Multi-parametric MRI of rectal cancer - do quantitative functional MR measurements correlate with radiologic and pathologic tumor stages?

Study of Comparison of Magnetic Resonance Imaging with Surgical and Pathological features in Carcinoma Rectum Patients

Colorectal cancer is the second-most common cancer in the females and third-most common cancer in males worldwide and it is the second-most common cause of mortality. In India, colorectal cancer is the fifth-most common cancer overall, constituting 6.3%. With the advent of high-resolution magnetic resonance imaging (MRI), it has become the investigation of choice for local staging of rectal cancers as well as in predicting the response to neoadjuvant treatment and streamlining the management. The aims and objectives of this study were to compare the results of MRI with surgicopathological findings in carcinoma (Ca) rectum patients in Indian patients from a tertiary regional Cancer care centre. An observational retrospective study was carried out in the Department of Surgical Oncology Acharya Harihar Regional Cancer Centre, Cuttack, from January 2021 to June 2022. All the patients who were admitted and planned for the definitive surgery for Ca Rectum and Recto sigmoid Ca were included in the study. A total of 68 patients were included, including both upfront and post-neoadjuvant treatment cases. All the patients who received neoadjuvant treatment underwent an MRI for local staging. The findings of MRI were compared with surgical and histopathology results. Results were compared in terms of T staging, N staging and response to neoadjuvant therapy among MRI and surgical and pathological findings. Overall, there was good agreement between MRI and operative findings and histopathological findings.

Deep Learning-Based Multiparametric MRI Model for Preoperative T-Stage in Rectal Cancer

BACKGROUND

Conventional MRI staging can be challenging in the preoperative assessment of rectal cancer. Deep learning methods based on MRI have shown promise in cancer diagnosis and prognostication. However, the value of deep learning in rectal cancer T-staging is unclear.

PURPOSE

To develop a deep learning model based on preoperative multiparametric MRI for evaluation of rectal cancer and to investigate its potential to improve T-staging accuracy.

STUDY TYPE

Retrospective.

POPULATION

After cross-validation, 260 patients (123 with T-stage T1-2 and 134 with T-stage T3-4) with histopathologically confirmed rectal cancer were randomly divided to the training (N = 208) and test sets (N = 52).

FIELD STRENGTH/SEQUENCE

3.0 T/Dynamic contrast enhanced (DCE), T2-weighted imaging (T2W), and diffusion-weighted imaging (DWI).

ASSESSMENT

The deep learning (DL) model of multiparametric (DCE, T2W, and DWI) convolutional neural network were constructed for evaluating preoperative diagnosis. The pathological findings served as the reference standard for T-stage. For comparison, the single parameter DL-model, a logistic regression model composed of clinical features and subjective assessment of radiologists were used.

STATISTICAL TESTS

The receiver operating characteristic curve (ROC) was used to evaluate the models, the Fleiss' kappa for the intercorrelation coefficients, and DeLong test for compare the diagnostic performance of ROCs. P-values less than 0.05 were considered statistically significant.

RESULTS

The Area Under Curve (AUC) of the multiparametric DL-model was 0.854, which was significantly higher than the radiologist's assessment (AUC = 0.678), clinical model (AUC = 0.747), and the single parameter DL-models including T2W-model (AUC = 0.735), DWI-model (AUC = 0.759), and DCE-model (AUC = 0.789).

DATA CONCLUSION

In the evaluation of rectal cancer patients, the proposed multiparametric DL-model outperformed the radiologist's assessment, the clinical model as well as the single parameter models. The multiparametric DL-model has the potential to assist clinicians by providing more reliable and precise preoperative T staging diagnosis.

EVIDENCE LEVEL

3 TECHNICAL EFFICACY: Stage 2.

Application value of simultaneous multislice readout-segmented echo-planar imaging for diffusion-weighted MRI in differentiation of rectal cancer grade

OBJECTIVE

To analyze the association of apparent diffusion coefficient (ADC) values measured by readout-segmented echo-planar imaging (rs-EPI) using different simultaneous multislice (SMS) acceleration factors and the differentiation of rectal cancer grade.

MATERIALS AND METHODS

Patients with non-mucinous rectal adenocarcinoma diagnosed by biopsy (endoscope-guided biopsy or surgical resection) were retrospectively collected, and each patient underwent an MRI examination. ADC values of rs-EPI, 2 × SMS rs-EPI, and 3 × SMS rs-EPI were recorded as ADC1, ADC2, and ADC3, respectively.

RESULTS

The scanning time of 2 × SMS rs-EPI was 60 s, 56.2% shorter than 137 s of rs-EPI sequence, while that of 3 × SMS rs-EPI was 51 s, 72.8% less than that of rs-EPI time. The ADC value of the three groups dropped with the decrease in cancer grade (p < 0.05). The AUC values of ADC1, ADC2, and ADC3 in predicting highly differentiated rectal cancer were 0.74, 0.729, and 0.687, respectively. The difference in AUC values between ADC1 and ADC2 was not statistically significant (p = 0.889).

DISCUSSION

SMS technology with an acceleration factor of 2 could be applied clinically to evaluate the pathological differentiation of rectal cancer grade.

Histogram analysis of dynamic contrast-enhanced magnetic resonance imaging to predict extramural venous invasion in rectal cancer

BACKGROUND

To explore the potential of histogram analysis (HA) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in the identification of extramural venous invasion (EMVI) in rectal cancer patients.

METHODS

This retrospective study included preoperative images of 194 rectal cancer patients at our hospital between May 2019 and April 2022. The postoperative histopathological examination served as the reference standard. The mean values of DCE-MRI quantitative perfusion parameters (Ktrans, Kep and Ve) and other HA features calculated from these parameters were compared between the pathological EMVI-positive and EMVI-negative groups. Multivariate logistic regression analysis was performed to establish the prediction model for pathological EMVI-positive status. Diagnostic performance was assessed and compared using the receiver operating characteristic (ROC) curve. The clinical usefulness of the best prediction model was further measured with patients with indeterminate MRI-defined EMVI (mrEMVI) score 2(possibly negative) and score 3 (probably positive).

RESULTS

The mean values of Ktrans and Ve in the EMVI-positive group were significantly higher than those in the EMVI-negative group (P = 0.013 and 0.025, respectively). Significant differences in Ktrans skewness, Ktrans entropy, Ktrans kurtosis, and Ve maximum were observed between the two groups (P = 0.001,0.002, 0.000, and 0.033, respectively). The Ktrans kurtosis and Ktrans entropy were identified as independent predictors for pathological EMVI. The combined prediction model had the highest area under the curve (AUC) at 0.926 for predicting pathological EMVI status and further reached the AUC of 0.867 in subpopulations with indeterminate mrEMVI scores.

CONCLUSIONS

Histogram Analysis of DCE-MRI Ktrans maps may be useful in preoperative identification of EMVI in rectal cancer, particularly in patients with indeterminate mrEMVI scores.

Watch-and-Wait Approach to Rectal Cancer: The Role of Imaging

The diagnosis and treatment of rectal cancer have evolved dramatically over the past several decades. At the same time, its incidence has increased in younger populations. This review will inform the reader of advances in both diagnosis and treatment. These advances have led to the watch-and-wait approach, otherwise known as nonsurgical management. This review briefly outlines changes in medical and surgical treatment, advances in MRI technology and interpretation, and landmark studies or trials that have led to this exciting juncture. Herein, the authors delve into current state-of-the-art methods to assess response to treatment with MRI and endoscopy. Currently, these methods for avoiding surgery can be used to detect a complete clinical response in as many as 50% of patients with rectal cancer. Finally, the limitations of imaging and endoscopy and future challenges will be discussed.

Investigating the effect of ARHGEF10L gene on tumor growth in gastric cancer in a nude mouse model using quantitative MRI parameters

Background

The quantitative magnetic resonance imaging (MRI) parameters were initially used in the study of central nervous system diseases and has since been widely used in the diagnosis of breast, liver, rectum, and prostate diseases. In our study, we aimed to evaluate the effect of ARHGEF10L gene on tumor growth in gastric cancer in nude mice using quantitative MRI parameters.

Subjects and Methods

A nude mice model of gastric cancer was established, and the mice were divided into a control group and an shARHGEF10L group (N = 10). T2-fs and intravoxel incoherent motions (IVIM) imaging were performed in the mice coil with a 3.0 T MR system. The differences in quantitative parameters (apparent diffusion coefficient [ADC], D, D *, f values) were compared between both groups, and the effect of ARHGEF10L expression on tumor growth in tumor-bearing mice was investigated. The data were analyzed using Statistical Package for the Social Sciences (SPSS) 17.0 software package.

Results

The ADC and D values of tumor imaging in the shARHGEF10L group were higher than those in the control group, and the differences were statistically significant. There was no significant difference in the D* or F values between both groups.

