Can CT replace MRI in preoperative assessment of the circumferential resection margin in rectal cancer?

Diagnostic Performance of MRI and FDG PET/CT for Preoperative Locoregional Staging of Colon Cancer: Systematic Review and Meta-Analysis

Background: CT is the standard-of-care test for colon cancer (CC) preoperative locoregional staging, but has limited diagnostic performance. More accurate preoperative staging would guide selection among expanding patient-tailored treatment options. Objective: To evaluate the diagnostic performance of MRI for T and N staging and of FDG PET/CT for N staging in CC locoregional staging through systematic review. Evidence Acquisition: PubMed, Embase, and Cochrane Library were searched through December 31, 2023 for studies reporting diagnostic performance of MRI or FDG PET/CT for primary (nonrectal) CC before resection without neoadjuvant therapy using histopathology as reference. Study quality was assessed using the QUADAS-2 tool. Publication bias was assessed with Deeks' funnel plot. Primary outcomes were estimated pooled predictive values, stratified by T and N categories for MRI and N categories for PET/CT. Secondary outcomes were pooled sensitivity and specificity. Evidence Synthesis: The systematic review included 11 MRI studies (686 patients) and five PET/CT studies (408 patients). Thirteen studies had at least one risk of bias or concern of applicability. Deeks' funnel plot asymmetry indicated possible publication bias in MRI studies for differentiation of T3cd-4 from T1-3ab disease and N- from N+ disease. For MRI, for discriminating T1-2 from T3-4 disease, PPV was 64.8% (95% CI [52.9-75.5%]), and NPV was 88.9% (95% CI [82.7-93.7%]); for discriminating T1-3ab from T3cd-4 disease, PPV was 83.4% (95% CI [75.0-90.3%]), and NPV was 74.6% (95% CI [58.2-86.7%]); for discriminating T1-3 from T4 disease, PPV was 94.0% (95% CI [89.4-97.3%]), and NPV was 39.9% (95% CI [24.9-56.6%]); for discriminating N- from N+ disease, PPV was 74.9% (95% CI [69.3-80.0%]), and NPV was 53.9% (95% CI [45.3-62.0%]). For PET/CT, for discriminating N- from N+ disease, PPV was 76.4% (95% CI [67.9-85.1%]), and NPV was 68.2% (95% CI [56.8-78.6%]). Across outcomes, MRI and PET/CT exhibited pooled sensitivity of 55.1-81.4% and pooled specificity of 70.3-88.1%. Conclusion: MRI had strongest predictive performance for T1-2 and T4 disease. MRI and PET/CT had otherwise limited predictive values, sensitivity, and specificity for evaluated outcomes related T and N staging. Clinical Impact: MRI and FDG PET/CT had overall limited utility for preoperative locoregional staging in colon cancer.

Artificial intelligence-assisted decision making: Prediction of optimal level of distal mesorectal margin during transanal total mesorectal excision (taTME) using deep neural network modeling

BACKGROUND

With steep posterior anorectal angulation, transanal total mesorectal excision (taTME) may have a risk of dissection in the wrong plane or starting higher up, resulting in leaving distal mesorectum behind. Although the distal mesorectal margin can be assessed by preoperative MRI, it needs skilled radiologist and high-definition image for accurate evaluation. This study developed a deep neural network (DNN) to predict the optimal level of distal mesorectal margin.

METHODS

A total of 182 pelvic MRI images extracted from the cancer image archive (TCIA) database were included. A DNN was developed using gender, the degree of anterior and posterior anorectal angles as input variables while the difference between anterior and posterior mesorectal distances from anal verge was selected as a target. The predictability power was assessed by regression values (R) which is the correlation between the predicted outputs and actual targets.

RESULTS

The anterior angle was an obtuse angle while the posterior angle varied from acute to obtuse with mean angle difference 35.5°±14.6. The mean difference between the anterior and posterior mesorectal end distances was 18.6±6.6mm. The developed DNN had a very close correlation with the target during training, validation, and testing (R=0.99, 0.81, and 0.89, P<0.001). The predicted level of distal mesorectal margin was closely correlated with the actual optimal level (R=0.91, P<0.001).

CONCLUSIONS

Artificial intelligence can assist in either making or confirming the preoperative decisions. Furthermore, the developed model can alert the surgeons for this potential risk and the necessity of re-positioning the proctectomy incision.

Progress of MRI in predicting the circumferential resection margin of rectal cancer: A narrative review

Rectal cancer (RC) is the third most frequently diagnosed cancer worldwide, and the status of its circumferential resection margin (CRM) is of paramount significance for treatment strategies and prognosis. CRM involvement is defined as tumor touching or within 1 mm from the outermost part of tumor or outer border of the mesorectal or lymph node deposits to the resection margin. The incidence of involved CRM varied from 5.4 % to 36 %, which may associate with an in consistent definition of CRM, the quality of surgeries, and the different examination modalities. Although T and N status are essential factors in determining whether a patient should receive neoadjuvant therapy before surgery, CRM status is a powerful predictor of local and distant recurrence as well as survival rate. This review explores the significance of CRM, the various assessment methods, and the role of magnetic resonance imaging (MRI) and artificial intelligence-based MRI in predicting CRM status. MRI showed potential advantage in predicting CRM status with a high sensitivity and specificity compared to computed tomography (CT). We also discuss MRI advancements in RC imaging, including conventional MRI with body coil, high-resolution MRI with phased-array coil, and endorectal MRI. Along with a discussion of artificial intelligence-based MRI techniques to predict the CRM status of RCs before and after treatments.

Precision Identification of Locally Advanced Rectal Cancer in Denoised CT Scans Using EfficientNet and Voting System Algorithms

BACKGROUND AND OBJECTIVE

Local advanced rectal cancer (LARC) poses significant treatment challenges due to its location and high recurrence rates. Accurate early detection is vital for treatment planning. With magnetic resonance imaging (MRI) being resource-intensive, this study explores using artificial intelligence (AI) to interpret computed tomography (CT) scans as an alternative, providing a quicker, more accessible diagnostic tool for LARC.

