How useful is endorectal ultrasound in the management of early rectal carcinoma?

Computer-aided diagnosis tool utilizing a deep learning model for preoperative T-staging of rectal cancer based on three-dimensional endorectal ultrasound

BACKGROUND

The prognosis and treatment outcomes for patients with rectal cancer are critically dependent on an accurate and comprehensive preoperative evaluation.Three-dimensional endorectal ultrasound (3D-ERUS) has demonstrated high accuracy in the T staging of rectal cancer. Thus, we aimed to develop a computer-aided diagnosis (CAD) tool using a deep learning model for the preoperative T-staging of rectal cancer with 3D-ERUS.

METHODS

We retrospectively analyzed the data of 216 rectal cancer patients who underwent 3D-ERUS. The patients were randomly assigned to a training cohort (n = 156) or a testing cohort (n = 60). Radiologists interpreted the 3D-ERUS images of the testing cohort with and without the CAD tool. The diagnostic performance of the CAD tool and its impact on the radiologists' interpretations were evaluated.

RESULTS

The CAD tool demonstrated high diagnostic efficacy for rectal cancer tumors of all T stages, with the best diagnostic performance achieved for T1-stage tumors (AUC, 0.85; 95% CI, 0.73-0.93). With assistance from the CAD tool, the AUC for T1 tumors improved from 0.76 (95% CI, 0.63-0.86) to 0.80 (95% CI, 0.68-0.94) (P = 0.020) for junior radiologist 2. For junior radiologist 1, the AUC improved from 0.61 (95% CI, 0.48-0.73) to 0.79 (95% CI, 0.66-0.88) (P = 0.013) for T2 tumors and from 0.73 (95% CI, 0.60-0.84) to 0.84 (95% CI, 0.72-0.92) (P = 0.038) for T3 tumors. The diagnostic consistency (κ value) also improved from 0.31 to 0.64 (P = 0.005) for the junior radiologists and from 0.52 to 0.66 (P = 0.005) for the senior radiologists.

CONCLUSION

A CAD tool utilizing a deep learning model based on 3D-ERUS images showed strong performance in T staging rectal cancer. This tool could improve the performance of and consistency between radiologists in preoperatively assessing rectal cancer patients.

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.

MRI cT1-2 rectal cancer staging accuracy: a population-based study

Background

Adequate MRI‐based staging of early rectal cancers is essential for decision‐making in an era of organ‐conserving treatment approaches. The aim of this population‐based study was to determine the accuracy of routine daily MRI staging of early rectal cancer, whether or not combined with endorectal ultrasonography (ERUS).

Methods

Patients with cT1–2 rectal cancer who underwent local excision or total mesorectal excision (TME) without downsizing (chemo)radiotherapy between 1 January 2011 and 31 December 2018 were selected from the Dutch ColoRectal Audit. The accuracy of imaging was expressed as sensitivity, specificity, and positive predictive value (PPV) and negative predictive value.

Results

Of 7382 registered patients with cT1–2 rectal cancer, 5539 were included (5288 MRI alone, 251 MRI and ERUS; 1059 cT1 and 4480 cT2). Among patients with pT1 tumours, 54·7 per cent (792 of 1448) were overstaged by MRI alone, and 31·0 per cent (36 of 116) by MRI and ERUS. Understaging of pT2 disease occurred in 8·2 per cent (197 of 2388) and 27·9 per cent (31 of 111) respectively. MRI alone overstaged pN0 in 17·3 per cent (570 of 3303) and the PPV for assignment of cN0 category was 76·3 per cent (2733 of 3583). Of 834 patients with pT1 N0 disease, potentially suitable for local excision, tumours in 253 patients (30·3 per cent) were staged correctly as cT1 N0, whereas 484 (58·0 per cent) and 97 (11·6 per cent) were overstaged as cT2 N0 and cT1–2 N1 respectively.

Conclusion

This Dutch population‐based analysis of patients who underwent local excision or TME surgery for cT1–2 rectal cancer based on preoperative MRI staging revealed substantial overstaging, indicating the weaknesses of MRI and missed opportunities for organ preservation strategies.