Conclusions

The ADC and D values of the quantitative IVIM imaging parameters can be used to effectively assess the growth of gastric cancer in nude mice, suggesting that ARHGEF10L may promote the growth of tumor cells.

Are We There Yet? The Value of Deep Learning in a Multicenter Setting for Response Prediction of Locally Advanced Rectal Cancer to Neoadjuvant Chemoradiotherapy

This retrospective study aims to evaluate the generalizability of a promising state-of-the-art multitask deep learning (DL) model for predicting the response of locally advanced rectal cancer (LARC) to neoadjuvant chemoradiotherapy (nCRT) using a multicenter dataset. To this end, we retrained and validated a Siamese network with two U-Nets joined at multiple layers using pre- and post-therapeutic T2-weighted (T2w), diffusion-weighted (DW) images and apparent diffusion coefficient (ADC) maps of 83 LARC patients acquired under study conditions at four different medical centers. To assess the predictive performance of the model, the trained network was then applied to an external clinical routine dataset of 46 LARC patients imaged without study conditions. The training and test datasets differed significantly in terms of their composition, e.g., T-/N-staging, the time interval between initial staging/nCRT/re-staging and surgery, as well as with respect to acquisition parameters, such as resolution, echo/repetition time, flip angle and field strength. We found that even after dedicated data pre-processing, the predictive performance dropped significantly in this multicenter setting compared to a previously published single- or two-center setting. Testing the network on the external clinical routine dataset yielded an area under the receiver operating characteristic curve of 0.54 (95% confidence interval [CI]: 0.41, 0.65), when using only pre- and post-therapeutic T2w images as input, and 0.60 (95% CI: 0.48, 0.71), when using the combination of pre- and post-therapeutic T2w, DW images, and ADC maps as input. Our study highlights the importance of data quality and harmonization in clinical trials using machine learning. Only in a joint, cross-center effort, involving a multidisciplinary team can we generate large enough curated and annotated datasets and develop the necessary pre-processing pipelines for data harmonization to successfully apply DL models clinically.

Native T1 mapping for differentiating the histopathologic type, grade, and stage of rectal adenocarcinoma: a pilot study

Background

Previous studies have indicated that T1 relaxation time could be utilized for the analysis of tissue characteristics. T1 mapping technology has been gradually used on research of body tumor. In this study, the application of native T1 relaxation time for differentiating the histopathologic type, grade, and stage of rectal adenocarcinoma was investigated.

Methods

One hundred and twenty patients with pathologically confirmed rectal adenocarcinoma were retrospectively evaluated. All patients underwent high-resolution anatomical magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI), and T1 mapping sequences. Parameters of T1 relaxation time and apparent diffusion coefficient (ADC) were measured between the different groups. The diagnostic power was evaluated though the receiver operating characteristic (ROC) curve.

Results

The T1 and ADC values varied significantly between rectal mucinous adenocarcinoma (MC) and non-mucinous rectal adenocarcinoma (AC) ([1986.1 ± 163.3 ms] vs. [1562.3 ± 244.2 ms] and [1.38 ± 0.23 × 10⁻³mm²/s] vs. [1.03 ± 0.15 × 10⁻³mm²/s], respectively; P < 0.001). In the AC group, T1 relaxation time were significantly different between the low- and high-grade adenocarcinoma cases ([1508.7 ± 188.6 ms] vs. [1806.5 ± 317.5 ms], P < 0.001), while no differences were apparent in the ADC values ([1.03 ± 0.14 × 10⁻³mm²/s] vs. [1.04 ± 0.18 × 10⁻³mm²/s], P > 0.05). No significant differences in T1 and ADC values were identified between the different T and N stage groups for both MC and AC (all P > 0.05).

Conclusions

Native T1 relaxation time can be used to discriminate MC from AC. The T1 relaxation time was helpful for differentiating the low- and high-grade of AC.

A model based on endorectal ultrasonography predicts lateral lymph node metastasis in low and middle rectal cancer

PURPOSE

To investigate the risk factors for lymph node (LN) metastasis in low and middle rectal tumors, construct a predictive model and test the model's diagnostic efficacy.

METHODS

The clinical and pathological data of 172 patients with rectal cancer confirmed by surgery were retrospectively evaluated, among whom 61 patients were finally included in this study. Patients were divided into positive groups and negative groups based on LN metastasis, and risk factors that might affect LN metastasis were analyzed. Finally, a risk predictive model was constructed based on the weights of each risk factor.

RESULTS

Compared with pathology, the efficacy of diagnosing LN metastasis only according to conventional endorectal ultrasonography (ERUS) features of LN was not high, with sensitivity 67%, specificity 86%, positive predictive value 76%, negative predictive value 80%, and accuracy 79%. Univariate analysis showed that circumferential angle of the tumor, ultrasonic T- stage (UT stage), conventional ultrasound features diagnosis of LN metastasis, strain ratio (SR) of tumor were risk factors for LN metastasis, while vascular resistance index of rectal tumor was protective factor. Multivariate analysis showed that UT stage (OR = 7.188, p = 0.049), conventional ultrasound features diagnosis of LN metastasis (OR = 8.010, p = 0.025) and SR (OR = 5.022, p = 0.031) were independent risk factors for LN metastasis. These risk factors were included in logistic regression analysis and the model was established, Y = -7.3 + 1.9 X10 + 2.1 X11 + 1.6 X13 (Y = Logit[P], P: LN metastasis rate, X10: UT stage, X11: conventional ultrasound features diagnosis of LN metastasis, X13: SR). The receiver operating characteristic (ROC) curve was used to test the model's predictive efficacy, the area under the curve was 0.95, sensitivity: 95%, specificity: 87%. Hosmer-Lemeshow goodness of fit test showed X2 = 6.015, p = 0.65 (p > 0.05), indicating that the model had a high predictive value.

CONCLUSION

Evaluation of perirectal LN metastasis only based on conventional ERUS features of LN was not effective enough. UT stage of tumor, conventional ultrasound features diagnosis of LN metastasis and SR were independent risk factors for LN metastasis. The predictive model had good assessment efficacy and had certain clinical application value.

Sources of variation in multicenter rectal MRI data and their effect on radiomics feature reproducibility

OBJECTIVES

To investigate sources of variation in a multicenter rectal cancer MRI dataset focusing on hardware and image acquisition, segmentation methodology, and radiomics feature extraction software.

METHODS

T2W and DWI/ADC MRIs from 649 rectal cancer patients were retrospectively acquired in 9 centers. Fifty-two imaging features (14 first-order/6 shape/32 higher-order) were extracted from each scan using whole-volume (expert/non-expert) and single-slice segmentations using two different software packages (PyRadiomics/CapTk). Influence of hardware, acquisition, and patient-intrinsic factors (age/gender/cTN-stage) on ADC was assessed using linear regression. Feature reproducibility was assessed between segmentation methods and software packages using the intraclass correlation coefficient.

RESULTS

Image features differed significantly (p < 0.001) between centers with more substantial variations in ADC compared to T2W-MRI. In total, 64.3% of the variation in mean ADC was explained by differences in hardware and acquisition, compared to 0.4% by patient-intrinsic factors. Feature reproducibility between expert and non-expert segmentations was good to excellent (median ICC 0.89-0.90). Reproducibility for single-slice versus whole-volume segmentations was substantially poorer (median ICC 0.40-0.58). Between software packages, reproducibility was good to excellent (median ICC 0.99) for most features (first-order/shape/GLCM/GLRLM) but poor for higher-order (GLSZM/NGTDM) features (median ICC 0.00-0.41).

CONCLUSIONS

Significant variations are present in multicenter MRI data, particularly related to differences in hardware and acquisition, which will likely negatively influence subsequent analysis if not corrected for. Segmentation variations had a minor impact when using whole volume segmentations. Between software packages, higher-order features were less reproducible and caution is warranted when implementing these in prediction models.

KEY POINTS

• Features derived from T2W-MRI and in particular ADC differ significantly between centers when performing multicenter data analysis. • Variations in ADC are mainly (> 60%) caused by hardware and image acquisition differences and less so (< 1%) by patient- or tumor-intrinsic variations. • Features derived using different image segmentations (expert/non-expert) were reproducible, provided that whole-volume segmentations were used. When using different feature extraction software packages with similar settings, higher-order features were less reproducible.

Role of MRI‑based radiomics in locally advanced rectal cancer (Review)

Colorectal cancer is the third most common type of cancer, with high morbidity and mortality rates. In particular, locally advanced rectal cancer (LARC) is difficult to treat and has a high recurrence rate. Neoadjuvant chemoradiotherapy (NCRT) is one of the standard treatment programs of LARC. If the response to treatment and prognosis in patients with LARC can be predicted, it will guide clinical decision‑making. Radiomics is characterized by the extraction of high‑dimensional quantitative features from medical imaging data, followed by data analysis and model construction, which can be used for tumor diagnosis, staging, prediction of treatment response and prognosis. In recent years, a number of studies have assessed the role of radiomics in NCRT for LARC. MRI‑based radiomics provides valuable data and is expected to become an imaging biomarker for predicting treatment response and prognosis. The potential of radiomics to guide personalized medicine is widely recognized; however, current limitations and challenges prevent its application to clinical decision‑making. The present review summarizes the applications, limitations and prospects of MRI‑based radiomics in LARC.

