Rationale for Imaging Referral Guidelines in Rectal Cancer Patients

Abstract

Rectal carcinoma is an important cause of cancer-related morbidity and mortality worldwide, with an increasing incidence among young patients. Rectal cancers differ anatomically from other colonic cancers due to their proximity to critical pelvic structures like the anal sphincters and urinary bladder. Advances in surgical techniques (total mesorectal excision) and the introduction of neoadjuvant chemoradiotherapy have improved survival, reduced recurrence, and significantly reduced postoperative incontinence in these patients.

Imaging is crucial for preoperative staging and prognostication, defining surgical planes, planning and assessing response to neoadjuvant therapy, and long-term surveillance. High-resolution pelvic magnetic resonance is considered the workhorse for evaluating rectal carcinoma malignancies. As a result, the radiologist is a vital part of the multidisciplinary team comprising surgeons, gastroenterologists, medical and radiation oncologists, and pathologists in managing rectal cancer.

This review aims to provide a comprehensive insight into the imaging recommendations for rectal cancer evaluation at different time points of the management algorithm of rectal carcinoma and the rationale behind them.

Keywords

rectal cancer - MRI - neoadjuvant chemotherapy - guidelines

Introduction

Colorectal cancer is the third most common cancer worldwide and the second leading cause of cancer-related deaths.[1] It is the seventh most common cancer in India, with a steep increase in its incidence, especially in individuals under the age of 50 years.[2] Rectal cancer forms a unique subset among these, primarily due to the surgical challenges that are faced due to the complex anatomy of the rectum and its surrounding structures, along with the need for sphincter preservation.

Surgery is the definite management of rectal cancer. The primary aim of surgery is to obtain a clear resection margin (R0) and prevent local tumor recurrence. Depending on the tumor stage, location, and size, patients may be candidates for local excision (transanal endoscopic resection) or radical resection (low anterior resection, abdominoperineal resection, pelvic exenteration) with total mesorectal excision.[3]

With improvements in neoadjuvant therapy, many patients with locally advanced tumors (where R0 excision may not be possible despite extensive nonanatomical resection) may become candidates for surgery after chemotherapy and/or radiotherapy (RT) administration. Moreover, a conservative “Wait and Watch” policy is being increasingly advocated in patients who show a complete response (on clinical, endoscopic, and imaging follow-up) after neoadjuvant therapy due to the significant morbidity and decreased quality of life associated with radical resections especially in low rectal cancers.[4]

Numerous guidelines have been developed for imaging in rectal cancer, reflecting variations in recommendations and approaches across different clinical settings.

The success of surgical and clinical decisions depends on the accurate staging and restaging of rectal carcinoma using various imaging techniques at initial presentation and after neoadjuvant therapy, respectively ([Table 1]). Magnetic resonance imaging (MRI) has become the modality of choice for baseline staging and surgical planning of rectal malignancies.

Table 1 Preferred imaging modalities at different clinical time points in patients with carcinoma rectum

	Imaging modality of choice	Time of study
Staging	High-resolution pelvic MRI in LARC ERUS/pelvic MRI in T1/T2 tumors depending on local expertise	At initial diagnosis
Evaluation of distant metastasis	CT chest + CECT/CE-MRI abdomen PET/CT only in inconclusive/ambiguous cases	At initial diagnosis
Planning of radiotherapy	NCCT pelvis or MRI	Prior to radiation therapy
Restaging after neoadjuvant therapy	High-resolution Pelvic MRI	6–8 weeks postcompletion of neoadjuvant therapy
Postop surveillance	CECT chest + abdomen + pelvis	Variable intervals depending on the tumor stage
Surveillance during “Wait and Watch” approach	MRI pelvis	3 monthly for the initial 2 years 6 monthly for the next 3–5 years
	CECT chest + abdomen + pelvis	6 monthly for the initial 2 years Annually for the next 3–5 years

Abbreviations: CE, contrast-enhanced; CT, computed tomography; ERUS, endorectal ultrasound; LARC, locally advanced rectal carcinoma; MRI, magnetic resonance imaging; NCCT, noncontrast computed tomography; PET, positron emission tomography.