Rectal Endoscopic Ultrasound in Clinical Practice

PURPOSE OF REVIEW

Endoscopic ultrasound (EUS) is routinely utilized for evaluation of disorders of the lower gastrointestinal tract. In this review, we summarize the current status of rectal EUS in clinical practice and describe recent developments in diagnostic and therapeutic rectal EUS.

RECENT FINDINGS

Recent guidelines recommend rectal EUS for rectal cancer staging as a second line modality in cases where MRI is contraindicated. Forward-viewing echoendoscopes and through the scope EUS miniprobes allow for EUS imaging of lesions through the entire colon and for evaluation beyond stenoses or luminal narrowings. EUS can be used to assess perianal disease and drain pelvic abscess associated with IBD, along with newer applications currently under investigation. For rectal varices, EUS can confirm the diagnosis, assess the optimal site for banding, guide therapy placement with sclerotherapy and/or coils, and assess response to treatment by confirming absence of flow. Therapeutic rectal EUS is emerging as a promising modality for drainage of pelvic fluid collection drainage and fiducial placement for rectal or prostatic cancer. Drug delivery mechanisms and substances that may increase the scope of therapy with rectal EUS are in varying stages of development. Rectal EUS continues to be an important modality for evaluation of benign and malignant disorders of the lower gastrointestinal tract, although its use as a cancer staging modality has declined due to improvements in MRI technology. Various technologies to enhance ultrasound imaging and for therapeutics have been developed that have or may contribute to expanded indications for rectal EUS.

Accuracy of endoscopic ultrasound in rectal cancer and its use in transanal endoscopic microsurgery

Introduction: This study evaluated the accuracy of endoscopic ultrasound (EUS) for preoperative staging of rectal cancer and guiding the treatment of transanal endoscopic microsurgery (TEM) in early rectal cancer.Material and methods: One-hundred-twenty-six patients with rectal cancer were staged preoperatively using EUS and the results were compared with postoperative histopathology results. Radical surgeries, including low anterior resection (LAR), abdominal-perineal resection (APR) and Hartmann surgeries, were performed on patients with advanced rectal cancers, and TEM was performed on patients with stage T1. The Kappa statistic was used to determine agreement between EUS-based staging and pathology staging.Results: The overall accuracies of EUS for T and N stage were 90.8% (Kappa = 0.709) and 76.7% (Kappa = 0.419), respectively. The accuracies of EUS for uT1, uT2, uT3, and uT4 stages were 96.8%, 92.1%, 84.1%, and 88.9%, respectively, and for uN0, uN1, and uN2 stages, they were 71.9%, 64.9%, and 93.0%, respectively. Twelve patients underwent TEM and received confirmed pathology results of early rectal cancer. After postoperative follow-up, there were no local recurrences or distant metastases.Conclusion: EUS is a good and comparable technique for postoperative staging of rectal cancer. Moreover, EUS is used as indicator for preoperative staging and tumor assessment strategy when considering TEM.

Factors Associated With Margin Positivity and Incidental Carcinoma in Patients Undergoing Transanal Endoscopic Microsurgery (TEMS) for the Management of Adenomatous and Dysplastic Rectal Lesions

PURPOSE

Colorectal cancer screening has resulted in an increased detection of early premalignant rectal lesions. Transanal endoscopic microsurgery (TEMS) is a minimally invasive procedure for the resection of dysplastic and selected early malignant lesions with organ and functional preservation. The aim of this study was to assess factors associated with positive resection margin and the underlying invasive component.

METHODS

This was an analysis of a prospective consecutive series of all TEMS procedures performed over the last 10-year period. Data was collated from hospital databases and operative theater registers. Statistical analysis was performed using Minitab-V18 with a P<0.05 regarded as significant.

RESULTS

In total, 328 procedures were performed on 292 patients. The cohort included 165 male patients and 127 female patients with a mean age of 66.3 years (19 to 95 years). A total of 274 procedures performed were en bloc excisions and 54 procedures were piecemeal debulking excisions for larger lesions follow by formal TEMs at an interval. The mean tumor size was 41.9 mm (10 to 150 mm), and the mean distance from anal verge was 9.3 cm (2 to 20 cm). Clear margins were achieved in 85% of cases. An overall 10.6% of patients had pathologic upgrading to invasive disease after TEMS. Lesion volume was found to influence the completeness of excision, and the widest diameter of the lesions was related to the presence of an invasive component on histology (P=0.002, 0.008, respectively).