Endorectal Ultrasound and Magnetic Resonance Imaging for Rectal Cancer Staging: A Modern Multimodality Approach

Preoperative staging represents a crucial point for the management, type of surgery, and candidacy for neoadjuvant therapy in patient with rectal cancer. The most recent clinical guidelines in oncology recommend an accurate preoperative evaluation in order to address early and advanced tumors to different therapeutic options. In particular, potential pitfalls may occur in the assessment of T3 tumors, which represents the most common stage at diagnosis. The depth of tumor invasion is known to be an important prognostic factor in rectal carcinoma; as a consequence, the T3 imaging classification has a substantial importance for treatment strategy and patient survival. However, the differentiation between tumor invasion of perirectal fat and mesorectal desmoplastic reactions remains a main goal for radiologists. Magnetic resonance imaging (MRI) is actually considered as the best imaging modality for rectal cancer staging. Although the endorectal ultrasound (ERUS) is the preferred staging method for early tumors, it could also be useful in identifying perirectal fat invasion. Moreover, the addiction of diffusion weighted imaging (DWI) improves the diagnostic performance of MRI in rectal cancer staging by adding functional information about rectal tumor and adjacent mesorectal tissues. This study investigated the diagnostic performance of conventional MRI alone, in combination with the DWI technique and ERUS in order to assess the best diagnostic imaging combination for rectal cancer staging.

Diffusion tensor imaging of rectal carcinoma: Clinical evaluation and its correlation with histopathological findings

OBJECTIVE

This study sought to assess the feasibility of diffusion tensor imaging (DTI) to noninvasively evaluate histological grade and lymph node metastasis in patients with rectal carcinoma (RC).

METHODS

Thirty-seven consecutive patients with histologically confirmed RC were examined by 1.5-T MRI. DTI was performed using a single-shot echo-planar imaging sequence with b values of 0 and 1000 s/mm² and motion-probing gradients in nine noncollinear directions. Fractional anisotropy (FA), axial diffusivity (AD), mean diffusivity (MD), and radial diffusivity (RD) maps were compared with histopathological findings.

RESULTS

The FA values (0.357 ± 0.047) of the RCs were significantly lower than those of the normal rectal wall, muscle, prostate, and uterus (P < 0.001 for all), while the AD, MD, and RD values (1.221 ± 0.131, 0.804 ± 0.075, and 0.667 ± 0.057 × 10^-3 mm²/s, respectively) were also significantly lower than their respective normal values (P < 0.001 for all). The FA, AD, MD, and RD values for RC additionally showed significant inverse correlations with histological grades (r = -0.781, r = -0.750, r = -0.718, and r = -0.682, respectively; P < 0.001 for all). Further, the FA (0.430 vs. 0.611), AD (1.246 vs. 1.608 × 10^-3 mm²/s), MD (0.776 vs. 1.036 × 10^-3 mm²/s), and RD (0.651 vs. 0.824 × 10^-3 mm²/s) (P < 0.001 for all) of the metastatic and nonmetastatic lymph nodes were significantly different.

CONCLUSIONS

DTI may be clinically useful for the noninvasive evaluation of histological grade and lymph node metastasis in patients with RC.

Prediction of different stages of rectal cancer: Texture analysis based on diffusion-weighted images and apparent diffusion coefficient maps

BACKGROUND

It is evident that an accurate evaluation of T and N stage rectal cancer is essential for treatment planning. It has not been extensively investigated whether texture features derived from diffusion-weighted imaging (DWI) images and apparent diffusion coefficient (ADC) maps are associated with the extent of local invasion (pathological stage T1-2 vs T3-4) and nodal involvement (pathological stage N0 vs N1-2) in rectal cancer.

AIM

To predict different stages of rectal cancer using texture analysis based on DWI images and ADC maps.

METHODS

One hundred and fifteen patients with pathologically proven rectal cancer, who underwent preoperative magnetic resonance imaging, including DWI, were enrolled, retrospectively. The ADC measurements (ADC_mean, ADC_min, ADC_max) as well as texture features, including the gray level co-occurrence matrix parameters, the gray level run-length matrix parameters and wavelet parameters were calculated based on DWI (b = 0 and b = 1000) images and the ADC maps. Independent sample t-tests or Mann-Whitney U tests were used for statistical analysis. Multivariate logistic regression analysis was conducted to establish the models. The predictive performance was validated by receiver operating characteristic curve analysis.

 

RESULTS

Dissimilarity, sum average, information correlation and run-length nonuniformity from DWI_b=0 images, gray level nonuniformity, run percentage and run-length nonuniformity from DWI_b=1000 images, and dissimilarity and run percentage from ADC maps were found to be independent predictors of local invasion (stage T3-4). The area under the operating characteristic curve of the model reached 0.793 with a sensitivity of 78.57% and a specificity of 74.19%. Sum average, gray level nonuniformity and the horizontal components of symlet transform (SymletH) from DWI_b=0 images, sum average, information correlation, long run low gray level emphasis and SymletH from DWI_b=1000 images, and ADC_max, ADC_mean and information correlation from ADC maps were identified as independent predictors of nodal involvement. The area under the operating characteristic curve of the model reached 0.802 with a sensitivity of 80.77% and a specificity of 68.25%.

CONCLUSION

Texture features extracted from DWI images and ADC maps are useful clues for predicting pathological T and N stages in rectal cancer.

Multiparametric MRI of rectal cancer-repeatability of quantitative data: a feasibility study

PURPOSE

In this study, we aimed to analyze the repeatability of quantitative multiparametric rectal magnetic resonance imaging (MRI) parameters with different measurement techniques.

METHODS

All examinations were performed with 3 T MRI system. In addition to routine sequences for rectal cancer imaging protocol, small field-of-view diffusion-weighted imaging and perfusion sequences were acquired in each patient. Apparent diffusion coefficient (ADC) was used for diffusion analysis and ktrans was used for perfusion analysis. Three different methods were used in measurement of these parameters; measurements were performed twice by one radiologist for intraobserver and separately by three radiologists for interobserver variability analysis. ADC was measured by the lowest value, the value at maximum wall thickness, and freehand techniques. Ktrans was measured at the slice with maximum wall thickness, by freehand drawn region of interest (ROI), and at the dark red spot with maximum value.

RESULTS

A total of 30 patients with biopsy-proven rectal adenocarcinoma were included in the study. The mean values of the parameters measured by the first radiologist on the first and second measurements were as follows: mean lowest ADC, 721.31±147.18 mm2/s and 718.96±135.71 mm2/s; mean ADC value on the slice with maximum wall thickness, 829.90±144.24 mm2/s and 829.48±149.23 mm2/s; mean ADC value measured by freehand ROI on the slice with maximum wall thickness, 846.56±136.31 mm2/s and 848.23±144.15 mm2/s; mean ktrans value on the slice with maximum wall thickness, 0.219±0.080 and 0.214±0.074; mean ktrans by freehand ROI technique (including as much tumoral tissue as possible), 0.208±0.074 and 0.207±0.069; mean ktrans measured from the dark red foci, 0.308±0.109 and 0.311±0.105. Intraobserver agreement was very good among diffusion and perfusion parameters obtained with all three measurement techniques. Interobserver agreement was very good, except for one of the measurement techniques. As far as interobserver variability is considered, only ADC value measured on the slice with maximum wall thickness differed significantly.

CONCLUSION

Multiparametric MRI of rectum, using ADC as the diffusion and ktrans as the perfusion parameter is a repeatable technique. This technique may potentially be used in prediction and evaluation of neoadjuvant treatment response. New studies with larger patient groups are needed to validate the role of multiparametric MRI.

Height of Rectal Cancer: A Comparison between Rectoscopic and Different MRI Measurements

Purpose

To compare rigid rectoscopy with three different MRI measurement techniques for rectal cancer height determination, all starting at the anal verge, in order to evaluate whether MRI measurements starting from the anal verge could be an alternative to rigid rectoscopy. Moreover, potential cut-off values for MRI in categorizing tumor height measurements were evaluated.

Methods

In this retrospective study, 106 patients (75 men, 31 female, mean age 64 ± 11.59 years) with primary rectal cancer underwent rigid rectoscopy as well as MR imaging. Three different measurements (MRI1-3) in T2w sagittal scans were used to evaluate the exact distance from the anal verge (AV) to the distal ending of the tumor (MRI1: two unbowed lines, AV to the upper ending of the anal canal and upper ending of the anal canal to the lower border of the tumor; MRI2: one straight line from the AV to the lower boarder of the tumor; MRI3: a curved line beginning at the AV and following the course of the rectum wall ending at the lower border of the tumor). Furthermore, agreement between the gold standard rigid rectoscopy (UICC classification: low part, 0-6 cm; mid part, 6-12 cm; and high part, >12 cm) and each MRI measuring technique was analyzed.