Diagnosis

The initial diagnosis of rectal cancer typically involves a combination of clinical assessment, endoscopy with biopsy, and histopathological confirmation.[5] Common symptoms include rectal bleeding, changes in bowel habits, or unexplained weight loss. While imaging plays an essential role in staging and treatment planning, it is not the primary tool for diagnosis. A digital rectal examination (DRE) and colonoscopy are commonly performed to visualize the lesion and obtain biopsy samples for histological evaluation.

In countries with colorectal cancer screening programs, colonoscopy is considered the investigation of choice—due to its ability to directly visualize and biopsy the tumor while also allowing for the detection of synchronous lesions in the colon. Computed tomography (CT) colonography (virtual colonoscopy) may be used as a less invasive and low-risk alternative test for screening colorectal malignancies. This is especially useful in patients who are unwilling or unable to undergo colonoscopy or in situations of failed colonoscopy.[6] Additionally, rectal cancer may be detected incidentally during cross-sectional imaging performed for unrelated complaints. When rectal cancer is identified through these imaging techniques, a colonoscopy is typically needed for further evaluation.

Staging

Accurate staging of rectal cancer is critical for optimizing treatment strategies, and different imaging modalities offer varying strengths and limitations. Few studies have compared the diagnostic performance of various imaging modalities (contrast-enhanced CT [CECT], MRI pelvis, and positron emission tomography-CT [PET/CT]) for the preoperative evaluation of rectal cancer, which have been tabulated in [Table 2].[7] [8] [9] [10] [11] [12] [13] [14] Majority of these studies are 5 to 10 years old and thus may not give an accurate picture in the current scenario because of constant advances in CT and MRI technology.

Table 2 Comparison of the diagnostic performance of CECT, MRI, and PET-CT for staging of rectal cancer

	T Staging			CRM	N staging			M staging
	Sensitivity (%)	Specificity (%)	Accuracy (%)	Accuracy (%)	Sensitivity (%)	Specificity (%)	Accuracy (%)	Sensitivity (%)	Specificity (%)
CECT	80–88	75–78	83–86	< 50	55–64	60–75	56–79	48–87	95–97
MRI	79–87	75- 85	67–86	92–95	80–94	67–90	57–85	87–95	87–94
PET/CT	−	−	87–100	-	61–74	53–67	−	78–95	97–98

Abbreviations: CE, contrast-enhanced; CRM, circumferential reception margin; CT, computed tomography; MRI, magnetic resonance imaging; PET, positron emission tomography.

Presently, high-resolution MR of the pelvis is the imaging modality of choice for the pretreatment staging of rectal cancer recommended by all major guidelines.[5] [6] [15] [16] The high soft tissue contrast of MR can help accurately detect the depth of infiltration, extramural tumor invasion (T stage), nodal burden (N staging), and mesorectal fascia involvement (circumferential resection margin), which is essential for surgical planning. MR is reliable for assessing local tumor spread (T stage), with accuracy, sensitivity, and specificity of 85, 87, and 75%, respectively.[17] The largest multicenter prospective trial to date evaluating the accuracy of MRI for the staging of rectal cancer has been the Magnetic Resonance Imaging and Rectal Cancer European Equivalence (MERCURY) study,[18] which demonstrated MRI to be equivalent to histopathology for the evaluation of local tumor spread to within 0.5 mm depth of invasion.[19]

MR can also assess for additional prognostic markers for surgery—relation of the lesion to the sphincter complex, extramural venous invasion (EMVI), and tumor deposits.[19] EMVI, tumor deposits, and pelvic sidewall involvement detected on MRI serve as independent poor prognostic markers for rectal cancer necessitating neoadjuvant chemotherapy.[20]

The acquisition of high-resolution images is paramount for staging carcinoma rectum. The European Society of Gastrointestinal and Abdominal Radiology (ESGAR) and the Society of Abdominal Radiology (SAR) recommend a minimal field strength of 1.5 T for MR performed for staging rectal malignancies. Nonfat-suppressed T2-weighted sequences in all three planes with small field of view (FOV) and ≤ 3 mm slice thickness are the most valuable sequences for staging. Adding a large FOV nonfat-suppressed T2-weighted sequence in the true axial plane helps to assess all pelvic lymph node compartments and the sigmoid takeoff.[21] The addition of diffusion-weighted images (DWIs) may help to differentiate hypercellular tumor tissue from adjacent desmoplastic reaction and inflammation.[22]

Although the SAR recommends DWI at baseline imaging and restaging, the ESGAR only recommends the addition of DWI at restaging MR.

