Magnetic resonance imaging in rectal cancer: A surgeon’s perspective

Imaging Assessment of the Response to Neoadjuvant Treatment in Rectal Cancer in Relation to Postoperative Pathological Outcomes

BACKGROUND AND OBJECTIVE

Rectal cancer remains a global health challenge with significant morbidity and mortality. Neoadjuvant therapy (NAT) is critical for downstaging tumors and improving surgical outcomes. This study aimed to compare the performance of magnetic resonance imaging (MRI) and computed tomography (CT) in evaluating tumor response to NAT in rectal cancer patients, focusing on imaging accuracy and correlation with histopathological findings.

MATERIALS AND METHODS

This retrospective study analyzed 201 patients diagnosed with rectal cancer who underwent NAT followed by surgery. Imaging evaluations were conducted pre-NAT and post-NAT using MRI or CT. Tumor responses were categorized into complete response, downstaging, stable disease, and upstaging. Statistical analyses included Chi-square, Mann-Whitney U, and Z-tests to assess differences in imaging performance and concordance with pathological outcomes.

RESULTS

Both imaging modalities identified significant downstaging post-NAT, with CT demonstrating a higher sensitivity for detecting complete responses (12.5% vs. 6.61% for MRI) and better local staging accuracy. CT showed superior performance in systemic metastasis detection but had limitations in distinguishing fibrosis from residual tumors. Overall diagnostic accuracy was 42.29%, with MRI having a statistically significant edge in detecting favorable tumor responses (p=0.043). The combined use of CT and MRI provided complementary insights, enhancing clinical decision making.

CONCLUSIONS

MRI excels in local tumor evaluation post-NAT, offering detailed imaging crucial for surgical planning and conservative strategies like "watch-and-wait" in complete responders. CT remains indispensable for systemic staging and metastasis detection. Integrating both modalities within a standardized protocol can optimize staging accuracy and treatment outcomes in rectal cancer.

Magnetic resonance imaging radiomics-based prediction of severe inflammatory response in locally advanced rectal cancer patients after neoadjuvant radiochemotherapy

PURPOSE

To predict severe inflammatory response after neoadjuvant radiochemotherapy in locally advanced rectal cancer (RC) patients using magnetic resonance imaging (MRI) radiomics models.

METHODS

This retrospective study included patients who underwent radical surgery for RC cancer after neoadjuvant radiochemotherapy between July 2017 and December 2019 at XXX Hospital. MRI radiomics features were extracted from T2WI images before (pre-nRCT-RF) and after (post-nRCT-RF) neoadjuvant radiochemotherapy, and the variation of radiomics features before and after neoadjuvant radiochemotherapy (delta-RF) were calculated. Eight, eight, and five most relevant features were identified for pre-nRCT-RF, post-nRCT-RF, and delta-RF, respectively.

RESULTS

Eighty-six patients were included and randomized 3:1 to the training and test set (n = 65 and n = 21, respectively). The prediction model based on delta-RF had areas under the curve (AUCs) of 0.80 and 0.85 in the training and test set, respectively. A higher rate of difficult operations was observed in patients with severe inflammation (65.5% vs. 42.9%, P = 0.045).

CONCLUSION

The prediction model based on MRI delta-RF may be a useful tool for predicting severe inflammatory response after neoadjuvant radiochemotherapy in locally advanced RC patients.

Imaging and Metabolic Diagnostic Methods in the Stage Assessment of Rectal Cancer

Rectal cancer (RC) is a prevalent malignancy with significant morbidity and mortality rates. The accurate staging of RC is crucial for optimal treatment planning and patient outcomes. This review aims to summarize the current literature on imaging and metabolic diagnostic methods used in the stage assessment of RC. Various imaging modalities play a pivotal role in the initial evaluation and staging of RC. These include magnetic resonance imaging (MRI), computed tomography (CT), and endorectal ultrasound (ERUS). MRI has emerged as the gold standard for local staging due to its superior soft tissue resolution and ability to assess tumor invasion depth, lymph node involvement, and the presence of extramural vascular invasion. CT imaging provides valuable information about distant metastases and helps determine the feasibility of surgical resection. ERUS aids in assessing tumor depth, perirectal lymph nodes, and sphincter involvement. Understanding the strengths and limitations of each diagnostic modality is essential for accurate staging and treatment decisions in RC. Furthermore, the integration of multiple imaging and metabolic methods, such as PET/CT or PET/MRI, can enhance diagnostic accuracy and provide valuable prognostic information. Thus, a literature review was conducted to investigate and assess the effectiveness and accuracy of diagnostic methods, both imaging and metabolic, in the stage assessment of RC.

