONCLUSION

Except tumour size and necrosis, conventional MR imaging findings did not correlate with the risk grade. However, the ADC value can be used as an imaging biomarker to assess the risk grade of GISTs, regardless of tumour size.

State of the Art in the Treatment of Gastrointestinal Stromal Tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most frequently diagnosed mesenchymal neoplasms of the gastrointestinal tract. Despite their biological and clinical heterogeneity, the majority of these tumors are positive for the receptor tyrosine kinase KIT and are driven by KIT- or platelet-derived growth factor receptor alpha (PDGFRA)-activating mutations. There are still uncertainties regarding their clinical and molecular characterization and the optimal treatment regimens, making it difficult to establish a universal treatment algorithm for these tumors.

SUMMARY

From a clinical perspective, the main difference between GISTs and other gastrointestinal neoplasms is that the benign or malignant behavior of GISTs cannot be predicted from histopathology, but instead relies on empirically established scoring systems. Clinical data suggest that malignant potential may be an inherent quality of some GISTs rather than a feature acquired by the tumor during disease progression. Thus, some patients may require prolonged anti-tumor treatment even after complete surgical removal of the tumor.

KEY MESSAGE

Although GISTs are the most frequently occurring mesenchymal neoplasms in the gastrointestinal tract, no universal treatment algorithms exist. This paper reviews the current evidence that guides the management of GISTs.

PRACTICAL IMPLICATIONS

The management of localized GISTs involves the use of surgical resection, with the inclusion of preoperative tyrosine kinase inhibitor treatment for locally advanced, primarily unresectable tumors and for resectable cases requiring extensive surgery. Imatinib is also indicated as adjuvant therapy after complete surgical removal of GISTs with a high estimated risk of recurrence unless specific mutations conferring imatinib resistance are present. The optimal duration of adjuvant treatment is still controversial. For patients with metastatic imatinib-sensitive GISTs, imatinib constitutes the first-line standard treatment. Molecular characterization of the tumor (with respect to the PDGFRA and KIT genes) is mandatory prior to imatinib therapy. Sunitinib and regorafenib are established as alternative treatments for patients demonstrating generalized disease progression on imatinib. New tyrosine kinase inhibitors such as ponatinib and crenolanib as well as drugs targeting alternative pathways are currently under investigation. Surgery and locally ablative treatments may be indicated in some metastatic patients.