Prognostic Aspects of DCE-MRI in Recurrent Rectal Cancer

MRI-Based Radiomics of Rectal Cancer: Assessment of the Local Recurrence at the Site of Anastomosis

RATIONALE AND OBJECTIVE

To investigate the significance of magnetic resonance imaging (MRI)-based radiomics model in differentiating local recurrence of rectal cancer from nonrecurrence lesions at the site of anastomosis.

MATERIALS AND METHODS

A total of 80 patients with clinically suspected lesions of anastomosis underwent 3.0T pelvic MRI consisting of T2-weighted imaging (T2WI), diffusion-weighted imaging (DWI), and contrast-enhanced T1-weighted volume interpolated body examination (VIBE) imaging. Radiomics features were extracted from volumes of interest (VOIs), delineated manually on multiple MRI sequences. Subsequently, principal component analysis reduced the dimensionality of features for T2WI, DWI, VIBE, and combined multisequences, respectively. On this basis, the extreme gradient boosting (XGBoost) classifier was trained to build Model_T2WI, Model_DWI, Model_VIBE, and Model_combination. Receiver operating characteristic curves were generated to determine the diagnostic performance of various models.

RESULTS

Principal component analysis selected eight, four, seven, and six principal components to construct the radiomics model for T2WI, DWI, VIBE, and combined multisequences, respectively. Model_combination had an area under the receiver operating characteristic curve of 0.864, with sensitivity and specificity of 81.82% and 75.86% in the validation set, demonstrating a more optimal performance compared to other models (p< 0.05). The decision curve analysis confirmed the clinical usefulness of the model.

CONCLUSION

This study demonstrated that MRI-based radiomics is a sophisticated and noninvasive tool for accurately distinguishing LR from nonrecurrence lesions at the site of anastomosis. Combining multiple sequences significantly improves its performance.

Dynamic contrast-enhanced MR imaging of rectal cancer using a golden-angle radial stack-of-stars VIBE sequence: comparison with conventional contrast-enhanced 3D VIBE sequence

PURPOSE

To compare conventional 3D volumetric-interpolated breath-hold examination (C-VIBE) sequence image quality to that of golden-angle radial stack-of stars acquisition scheme (R-VIBE) in rectal cancer patients.

METHODS

Seventy-eight patients had undergone pre-contrast C-VIBE, followed by DCE-MRI with R-VIBE and post-contrast C-VIBE in the visualization of rectal cancer. The first phase and the last phase of R-VIBE sequence were compared with pre-contrast and post-contrast C-VIBE sequences, respectively. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of rectal neoplasms, gluteus maximus, and subcutaneous fat were compared between the two different sequences. A further qualitative score system (graded 1-5) was used to evaluate the overall image. Quantitative and qualitative parameters from the two sequences were compared.

RESULTS

In all patients, R-VIBE achieved the same SNR and CNR ratings in pre- and post-contrast (all P > 0.05), with the exception of a higher SNR of fat in pre-contrast images (P = 0.037). In addition, there were no significant differences in scores of overall image quality, lesion conspicuity, and rectal wall boundary (all P > 0.05). There was an improved score in artifacts of post-contrast R-VIBE sequence (P = 0.005).

CONCLUSION

R-VIBE sequence can provide comparable image quality and less motion artifacts to that of C-VIBE sequence and is feasible for imaging of rectal cancer.

Current controversy, confusion, and imprecision in the use and interpretation of rectal MRI

There has been a rapid increase in the utilization of MRI in rectal cancer staging in the USA essentially replacing endorectal ultrasound and mimicking the trend in Europe seen in the 1990s and 2000s. Accompanying this trend, there is a demand, and recognized need, for greater precision and clarification of confusing, misunderstood and poorly understood concepts, facts, statements and nomenclature regarding rectal cancer and the use of pelvic MRI for diagnosis. As such, this Review, part evidence-based and part expert opinion, will attempt to elucidate and clarify several concepts the authors have encountered in 25 years of imaging rectal cancer, focusing on MRI.

Use of magnetic resonance imaging in rectal cancer patients: Society of Abdominal Radiology (SAR) rectal cancer disease-focused panel (DFP) recommendations 2017

PURPOSE

To propose guidelines based on an expert-panel-derived unified approach to the technical performance, interpretation, and reporting of MRI for baseline and post-treatment staging of rectal carcinoma.