Both the ESGAR and SAR do not recommend the routine use of gadolinium-based MR contrast due to the lack of additional information and the consequent increase in scan time and costs. However, few studies have demonstrated increased sensitivity in detecting EMVI after intravenous contrast administration.[23] Dynamic CE (DCE) MRI is a quantitative imaging technique that measures tumor perfusion characteristics that correlate with the degree of tumor angiogenesis and aggressiveness. Perfusion parameters like K-trans may help predict tumor grade during the primary staging of rectal carcinoma but are not a part of the recommended sequences.[24]

Multiple guidelines have recommended standards for preprocedure patient preparation for MRI protocols for assessing rectal cancers, as they help create uniformity and improve the accuracy of tumor staging ([Table 3]).

Table 3 Recommendations for patient preparation before staging or restaging MRI pelvis for rectal cancer

	Advantages and disadvantages	Current recommendations
Phased array external coil	● Improved quality of the scan  ● Good patient acceptability	Recommended
Endorectal coil	● Improved quality of scan but poor patient compliance, especially in stenotic disease	Not recommended
Spasmolytic agents (Buscopan)	● Reduced motion artifacts due to peristalsis	Optional in high rectal cancer, not routinely recommended
Endorectal jelly	● Rectal distention improves visualization of small tumors and polypoidal lesions.  ● Reduction of susceptibility due to air, leading to better DWI  ● Compression of the mesorectum may lead to overestimation of mesorectal fascia infiltration and poor node detection	Not recommended[a]
Rectal enema	● Removes rectal air and susceptibility artifacts during DWI	Optional during restaging, microenema[a]

Abbreviations: DWI, diffusion-weighted image; ESGAR, European Society of Gastrointestinal and Abdominal Radiology; MRI, magnetic resonance imaging; SAR, Society of Abdominal Radiology.

^a ESGAR and SAR guidelines.

While MR can accurately differentiate early rectal cancer (T1/T2) from locally advanced rectal cancer (T3/T4) by visualization of the disrupted hypointense muscularis propria, it has limited use in discriminating between T1 (submucosal) and T2 (extension up to the muscularis propria) lesions due to its limited spatial resolution.[25]

Endorectal ultrasound (ERUS) is a valuable modality for evaluating early rectal malignancies (T1 and T2) since its high resolution can help discriminate between the different rectal wall layers.[26] ERUS provides no additional benefit over MR in differentiating T2 from T3 disease and assessing mesorectal nodes.

However, it is highly operator-dependent and has limited depth resolution, making it a poor modality for bulky disease, adjacent pelvic organ involvement, or distant spread. While the European Society of Medical Oncology (ESMO) and ESGAR recommend ERUS as the modality of choice for early rectal cancer (T1/T2), the National Comprehensive Cancer Network (NCCN) clinical practice guidelines recommend ERUS as an alternative to MR in cases where MR is contraindicated and in superficial rectal lesions.

Pelvic CECT is not recommended for the local assessment of rectal cancer due to its low contrast resolution, which results in poor determination of the T status and suboptimal prediction of the circumferential reception margin. CECT performs poorly in the discrimination of tumor from the native rectal wall, tumor versus EMVI, and recognizing infiltration of adjacent pelvic organs ([Figs. 1] [2] [3]). Moreover, CECT also shows poor sensitivity and specificity for nodal stage assessment in these cases.

Fig. 1 (A–D) Comparison of contrast-enhanced computed tomography (CECT) versus magnetic resonance imaging (MRI) pelvis for local staging of rectal carcinoma. (A) CECT pelvis in a 63-year-old male with per rectal bleeding demonstrates circumferential thickening of the lower rectum. However, the exact distinction between the tumor and the rectal wall cannot be made out. There is apparent loss of fat planes with the prostate (long arrow) and doubtful extension into the mesorectal fat. (B) Axial T2-weighted MR image of the same patient as (A) demonstrates T2 intermediate signal intensity circumferential thickening of the rectum confined to the rectal wall with no extension into the mesorectal fat and preserved fat planes with the prostate, thus downstaging the lesion to T2. (C) CECT pelvis in a 49-year-old male with anemia demonstrates circumferential thickening of the mid-rectum with loss of fat planes with the prostate (long arrow) and sacrum. (D) High contrast resolution of the axial T2-weighted MR of the same patient as in (C) better demonstrates the invasion into the prostate (*) with no involvement of the sacrum (short arrow).