Validation of pelvic magnetic resonance imaging as the method of choice to determine the distance to the anal margin in rectal cancer

INTRODUCTION

Distance from anal verge of rectal tumours and their anatomical relationships contribute to determine the multidisciplinary therapeutic strategy based on the combination of radio-chemotherapy and radical surgery. Our aims are to investigate which is the most accurate method for the preoperative measuring of the distance from the anal verge in rectal tumours and if the pelvic MRI can substitute the classical instrumental methods.

METHODS

Prospective study of diagnostic precision between flexible colonoscopy (FC), preoperative rigid rectosigmoidoscopy (pRR) and pelvic MRI in patients scheduled to radical surgery. Rigid intraoperative rectoscopy (iRR) was considered the reference test. The correlations between the different techniques and their determination coefficient as well as the intraclass correlation coefficient and the degree of agreement between the different tests were analyzed.

RESULTS

96 patients (65% males), mean age (SD): 68 (14.1) years were included. 72% received neoadjuvant treatment. The mean distance to the anal margin measured by FC = 103.5 mm, was significantly greater than others, which had similar values: pRR = 81.1; MRI = 77.4; iRR = 82.9 mm (P < .001). A significant intraclass correlation was observed and there was high agreement between all pre- and intraoperative measurements except for the performed by FC, which overestimated the results. MRI provided more individualized and accurate information.

CONCLUSIONS

There is variability between the measurement methods, being colonoscopy the least reliable. MRI offers objective, comparable, accurate and individualized values that can replace those obtained by pRR for tumours of any location in the rectum.

Outcomes of rectal cancer patients with a positive pathological circumferential resection margin

PURPOSE

Evidence-based management of positive pathological circumferential resection margin (pCRM) following preoperative radiation and an adequate rectal resection for rectal cancers is lacking.

METHODS

Retrospective analysis of prospectively maintained single-centre institutional database was done to study the patterns of failure and management strategies after a rectal cancer surgery with a positive pCRM.

RESULTS

A total of 86 patients with rectal adenocarcinoma with a positive pCRM were identified over 8 years (2011-2018). Majority had low-lying rectal cancers (90.7%) and were operated after preoperative radiotherapy (95.3%). Operative procedures included abdomino-perineal resections, inter-sphincteric resections, low anterior resections and pelvic exenteration in 61 (70.9%), 9 (10.5%), 11(12.8%) and 5 (5.8%) patients respectively. A total of 83 (96.5%) received chemotherapy as the sole adjuvant treatment modality while 2 patients (2.3%) were given post-operative radiotherapy and 1 patient underwent revision surgery. A total of 53 patients (61.6%) had recurrence, with 16 (18.6%), 20 (23.2%), 8(9.3%) and 9 (10.5%) patients having locoregional, systemic, peritoneal and simultaneous local-systemic relapse. Systemic recurrences were more often detected either by surveillance in an asymptomatic patient (20.1%) while local (13.1%) and peritoneal (13.2%) recurrences were more often symptomatic (p = 0.000). The 2-year overall survival (OS) and disease-free survival (DFS) of the cohort was 82.4% and 74.0%. Median local recurrence-free survival (LRFS) was 10.3 months.

CONCLUSIONS

Patients with a positive pCRM have high local and distal relapse rates. Systemic relapses are more often asymptomatic as compared to peritoneal or locoregional relapse and detected on follow-up surveillance. Hence, identification of such recurrences while still salvageable via an intensive surveillance protocol is desirable.