METHODS

In this retrospective study, CT images of 1070 T3-4 rectal cancer patients from 2010 to 2022 were analyzed. AI models, trained on 739 cases, were validated using two test sets of 134 and 197 cases. By utilizing techniques such as nonlocal mean filtering, dynamic histogram equalization, and the EfficientNetB0 algorithm, we identified images featuring characteristics of a positive circumferential resection margin (CRM) for the diagnosis of locally advanced rectal cancer (LARC). Importantly, this study employs an innovative approach by using both hard and soft voting systems in the second stage to ascertain the LARC status of cases, thus emphasizing the novelty of the soft voting system for improved case identification accuracy. The local recurrence rates and overall survival of the cases predicted by our model were assessed to underscore its clinical value.

RESULTS

The AI model exhibited high accuracy in identifying CRM-positive images, achieving an area under the curve (AUC) of 0.89 in the first test set and 0.86 in the second. In a patient-based analysis, the model reached AUCs of 0.84 and 0.79 using a hard voting system. Employing a soft voting system, the model attained AUCs of 0.93 and 0.88, respectively. Notably, AI-identified LARC cases exhibited a significantly higher five-year local recurrence rate and displayed a trend towards increased mortality across various thresholds. Furthermore, the model's capability to predict adverse clinical outcomes was superior to those of traditional assessments.

CONCLUSION

AI can precisely identify CRM-positive LARC cases from CT images, signaling an increased local recurrence and mortality rate. Our study presents a swifter and more reliable method for detecting LARC compared to traditional CT or MRI techniques.

Sense and non-sense of imaging in the era of organ preservation for rectal cancer

This review summarizes the current applications and benefits of imaging modalities for organ preservation in the treatment of rectal cancer. The concept of organ preservation in the treatment of rectal cancer has revolutionized the way rectal cancer is managed. Initially, organ preservation was limited to patients with locally advanced rectal cancer who needed neoadjuvant therapy to reduce tumor size before surgery and achieved complete response. However, neoadjuvant therapy is now increasingly utilized for smaller and less aggressive tumors to achieve primary organ preservation. Additionally, more intensive neoadjuvant strategies are employed to improve complete response rates and increase the chances of successful organ preservation. The selection of patients for organ preservation is a critical component of treatment, and imaging techniques such as digital rectal exam, endoscopy, and MRI are commonly used for this purpose. In this review, we provide an overview of what imaging modalities should be chosen and how they can aid in the selection and follow-up of patients undergoing organ-preserving strategies.

Rectal MRI Interpretation After Neoadjuvant Therapy

In recent years, several key advances in the management of locally advanced rectal cancer have been made, including the implementation of total mesorectal excision as the standard surgical approach; use of neoadjuvant chemoradiotherapy in selected patients with a high risk of local recurrence, and finally, adoption of organ preservation strategies, through either local excision or nonoperative management in selected patients with clinical complete response following neoadjuvant chemoradiotherapy. This review aims to shed light on the role of rectal MRI in the assessment of treatment response after neoadjuvant therapy, which is especially important given the growing feasibility of nonoperative management. First, an overview of current neoadjuvant therapies and response assessment based on digital rectal examination, endoscopy, and MRI will be provided. Second, the use of a high-quality restaging rectal MRI protocol will be presented. Third, a step-by-step approach to assessing treatment response on restaging rectal MRI following neoadjuvant treatment will be outlined, acknowledging challenges faced by radiologists during MRI interpretation. Finally, research related to response assessment will be discussed. LEVEL OF EVIDENCE: 4 TECHNICAL EFFICACY: Stage 3.

Can CT Pelvimetry Be Used to Predict Circumferential Resection Margin Positivity in Laparoscopic Resection of Middle and Lower Rectum Cancer?

Background Previous studies have shown that pelvimetry can be valuable in predicting surgical difficulties in rectal cancer operations. However, its usability in predicting circumferential resection margin (CRM) involvement remains debatable. This study investigated the factors affecting CRM status and the importance of computed tomography (CT) pelvimetry in predicting CRM involvement in laparoscopic resection of middle and lower rectal cancer. Methodology In this study, we retrospectively investigated the data of 111 patients who underwent a laparoscopic operation for middle and lower rectum cancer at Ankara University Faculty of Medicine, Department of Surgical Oncology between January 2014 and January 2020. The predictive value of CT pelvimetry and other variables on the CRM status was analyzed. Results The following four pelvic parameters differed significantly between the genders: transverse diameter of the pelvic inlet (p = 0.024), anteroposterior diameter of the pelvic outlet (p = 0.003), transverse diameter of the pelvic outlet (p < 0.001), and pelvic depth (p < 0.001). The effect of pelvic anatomic parameters on CRM involvement was not found to be significant. It was found that tumor height from the anal verge (p = 0.004), tumor size (p < 0.001), and gender (p = 0.033) were significant risk factors for CRM involvement. Survival was poor in patients with male gender (p = 0.032), perineural invasion (p < 0.001), and grade 3 tumor. Conclusions In this study, no benefit was found in predicting CRM positivity from CT pelvimetry in the laparoscopic resection of middle and lower rectal cancer. Besides, tumor height from the anal verge, tumor size, and gender were important factors for CRM positivity. Although our study sheds light on this issue, prospective randomized studies with larger sample sizes are needed.

Computed tomography and magnetic resonance imaging findings in dogs with vaginal leiomyoma and leiomyosarcoma

BACKGROUND

In humans, magnetic resonance imaging (MRI) is preferred over computed tomography (CT) for the assessment of pelvic lesions. Although CT findings of several pelvic tumours have been reported in veterinary medicine, MRI findings are limited.

OBJECTIVES

The purpose of this study was to retrospectively compare the CT and MRI findings in dogs with vaginal leiomyoma and leiomyosarcoma.

METHODS

This retrospective study of five dogs compared the CT and MRI findings of intrapelvic lesions, including vaginal leiomyoma (n = 4) and leiomyosarcoma (n = 1). No invasion of the surrounding tissue was detected on histopathological examination. In this retrospective study, the following parameters of CT and MRI were recorded for each dog: the border between the lesion and the adjacent pelvic organs, including the prostate, rectum or urethra; signal intensity (SI) of the lesion; enhancement pattern; presence of haemorrhage; necrosis or cystic areas and lymphadenopathy. Because SI on MRI is affected by cell density, tumour cell density was analysed using a microscope slide.