Fig. 2 (A, B) Case highlighting the differences between contrast-enhanced computed tomography (CECT) and magnetic resonance imaging (MRI) for determination of T staging, circumferential reception margin (CRM), and extramural venous invasion (EMVI) in rectal cancer. Axial CECT pelvis (A) in a 56-year-old male patient shows contiguous extension of the asymmetrical rectal wall thickening (*) beyond the muscularis propria with extension up to the mesorectal fascia (short arrow) s/o T3c tumor with positive CRM. Axial T2 (A) images in the same patient reveal a T2 intermediate signal intensity, circumferential rectal wall thickening in the mid-rectum (arrowhead). Multiple nodular, linear hypointense structures are contiguous with the wall thickening at 5 to 8 o'clock (long arrow) s/o EMVI (T3b tumor with negative CRM).

Fig. 3 (A–D) Comparison of contrast-enhanced computed tomography (CECT) versus magnetic resonance imaging (MRI) pelvis for local staging of rectal carcinoma. Axial CECT (A, B) images of the pelvis in a 57-year-old female show soft tissue attenuation content within the rectum with obliteration of the rectal wall. The exact delineation of tumor and the rectal wall cannot be made out due to poor contrast resolution. Axial T2-weighted MRI (C, D) images demonstrate a T2 intermediate tumor within the rectum (*) without extension across the muscularis propria (hypointense line marked by arrowhead).

While MRI is the preferred modality for local staging, its high cost and limited availability may necessitate alternative approaches. EUS provides superior resolution for early-stage tumors (T1–T2) and is valuable for guiding local therapies, though it is highly operator-dependent and has limited utility for advanced disease. CT is widely available and cost-effective, making it the most accessible modality for staging in many settings, but its lower soft-tissue contrast results in suboptimal accuracy for T and N staging, particularly in distinguishing T3 from T4 tumors. PET-CT is primarily used for detecting distant metastases (M staging) and restaging after neoadjuvant therapy but is not routinely indicated for initial staging. Incorrect staging can have significant clinical consequences—understaging may lead to incomplete resection or increased rates of local recurrence, while overstaging can result in denial of surgery in resectable cases. Thus, MRI pelvis should be done wherever feasible for local staging while CECT chest, abdomen, and pelvis (CAP) remains the workhorse for distant metastasis.

Evaluation of Distant Metastasis

Workup for metastatic lesions to the chest and abdomen must be performed prior to radical surgery. Twenty percent of patients with colorectal cancer present with synchronous metastasis, while 7 to 23% of patients develop metachronous metastasis following curative treatment. In patients with metastatic rectal cancer, the most common sites of metastasis are the liver (70%) and lungs (47%) followed by bone (12%).[27] [28] The NCCN recommends preoperative CT chest for assessing metastatic lesions in the chest due to its high sensitivity.[29] Routine use of chest radiographs is not recommended to exclude chest metastasis due to its low sensitivity for identifying metastasis ([Fig. 4]).

Fig. 4 (A–C) Nonvisualization of lung metastasis on chest X-ray compared with contrast-enhanced computed tomography (CECT) chest in a patient with rectal carcinoma. Chest X-ray posteroanterior (PA) view (A) in a 56-year-old female with rectal carcinoma was reported as normal with no obvious metastatic lesion. Axial CECT sections in the lung (B) and the soft tissue window (C) demonstrates a well-defined solid nodule in the anteromedial segment of the left lower lobe (arrowhead) suggestive of lung metastasis. Lesion was inconspicuous on the chest X-ray likely due to its retrocardiac location.

Since the rest of the abdominal organs need to be evaluated for distant metastasis, it is recommended to perform either CECT or MRI of the abdomen before surgery.