Validation of pelvic magnetic resonance imaging as the method of choice to determine the distance to the anal margin in rectal cancer

INTRODUCTION

Distance from anal verge of rectal tumors and their anatomical relationships contribute to determine the multidisciplinary therapeutic strategy based on the combination of radio-chemotherapy and radical surgery. Our aims are to investigate which is the most accurate method for the preoperative measuring of the distance from the anal verge in rectal tumors and if the pelvic MRI can substitute the classical instrumental methods.

METHODS

Prospective study of diagnostic precision between flexible colonoscopy (FC), preoperative rigid rectosigmoidoscopy (pRR) and pelvic MRI in patients scheduled to radical surgery. Rigid intraoperative rectoscopy (iRR) was considered the reference test. The correlations between the different techniques and their determination coefficient as well as the intraclass correlation coefficient and the degree of agreement between the different tests were analyzed.

RESULTS

96 patients (65% males), mean age (SD): 68 (14.1) years were included. 72% received neoadjuvant treatment. The mean distance to the anal margin measured by FC=103.5mm, was significantly greater than others, which had similar values: pRR=81.1; MRI=77.4; iRR=82.9mm (P<.001). A significant intraclass correlation was observed and there was high agreement between all pre- and intraoperative measurements except for the performed by FC, which overestimated the results. MRI provided more individualized and accurate information.

CONCLUSIONS

There is variability between the measurement methods, being colonoscopy the least reliable. MRI offers objective, comparable, accurate and individualized values that can replace those obtained by pRR for tumors of any location in the rectum.

A deep learning nomogram kit for predicting metastatic lymph nodes in rectal cancer

BACKGROUND

Preoperative diagnoses of metastatic lymph nodes (LNs) by the most advanced deep learning technology of Faster Region-based Convolutional Neural Network (Faster R-CNN) have not yet been reported.

MATERIALS AND METHODS

In total, 545 patients with pathologically confirmed rectal cancer between January 2016 and March 2019 were included and were randomly allocated with a split ratio of 2:1 to the training and validation sets, respectively. The MRI images for metastatic LNs were evaluated by Faster R-CNN. Multivariate regression analyses were used to develop the predictive models. Faster R-CNN nomograms were constructed based on the multivariate analyses in the training sets and were validated in the validation sets.

RESULTS

The Faster R-CNN nomogram for predicting metastatic LN status contained predictors of age, metastatic LNs by Faster R-CNN and differentiation degrees of tumors, with areas under the curves (AUCs) of 0.862 (95% CI: 0.816-0.909) and 0.920 (95% CI: 0.876-0.964) in the training and validation sets, respectively. The Faster R-CNN nomogram for predicting LN metastasis degree contained predictors of metastatic LNs by Faster R-CNN and differentiation degrees of tumors, with AUCs of 0.859 (95% CI: 0.804-0.913) and 0.886 (95% CI: 0.822-0.950) in the training and validation sets, respectively. Calibration plots and decision curve analyses demonstrated good calibrations and clinical utilities. The two nomograms were used jointly as a kit for predicting metastatic LNs.

CONCLUSION

The Faster R-CNN nomogram kit exhibits excellent performance in discrimination, calibration, and clinical utility and is convenient and reliable for predicting metastatic LNs preoperatively.

CLINICAL TRIAL REGISTRATION

ChiCTR-DDD-17013842.

Radiomic Features of Primary Rectal Cancers on Baseline T2 -Weighted MRI Are Associated With Pathologic Complete Response to Neoadjuvant Chemoradiation: A Multisite Study

BACKGROUND

Twenty-five percent of rectal adenocarcinoma patients achieve pathologic complete response (pCR) to neoadjuvant chemoradiation and could avoid proctectomy. However, pretreatment clinical or imaging markers are lacking in predicting response to chemoradiation. Radiomic texture features from MRI have recently been associated with therapeutic response in other cancers.

PURPOSE

To construct a radiomics texture model based on pretreatment MRI for identifying patients who will achieve pCR to neoadjuvant chemoradiation in rectal cancer, including validation across multiple scanners and sites.

STUDY TYPE

Retrospective.

SUBJECTS

In all, 104 rectal cancer patients staged with MRI prior to long-course chemoradiation followed by proctectomy; curated from three institutions.