RESULTS

In vaginal leiomyoma, the border between the lesion and the surrounding pelvic organ tends to be clearer on MRI than on CT. In vaginal leiomyosarcoma, the border was comparable between MRI and CT. Each lesion showed heterogeneous enhancement on CT and MRI scans. In each lesion, the assessment of haemorrhage, necrosis, cystic areas and lymphadenopathy was comparable between MRI and CT. The SI of the lesion on T2WI of the vaginal leiomyoma and leiomyosarcoma were hyperintense in four cases (4/4; 100%) and mixed intense in one case (1/1; 100%), respectively. The cell density of leiomyosarcoma is higher than that of leiomyomas.

CONCLUSIONS

The SI on T2WI may be useful for differentiating leiomyoma from leiomyosarcoma. MRI may be useful to differentiate vaginal leiomyomas from leiomyosarcomas and evaluate margins.

The importance of MRI for rectal cancer evaluation

Magnetic resonance imaging (MRI) has gained increasing importance in the management of rectal cancer over the last two decades. The role of MRI in patients with rectal cancer has expanded beyond the tumor-node-metastasis (TNM) system in both staging and restaging scenarios and has contributed to identifying "high" and "low" risk features that can be used to tailor and personalize patient treatment; for instance, selecting the patients for neoadjuvant chemoradiation (NCRT) before the total mesorectal excision (TME) surgery based on risk of recurrence. Among those features, the status of the circumferential resection margin (CRM), extramural vascular invasion (EMVI), and tumor deposits (TD) have stood out. Moreover, MRI also has played a role in surgical planning, especially when the tumor is located in the low rectum, when the relationship between tumor and the anal canal is important to choose the best surgical approach, and in cases of locally advanced or recurrent tumors invading adjacent pelvic organs that may require more complex surgeries such as pelvic exenteration. As approaches using organ preservation emerge, including transanal local excision and "watch-and-wait", MRI may help in the patient selection for those treatments, follow up, and detection of tumor regrowth. Additionally, potential MRI-based prognostic and predictive biomarkers, such as quantitative and semi-quantitative metrics derived from functional sequences like diffusion-weighted imaging (DWI) and dynamic contrast-enhanced (DCE), and radiomics, are under investigation. This review provides an overview of the current role of MRI in rectal cancer in staging and restaging and highlights the main areas under investigation and future perspectives.

Accuracy of High Resolution Multidetector Computed Tomography in the Local Staging of Rectal Cancer

Background Magnetic resonance imaging (MRI) is the gold standard for local staging of rectal cancer. Advanced computed tomography (CT) machines are now capable of high-resolution images of rectal cancer and utilized for CT perfusion. The possibility of local staging of rectal cancer by CT needs to be explored.

Purpose The aim of the study is to evaluate accuracy of high-resolution CT for local rectal cancer staging.

Methods A high-resolution CT was performed for local staging of rectal cancer in our study group of 93 patients, where 64 underwent primary surgery and 29 underwent surgery post neoadjuvant chemoradiotherapy (NACRT).

Results In differentiating stages T2-and-less than T2 from T3–T4 rectal cancer, accuracy, sensitivity, specificity, and kappa score in overall patients were 91%, 87%, 94%, and 0.8; in primary surgery group were 89%, 76%, 94%, and 0.7; in NACRT group were 97%, 100%, 94%, and 0.9; in low rectal group were 94%, 89%, 97%, and 0.82, respectively.

Conclusion High resolution CT is an accurate tool for local staging of rectal cancer.

Local Staging of Colon Cancer: A Cross-Sectional Analysis for Diagnostic Performance of Magnetic Resonance Imaging and by Experience

Preoperative magnetic resonance imaging was analyzed by four radiologists regarding local tumor staging (T and N) and the presence of extramural vascular involvement. An astonishingly high sensitivity for the detection of T 3/4 tumors (κ (quadratic weighted statistics constant) = 0.67), with considerably lower sensitivity for T 3 cd/4 tumors (κ = 0.51), high sensitivity for serosal involvement 76-87% (κ = 0.65) and extramural vascular involvement (87-98%, κ = 0.56). Sensitivity and specificity for lymph node involvement is lower (κ = 0.57). Magnetic resonance imaging with adequate experience can accurately detect tumors with invasion through the bowel wall and their prognostic factors.

Radiological staging of rectal cancer in a resource limited setting

Objective

Current guidelines on rectal cancer (RC) management recommend pre-operative MRI for loco-regional staging and CT for staging of metastases. This allows appropriate selection of patients for chemo-radiotherapy (CRT). However, MRI is not freely available in many low-income countries. We assessed the status of pre-operative imaging for RC in Sri Lanka and evaluated the performance of CT in RC staging.

Results

A pre-tested interview-administered questionnaire was used to assess the pre-operative use of MRI and CT in RC. CT findings from 37 RC patients were then compared with histopathology findings. Of the 64 surgeons interviewed, 57 (89.1%) did not request an MRI for their RC patients. Reasons cited included limited availability and long waiting times due to competing health needs. A CT was requested by all. In RC, the overall accuracy of CT for T staging was 43.2% and 29.7% of T1–T2 tumours were over-staged as T3. The overall accuracy of CT for regional lymph node staging was 70.3%. In summary, CT alone is not suitable for RC staging in any setting. It leads to over-staging and patients may thus receive unnecessary CRT. Steps must be taken to improve access to pre-operative MRI among Sri Lankan RC patients.

Imaging and Management of Rectal Cancer

High-resolution phased array external magnetic resonance imaging (MRI) is the first investigation of choice in rectal cancer for local staging, both in the primary and restaging situations. Use of MRI helps differentiate between those with good prognosis, which can be offered upfront surgery and the poor prognostic cases where treatment intensification is needed. MRI identified poor prognostic factors are threatened or involved mesorectal fascia, T3 tumors with >5 mm extramural spread, those with extramural vascular invasion, pelvic sidewall nodes and mucinous tumors. At restaging, use of MRI helps evaluate response and an MR tumor regression grading system is being evaluated. Complete response seen on clinical examination and endoscopy, needs confirmation on MRI using both T2-weighted and diffusion-weighted sequences to justify a "watch and wait" approach. In this subset of patients, MRI also plays a role in monitoring and detecting early regrowth. In those with partial response, MRI helps define surgical margins and can be used as a roadmap to decide between sphincter preserving surgeries and radical sphincter sacrificing surgeries; pelvic exenteration and pelvic sidewall lymph node dissection. Poor responders on MRI may benefit from adjuvant chemotherapy. Use of MRI thus helps in individualizing treatment in rectal cancer.