DWI is superior to T2-weighted MR sequences and comparable to CE-MR for detecting hepatic metastasis. It may be used as an alternative in patients with contraindications to contrast administration.[30]

A fluorodeoxyglucose F-18 (18-FDG) PET scan is not routinely recommended for preoperative staging and detection of distal metastasis of rectal cancer.[5] [15] However, PET-CT may provide additional information in cases with equivocal findings on CECT[31] and patients with contraindications to iodinated contrast. The ESMO guidelines additionally recommend 18-FDG-PET in addition to CECT abdomen in patients with a high risk of metastasis (extensive EMVI or high carcinoembryonic antigen [CEA] levels).[5]

RT Planning

Both short-course and long-course neoadjuvant RT show a significant reduction in postsurgery recurrence in locally advanced rectal cancer.[32] RT success depends on accurate preprocedure planning whereby an adequate dose is delivered to the tumor while sparing adjacent organs, mitigating radiation-induced anorectal and genitourinary dysfunction. Techniques like three-dimensional conformal and intensity-modulated RT technology are recommended as they ensure less dose to adjacent vital organs compared with two-dimensional RT. RT planning CECT covering the thorax, abdomen, and pelvis is usually advised following neoadjuvant chemotherapy before RT during total neoadjuvant therapy protocols to exclude progression after chemotherapy.

The better contrast resolution of MRI shows improved margin delineation than cone-beam CT. However, due to inhomogeneity within the tumor, MRI cannot determine the tissue electron densities for accurate radiation dose calculation. Therefore, CT remains the gold standard for RT dose planning.[33] [34]

MRI may also be used for brachytherapy planning in patients with regrowth after local treatment or after a watch and wait period.

Restaging

Restaging after neoadjuvant treatment is a critical component of the rectal cancer treatment protocol. Approximately 20% of patients demonstrate complete response after neoadjuvant chemoradiotherapy and may be considered for a “wait and watch” approach.[35]

A complete response on DRE, colonoscopy, and restaging MRI is essential to justify a conservative nonoperative approach with surveillance in rectal cancers.

The MERCURY trial validated using high-resolution MR for restaging after neoadjuvant chemoradiotherapy with tumor regression grade (TRG) on restaging MRI correlating with disease-free survival ([Fig. 5]).[36]

Fig. 5 (A, B) Post-neoadjuvant chemotherapy response assessment on contrast-enhanced computed tomography (CECT) versus magnetic resonance imaging (MRI). Axial CECT pelvis (A) in a 67-year-old male with carcinoma rectum post-neoadjuvant chemotherapy demonstrates ill-defined thickening of the lower rectum with loss of fat planes with the prostate and the bilateral puborectalis. Axial T2-weighted image (B) shows rectal wall thickening confined to the muscularis propria with no obvious infiltration of the prostate gland or the puborectalis. CECT overestimates tumor extension due to lower contrast resolution and associated edema post-neoadjuvant therapy.

The protocol for a restaging MR is similar to primary staging MR for rectal tumors. Comparing the posttreatment scan with the pretreatment scan is essential, as the tumor may be difficult to visualize in the posttreatment scans due to edema and tumor shrinkage.

High-resolution, small FOV, nonfat-suppressed T2-weighted images in the oblique axial and coronal planes, perpendicular and parallel to the tumor, respectively, are recommended for evaluating the tumor and mesorectal nodes. A large FOV T2 nonfat-saturated sequence in the true axial plane is recommended for assessing the entire pelvis.

DWI in the oblique axial plane with a high b value (≥ 800 second/mm²) significantly increases confidence in tumor response assessment and is an integral part of restaging MR.[37] Due to significant reliance on DWI during restaging MR, the use of rectal microenema prior to MRI may be preferable as it displaces rectal gas and reduces susceptibility artifact on DWI.[38]

The use of gadolinium contrast is optional during restaging MR for rectal malignancy and is not recommended by either the ESGAR or SAR. CE-MR may help differentiate fibrosis from tumor due to different enhancement patterns—delayed enhancement of fibrosis versus heterogeneous enhancement of tumoral tissue in the early enhancement phase.[39] Change in semiquantitative perfusion parameters obtained from DCE-MRI after neoadjuvant therapy may be helpful in the assessment of response to rectal carcinoma.