Results

Only a fair correlation in terms of individual measures between rectoscopy and all 3 MRI measurement techniques was shown. The proposed new cut-off values utilizing ROC analysis for the three different MRI beginning at the anal verge were low 0-7.7 cm, mid 7.7-13.3 cm, and high > 13.3 cm (MRI1); low 0-7.4 cm, mid 7.4-11.2 cm, and high > 11.2 cm (MRI2); and low 0-7.1 cm, mid 7.1-13.7 cm, and high > 13.7 cm (MRI3). For MRI1 and MRI3, the agreement to the gold standard was substantial (r = 0.66, r = 0.67, respectively).

Conclusion

This study illustrates that MRI1 and MRI3 measures can be interchangeably used as a valid method to determine tumor height compared to the gold standard rigid rectoscopy.

Multiparametric MRI in rectal cancer

MRI has a pivotal role in both pretreatment staging and posttreatment evaluation of rectal cancer. The accuracy of MRI in pretreatment staging is higher compared with posttreatment evaluation. This occurs due to similar signal intensities of tumoral and posttreatment fibrotic, necrotic, and inflamed tissue. This limitation occurs with conventional MRI of the rectum with morphologic sequences. There is a need towards increasing the accuracy of MRI, especially for posttreatment evaluation. The term multiparametric MRI implies addition of functional sequences, namely, diffusion and perfusion to the routine protocol. This review summarizes the technique, potential implications and previously published studies about multiparametric MRI of rectal cancer.

Histological grades of rectal cancer: whole-volume histogram analysis of apparent diffusion coefficient based on reduced field-of-view diffusion-weighted imaging

Background

To explore the role of whole-lesion histogram analysis of apparent diffusion coefficient (ADC) derived from reduced field-of-view (rFOV) diffusion-weighted imaging (DWI) technique in discriminating histological grades of rectal carcinoma.

Methods

Altogether, 49 patients with rectal cancer were enrolled in this retrospective study. All patients received preoperative 3.0 T MR scan. Histogram parameters from rFOV DWI were calculated and correlated with histological differentiation of rectal cancer. The parameters were compared between different histological grades of rectal cancer by independent Student's t-test or Man-Whitney U-test. The Spearman correlation test analyzed correlations between histological grade and histogram parameters. The diagnostic performance of individual parameters for distinguishing poorly from well-/moderately differentiated tumors was assessed by receiver operating characteristic curve (ROC) analysis.

Results

There were significant differences for ADCmean, 25^th, 50^th, 75^th, 90^th, 95^th percentiles, skewness, and kurtosis of rFOV DWI sequence between well-, moderately, and poorly differentiated rectal cancers (P<0.05). Significant correlations were noted between histological grades and the above histogram parameters (r=0.679, 0.540, 0.701, 0.730, 0.669, 0.574, -0.730, and -0.760 respectively, P<0.001). Among the individual histogram parameter, kurtosis achieved the highest AUC of 0.882 with an optimal cutoff value of 1.934 in distinguishing poorly from well-/moderately differentiated rectal cancers. The combination of ADCmean, 75^th percentile, and kurtosis yielded the highest AUC of 0.927 with a sensitivity of 88.00% and a sensitivity of 91.7% using logistic regression.

Conclusions

Quantitative whole-lesion ADC histogram analysis based on the rFOV DWI technique could help differentiate histological grades of rectal cancer. The combination of ADCmean, 75^th percentile, and kurtosis may be the best choice.

Rectal Cancer Invasiveness: Whole-Lesion Diffusion-Weighted Imaging (DWI) Histogram Analysis by Comparison of Reduced Field-of-View and Conventional DWI Techniques

To explore the role of whole-lesion histogram analysis of apparent diffusion coefficient (ADC) for discriminating between T stages of rectal carcinoma by comparison of reduced field-of-view (FOV) and conventional DWI techniques. 102 patients with rectal cancer were enrolled in this retrospective study. All patients received preoperative MR scan at 3 T, including reduced and full FOV DWI sequences. Histogram parameters from two DWI methods were calculated and correlated with histological T stage of rectal cancer. The diagnostic performance of individual parameter for differentiating stage pT1-2 and pT3-4 tumors from both DWI techniques was assessed by receiver operating characteristic curve analysis. There were significant differences for the parameters of ADCmean, 50th, 75th, 90th, 95th percentiles, skewness and kurtosis of both DWI sequences in patients with pT1-2 as compared to those with pT3-4 tumors (P < 0.05), in addition to parameters including ADCmin (P = 0.015) and 25th percentile (P = 0.006) from rFOV DWI. Correlations were noted between T staging and above histogram parameters from rFOV DWI (r: −0.741–0.682) and fFOV DWI (r: −0.449–0.449), besides parameters of ADCmin (0.370) and 25th percentile (−0.425) from rFOV DWI. The AUCs of 75th and 90th percentiles from rFOV DWI were significantly higher than that from fFOV DWI (P = 0.0410 and P = 0.0208). The whole-lesion histogram analysis based on rFOV DWI was overall more advantageous than the one based on fFOV DWI in differentiating T staging of rectal cancer and the 90th percentile ADC from rFOV DWI was the value with the highest AUC (0.932).

Trends in combined radio-chemotherapy for locally advanced rectal cancer: a survey among radiation oncology centers of Sicily region on behalf of AIRO

AIM

To conduct a survey among Sicilian centers of radiation oncology belonging to Associazione Italiana di Radioterapia ed Oncologia Clinica (AIRO), to record the different methods of integration of radio-chemotherapy both in neoadjuvant and adjuvant settings, to evaluate surgical procedures in relation to the sphincter preservation and to report the different toxicity profiles of the treatment strategies.

METHODS

A questionnaire was sent at the end of 2017 to all the radiation oncology centers of Sicily region in order to collect the data from individual centers and the treatment characteristics retrospectively over the previous 5 years, from 2012 to 2016. The required data were collected from 13 centers out of 17 which, in relation to the single catchment areas, correspond to approximately 85% of the Sicilian population. The requested data concerned the type of integrated treatment (neoadjuvant vs adjuvant vs radical), combination with chemotherapy (induction, concomitant, adjuvant), type of surgical intervention (sphincter-saving vs abdomino-perineal resection), disease stage, schedule and radiotherapy technique adopted, as well as toxicity detected over the treatment period.

RESULTS

A total of 784 pts (M/F: 509/275) were treated between 2012 and 2016, with a median age of 67 years (range 25-92). The majority of patients was treated in the neoadjuvant phase (62% of the total) compared to the adjuvant phase (31%) and to those treated radically (7%). Twenty-five percent of patients did not receive combination chemotherapy mainly for cardiovascular problems. Chemotherapy used concomitantly to radiotherapy was single-agent capecitabine (73% of patients) or 5-fluorouracil (27%). The use of chemotherapy alone before concomitant treatment is more common for patients treated in the adjuvant phase (64% of this subgroup), while 14% of patients treated in the neoadjuvant phase received induction chemotherapy before the concomitant phase; in both cases of chemotherapy alone, the majority of patients (91%) received oxaliplatin-based protocols (FOLFOX/XELOX/CAPOX). Few patients (3%) received chemotherapy alone after the concomitant phase. Information on the surgical treatment received is available for 88% of the sample. Of these, 93% received a surgical treatment. The overall rate of sphincter-saving surgery (anterior resection) was 72%, but the contribution of neoadjuvant treatment allowed to reach a rate of 83% in this subgroup (against 65% found in the subgroup of patients treated in adjuvant phase). Traditional radiotherapy schedule (45-50 Gy in 25-28 fractions) was used in 90% of patients, of which an intensified treatment in neoadjuvant phase (45 Gy + boost of 9-10 Gy) was used in 11% of patients. A short-course regimen (25 Gy in 5 fraction) in neoadjuvant setting was opted rarely (7%). Three-dimensional conformal technique was preferred over intensity-modulated ones (73% vs 27%). Toxicity was mainly of grade I-II CTCAE (skin 23%, gastrointestinal 39%, genitourinary 14%) compared to grade III (gastrointestinal 4%, genitourinary and hematological < 1%). Interestingly, the toxicity rates were significantly higher in the adjuvant group compared to the neoadjuvant (GI: 58% vs 31%, GU: 21% vs 10%).

CONCLUSION

The present survey shows that in the Sicily region integrated therapies for rectal cancer have allowed a neoadjuvant approach in the majority of patients, thus resulting in a greater use of sphincter conservative surgery. The toxicity has also been reported to be significantly less in this treatment setting.