FIELD STRENGTH/SEQUENCE

1.5T-3.0T, axial higher resolution T2 -weighted turbo spin echo sequence.

ASSESSMENT

Pathologic response was graded on postsurgical specimens. In total, 764 radiomic features were extracted from single-slice sections of rectal tumors on processed pretreatment T2 -weighted MRI.

STATISTICAL TESTS

Three feature selection schemes were compared for identifying radiomic texture descriptors associated with pCR via a discovery cohort (one site, N = 60, cross-validation). The top-selected radiomic texture features were used to train and validate a random forest classifier model for pretreatment identification of pCR (two external sites, N = 44). Model performance was evaluated via area under the curve (AUC), accuracy, sensitivity, and specificity.

RESULTS

Laws kernel responses and gradient organization features were most associated with pCR (P ≤ 0.01); as well as being commonly identified across all feature selection schemes. The radiomics model yielded a discovery AUC of 0.699 ± 0.076 and a hold-out validation AUC of 0.712 with 70.5% accuracy (70.0% sensitivity, 70.6% specificity) in identifying pCR. Radiomic texture features were resilient to variations in magnetic field strength as well as being consistent between two different expert annotations. Univariate analysis revealed no significant associations of baseline clinicopathologic or MRI findings with pCR (P = 0.07-0.96).

DATA CONCLUSION

Radiomic texture features from pretreatment MRIs may enable early identification of potential pCR to neoadjuvant chemoradiation, as well as generalize across sites.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Long-term outcomes of real world 'watch and wait' data for rectal cancer after neoadjuvant chemoradiotherapy

AIM

A 'watch and wait' (W&W) strategy after neoadjuvant long-course chemoradiotherapy (NACRT) remains controversial. Whilst encouraging short-term data exist, the strategy will be judged on long-term data. We present long-term, real-world UK data from a single National Health Service trust.

METHODS

An analysis was performed of a prospectively maintained W&W database over 9 years between 2010 and 2018. Outcome measures include incidence and time to regrowth and overall and disease-free survival.

RESULTS

We diagnosed 563 rectal cancers in 9 years. In all, 283 patients underwent rectal resection (50.3%). NACRT was used in 155 patients for margin-threatened tumours on staging MRI. Forty-nine patients (31.6%) experienced either a 'near complete' or a complete clinical response (cCR) at their 10 weeks post-NACRT assessment (MRI and endoscopy). The median age was 69 years (range 44-83), and the male to female ratio was 32:17. The median follow-up was 38 months (range 12-96). The median tumour distance from the anal verge was 7 cm (1-15 cm). Twenty-two patients had a cCR on initial assessment and 27 patients had a 'near' cCR. Of those 27 who experienced a 'near' cCR, 17 (63%) progressed to cCR on repeat assessment and 10 (37%) did not. Of these 10 patients, seven underwent standard surgical resection and three were unfit for surgery. R0 for the seven with delayed resection was 100%. Of 39 patients (22 cCR and 17 'near' cCR who progressed to cCR) (25.2% of those receiving NACRT), six patients experienced local regrowth (15.4%). The median time to local regrowth was 29 months (15-60 months). One of these six patients underwent salvage abdominoperineal resection, one was advised to have contact radiotherapy and four opted against surgery and also had contact radiotherapy. The overall survival was 100% at 2 years and 90% at 5 years. Disease-free survival was 90.47% at 2 years and 74.8% at 5 years.

CONCLUSION

A W&W treatment strategy was employed safely in this patient cohort with acceptable rates of local regrowth and survival.

Artificial intelligence system of faster region-based convolutional neural network surpassing senior radiologists in evaluation of metastatic lymph nodes of rectal cancer

BACKGROUND

An artificial intelligence system of Faster Region-based Convolutional Neural Network (Faster R-CNN) is newly developed for the diagnosis of metastatic lymph node (LN) in rectal cancer patients. The primary objective of this study was to comprehensively verify its accuracy in clinical use.