CONCLUSIONS

TEMS is a minimally invasive technique for the resection of rectal lesions that are not amenable to endoscopic removal. Lesion size and endoscopic diameter were associated with invasive component and margin positivity, respectively. These factors should be taken into consideration when considering TEMS.

Radiologic Evaluation of Clinically Benign Rectal Neoplasms May Not Be Necessary Before Local Excision

BACKGROUND

Local excision may be curative for benign and malignant rectal neoplasms. Because many early rectal cancers are discovered incidentally after local excision of clinically benign lesions, it is unclear whether preoperative imaging with transrectal ultrasound or MRI affects management.

OBJECTIVE

The purpose of this study was to determine the diagnostic characteristics and effect of preoperative imaging on the incidence of malignancy in benign rectal lesions undergoing local excision.

DESIGN

Prospective data from 2 institutions were included. Coarsened exact matching created a balanced cohort comparing imaging and no-imaging groups.

SETTING

The study was conducted at high-volume specialist referral hospitals.

PATIENTS

Adult patients undergoing local excision via transanal endoscopic surgery between 1997 and 2016 for clinically benign rectal neoplasms were included.

INTERVENTION

The study intervention included preoperative imaging with transrectal ultrasound and/or MRI.

MAIN OUTCOME MEASURES

We measured the incidence of malignancy and diagnostic accuracy of preoperative imaging.

RESULTS

A total of 620 patients were included (272 with preoperative imaging and 348 without). There were 250 patients undergoing transrectal ultrasound, and 24 patients undergoing MRI (2 patients underwent both). Transrectal ultrasound and MRI correctly identified malignant polyps in 50% (11/22) and 44% (8/18). Overall agreement for benign versus malignant polyps between preoperative imaging and final pathology was κ = 0.30 (95% CI, 0.18-0.41) for transrectal ultrasound and 0.29 (95% CI, 0.01-0.57) for MRI. In both the overall and unmatched cohorts, the incidence of malignancy, margin involvement, and proportion of patients requiring salvage surgery was similar.

LIMITATIONS

Data were obtained from 2 institutions with different equipment over a long time period.

CONCLUSIONS

Preoperative imaging did not accurately identify malignancy in clinically benign rectal lesions and did not affect the incidence of malignancy, margin involvement, or proportion of patients requiring salvage surgery. Therefore, preoperative imaging may not be necessary for clinically benign lesions undergoing local excision. See Video Abstract at http://links.lww.com/DCR/A695.

Ex vivo MR imaging of colorectal carcinoma before and after formalin fixation: correlation with histopathologic findings

PURPOSE

We aimed to assess and compare ex vivo MRI of resected colorectal carcinoma before and after formalin fixation.

METHODS

We enrolled 45 consecutive patients (47 carcinomas) who underwent colorectal carcinoma surgery. Specimens underwent two MR scans at 1.5 T (after resection and 24 h after formalin fixation). Two radiologists evaluated all MR images independently regarding T-staging and the subserosal linear architecture. T-stage accuracy and frequency of linear architecture were calculated. A third radiologist measured vertical tumor distance and contrast-to-noise ratio (CNR) of the mucosa, submucosa, muscularis propria, subserosa, and tumor.

RESULTS

T-stage accuracy compared to histopathology by the two readers was 91.5% and 87.2% before fixation and 91.5% and 85.1% after fixation, respectively. Linear architecture was observed in 11.1% of T2 tumors and 100% of T3 tumors by both readers. The vertical tumor distance between histopathological and MRI findings was well correlated before and after fixation. The measurement error of the vertical tumor distance between before and after fixation was within 3 mm. CNR of the tumor was significantly lower than those of the submucosa and subserosa before and after fixation (p < 0.05). CNRs of the tumor and muscularis propria were decreased after formalin fixation (p < 0.05).