Amide proton transfer imaging to predict tumor response to neoadjuvant chemotherapy in locally advanced rectal cancer

BACKGROUND AND AIM

The amount of proteins and peptides can be estimated with amide proton transfer (APT) imaging. Previous studies demonstrated the usefulness of APT imaging to predict tumor malignancy. We determined whether APT imaging can predict the tumor response to neoadjuvant chemotherapy (NAC) in patients with locally advanced rectal cancer (LARC).

METHODS

Seventeen patients with LARC who underwent a pretherapeutic magnetic resonance examination including APT imaging and NAC (at least two courses) were enrolled. The APT-weighted imaging (WI) signal intensity (SI) (%) was defined as magnetization transfer ratio asymmetry (MTR_asym ) at the offset of 3.5 ppm. Each tumor was histologically evaluated for the degree of degeneration and necrosis and then classified as one of five histological Grades (0, none; 1a, less than 1/3; 1b, 1/3 to 2/3; 2, more than 2/3; 3, all). We compared the mean APTWI SIs of the tumors between the Grade 0/1a/1b (low-response group) and Grade 2/3 (high-response group) by Student's t-test. We used receiver operating characteristics curves to determine the diagnostic performance of the APTWI SI for predicting the tumor response.

RESULTS

The mean APTWI SI of the low-response group (n = 12; 3.05 ± 1.61%) was significantly higher than that of the high-response group (n = 5; 1.14 ± 1.13%) (P = 0.029). The area under the curve for predicting the tumor response using the APTWI SI was 0.87. When ≥2.75% was used as an indicator of low-response status, 75% sensitivity and 100% specificity of the APTWI SI were obtained.

CONCLUSION

Pretherapeutic APT imaging can predict the tumor response to NAC in patients with LARC.

Readout-segmented echo-planar diffusion-weighted MR for the evaluation of aggressive characteristics of rectal cancer

To evaluate whether aggressive characteristics of rectal cancer can be predicted by the apparent diffusion coefficient (ADC) obtained using readout-segmented echo-planar imaging (rs-EPI) diffusion-weighted magnetic resonance. We enrolled one hundred and fifteen patients. The image quality of ADC maps by rs-EPI was compared with that by traditional single-shot echo-planar imaging (ss-EPI), and ADC measurement was performed on the rs-EPI based ADC maps. Differences in ADC values of tumors grouped according to differentiation grade, clinical T stage and plasmatic carcinoembryonic antigen (CEA) level were tested. The correlation between each aggressive characteristic and the corresponding ADC values was evaluated. The image quality of ADC maps obtained by rs-EPI was superior toss-EPI (P < 0.05). The ADC values of tumor were categorized based on the following differentiation grades: poor (0.89 ± 0.12 × 10⁻³ mm²/s), moderate (1.13 ± 0.25 × 10⁻³ mm²/s), and good (1.31 ± 0.19 × 10⁻³ mm²/s); P < 0.001. Tumors with lower differentiation grades corresponded to lower ADC values (r = 0.59, P < 0.001). However, ADC differences were not observed in different clinical T stage (P = 0.22) and plasmatic CEA level (P = 0.38). Rs-EPI sequence-based ADC values represent a potential imaging marker for the aggressive rectal cancer characteristics.

Application of Diffusion Kurtosis Imaging and Histogram Analysis for Assessing Preoperative Stages of Rectal Cancer

Objective

To explore the value of diffusion kurtosis imaging (DKI) and histogram analysis for assessing preoperative stages and heterogeneity in rectal cancer.

Methods

Fifty patients with pathologically confirmed rectal adenocarcinoma were enrolled. The value of DKI parameters and histogram metrics for assessing the preoperative stages and heterogeneity in rectal cancer was analyzed retrospectively.

Results

(1) ADC-10th percentile and ADC-25th percentile were significantly higher in T1-2 than in the T3-4 rectal cancer (the ADC values were 0.65 ± 0.08 × 10⁻³ mm²/s versus 0.58 ± 0.11 × 10⁻³ mm²/s and 0.73 ± 0.11 × 10⁻³ mm²/s versus 0.65 ± 0.11 × 10⁻³ mm²/s; p values were 0.035 and 0.024, resp.). (2) D-10th percentile and D-25th percentile were also significantly higher in T1-2 than in T3-4 rectal cancer (the D values were 0.96 ± 0.19 × 10⁻³ mm²/s versus 0.84 ± 0.16 × 10⁻³ mm²/s and 1.15 ± 0.27 × 10⁻³ mm²/s versus 0.99 ± 0.18 × 10⁻³ mm²/s; p values were 0.017 and 0.044, resp.). (3) K value and its histogram metrics showed no statistically significant difference between T1-2 and T3-4. (4) D-10th had the largest area under the curve (AUC 0.799) among all the parameters; the sensitivity and specificity were 84.2 and 61.3%, respectively. (5) DKI combined with traditional MRI had an accuracy of 68% while assessing the lymph node of rectal cancer.

Conclusion

DKI parameters and histogram metrics are rather valuable in assessing the preoperative stages of rectal cancer; D-10th percentile exhibits the highest diagnostic efficiency.

Variability and Reproducibility of 3rd-generation dual-source dynamic volume perfusion CT Parameters in Comparison to MR-perfusion Parameters in Rectal Cancer

To compare in patients with untreated rectal cancer quantitative perfusion parameters calculated from 3^rd-generation dual-source dynamic volume perfusion CT (dVPCT) with 3-Tesla-MR-perfusion with regard to data variability and tumour differentiation. In MR-perfusion, plasma flow (PF), plasma volume (PV) and mean transit time (MTT) were assessed in two measurements (M1 and M2) by the same reader. In dVPCT, blood flow (BF), blood volume (BV), MTT and permeability (PERM) were assessed respectively. CT dose values were calculated. 20 patients (60 ± 13 years) were analysed. Intra-individual and intra-reader variability of duplicate MR-perfusion measurements was higher compared to duplicate dVPCT measurements. dVPCT-derived BF, BV and PERM could differentiate between tumour and normal rectal wall (significance level for M1 and M2, respectively, regarding BF: p < 0.0001*/0.0001*; BV: p < 0.0001*/0.0001*; MTT: p = 0.93/0.39; PERM: p < 0.0001*/0.0001*), with MR-perfusion this was true for PF and PV (p-values M1/M2 for PF: p = 0.04*/0.01*; PV: p = 0.002*/0.003*; MTT: p = 0.70/0.27*). Mean effective dose of CT-staging incl. dVPCT was 29 ± 6 mSv (20 ± 5 mSv for dVPCT alone). In conclusion, dVPCT has a lower data variability than MR-perfusion while both dVPCT and MR-perfusion could differentiate tumour tissue from normal rectal wall. With 3^rd-generation dual-source CT dVPCT could be included in a standard CT-staging without exceeding national dose reference values.

Intravoxel Incoherent Motion MRI of Rectal Cancer: Correlation of Diffusion and Perfusion Characteristics With Prognostic Tumor Markers

OBJECTIVE

The objective of our study was to evaluate the intravoxel incoherent motion (IVIM)-DWI derived parameters and their relationships with tumor prognostic markers using 3-T MRI in patients with rectal cancer.

SUBJECTS AND METHODS

Fifty-two patients with histopathologically proven rectal cancer who underwent preoperative pelvic MRI were prospectively enrolled in this study. Diffusion and perfusion parameters including the apparent diffusion coefficient (ADC), pure diffusion coefficient, perfusion fraction, and pseudodiffusion coefficient derived from IVIMDWI were independently measured by two radiologists. Comparisons of IVIM-DWI-derived parameters in patients with different tumor prognostic markers were made using the independent-samples t test, ANOVA, and Mann-Whitney U test. The correlations between IVIM-DWI-derived parameters and tumor grade and tumor stage were further evaluated using Spearman correlation analysis. Interobserver agreement was evaluated using the intraclass correlation coefficient (ICC).

RESULTS

Excellent interobserver reproducibility was obtained for the IVIM-DWI-derived parameters (range of ICCs with 95% limits of agreement = 0.9309-0.9948, which is narrow). ADC, pseudodiffusion coefficient, and perfusion fraction tended to rise with greater tumor differentiation (r = 0.520, p < 0.001; r = 0.447, p = 0.001; r = 0.354, p = 0.010, respectively). The pure diffusion coefficient and pseudodiffusion coefficient showed a trend of decreasing with increasing tumor stages (r = 0.479, p < 0.001; r = 0.517, p < 0.001). The group of patients with extramural vascular invasion (EMVI) showed lower pseudodiffusion coefficient values than the group of patients with no EMVI (p < 0.05).

CONCLUSION

IVIM-DWI-derived parameters in patients with rectal cancer, especially the pseudodiffusion coefficient, are associated with tumor grade and tumor stage and show statistically significant differences between subjects with EMVI and those without EMVI. IVIM-DWI-derived parameters would be helpful in predicting tumor aggressiveness and prognosis.