METHODS

Four hundred fourteen patients with rectal cancer discharged between January 2013 and March 2015 were collected from 6 clinical centers, and the magnetic resonance imaging data for pelvic metastatic LNs of each patient was identified by Faster R-CNN. Faster R-CNN based diagnoses were compared with radiologist based diagnoses and pathologist based diagnoses for methodological verification, using correlation analyses and consistency check. For clinical verification, the patients were retrospectively followed up by telephone for 36 months, with post-operative recurrence of rectal cancer as a clinical outcome; recurrence-free survivals of the patients were compared among different diagnostic groups, by methods of Kaplan-Meier and Cox hazards regression model.

RESULTS

Significant correlations were observed between any 2 factors among the numbers of metastatic LNs separately diagnosed by radiologists, Faster R-CNN and pathologists, as evidenced by rradiologist-Faster R-CNN of 0.912, rPathologist-radiologist of 0.134, and rPathologist-Faster R-CNN of 0.448 respectively. The value of kappa coefficient in N staging between Faster R-CNN and pathologists was 0.573, and this value between radiologists and pathologists was 0.473. The 3 groups of Faster R-CNN, radiologists and pathologists showed no significant differences in the recurrence-free survival time for stage N0 and N1 patients, but significant differences were found for stage N2 patients.

CONCLUSION

Faster R-CNN surpasses radiologists in the evaluation of pelvic metastatic LNs of rectal cancer, but is not on par with pathologists.

TRIAL REGISTRATION

www.chictr.org.cn (No. ChiCTR-DDD-17013842).

Identification of Metastatic Lymph Nodes in MR Imaging with Faster Region-Based Convolutional Neural Networks

MRI is the gold standard for confirming a pelvic lymph node metastasis diagnosis. Traditionally, medical radiologists have analyzed MRI image features of regional lymph nodes to make diagnostic decisions based on their subjective experience; this diagnosis lacks objectivity and accuracy. This study trained a faster region-based convolutional neural network (Faster R-CNN) with 28,080 MRI images of lymph node metastasis, allowing the Faster R-CNN to read those images and to make diagnoses. For clinical verification, 414 cases of rectal cancer at various medical centers were collected, and Faster R-CNN-based diagnoses were compared with radiologist diagnoses using receiver operating characteristic curves (ROC). The area under the Faster R-CNN ROC was 0.912, indicating a more effective and objective diagnosis. The Faster R-CNN diagnosis time was 20 s/case, which was much shorter than the average time (600 s/case) of the radiologist diagnoses.Significance: Faster R-CNN enables accurate and efficient diagnosis of lymph node metastases. Cancer Res; 78(17); 5135-43. ©2018 AACR.

Long-term oncological outcomes of robotic versus laparoscopic total mesorectal excision of mid-low rectal cancer following neoadjuvant chemoradiation therapy

PROPOSE

The use of robotic surgery and neoadjuvant chemoradiation therapy (CRT) for rectal cancer is increasing steadily worldwide. However, there are insufficient data on long-term outcomes of robotic surgery in this clinical setting. The aim of this study was to compare the 5-year oncological outcomes of laparoscopic vs. robotic total mesorectal excision for mid-low rectal cancer after neoadjuvant CRT.

MATERIALS AND METHODS

One hundred thirty-eight patients who underwent robotic (n = 74) or laparoscopic (n = 64) resections between January 2006 and December 2010 for mid and low rectal cancer after neoadjuvant CRT were identified from a prospective database. The long-term oncological outcomes of these patients were analyzed using prospective follow-up data.

RESULTS

The median follow-up period was 56.1 ± 16.6 months (range 11-101). The 5-year overall survival (OS) rate of the laparoscopic and robotic groups was 93.3 and 90.0 %, respectively, (p = 0424). The 5-year disease-free survival (DFS) rate was 76.0 % (laparoscopic) vs. 76.8 % (robotic) (p = 0.834). In a subgroup analysis according to the yp-stage (complete pathologic response, yp-stage I, yp-stage II, or yp-stage III), the between-group oncological outcomes were not significantly different. The local recurrence rate was 6.3 % (laparoscopic, n = 4) vs. 2.7 % (robotic, n = 2) (p = 0.308). The systemic recurrence rate was 15.6 % (laparoscopic, n = 10) vs. 18.9 % (robotic, n = 14) (p = 0.644). All recurrences occurred within less than 36 months in both groups. The median period of recurrence was 14.2 months.