CONCLUSIONS

Subserosal linear architecture represented fibrosis with tumoral invasion, suggesting a T3-4 tumor. The submucosa and subserosa showed high intensity and the mucosa and muscularis propria showed low intensity compared with tumor. CNRs of the tumor and muscularis propria were decreased by formalin fixation.

Efficacy of 3-Dimensional Endorectal Ultrasound for Staging Early Extraperitoneal Rectal Neoplasms

BACKGROUND

Adequate oncologic staging of rectal neoplasia is important for treatment and prognostic evaluation of the disease. Diagnostic methods such as endorectal ultrasound can assess rectal wall invasion and lymph node involvement.

OBJECTIVE

The purpose of this study was to correlate findings of 3-dimensional endorectal ultrasound and pathologic diagnosis of extraperitoneal rectal tumors with regard to depth of rectal wall invasion, lymph node involvement, percentage of rectal circumference involvement, and tumor extension.

DESIGN

Consecutive patients with extraperitoneal rectal tumors were prospectively assessed by 3-dimensional endorectal ultrasound blind to other staging methods and pathologic diagnosis.

PATIENTS

Patients who underwent endorectal ultrasound followed by surgery were included in the study.

SETTINGS

The study was conducted at a single academic institution.

MAIN OUTCOME MEASURES

Sensitivity, specificity, positive and negative predictive values, area under curve, and κ coefficient between 3-dimensional endorectal ultrasound and pathologic diagnosis were determined. Intraclass correlation coefficient was calculated for tumor extension and percentage of rectal wall involvement.

RESULTS

Forty-four patients (27 women; mean age = 63.5 years) were evaluated between September 2010 and June 2014. Most lesions were malignant (72.7%). For depth of submucosal invasion, 3-dimensional endorectal ultrasound showed sensitivity of 77.3%, specificity of 86.4%, positive predictive value of 85.0%, a negative predictive value of 79.2%, and an area under curve of 0.82. The weighted κ coefficient for depth of rectal wall invasion staging was 0.67, and there was no agreement between 3-dimensional endorectal ultrasound and pathologic diagnosis for lymph node involvement (κ = -0.164). Intraclass correlation coefficient for lesion extension and percentage of rectal circumference involvement were 0.45 and 0.66. A better correlation between 3-dimensional endorectal ultrasound and pathologic diagnosis was observed in tumors <5 cm and with <50% of rectal wall involvement.

LIMITATIONS

The relatively small sample size of patients with early rectal lesions referred directly for surgery could represent a potential selection bias.

CONCLUSIONS

Three-dimensional endorectal ultrasound was effective for determining rectal wall invasion and lesion extension in tumors <5 cm and with <50% of rectal wall invasion but was limited for detecting lymph node involvement in early rectal lesions.

Transanal endoscopic microsurgery for giant circumferential rectal adenomas

AIM

Transanal endoscopic microsurgery (TEM) was originally invented by Buess et al. (Chirurg, 1984, 55, 677-80) for the treatment of infraperitoneal rectal adenomas. Its indications have progressively expanded to include larger and more advanced lesions. The aim of the study was to report the results of TEM used for the treatment of circumferential rectal lesions.

METHOD

We retrospectively reviewed the medical records of 17 consecutive patients [median age 69 (32-89) years; nine men] who underwent TEM for a circumferential rectal lesion in our department between September 2010 and January 2015.

RESULTS

The median distance from the anal verge was 4 (3-11) cm, the median longitudinal extent was 7 (3-10) cm and the median surface area was 75 (40-255) cm(2) . An end-to-end anastomosis without proximal bowel mobilization was completed endoscopically in all cases. The median operating time was 120 (40-240) min. Persistent, endoscopically uncontrollable endoluminal bleeding in one patient was successfully treated with a second TEM procedure. One patient underwent preoperative radiotherapy for adenocarcinoma detected at the preoperative assessment. Surgical histology showed a pT3 cancer in one patient who refused further surgery, a pT2 cancer in two who subsequently underwent abdominoperineal resection, a pT1 cancer in four and a ypT0 in one patient. All are at present free of disease. No patients developed faecal incontinence or urinary or sexual dysfunction. Four patients required endoscopic balloon dilatation for stenosis.