Hepatic neuroendocrine tumour: Apparent diffusion coefficient as a potential marker of prognosis associated with tumour grade and overall survival

OBJECTIVES

To evaluate the correlation between grade of hepatic neuroendocrine tumours (NETs) according to the 2010 World Health Organization (WHO) classification and the apparent diffusion coefficient (ADC) and to assess whether ADC value can predict overall survival (OS) after diagnosis of hepatic NETs.

METHODS

The study included 63 patients who underwent magnetic resonance (MR) imaging with diffusion-weighted images for the evaluation of hepatic NETs. The correlation between qualitative and quantitative MR imaging findings, including ADC values, and WHO classifications was assessed. The association between ADC value and OS was analyzed.

RESULTS

The ADC values and WHO classification of hepatic NETs were moderately negatively correlated in a statistically significant manner (ρ = -0.57, p < 0.001). The OS rates were significantly different according to the ADC value (low ADC vs. high ADC, p = 0.006) as well as WHO classifications (G1+ G2 vs. G3, p = 0.038). However, multivariate analysis revealed that the only independent predictor for OS was a low ADC value (hazard ratio: 3.37, p = 0.010).

CONCLUSION

There was a significant correlation between the ADC value of hepatic NETs and the WHO tumour grade. Additionally, the ADC value of a hepatic NET might be more accurate than the current WHO tumour grade for predicting OS.

KEY POINTS

• ADC values of hepatic NET and WHO tumour grade were negatively correlated. • Lower ADC values of hepatic NET were significantly correlated with worse OS. • ADC value might be more accurate than WHO grade for predicting OS.

Magnetic resonance imaging of rectal cancer

Magnetic resonance imaging (MRI) is still the most commonly used imaging technique for the diagnosis of rectal cancer with the highest degree of accuracy, and it is also recommended by the National Comprehensive Cancer Network, European Society for Medical Oncology, and Chinese guidelines for diagnosis and treatment of colorectal cancer. The application of diffusion weighted imaging, apparent diffusion coefficient, diffusion weighted imaging with background signal suppression, intravoxel incoherent motion, perfusion imaging, magnetic resonance spectroscopy, and molecular imaging has provided many choices for tumor detection and preoperative staging, differential diagnosis of benign and malignant rectum lesions, postoperative follow-up, recurrence monitoring, and efficacy evaluation. We believe that with the development of basic theory and related technology, MRI for rectal cancer assessment will become more efficient.

Haralick's texture features for the prediction of response to therapy in colorectal cancer: a preliminary study

PURPOSE

Haralick features Texture analysis is a recent oncologic imaging biomarker used to assess quantitatively the heterogeneity within a tumor. The aim of this study is to evaluate which Haralick's features are the most feasible in predicting tumor response to neoadjuvant chemoradiotherapy (CRT) in colorectal cancer.

MATERIALS AND METHODS

After MRI and histological assessment, eight patients were enrolled and divided into two groups based on response to neoadjuvant CRT in complete responders (CR) and non-responders (NR). Oblique Axial T2-weighted MRI sequences before CRT were analyzed by two radiologists in consensus drawing a ROI around the tumor. 14 over 192 Haralick's features were extrapolated from normalized gray-level co-occurrence matrix in four different directions. A dedicated statistical analysis was performed to evaluate distribution of the extracted Haralick's features computing mean and standard deviation.

RESULTS

Pretreatment MRI examination showed significant value (p < 0.05) of 5 over 14 computed Haralick texture. In particular, the significant features are the following: concerning energy, contrast, correlation, entropy and inverse difference moment.

CONCLUSIONS

Five Haralick's features showed significant relevance in the prediction of response to therapy in colorectal cancer and might be used as additional imaging biomarker in the oncologic management of colorectal patients.

Correlations between intravoxel incoherent motion (IVIM) parameters and histological findings in rectal cancer: preliminary results

Our purpose was to correlate different intravoxel incoherent motion (IVIM), histopathological and clinical parameters in rectal cancer. 17 patients with histologically proven rectal cancer investigated on a 3.T device were included into the study. DWI was performed using a multi-slice single-shot echo-planar imaging sequence with b values of 0, 50, 200, 500 and 1000 s/mm.² A polygonal region of interest was drawn within the tumors on every b image. The following parameters were retrieved from IVIM: apparent diffusion coefficient (ADC), true diffusion (D), pseudo diffusion coefficient (D*), perfusion factor (f), and relative perfusion f·D*. In every case, cell count, nucleic areas, proliferation index KI 67, and microvessel density were estimated on histopathological specimens. Pearson's correlation coefficient was used to analyze the association between the parameters. ADC correlated well with KI 67 index and D tended to correlate with cell count and KI 67. ADC and D tended to correlate with total nucleic area. The perfusion factor f correlated well with stained vessel area, total vessel area, and vessel count. D* and fD* correlated with mean vessel diameter. Distant metastasized tumors had higher D* and fD* values. IVIM parameter reflected different clinical and histopathological features in rectal cancer.

Comparison of perfusion models for quantitative T1 weighted DCE-MRI of rectal cancer

In this work, the two compartment exchange model and two compartment uptake model were applied to obtain quantitative perfusion parameters in rectum carcinoma and the results were compared to those obtained by the deconvolution algorithm. Eighteen patients with newly diagnosed rectal carcinoma underwent 3 T MRI of the pelvis including a T₁ weighted dynamic contrastenhanced (DCE) protocol before treatment. Mean values for Plasma Flow (PF), Plasma Volume (PV) and Mean Transit Time (MTT) were obtained for all three approaches and visualized in parameter cards. For the two compartment models, Akaike Information Criterion (AIC) and [Formula: see text] were calculated. Perfusion parameters determined with the compartment models show results in accordance with previous studies focusing on rectal cancer DCE-CT (PF_2CX = 68 ± 44 ml/100 ml/min, PF_2CU = 55 ± 36 ml/100 ml/min) with similar fit quality (AIC:169 ± 81/179 ± 77, [Formula: see text]:10 ± 12/9 ± 10). Values for PF are overestimated whereas PV and MTT are underestimated compared to results of the deconvolution algorithm. Significant differences were found among all models for perfusion parameters as well as between the AIC and [Formula: see text] values. Quantitative perfusion parameters are dependent on the chosen tracer kinetic model. According to the obtained parameters, all approaches seem capable of providing quantitative perfusion values in DCE-MRI of rectal cancer.

DWI for Assessment of Rectal Cancer Nodes After Chemoradiotherapy: Is the Absence of Nodes at DWI Proof of a Negative Nodal Status?

OBJECTIVE

When considering organ preservation in patients with rectal cancer with good tumor response, assessment of a node-negative status after chemoradiation therapy (CRT) is important. DWI is a very sensitive technique to detect nodes. The study aim was to test the hypothesis that the absence of nodes at DWI after CRT is concordant with a ypN0 status.

MATERIALS AND METHODS

A retrospective study was performed of 90 patients with rectal cancer treated with CRT followed by restaging MRI at 1.5 T, including DWI (highest b value, 1000 s/mm²). Two independent readers counted the number of nodes visible in the mesorectal compartment on DW images obtained after CRT. The number of nodes on DWI (0 vs ≥ 1) was compared with the number of metastatic nodes at histopathology or long-term clinical follow-up (yN0 vs yN-positive status).

RESULTS

Seventy-one patients had a yN0 status, and 19 had a yN-positive status. For 10 patients, no nodes were observed at DWI, which was concordant with a yN0 status in 100% of cases. In the other 61 patients with a yN0 status, the median number of nodes detected at DWI was three (range, 1-17 nodes). To differentiate between yN0 and yN-positive status, sensitivity was 100%, specificity was 14%, the positive predictive value was 24%, and the negative predictive value was 100%.

CONCLUSION

Although the absence of nodes at DWI is not a frequent finding, it appears to be a reliable predictor of yN0 status after CRT in patients with rectal cancer. DWI may thus be a helpful adjunct in assessing response after CRT and may help select patients for organ-saving treatment.

Comparison of non-Gaussian and Gaussian diffusion models of diffusion weighted imaging of rectal cancer at 3.0 T MRI

Water molecular diffusion in vivo tissue is much more complicated. We aimed to compare non-Gaussian diffusion models of diffusion-weighted imaging (DWI) including intra-voxel incoherent motion (IVIM), stretched-exponential model (SEM) and Gaussian diffusion model at 3.0 T MRI in patients with rectal cancer, and to determine the optimal model for investigating the water diffusion properties and characterization of rectal carcinoma. Fifty-nine consecutive patients with pathologically confirmed rectal adenocarcinoma underwent DWI with 16 b-values at a 3.0 T MRI system. DWI signals were fitted to the mono-exponential and non-Gaussian diffusion models (IVIM-mono, IVIM-bi and SEM) on primary tumor and adjacent normal rectal tissue. Parameters of standard apparent diffusion coefficient (ADC), slow- and fast-ADC, fraction of fast ADC (f), α value and distributed diffusion coefficient (DDC) were generated and compared between the tumor and normal tissues. The SEM exhibited the best fitting results of actual DWI signal in rectal cancer and the normal rectal wall (R² = 0.998, 0.999 respectively). The DDC achieved relatively high area under the curve (AUC = 0.980) in differentiating tumor from normal rectal wall. Non-Gaussian diffusion models could assess tissue properties more accurately than the ADC derived Gaussian diffusion model. SEM may be used as a potential optimal model for characterization of rectal cancer.