Role of the status of the mesorectal fascia in the selection of patients with rectal cancer for preoperative radiation therapy: a retrospective cohort study

Background

Patients with rectal cancer in whom the mesorectal fascia is threatened by tumour are more likely than all patients with stage II/III disease to benefit from preoperative radiotherapy (RT). The objective of this study was to assess whether the status of the mesorectal fascia versus a stage II/III designation can best inform the use of preoperative RT in patients undergoing major rectal cancer resection.

Methods

We reviewed the charts of consecutive patients with primary rectal cancer treated by a single surgeon at McMaster University, Hamilton, Ontario, between March 2006 and December 2012. The status of the mesorectal fascia was assessed by digital rectal examination, pelvic computed tomography and, when needed, pelvic magnetic resonance imaging (MRI). Patients whose mesorectal fascia was threatened or involved by tumour received preoperative RT. The study outcomes were rates of positive circumferential radial margin (CRM) and local tumour recurrence.

Results

A total of 153 patients were included, of whom 76 (49.7%) received preoperative RT because of concerns of a compromised mesorectal fascia. The median length of follow-up was 4.5 years. The number of CRM-positive cases in the RT and no-RT groups was 16 (22%) and 1 (1%), respectively (p < 0.01), and the number of cases of local tumour recurrence was 5 (7%) and 2 (3%), respectively (p = 0.2). Rates were similar when only patients with stage II/III tumours were included. Overall, 26 patients (17.0%) received MRI.

Conclusion

The status of the mesorectal fascia, not tumour stage, may best identify patients for preoperative RT.

Evaluation of anatomical landmarks for transanal total mesorectal excision based on MRI

BACKGROUND

Transanal total mesorectal excision (taTME) is a novel sphincter-preserving procedure for low rectal cancer. This "bottom to up" approach is unfamiliar to colorectal surgeons and the crucial anatomical landmarks also remain unclear.

METHODS

Two hundred and five cases of pelvic magnetic resonance imaging (MRI) from 2015 to 2016 were reviewed. Curvature of posterior mesorectal fascia, distal mesorectal angle, length of posterior mesorectal fascia, main structures around the mesorectum were measured and analyzed. The landmarks identified on MRI were verified in taTME procedures of five rectal cancer patients.

RESULTS

The most of acute angles of posterior mesorectal fascia located at the joint of anococcygeal ligament-coccyx. Degree of distal mesorectal angle was independently correlated with gender and degree of angle of anococcygeal ligament-coccyx. Candidate landmarks evaluated by MRI with verification during taTME procedures included: anterior: seminal vesicle for male while cervix for female. And peritoneal reflection was a substitute landmark when cervix was hardly confirmed in operation; posterior: the joint of anococcygeal ligament-coccyx. The area between the joint of anococcygeal ligament-coccyx and S3S4 was a "transitional zone", the level of S3S4 could be the as the terminal landmark of transanal posterior dissection during taTME.

CONCLUSIONS

Preoperative MRI geometrical measurement of mesorectum might play an important role in evaluating the difficulty of taTME procedure before operation, as well as standardizing landmarks during taTME procedure.

Magnetic resonance-based pelvimetry and tumor volumetry can predict surgical difficulty and oncologic outcome in locally advanced mid-low rectal cancer

PURPOSE

To investigate the impact of the pelvic dimensions and tumor volume on surgery in locally advanced rectal cancer.

METHODS

Patients who underwent open surgery after neoadjuvant long-course chemoradiation for primary rectal cancer were included. The predictive value of magnetic resonance-based pelvic measurements and tumor volume on the surgical difficulty and oncologic outcome were analyzed.

RESULTS

125 patients were included. The independent risk factors related to the circumferential resection margin status were the pT stage [odds ratio (OR) 3.64, confidence interval (CI) 1.409-7.327] and tumor volume after neoadjuvant chemoradiotherapy (OR 1.59, CI 1.018-2.767). The operative time (p = 0.014, OR 1.453) and pelvic depth (p = 0.023, OR 1.116) were independent predictive factors for anastomotic leak. The median follow-up was 72 (2-113) months. Local recurrence was seen in 17 (14.1%) patients. Anastomotic leak (OR 1.799, CI 0.978-3.277), the circumferential resection margin status (OR 3.217, CI 1.262-7.870) and the relative tumor volume rate (OR 1.260, CI 1.004-1.912) were independent prognosticators of local recurrence. The 5-year overall survival was 66.7%. The circumferential resection margin status (hazard ratio: 4.739, CI 2.276-9.317), pN stage (OR 3.267, CI 1.195-8.930) and relative tumor volume rate (OR 2.628, CI 1.042-6.631) were independent prognostic factors for the overall survival.

CONCLUSIONS

Relative dimensions of the tumor in the pelvis influence the local recurrence and overall survival rates. Magnetic resonance-based measurements can predict the difficulty of surgery and allow surgeons to consider the appropriate surgical approach.

Quality of preoperative pelvic computed tomography (CT) and magnetic resonance imaging (MRI) for rectal cancer in a region in Ontario: A retrospective population-based study

BACKGROUND AND OBJECTIVES

Treatment decisions for rectal cancer rely on preoperative staging with CT and MRI scans. We assessed the quality of such scans in a region of Ontario.

METHODS

We retrospectively collected data for patients undergoing rectal cancer surgery between July 2011 and December 2014. We measured three aspects of quality: use; comprehensiveness of reporting T-category, N-category, mesorectal fascia (MRF) status; and in non-radiated patients sensitivity and specificity of reports for relevant elements.

RESULTS

A total of 559 patients underwent major rectal cancer surgery. Preoperative staging with CT and MRI was performed in 93% and 50% of patients. CT scan reports provided information on T-category, N-category, and MRF status in 41%, 92%, and 16% of cases. These same elements were reported on MRI in 88%, 93%, and 62% of cases. CT scan sensitivity and specificity was 80% and 80% for T-category, and 85% and 39% for N-category. MRI sensitivity and specificity was 75% and 81% for T-category, 79% and 37% for N-category, and 33% and 89% for MRF status.

CONCLUSION

In this region of Ontario, pre-operative MRI was underutilized, CT reporting of MRF status was low, and when reported sensitivity and specificity of T- and N-category were similar for CT and MRI.

MRI for Local Staging of Colon Cancer: Can MRI Become the Optimal Staging Modality for Patients With Colon Cancer?