CONCLUSION

Robotic surgery for rectal cancer after neoadjuvant CRT can be performed safely, with long-term oncological outcomes comparable to those obtained with laparoscopic surgery. More large-scale studies and long-term follow-up data are needed.

Long-term oncological outcomes of robotic versus laparoscopic total mesorectal excision of mid-low rectal cancer following neoadjuvant chemoradiation therapy

PROPOSE

The use of robotic surgery and neoadjuvant chemoradiation therapy (CRT) for rectal cancer is increasing steadily worldwide. However, there are insufficient data on long-term outcomes of robotic surgery in this clinical setting. The aim of this study was to compare the 5-year oncological outcomes of laparoscopic vs. robotic total mesorectal excision for mid-low rectal cancer after neoadjuvant CRT.

MATERIALS AND METHODS

One hundred thirty-eight patients who underwent robotic (n = 74) or laparoscopic (n = 64) resections between January 2006 and December 2010 for mid and low rectal cancer after neoadjuvant CRT were identified from a prospective database. The long-term oncological outcomes of these patients were analyzed using prospective follow-up data.

RESULTS

The median follow-up period was 56.1 ± 16.6 months (range 11-101). The 5-year overall survival (OS) rate of the laparoscopic and robotic groups was 93.3 and 90.0 %, respectively, (p = 0424). The 5-year disease-free survival (DFS) rate was 76.0 % (laparoscopic) vs. 76.8 % (robotic) (p = 0.834). In a subgroup analysis according to the yp-stage (complete pathologic response, yp-stage I, yp-stage II, or yp-stage III), the between-group oncological outcomes were not significantly different. The local recurrence rate was 6.3 % (laparoscopic, n = 4) vs. 2.7 % (robotic, n = 2) (p = 0.308). The systemic recurrence rate was 15.6 % (laparoscopic, n = 10) vs. 18.9 % (robotic, n = 14) (p = 0.644). All recurrences occurred within less than 36 months in both groups. The median period of recurrence was 14.2 months.

CONCLUSION

Robotic surgery for rectal cancer after neoadjuvant CRT can be performed safely, with long-term oncological outcomes comparable to those obtained with laparoscopic surgery. More large-scale studies and long-term follow-up data are needed.

Assessment of colon and bladder crosstalk in an experimental colitis model using contrast-enhanced magnetic resonance imaging

BACKGROUND

Inflammatory bowel disease (IBD) consists of two chronic remitting-relapsing inflammatory disorders in the colon referred to as ulcerative colitis and Crohn's disease (CD). Inflammatory bowel disease affects about 1.4 million Americans. 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis is a widely used model of experimental intestinal inflammation with characteristic transmural and segmental lesions that are similar to CD.

METHODS

Here, we report on the use of contrast-enhanced magnetic resonance imaging (CE-MRI) to monitor in vivo bladder permeability changes resulting from bladder crosstalk following colon TNBS exposure, and TNBS-induced colitis. Changes in MRI signal intensities and histology were evaluated for both colon and bladder regions.

KEY RESULTS

Uptake of contrast agent in the colon demonstrated a significant increase in signal intensity (SI) for TNBS-exposed rats (p < 0.01) compared to controls. In addition, a significant increase in bladder SI for colon TNBS-exposed rats (p < 0.001) was observed compared to saline controls. Histological damage within the colon was observed, however, bladder histology indicated a normal urothelium in rats with TNBS-induced colitis, despite increased permeability seen by CE-MRI.

CONCLUSIONS & INFERENCES

Contrast-enhanced MRI was able to quantitatively measure inflammation associated with TNBS-induced colitis, and assess bladder crosstalk measured as an increase in urothelial permeability. Although CE-MRI is routinely used to assess inflammation with IBD, currently there is no diagnostic test to assess bladder crosstalk with this disease, and our developed method may be useful in providing crosstalk information between organ and tissue systems in IBD patients, in addition to colitis.