Diffusion Kurtosis Imaging Study of Rectal Adenocarcinoma Associated with Histopathologic Prognostic Factors: Preliminary Findings

Purpose To determine the correlation between diffusion kurtosis imaging (DKI)-derived parameters and prognostic factors for rectal adenocarcinoma. Materials and Methods This study was approved by the local institute review board, and written informed consent was obtained from each patient. Data from 56 patients (median age, 59.5 years; age range, 31-86 years) with rectal adenocarcinoma between April 2014 and September 2015 were involved in this prospective study. DKI (b = 0, 700, 1400, and 2100 sec/mm²) and conventional diffusion-weighted imaging (b = 0, 1000 sec/mm²) were performed. Kurtosis and diffusivity from DKI and apparent diffusion coefficients (ADCs) from diffusion-weighted imaging were measured by two radiologists. Student t test, receiver operating characteristic curves, and Spearman correlation were used for statistical analysis. Results Kurtosis was significantly higher in high-grade than in low-grade rectal adenocarcinomas on the basis of both the number of poorly differentiated clusters (PDCs) (1.136 ± 0.086 vs 0.988 ± 0.060, P < .05) and World Health Organization (WHO) grades (1.103 ± 0.086 [standard deviation] vs 1.034 ± 0.103, P < .05). In PDC grading, the diffusivity and ADC were significantly lower in high-grade tumors than in low-grade tumors (1.187 ± 0.150 vs 1.306 ± 0.129 and 1.020 ± 0.113 vs 1.108 ± 0.097, respectively; P < .05) and showed similar correlations with histologic grades (r = -0.486 and r = -0.406, respectively; P > .05). Compared with both diffusivity and ADC, kurtosis showed significantly higher sensitivity (83.3% [20 of 24] vs 70.8% [17 of 24] and 70.8% [17 of 24], respectively) and specificity (96.8% [31 of 32] vs 84.4% [24 of 32] and 81.3% [26 of 32], respectively). Kurtosis showed a better correlation with PDC grades than with WHO grades (r = 0.797 vs r = 0.293, P < .05). Kurtosis was significantly higher in pN1-2 than in pN0 tumors (1.086 ± 0.103 vs 1.009 ± 0.086, P < .05). Conclusion Kurtosis derived from DKI demonstrated a higher correlation with histologic grades compared with diffusivity and ADC. It also showed better performance in differentiating between high- and low-grade rectal adenocarcinomas and between pN1-2 and pN0 tumors. ^© RSNA, 2016.

Radiological assessment of anal cancer: an overview and update

Anal cancer is uncommon neoplasm with an incidence of 2 new cases per 100,000 per year in the USA, accounting approximately 0.4 % of all tumors and 2.5 % of gastrointestinal malignancies. An early detection of the anal cancer is crucial for the patient management, whereas the diagnosis at an early stage allows conservative management with sphincter sparing, on the contrary a delays in diagnosis might lead to an advance cancer stage at presentation with worst survival. According to National Comprehensive Cancer Network (NCCN) Anal Carcinoma guidelines the patients should be subjected to a careful clinical examination, including a digital rectal examination (DRE), an anoscopic examination, and palpation of inguinal nodes. The guidelines recommended for the assessment of T stage, only a clinical examination, while the role of imaging techniques, as Magnetic Resonance imaging (MRI) is limited to the identification of regional nodes. Instead, the endoanal ultrasound (EAUS) is not recommended. This paper presents an overview and some updates about 3D EAUS and MRI in detection, staging and assessment post therapy of anal cancer patients.

Application of texture analysis based on apparent diffusion coefficient maps in discriminating different stages of rectal cancer

PURPOSE

To explore the potential of texture analysis based on apparent diffusion coefficient (ADC) maps, as a predictor of local invasion depth (stage pT1-2 versus pT3-4) and nodal status (pN0 versus pN1-2) of rectal cancer.

MATERIALS AND METHODS

Sixty-eight patients with rectal cancer underwent preoperative magnetic resonance (MR) imaging including diffusion weighted imaging (DWI) at a 3.0 Tesla system. Routine ADC variables (ADC_mean , ADC_min , ADC_max ), histogram features (skewness, kurtosis) and gray level co-occurrence matrix features (entropy, contrast, correlation) were compared between pT1-2 and pT3-4 stages, between pN0 and pN1-2 stages.

RESULTS

Skewness, entropy, and contrast were significantly lower in patients with pT1-2 as compared to those with pT3-4 tumors (0.166 versus 0.476, P = 0.015; 3.212 versus 3.441 P = 0.004; 10.773 versus 13.596, P = 0.017). Furthermore, skewness and entropy were identified as independent predictors for extramural invasion of tumors (stage pT3-4). Significant differences were observed between pN0 and pN1-2 tumors with respect to ADC_mean (1.152 versus 1.044, P = 0.029), ADC_max (1.692 versus 1.460, P = 0.006) and entropy (3.299 versus 3.486, P = 0.015). ADC_max. and entropy were independent predictors of positive nodal status.

CONCLUSION

Texture analysis on ADC maps could provide valuable information in identifying locally advanced rectal cancer.

LEVEL OF EVIDENCE

3 J. MAGN. RESON. IMAGING 2017;45:1798-1808.

Performance of diffusion-weighted imaging, perfusion imaging, and texture analysis in predicting tumoral response to neoadjuvant chemoradiotherapy in rectal cancer patients studied with 3T MR: initial experience

PURPOSE

To determine the performance of texture analysis (TA), diffusion-weighted imaging, and perfusion MR (pMRI) in predicting tumoral response in patients treated with neoadjuvant chemoradiotherapy (CRT).

METHODS

12 consecutive patients (8 females, 4 males, 63.2 ± 13.4 years) with rectal cancer were prospectively enrolled, and underwent pre-treatment 3T MRI. Treatment protocol consisted of neoadjuvant CRT with oxaliplatin and 5-fluorouracile. Unenhanced T2-weighted images TA (kurtosis), apparent diffusion coefficient (ADC), and pMRI parameters (Ktrans, Kep, Ve, IAUGC) were quantified by manually delineating a region of interest around the tumor outline. After CRT, all patients underwent complete surgical resection and the surgical specimen served as the gold standard. Receiver operating characteristic (ROC) curve analysis was performed to assess the discriminatory power of each quantitative parameter to predict complete response.

RESULTS

Pathological complete response (pCR) was reported in six patients and partial response (PR) in three patients. Three patients were classified as non-responders (NR). Pre-treatment kurtosis was significantly lower in the pCR sub-group in comparison with PR + NR (p = .01). Among ADC and pMRI parameters, only Ve was significantly lower in the pCR sub-group compared with PR + NR (p = .01). A significant negative correlation between kurtosis and ADC (r = -0.650, p = .022) was observed. Pre-treatment area under the ROC curves (AUC), to discriminate between pCR and PR + NR, was significantly higher for kurtosis (0.861, p = .001) and Ve (0.861, p = .003) compared to all other parameters. The optimal cutoff value for pre-treatment kurtosis and Ve was ≤0.19 (100% sensitivity, 67% specificity) and ≤0.311 (83% sensitivity, 83% specificity), respectively.

CONCLUSION

Pre-treatment kurtosis derived from T2w images and Ve from pMRI have the potential to act as imaging biomarkers of rectal cancer response to neoadjuvant CRT.

Locally advanced rectal cancer: Qualitative and quantitative evaluation of diffusion-weighted MR imaging in the response assessment after neoadjuvant chemo-radiotherapy

PURPOSE

to investigate the added value of qualitative and quantitative evaluation of diffusion weighted (DW) magnetic resonance (MR) imaging in response assessment after neoadjuvant chemo-radiotherapy (CRT) in patients with locally advanced rectal cancer (LARC).

METHODS

31 patients with LARC (stage ≥ T3) were enrolled in the study. All patients underwent conventional MRI and DWI before starting therapy and after neoadjuvant CRT. All patients underwent surgery; pathologic staging represented the reference standard. For qualitative analysis, two radiologists retrospectively reviewed conventional MR images and the combined set of conventional and DW MR images and recorded their confidence level with respect to complete response (ypCR). For quantitative analysis, tumor's apparent diffusion coefficient (ADC) values were measured at each examination. ADC pre-CRT, ADC post-CRT and Δ ADC post-ADC pre of the three groups of response (ypCR, partial response ypPR, stable disease ypSD) were compared. Receiver-operating characteristics (ROC) curve analysis was employed to investigate the discriminatory capability for ypCR, responders (ypCR, ypPR) and ypSD of each measure.