BACKGROUND

Colon cancer is currently staged with CT. However, MRI is superior in the detection of colorectal liver metastasis, and MRI is standard in local staging of rectal cancer. Optimal (local) staging of colon cancer could become crucial in selecting patients for neoadjuvant treatment in the near future (Fluoropyrimidine Oxaliplatin and Targeted Receptor Preoperative Therapy trial).

OBJECTIVE

The purpose of this study was to evaluate the diagnostic performance of MRI for local staging of colon cancer.

DESIGN

This was a retrospective study.

SETTINGS

The study was conducted at the Maastricht University Medical Centre.

PATIENTS

In total, 55 patients with biopsy-proven colon carcinoma were included.

MAIN OUTCOME MEASURES

All of the patients underwent an MRI (1.5-tesla; T2 and diffusion-weighted imaging) of the abdomen and were retrospectively analyzed by 2 blinded, independent readers. Histopathology after resection was the reference standard. Both readers evaluated tumor characteristics, including invasion through bowel wall (T3/T4 tumors), invasion beyond bowel wall of ≥5 mm and/or invasion of surrounding organs (T3cd/T4), serosal involvement, extramural vascular invasion, and malignant lymph nodes (N+). Interobserver agreement was compared using κ statistics.

RESULTS

MRI had a high sensitivity (72%-91%) and specificity (84%-89%) in detecting T3/T4 tumors (35/55) and a low sensitivity (43%-67%) and high specificity (75%-88%) in detecting T3cd/T4 tumors (15/55). For detecting serosal involvement and extramural vascular invasion, MRI had a high sensitivity and moderate specificity, as well as a moderate sensitivity and specificity in the detection of nodal involvement. Interobserver agreements were predominantly good; the more experienced reader achieved better results in the majority of these categories.

LIMITATIONS

The study was limited by its retrospective nature and moderate number of inclusions.

CONCLUSIONS

MRI has a good sensitivity for tumor invasion through the bowel wall, extramural vascular invasion, and serosal involvement. In addition, together with its superior liver imaging, MRI might become the optimal staging modality for colon cancer. However, more research is needed to confirm this. See Video Abstract at http://links.lww.com/DCR/A309.

Effectiveness of a Tailored Anterior Saturation Band in the Improvement of the Image Quality of Pelvic Magnetic Resonance for Assessing Rectal Cancer

PURPOSE

We sought to test the effectiveness of the application of a tailored anterior saturation band (ASB) to improve the image quality of pelvic magnetic resonance imaging (MRI) for assessing rectal cancer.

METHODS

A total of 165 patients with MRI assessment of rectal cancer between 2013 and 2015 were included. The image quality scores (4-point scale: 1, nondiagnostic through 4, excellent) of MRI without and with tailored ASBs were compared. Sensitivity, specificity, positive and negative predictive values, and accuracy of pelvic MRIs with and without a tailored ASB for T-staging in 65 patients with direct surgery and 67 patients with chemoradiotherapy before surgery were evaluated.

RESULTS

Two independent raters exhibited moderate-to-excellent interobserver agreements (κ = 0.529-0.879) in the grading of MRI image quality. Overall, the quality scores of sagittal and axial T2-weighted images with tailored ASBs were significantly improved compared with MRIs without ASBs (3.5 ± 0.3 vs. 2.7 ± 0.8 [mean ± SD]; P < .001, and 3.6 ± 0.3 vs. 2.8 ± 0.8; P < .001, respectively). The application of tailored ASBs in MRIs improved the averaged accuracies for staging of ≤ T2, T3, and T4 tumors from 87.7%, 78.5%, and 90.8% to 93.1%, 86.9%, and 97.7%, respectively. In post-chemoradiotherapy MRI follow-ups, the use of tailored ASBs also improved the average accuracies for staging of yT0, yT1-2, yT3, and yT4 tumors from 80.6%, 73.1%, 73.9%, and 91.0%, to 85.8%, 82.9%, 85.1%, and 94.0%, respectively.

CONCLUSIONS

Application of a tailored ASB in pelvic MRI is effective in substantially reducing motion artifacts, significantly upgrading image quality, and improving accuracies of rectal tumor staging.

Imaging Procedures for Colorectal Cancer

BACKGROUND

Radiological imaging plays an important role in the setting of staging, follow-up, and imaging-guided treatment of colorectal carcinoma (CRC).

METHODS

This review aims to summarize the current state of the art of the different radiological imaging procedures in CRC including an overview over recently published national and European guidelines and consensus statements concerning the imaging of CRC patients.

RESULTS AND CONCLUSION

Radiological imaging is widely embedded in national and international guidelines, and structured reporting is recommended.

Rectal cancer staging: Multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion

AIM: To assess the diagnostic accuracy of multidetector-row computed tomography (MDCT) as compared with conventional magnetic resonance imaging (MRI), in identifying mesorectal fascia (MRF) invasion in rectal cancer patients.

METHODS: Ninety-one patients with biopsy proven rectal adenocarcinoma referred for thoracic and abdominal CT staging were enrolled in this study. The contrast-enhanced MDCT scans were performed on a 256 row scanner (ICT, Philips) with the following acquisition parameters: tube voltage 120 KV, tube current 150-300 mAs. Imaging data were reviewed as axial and as multiplanar reconstructions (MPRs) images along the rectal tumor axis. MRI study, performed on 1.5 T with dedicated phased array multicoil, included multiplanar T2 and axial T1 sequences and diffusion weighted images (DWI). Axial and MPR CT images independently were compared to MRI and MRF involvement was determined. Diagnostic accuracy of both modalities was compared and statistically analyzed.

RESULTS: According to MRI, the MRF was involved in 51 patients and not involved in 40 patients. DWI allowed to recognize the tumor as a focal mass with high signal intensity on high b-value images, compared with the signal of the normal adjacent rectal wall or with the lower tissue signal intensity background. The number of patients correctly staged by the native axial CT images was 71 out of 91 (41 with involved MRF; 30 with not involved MRF), while by using the MPR 80 patients were correctly staged (45 with involved MRF; 35 with not involved MRF). Local tumor staging suggested by MDCT agreed with those of MRI, obtaining for CT axial images sensitivity and specificity of 80.4% and 75%, positive predictive value (PPV) 80.4%, negative predictive value (NPV) 75% and accuracy 78%; while performing MPR the sensitivity and specificity increased to 88% and 87.5%, PPV was 90%, NPV 85.36% and accuracy 88%. MPR images showed higher diagnostic accuracy, in terms of MRF involvement, than native axial images, as compared to the reference magnetic resonance images. The difference in accuracy was statistically significant (P = 0.02).