CONCLUSION

Transanal endoscopic microsurgery is a feasible and safe technique for large circumferential lesions with a satisfactory outcome. Preoperative staging may be inaccurate.

Advances in endoscopic ultrasound imaging of colorectal diseases

The development of endoscopic ultrasound (EUS) has had a significant impact for patients with digestive diseases, enabling enhanced diagnostic and therapeutic procedures, with most of the available evidence focusing on upper gastrointestinal (GI) and pancreatico-biliary diseases. For the lower GI tract the main application of EUS has been in staging rectal cancer, as a complementary technique to other cross-sectional imaging methods. EUS can provide highly accurate in-depth assessments of tumour infiltration, performing best in the diagnosis of early rectal tumours. In the light of recent developments other EUS applications for colorectal diseases have been also envisaged and are currently under investigation, including beyond-rectum tumour staging by means of the newly developed forward-viewing radial array echoendoscope. Due to its high resolution, EUS might be also regarded as an ideal method for the evaluation of subepithelial lesions. Their differential diagnosis is possible by imaging the originating wall layer and the associated echostructure, and cytological and histological confirmation can be obtained through EUS-guided fine needle aspiration or trucut biopsy. However, reports on the use of EUS in colorectal subepithelial lesions are currently limited. EUS allows detailed examination of perirectal and perianal complications in Crohn’s disease and, as a safe and less expensive investigation, can be used to monitor therapeutic response of fistulae, which seems to improve outcomes and reduce the need for additional surgery. Furthermore, EUS image enhancement techniques, such as the use of contrast agents or elastography, have recently been evaluated for colorectal indications as well. Possible applications of contrast enhancement include the assessment of tumour angiogenesis in colorectal cancer, the monitoring of disease activity in inflammatory bowel disease based on quantification of bowel wall vascularization, and differentiating between benign and malignant subepithelial tumours. Recent reports suggest that EUS elastography enables highly accurate discrimination of colorectal adenocarcinomas from adenomas, while inflammatory bowel disease phenotypes can be distinguished based on the strain ratio calculation. Among EUS-guided therapies, the drainage of abdominal and pelvic collections has been regarded as a safe and effective procedure to be used as an alternative for the transcutaneous route, while the placing of fiducial markers under EUS guidance for targeted radiotherapy in rectal cancer or the use of contrast microbubbles as drug-delivery vehicles represent experimental therapeutic applications that could greatly impact the forthcoming management of patients with colorectal diseases, pending on further investigations.

Transanal endoscopic microsurgery for rectal cancer

Since its introduction in the 1980s, total mesorectal excision (TME) has been the standard surgical technique for treating rectal cancer. This procedure involves removing the rectum and the surrounding envelope of fat along the plane of the mesorectal fascia. Resecting this embryological unit reduces the local recurrence rate by removing all local lymph nodes, including those with occult metastatic disease; however, this surgery is associated with mortality and morbidity. Complications include incontinence for patients given an anastomosis, long-term stoma formation, and sexual and bladder dysfunction. Local excision of rectal cancer using the transanal endoscopic microsurgery (TEM) technique is associated with fewer complications, and therefore, is used as an alternative in specific circumstances. We outline the technique, its indications, imaging appearances and complications.

Transanal endoscopic microsurgery: Current application and future prospects

Rectal neoplasms pose serious harm to human health. The options of surgical procedure for these patients have been limited because of the special features of anal and rectal anatomy and physiology. Tumors with a diameter less than 3 cm can be resected through the anus or soft microscope; however, those with a large diameter and wide base which are cancerous and relapse easily still need conventional laparotomy procedures. Transanal endoscopic microsurgery (TEM) was designed to avoid laparotomy for these patients. Using special instruments, TEM allows to totally resect tumors located 4-25 cm from the anus with safe margin and lower rate of complications. Because of minimal invasiveness, shorter operative time and lower rate of complications, TEM can be widely applied in rectal polyps and adenomas. Currently, there are still arguments about TEM usage in early-stage and advanced rectal cancer. This paper reviews the current situation of application and research of TEM, with emphasis put on its indications, clinical efficiency and future development.