RESULTS

addition of DWI to conventional T2-weighted sequences improved diagnostic performance of MRI in the evaluation of ypCR. A low tumor ADC value in the pre-CRT examination, a high ADC value in the post-CRT examination, a high Δ ADC post-ADC pre [>0.3 (×10(-3) mm(2)/s)] were predictive of ypCR.

CONCLUSIONS

DW sequences improve MR capability to evaluate tumor response to CRT. Nevertheless, no functional MR technique alone seems accurate enough to safely select patients with ypCR.

Advanced imaging of colorectal cancer: From anatomy to molecular imaging

Imaging techniques play a key role in the management of patients with colorectal cancer. The introduction of new advanced anatomical, functional, and molecular imaging techniques may improve the assessment of diagnosis, prognosis, planning therapy, and assessment of response to treatment of these patients. Functional and molecular imaging techniques in clinical practice may allow the assessment of tumour-specific characteristics and tumour heterogeneity. This paper will review recent developments in imaging technologies and the evolving roles for these techniques in colorectal cancer.

TEACHING POINTS

• Imaging techniques play a key role in the management of patients with colorectal cancer. • Advanced imaging techniques improve the evaluation of these patients. • Functional and molecular imaging allows assessment of tumour hallmarks and tumour heterogeneity.

JOURNAL CLUB: Preoperative MRI Evaluation of Primary Rectal Cancer: Intrasubject Comparison With and Without Rectal Distention

OBJECTIVE

The aim of this study was to determine whether rectal distention influences the accuracy of MRI for tumor staging and for measuring of maximal extramural depth of tumor spread and distance between tumor and mesorectal fascia (MRF).

SUBJECTS AND METHODS

Fifty patients with rectal carcinoma underwent MRI before and after rectal distention. Both sets of MR images were reviewed by two radiologists. The scores for depiction of the mass (1-4 scale), T and N category, distance from normal rectal wall to MRF, maximal extramural depth of tumor spread, and distance between tumor and MRF were evaluated.

RESULTS

The visualization scores on MR images obtained with the rectum distended were significantly higher than those on images obtained without distention (90% vs 58% for score 4, p < 0.001). The accuracy of T category assessed on distended images was slightly higher than the accuracy on nondistended images (88.6% vs 84.1% for observer 1, 84.1% vs 81.8% for observer 2), but the accuracy of N category was stable. The distance between normal rectal wall and MRF was significantly less on distended images than on nondistended images (p < 0.05). However, there was no significant difference between nondistended and distended images for maximal extramural depth and distance between tumor and MRF (p > 0.05).

CONCLUSION

Rectal distention significantly improved visualization of tumors on MR images. It also improved T category assessment to some extent. Although the distance between normal rectal wall and MRF was significantly less with rectal distention than without rectal distention, maximal extramural depth and the distance between tumor and MRF did not vary significantly with or without rectal distention.

Preoperative diffusion-weighted imaging value of rectal cancer: preoperative T staging and correlations with histological T stage

PURPOSE

To assess the ability of diffusion-weighted imaging (DWI) for evaluating T stage and correlation with histological T stage of rectal cancer.

METHOD

The diagnostic accuracy, sensitivity, and specificity of T2WI and DWI combined with T2WI for T stage were evaluated. Mean tumor apparent diffusion coefficient (ADC) was compared with histological T stage.

RESULT

There were no significant differences in the diagnostic accuracy, sensitivity, and specificity no matter what kind of T stage was concerned. The difference between ADC values and histological T stage were significantly different.

CONCLUSION

DWI was useful for evaluating T stage of rectal cancer. The ADC may predict the histological grade.

[Local imaging of rectal cancer--update 2015: MRI as imaging biomarker]

The significance of state of the art magnetic resonance imaging (MRI) for rectal cancer goes far beyond the detection and diagnostics of local dispersion and is increasingly focusing on patient prognosis. The identification of prognostic factors, such as tumor (T) and nodal (N) status, involvement of the circumferential resection margin, presence of extramural vascular invasion, tumor response prediction following neoadjuvant therapy, therapy-related changes in microcirculation, permeability and tissue cellularity and structured reporting are important elements of advanced rectal cancer imaging. In this context, multiparametric MRI is progressively evolving into a powerful imaging biomarker.

Clinical relevance of morphologic MRI criteria for the assessment of lymph nodes in patients with rectal cancer

AIM

The aim of this study is the evaluation of lymph node staging by magnetic resonance imaging (MRI) within clinical routine in patients with rectal cancer.

METHOD

Routine MRI reports (3 T) of 65 consecutive patients with rectal cancer were retrospectively categorized in lymph node tumor positive or negative (mriN+; mriN0) and compared to the final histopathological results (pN+; pN0). Sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and accuracy were calculated. The original MRI readings were then reanalyzed in order to identify the longest short-axis lymph node diameter for each patient. A receiver operating characteristic (ROC) curve was used to calculate a possible cutoff value for the short-axis lymph node diameter.

RESULTS

Overall sensitivity was 94 %, specificity 13 %, NPV 86 %, PPV 28 %, and accuracy 34 %. The best accuracy could be calculated for a short-diameter cutoff of ≤5 mm (83 %); pN+ and pN0 groups were then significantly different (p < 0.0001).

CONCLUSION

In clinical routine, lymph node assessment in patients with rectal cancer through MRI tends to overstage malignant lymphadenopathy. A ≤5-mm cutoff value for the short-axis lymph node diameter of benign nodes is able to improve the accuracy and has potential to lower the risk of overstaging.

Prognostic significance of clinical and pathological stages on locally advanced rectal carcinoma after neoadjuvant chemoradiotherapy

Objective

To investigate prognostic significance of clinical and pathological stages in patients with locally advanced rectal carcinoma treated with neoadjuvant chemoradiotherapy (neo-CRT) and total mesorectal excision.

Patients and methods

210 patients with locally advanced rectal carcinoma (cT3-4 or cN+) treated with neo-CRT followed by total mesorectal excision. Treatment outcomes were compared according to clinical and pathological stage. Overall survival (OS), disease free survival (DFS) among patients with different clinical stage and pathological stage after neo-CRT.

Results

The median follow-up time was 47 months (range, 14–98 months). Clinical T stage was associated with 5 year OS (p = 0.042) and 5 year DFS (p = 0.014) while clinical N stage was not associated with 5 year OS (p = 0.440), 5 year DFS (p = 0.711). Pathological T stage was associate with 5 year OS (p = 0.001) and 5 year DFS (p = 0.046); and N stage was associated with 5 year OS (p = 0.001), 5 year DFS (p = 0.002). The pathological stage was further classified into three groups: ypT0–2N0 in 91 patients (43.3 %), ypT3–4N0 in 69 patients (32.9 %) and ypT0–4N+ in 50 patients (23.8 %). While pathological stage (ypT0–2 vs ypT3–4N0 vs ypT0–4N+) was associated with 5 year OS (87.9 %, 75.5 %, 56.7 %, p = 0.000), 5 year DFS (74.5 %, 77.4 %, 50.5 %, p = 0.003). Multivariate analysis showed that ypN stage was an independent prognostic factor for patients 5 year DFS.

Conclusions

Pathological stage is strongly associated with treatment outcomes in patients with locally advanced rectal carcinoma treated with neo-CRT followed by total mesorectal excision, which may be used as guidance for further individualized treatment.

Magnetic resonance imaging and endorectal ultrasound for diagnosis of rectal lesions

Endorectal ultrasonography (ERUS) and magnetic resonance imaging (MRI) allow exploring the morphology of the rectum in detail. Use of such data, especially assessment of the rectal wall, is an important tool for ascertaining the perianal fistula localization as well as stage of the cancer and planning it appropriate treatment, as stage T3 tumors are usually treated with neoadjuvant therapy, whereas T2 tumors are initially managed surgically. The only advantage of ERUS over MRI is the possibility of assessing T1 tumors that could be treated by transanal endoscopic microsurgery. However, MRI is better for visualizing most radiological prognostic features in rectal or anal cancer such as a circumferential resection margin less than 1 mm, T stage at T1-T2 or T3 tumors with extramural extension less than 5 mm, absence of extramural vascular invasion, N stage at N0/N1, and tumors located in the middle or upper third of the rectum. It can also evaluate the intersphincteric space or levator ani muscle involvement. Increased signal on diffusion weighted imaging (DWI) and low apparent diffusion coefficient (ADC) values as well as an irregular contour and heterogeneous internal signal intensity seem to predict the involvement of pelvic lymphatic nodes better than their size alone. Computed tomography as well as other examination techniques, including digital rectal examination, contrast edema, recto- and colonoscopy, are less useful in staging of rectal cancer but still are very important screening tools.