CONCLUSION: New generation CT scanner, using high resolution MPR images, represents a reliable diagnostic tool in assessment of loco-regional and whole body staging of advanced rectal cancer, especially in patients with MRI contraindications.

Clinical practice guidelines for the surgical treatment of rectal cancer: a consensus statement of the Hellenic Society of Medical Oncologists (HeSMO)

In rectal cancer management, accurate staging by magnetic resonance imaging, neo-adjuvant treatment with the use of radiotherapy, and total mesorectal excision have resulted in remarkable improvement in the oncological outcomes. However, there is substantial discrepancy in the therapeutic approach and failure to adhere to international guidelines among different Greek-Cypriot hospitals. The present guidelines aim to aid the multidisciplinary management of rectal cancer, considering both the local special characteristics of our healthcare system and the international relevant agreements (ESMO, EURECCA). Following background discussion and online communication sessions for feedback among the members of an executive team, a consensus rectal cancer management was obtained. Statements were subjected to the Delphi methodology voting system on two rounds to achieve further consensus by invited multidisciplinary international experts on colorectal cancer. Statements were considered of high, moderate or low consensus if they were voted by ≥80%, 60-80%, or <60%, respectively; those obtaining a low consensus level after both voting rounds were rejected. One hundred and two statements were developed and voted by 100 experts. The mean rate of abstention per statement was 12.5% (range: 2-45%). In the end of the process, all statements achieved a high consensus. Guidelines and algorithms of diagnosis and treatment were proposed. The importance of centralization, care by a multidisciplinary team, adherence to guidelines, and personalization is emphasized.

Comparison of computed tomography and magnetic resonance imaging in the discrimination of intraperitoneal and extraperitoneal rectal cancer: initial experience

OBJECTIVES

To compare computed tomography (CT) and magnetic resonance imaging (MRI) in evaluation of intraperitoneal/extraperitoneal location of rectal cancers.

METHODS AND MATERIALS

We assessed the identification of the anterior peritoneal reflection (APR) and the distance from the inferior edge of tumors to the anal verge and from the APR to the anal verge.

RESULTS

Distances obtained with CT and MRI showed a strong correlation [Spearman's coefficient of rank correlation (rho): 0.995; P<.0001]. Magnetic resonance showed sensitivity of 100% (95% CI: 89.62-100.00%), specificity of 75% (95% CI: 20.34-95.88%), positive predictive value (PPV) of 97.14% (95% CI: 85.03-99.52%), and negative predictive value (NPV) of 100% (95% CI: 30.48-100.00%). CT showed a sensitivity of 100% (95% CI: 89.32-100.00%), specificity of 60% (95% CI: 15.40-93.51%), PPV of 94.29% (95% CI: 80.81-99.13%), and NPV of 100% (95% CI: 30.48-100.00%).

CONCLUSIONS

CT demonstrated a potential supporting role in the evaluation of rectal cancer, showing a strong correlation with MRI.

Imaging in rectal cancer with emphasis on local staging with MRI

Imaging in rectal cancer has a vital role in staging disease, and in selecting and optimizing treatment planning. High-resolution MRI (HR-MRI) is the recommended method of first choice for local staging of rectal cancer for both primary staging and for restaging after preoperative chemoradiation (CT-RT). HR-MRI helps decide between upfront surgery and preoperative CT-RT. It provides high accuracy for prediction of circumferential resection margin at surgery, T category, and nodal status in that order. MRI also helps assess resectability after preoperative CT-RT and decide between sphincter saving or more radical surgery. Accurate technique is crucial for obtaining high-resolution images in the appropriate planes for correct staging. The phased array external coil has replaced the endorectal coil that is no longer recommended. Non-fat suppressed 2D T2-weighted (T2W) sequences in orthogonal planes to the tumor are sufficient for primary staging. Contrast-enhanced MRI is considered inappropriate for both primary staging and restaging. Diffusion-weighted sequence may be of value in restaging. Multidetector CT cannot replace MRI in local staging, but has an important role for evaluating distant metastases. Positron emission tomography-computed tomography (PET/CT) has a limited role in the initial staging of rectal cancer and is reserved for cases with resectable metastatic disease before contemplating surgery. This article briefly reviews the comprehensive role of imaging in rectal cancer, describes the role of MRI in local staging in detail, discusses the optimal MRI technique, and provides a synoptic report for both primary staging and restaging after CT-RT in routine practice.

Factors influencing response to neoadjuvant chemoradiation and outcomes in rectal cancer patients: tertiary Indian cancer hospital experience

BACKGROUND

In the treatment of rectal cancers several randomized trials have demonstrated benefits of neoadjuvant chemoradiotherapy (NACRT) in downstaging as well as survival among these patients. We investigated the patient and tumor related variables dictating the outcomes in these patients.

METHODS

Biopsy proven treatment naive 182 rectal cancer patients underwent NACRT from June 2006 to December 2010. The entire patients received long course conventionally fractionated external beam radiotherapy with concurrent oral Capecitabine. At 6 weeks from completion of NACRT clinico-radiological assessment was carried out for surgical feasibility. All patients were given postoperative adjuvant chemotherapy either single agent or multi drug regimen depending upon biopsy report.

RESULTS

Among 182 patients, 131 (72%) underwent surgery and initial T stage and signet ring cell morphology were major determinant of operability. Among the 131 operated patients at median follow up of 36 months, 94 (72%) are alive and disease free. With a median follow up of 42 months the 5-year disease free survival (DFS) and overall survival (OS) was 60% and 77%. The majority of the failures were distal but with more advanced disease at presentation both local and distal failures were similar. While assessing survival by multivariate analysis patients having positive nodes post-surgery had a significantly poorer DFS (P=0.001), while signet ring cell morphology and pre-treatment carcino-embryonic antigen (CEA) levels strongly influenced OS (P=0.03).

CONCLUSIONS

The outcome of our patients were similar to World Literature and signet ring cell morphology, pre-treatment CEA level, and pathological nodal staging all were influential in determining survival. Besides this, the study also highlights the fact that tumours with signet ring cell morphology appearing in younger population with poor survival needs prospective evaluation for more intense CRT regimen and aggressive surgical resections.

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.