METHODS

A consensus-based questionnaire adopted with permission and modified from the European Society of Gastrointestinal and Abdominal Radiologists was sent to a 17-member expert panel from the Rectal Cancer Disease-Focused Panel of the Society of Abdominal Radiology containing 268 question parts. Consensus on an answer was defined as ≥ 70% agreement. Answers not reaching consensus (< 70%) were noted.

RESULTS

Consensus was reached for 87% of items from which recommendations regarding patient preparation, technical performance, pulse sequence acquisition, and criteria for MRI assessment at initial staging and restaging exams and for MRI reporting were constructed.

CONCLUSION

These expert consensus recommendations can be used as guidelines for primary and post-treatment staging of rectal cancer using MRI.

Value of DCE-MRI for staging and response evaluation in rectal cancer: A systematic review

PURPOSE

Aim was to perform a systematic review to evaluate the clinical value of dynamic contrast-enhanced (DCE) MRI in rectal cancer.

METHODS AND MATERIALS

A systematic search was performed on Pubmed, Embase and the Cochrane library. Studies that evaluated DCE-MRI for tumour aggressiveness, primary staging and restaging after chemoradiation (CRT) were included. Information on population, DCE technique, DCE parameters and outcome (angiogenesis, staging and response) were extracted.

RESULTS

19 studies were identified; 10 evaluated quantitative analyses, 6 semiquantitative analyses and 3 evaluated both. 8 studies evaluated correlation between DCE-parameters and angiogenesis or tumour aggressiveness, 11 studies evaluated response prediction pre- and post-CRT. Semiquantitative washin parameters showed a significantly positive correlation with angiogenesis, while for quantitative analyses conflicting results were found. Conflicting results were also reported for the correlation between DCE parameters and tumour aggressiveness: both higher and lower vascularity in more aggressive tumours are reported, while some studies report no correlation. Six studies showed a predictive value of Ktrans for response. A high Ktrans pre-CRT was significantly correlated with a complete/good response, but the reported pre-CRT Ktrans varied substantially (0.36-1.93). After CRT a reduction in Ktrans of 32%-36% was significantly associated with response. For semiquantitative analyses pre-CRT late slope was reported to be significantly lower in good responders, however only few studies exist on semiquantitative analyses of post-CRT DCE-MRI.

CONCLUSION

DCE-MRI in rectal cancer is promising mainly for prediction and assessment of response to CRT, where a high pre-CRT Ktrans and a decrease in Ktrans are significantly predictive for response.

Prognostic aspects of dynamic contrast-enhanced magnetic resonance imaging in synchronous distant metastatic rectal cancer

OBJECTIVES

To explore the correlations between DCE-MRI quantitative parameters and synchronous distant metastasis and the clinicopathological factors in rectal cancers.

METHODS

Sixty-three patients with rectal cancer (synchronous distant metastasis, n = 31; non-metastasis, n = 32) were enrolled in this study. Student's t test and ANOVA were used to compare DCE-MRI parameters (K ^trans , K _ep and V _e ). The receiver operating characteristic (ROC) analysis was used to find the reasonable threshold of DCE-MRI parameters to differentiate lesions with synchronous distant metastasis from those without metastasis.

RESULTS

The K ^trans , K _ep , and V _e value were significantly higher in the lesions with distant metastasis than in the lesions without distant metastasis (0.536 ± 0.242 vs. 0.299 ± 0.118 min^-1, p < 0.001; 1.598 ± 0.477 vs. 1.341 ± 0.390 min^-1, p = 0.022; and 0.324 ± 0.173 vs. 0.249 ± 0.091, p = 0.034; respectively). The K ^trans showed the highest AUCs of 0.788 (p < 0.001), with sensitivity of 61.29 % and specificity of 87.5 %, respectively.

CONCLUSIONS

DCE-MRI parameters may represent a prognostic indicator for synchronous distant metastases in patients with rectal cancer.

KEY POINTS

• The K ^trans , K _ep and V _e values correlated with synchronous distant metastasis. • Higher K ^trans , K _ep and V _e values were noted among patients with metastasis. • DCE-MRI parameters might represent a prognostic indicator for synchronous distant metastases.

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.

MRI of Rectal Cancer: An Overview and Update on Recent Advances

OBJECTIVE

MRI is the modality of choice for rectal cancer staging. The high soft-tissue contrast of MRI accurately assesses the extramural tumor spread and relation to mesorectal fascia and the sphincter complex. This article reviews the role of MRI in the staging and treatment of rectal cancer. The relevant anatomy, MRI techniques, preoperative staging, post-chemoradiation therapy (CRT) imaging, and tumor recurrence are discussed with special attention to recent advances in knowledge.