Effectiveness of MRI for the assessment of mesorectal fascia involvement in patients with rectal cancer: a systematic review and meta-analysis

AIMS

Defining the most appropriate definition of mesorectal fascia involvement (MRF+) by reviewing literature and using new inclusion criteria to re-evaluate the effectiveness of MRI in the assessment of MRF+ for rectal cancer.

METHODS

PubMed, Medline, Embase, and the Cochrane Library databases were electronically searched from 1999 to 2012. The bivariate random effects model was used to estimate the pooled outcomes of each subgroup. The definition of MRF+ in MRI and the influence of neoadjuvant chemoradiotherapy (neo-ChRT) were especially discussed.

RESULTS

Fourteen studies involving 1,600 patients were included. Different definitions of MRF+ (≤ 1, ≤ 2 and ≤ 5 mm) in MRI exhibited different pooled sensitivity (76, 79 and 92%), specificity (88, 66 and 48%) and diagnostic odds ratio (DOR) (22.4, 6.6 and 16.0). The definition of MRF+ at ≤ 1 mm showed the highest DOR. The specificity (88 vs. 93%, p = 0.026) and DOR (15.5 vs. 39.0, p = 0.001) were lower in patients who underwent neo-ChRT than those who did not while using ≤ 1 mm as the definition of MRF+. However, the sensitivity showed no significant difference (67 vs. 74%, p = 0.129).

CONCLUSIONS

MRI is valuable for the assessment of MRF. The most appropriate definition of MRF+ in MRI is ≤ 1 mm. The effectiveness is higher in patients who did not undergo neo-ChRT.

Multimodal imaging evaluation in staging of rectal cancer

Rectal cancer is a common cancer and a major cause of mortality in Western countries. Accurate staging is essential for determining the optimal treatment strategies and planning appropriate surgical procedures to control rectal cancer. Endorectal ultrasonography (EUS) is suitable for assessing the extent of tumor invasion, particularly in early-stage or superficial rectal cancer cases. In advanced cases with distant metastases, computed tomography (CT) is the primary approach used to evaluate the disease. Magnetic resonance imaging (MRI) is often used to assess preoperative staging and the circumferential resection margin involvement, which assists in evaluating a patient’s risk of recurrence and their optimal therapeutic strategy. Positron emission tomography (PET)-CT may be useful in detecting occult synchronous tumors or metastases at the time of initial presentation. Restaging after neoadjuvant chemoradiotherapy (CRT) remains a challenge with all modalities because it is difficult to reliably differentiate between the tumor mass and other radiation-induced changes in the images. EUS does not appear to have a useful role in post-therapeutic response assessments. Although CT is most commonly used to evaluate treatment responses, its utility for identifying and following-up metastatic lesions is limited. Preoperative high-resolution MRI in combination with diffusion-weighted imaging, and/or PET-CT could provide valuable prognostic information for rectal cancer patients with locally advanced disease receiving preoperative CRT. Based on these results, we conclude that a combination of multimodal imaging methods should be used to precisely assess the restaging of rectal cancer following CRT.

The accuracy of multi-detector row computerized tomography in staging rectal cancer compared to endoscopic ultrasound

BACKGROUND/AIM

Our aim was to evaluate the diagnostic accuracy of multi-detector row computerized tomography (MDCT) in staging of rectal cancer by comparing it to rectal endoscopic ultrasound (EUS).

MATERIALS AND METHODS

We prospectively included all patients with rectal cancer referred to our gastroenterology unit for staging of rectal cancer from December 2007 until February 2011, 53 patients whose biopsy had proven rectal cancer underwent both MDCT scan of the pelvis and rectal EUS. Both imaging modalities were compared and the agreement between T- and N-staging of the disease was assessed.

RESULTS

We staged 62 patients with rectal cancer during the study period. Of these, 53 patients met the inclusion criteria and were evaluated (25 women and 28 men). The mean age was 57.79 ± 14.99 years (range 21-87). MDCT had poor accuracy compared with EUS in T-staging with a low degree of agreement (kappa = 0.26), while for N-staging MDCT had a better accuracy and a moderate degree of agreement with EUS (kappa = 0.45).

CONCLUSIONS

MDCT has a poor accuracy for predicting tumor invasion compared to EUS for T-staging while it has moderate accuracy for N-staging.

[Rectal cancer - local staging and imaging under neoadjuvant therapy]

CLINICAL/METHODICAL ISSUE

Rectal cancer restaging after neoadjuvant therapy is based on two principles: an anatomic definition of the tumor allowing surgical planning and prognostic stage grouping.

STANDARD RADIOLOGICAL METHODS

Emerging data suggest that reassessment using a combination of different imaging modalities may help to provide valuable prognostic information before definitive surgery.

METHODICAL INNOVATIONS

Perfusion computed tomography (CT) may provide special information regarding tumor vascularity.

PERFORMANCE

Evaluation of therapy response, especially of the circumferential resection margin (CRM) is necessary for surgical planning.

ACHIEVEMENTS

For local staging high-resolution and diffusion-weighted magnetic resonance imaging has proven to be of high diagnostic accuracy.

PRACTICAL RECOMMENDATIONS

The M status should be assessed using multidetector computed tomography (MDCT) according to response evaluation criteria in solid tumors (RECIST) while lymph node evaluation requires either magnetic resonance imaging or positron emission tomography/computed tomography scanning.

[Local diagnostics for rectal cancer. What is realistic?]

Accurate pretherapeutic staging of rectal cancer is crucial for further therapeutic management and important for prognosis. The most accurate diagnostic tools in the assessment of T and N categories of rectal cancer are endorectal ultrasound (EUS) and magnetic resonance imaging (MRI). Furthermore, MRI can accurately predict the distance of the tumor to the colorectal membrane (CRM) and computed tomography (CT) is more suitable for detecting distant metastases. In the routine care of rectal cancer EUS is the most frequently used diagnostic tool for local staging. The achieved accuracy for determining T category by EUS in routine clinical staging is lower than results reported in the literature. Furthermore, the accuracy of EUS depends on the experience of the examiner. Currently the frequency of using MRI for routine clinical staging of rectal cancer is low and in one out of five cases the local staging of rectal cancer is exclusively carried out by CT.