CONCLUSION

MRI is the modality of choice for staging rectal cancer to assist surgeons in obtaining negative surgical margins. MRI facilitates the accurate assessment of mesorectal fascia and the sphincter complex for surgical planning. Multiparametric MRI may also help in the prediction and estimation of response to treatment and in the detection of recurrent disease.

Role of Radiotherapy and Newer Techniques in the Treatment of GI Cancers

The role of radiotherapy in multidisciplinary treatment of GI malignancies is well established. Recent advances in imaging as well as radiotherapy planning and delivery techniques have made it possible to target tumors more accurately while sparing normal tissues. Intensity-modulated radiotherapy is an advanced method of delivering radiation using cutting-edge technology to manipulate beams of radiation. The role of intensity-modulated radiotherapy is growing for many GI malignancies, such as cancers of the stomach, pancreas, esophagus, liver, and anus. Stereotactic body radiotherapy is an emerging treatment option for some GI tumors such as locally advanced pancreatic cancer and primary or metastatic tumors of the liver. Stereotactic body radiotherapy requires a high degree of confidence in tumor location and subcentimeter accuracy of the delivered dose. New image-guided techniques have been developed to overcome setup uncertainties at the time of treatment, including real-time imaging on the linear accelerator. Modern imaging techniques have also allowed for more accurate pretreatment staging and delineation of the primary tumor and involved sites. In particular, magnetic resonance imaging and positron emission tomography scans can be particularly useful in radiotherapy planning and assessing treatment response. Molecular biomarkers are being investigated as predictors of response to radiotherapy with the intent of ultimately moving toward using genomic and proteomic determinants of therapeutic strategies. The role of all of these new approaches in the radiotherapeutic management of GI cancers and the evolving role of radiotherapy in these tumor sites will be highlighted in this review.

Use of Imaging for GI Cancers

GI cancers are a heterogeneous group of neoplasms that differ in their biologic and physical behaviors depending on the organ of origin, location within the organ, and degree of differentiation. As a result, evaluation of these tumors is complex, requiring integration of information from a patient's clinical history, physical examination, laboratory data, and imaging. With advances in anatomic and functional imaging techniques, we now have tools for assessing patients with these tumors at diagnosis, staging, and treatment assessment. It is difficult for a single imaging modality to provide all the necessary information for a given GI tumor. However, well-chosen combinations of available imaging modalities based on the indications, strength, and limitations of the modalities will provide optimal evaluation of patients with these malignancies.

The Impact of Flip Angle and TR on the Enhancement Ratio of Dynamic Gadobutrol-enhanced MR Imaging: In Vivo VX2 Tumor Model and Computer Simulation

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is widely used to diagnose cancer and monitor therapy. The maximum enhancement ratio (ERmax) obtained from the curve of signal intensity over time could be a biomarker to distinguish cancer from normal tissue or benign tumors. We evaluated the impact of flip angle (FA) and repetition time (TR) on the ERmax values of dynamic gadobutrol-enhanced MR imaging, obtaining T1-weighted (T1W) MR imaging of VX2 tumors using 2-dimensional fast spoiled gradient echo (2D FSPGR) with various FAs (30°, 60° and 90°) at 1.5 tesla before and after injection of 0.1 mmol/kg gadobutrol. In vivo study indicated significant differences between ERmax values and area under the ER-time curve (AUC100) of VX2 tumors and muscle tissue, with the highest ERmax and AUC100 at FA 90°. Computer simulation also demonstrated the ER as a strictly increasing monotonic function in the closed interval [0°, 90°] for a given TR when using T1W FSPGR, and the highest ER value always occurred at FA 90°. The FA for the highest ER differed from that for the highest signal-to-noise or contrast-to-noise ratio. For long TR, the ER value increases gradually. However, for short TR, the ER value increases rapidly and plateaus so that the ER value changes little beyond a certain FA value. Therefore, we suggest use of a higher FA, near 90°, to obtain a higher ERmax for long TR in 2D SPGR or FSPGR and a smaller FA, much less than 90°, to reach an appropriate ERmax for short TR in 3D SPGR or FSPGR. This information could be helpful in setting the optimal parameters for DCE-MRI.