Shifting concepts in rectal cancer management: a review of contemporary primary rectal cancer treatment strategies

The management of rectal cancer has transformed over the last 3 decades and continues to evolve. Some of these changes parallel progress made with other cancers: refinement of surgical technique to improve organ preservation, selective use of neoadjuvant (and adjuvant) therapy, and emergence of criteria suggesting a role for individually tailored therapy. Other changes are driven by fairly unique issues including functional considerations, rectal anatomic features, and surgical technical issues. Further complexity is due to the variety of staging modalities (each with its own limitations), neoadjuvant treatment alternatives, and competing strategies for sequencing multimodal treatment even for nonmetastatic disease. Importantly, observations of tumor response made in the era of neoadjuvant therapy are reshaping some traditionally held concepts about tumor behavior. Frameworks for prioritizing and integrating complex data can help to formulate treatment plans for patients.

[The role of cross-sectional imaging in staging of rectal cancer]

The ongoing diversification of treatment strategies for rectal cancer justifies the demand for highly specialized radiological imaging. Currently, numerous studies have underlined the ability of magnetic resonance imaging (MRI) to determine those parameters that are critical for therapeutic decision-making and prognosis in rectal cancer. Computed tomography (CT) does not meet the criteria of a first line diagnostic procedure with regard to local staging but will remain the workhorse in the search for distant metastases. The increasing acceptance of extended MRI-based concepts will, however, improve cost-effectiveness and simplify patient management. Response evaluation and detection of recurrent disease are the major indications for positron emission tomography (PET)/CT, which is currently not routinely recommended.

Primary staging and response assessment postchemoradiotherapy in rectal cancer

SUMMARY Initial assessment of newly diagnosed patients with rectal cancer includes clinical examination, colonoscopy, pelvic MRI and CT scan of the thorax, abdomen and pelvis. Radiological staging can objectively evaluate both surgical and biological prognostic features of rectal cancer. MRI has emerged to be the most useful preoperative prognostic staging tool and it can predict the risk of tumor involvement of surgical circumferential resection margin. An agreed definition of favorable tumor response to chemoradiotherapy is controversial. The importance of detecting and assessing good versus poor responders to chemoradiotherapy is of increasing relevance. MRI has been found to be useful in assessing tumor response postchemoradiotherapy, especially the assessment of potential circumferential resection margin and magnetic resonance tumor regression grade. These imaging markers predict survival outcomes for good and poor responders and provide an opportunity for clinicians to offer additional neoadjuvant and adjuvant treatments to reduce local or distance failure for the poor responders.

Rectal cancer: primary staging and assessment after chemoradiotherapy

Rectal cancer staging is based on 2 principles. The first is an anatomic definition of the tumor allowing for surgical planning. The second is prognostic stage grouping. A given prognostic stage carries different risks of both local and distant recurrence, a selective and tailored approach to preoperative therapy is appropriate. Increasingly, selective approaches enable an overall reduction in morbidity from overtreatment, while allowing aggressive treatment of high-risk patients. Therefore, the aim of preoperative staging is to accurately and reproducibly differentiate between good and poor prognosis tumors. In the preoperative setting, superficial and flat rectal cancers are probably best initially staged using endoscopic ultrasound, and where available magnetic resonance imaging is used for all other rectal cancers because of its proven high sensitivity and specificity in identifying poor-risk patients based on circumferential margin status, the depth of extramural spread, extramural venous invasion, and nodal status. Restaging after neoadjuvant therapy is a challenge to all modalities because of radiation-induced changes, namely fibrosis, edema, inflammation, and necrosis. However, emerging data suggest that reassessment using a combination of high-resolution magnetic resonance imaging, diffusion-weighted imaging, and positron emission tomography/computed tomography scanning may help to provide valuable prognostic information before definitive surgery.

Outcomes following a limited approach to radiotherapy in rectal cancer

BACKGROUND

Variation in the use of neoadjuvant and adjuvant radiotherapy for rectal cancer suggests an opportunity to avoid it in all but patients at highest risk of local recurrence.

METHODS

Between 1 July 1999 and 1 February 2006, patients with primary rectal cancer were treated by a single surgeon operating at McMaster University, Hamilton, Ontario, Canada. Digital rectal examination and pelvic computed tomography were used to determine whether the mesorectal margin was threatened by tumour and thus whether preoperative radiotherapy would be needed. The study outcome was local tumour recurrence.

RESULTS

Forty-six (48 per cent) of 96 patients received preoperative radiation therapy. The median follow-up was 4·2 years. Tumours were fixed or tethered in 31 (67 per cent) of the 46 irradiated patients. In contrast, no tumour was fixed in unirradiated patients and only ten (20 per cent) of the 50 tumours were tethered. The proportion of patients with stage I or II tumours based on final pathology was similar: 61 per cent (28 of 46) and 56 per cent (28 of 50) in irradiated and unirradiated groups respectively (P = 0·287). There were four (9 per cent) and two (4 per cent) local recurrences among irradiated and unirradiated patients respectively (P = 0·422).

CONCLUSION

Limiting preoperative radiotherapy in rectal cancer to patients with a threatened circumferential margin does not compromise patient outcome.

Current trends in staging rectal cancer

Management of rectal cancer has evolved over the years. In this condition preoperative investigations assist in deciding the optimal treatment. The relation of the tumor edge to the circumferential margin (CRM) is an important factor in deciding the need for neoadjuvant treatment and determines the prognosis. Those with threatened or involved margins are offered long course chemoradiation to enable R₀ surgical resection. Endoanal ultrasound (EUS) is useful for tumor (T) staging; hence EUS is a useful imaging modality for early rectal cancer. Magnetic resonance imaging (MRI) is useful for assessing the mesorectum and the mesorectal fascia which has useful prognostic significance and for early identification of local recurrence. Computerized tomography (CT) of the chest, abdomen and pelvis is used to rule out distant metastasis. Identification of the malignant nodes using EUS, CT and MRI is based on the size, morphology and internal characteristics but has drawbacks. Most of the common imaging techniques are suboptimal for imaging following chemoradiation as they struggle to differentiate fibrotic changes and tumor. In this situation, EUS and MRI may provide complementary information to decide further treatment. Functional imaging using positron emission tomography (PET) is useful, particularly PET/CT fusion scans to identify areas of the functionally hot spots. In the current state, imaging has enabled the multidisciplinary team of surgeons, oncologists, radiologists and pathologists to decide on the patient centered management of rectal cancer. In future, functional imaging may play an active role in identifying patients with lymph node metastasis and those with residual and recurrent disease following neoadjuvant chemoradiotherapy.