Restaging MR is usually performed at 6 to 8 weeks after completion of neoadjuvant chemotherapy. The timing of MR is controversial, with certain groups advocating early MR to identify poor responders and a reluctance to operate after 8 weeks due to post-RT pelvic fibrosis.[38] Conducting MRI within 6 weeks of completing therapy may yield suboptimal results due to ongoing inflammation, edema, and treatment-related changes that can obscure the distinction between residual tumor and fibrosis. Inflammation from chemoradiotherapy typically decreases over time, with tumor regression appearing more distinctly after this period.

Delayed scans (at 15–16 weeks) may help better identify patients with complete tumor response, especially in patients with near-complete response on MRI at 8 weeks posttreatment.[38]

Pathologists initially developed tumor regression grading systems to asses for tumor response postneoadjuvant therapy. Various MR-based TRG (mrTRG) systems were developed in accordance with their pathological correlates. However, they have yet to be widely adopted and vary according to institutional policies. mrTRG is currently being evaluated as an imaging biomarker to assess for complete response and direct a “Wait and Watch” approach (TRIGGER trial).[40]

Additional chest and abdomen imaging is also required to assess for distant disease, with current guidelines advocating a chest CT, abdominal CT, or MRI along with a pelvic MRI for restaging.[41]

New studies evaluating the role of PET-CT for posttreatment assessment have been performed, and they show an emerging role for PET-CT in assessing posttreatment response ([Table 4]).[13] [42] [43] [44]

Table 4 Comparison of CECT, MRI, and PET/CT for the assessment of response to treatment of rectal carcinoma

Response to treatment	CECT	MRI	PET/CT
Sensitivity (%)	54–81	65–95	89–100
Specificity (%)	60–82	63–93	80–93

Abbreviations: CE, contrast-enhanced; CT, computed tomography; MRI, magnetic resonance imaging; PET, positron emission tomography.

Surveillance

Postoperative surveillance in rectal cancers is crucial for detecting recurrence and any metachronous lesions early. Clinical examination, CEA levels, colonoscopy/proctoscopy, and imaging form the cornerstones of surveillance. CT is a part of this surveillance algorithm and is the most familiar imaging modality in clinical practice. The primary goal of a CT CAP with intravenous contrast is to detect metastatic disease in the lungs and liver and to determine their potential resectability.

The risk of local recurrence is considered to be maximum in the first 3 years postsurgery[45] with a cumulative incidence of recurrence of 2.7 and 6.4% at 1 and 3 years, respectively.[46]

The ESMO guidelines recommend six monthly CT CAP during this time. The NCCN recommends a CT surveillance schedule based on staging. For stage 2 to 3 rectal cancer, CT should be obtained every 6 to 12 months for 5 years total. For stage 4 rectal cancer, CT should be obtained every 3 to 6 months for the first 2 years before spacing out to every 6 to 12 months for the remaining 3 years.[15]

Protocols for follow-up are more intensive in cases where a “Wait and Watch” approach is being followed. Consensus recommends that these patients be assessed every 3 to 4 months with DRE, endoscopy, and pelvic MRI for the first 2 years and then six monthly for the next 3 to 5 years after treatment. CECT CAP should be performed every 6 months for the first 2 years and then annually for the next 3 to 5 years.[47] [48]

Other surveillance modalities, such as PET, are not recommended in primary surveillance strategies. However, PET may be most useful after detecting equivocal CECT lesions or in the setting of an elevated CEA with negative, high-quality CT scans.

Conclusion

Advances in rectal cancer treatment strategies have resulted in a reduction in local recurrence and postoperative morbidity. Focusing on organ preservation, sphincter preservation, and nonsurgical management of rectal malignancies requires high-quality pelvic MRI. This can accurately delineate tumor margins, depth of tumor invasion, adjacent organ infiltration, nodal status, and poor prognostic features requiring additional neoadjuvant therapy like sphincter involvement, EMVI, and threatened resection margin. Moreover, pelvic MRI is also used for response assessment after neoadjuvant chemotherapy and subsequent treatment planning. CECT plays little role in the local staging of rectal cancer. However, it is recommended for the evaluation of distant disease, which may potentially render the cancer unresectable.

Conflict of Interest

None declared.

• References

• 1 Sung H, Ferlay J, Siegel RL. et al. Global Cancer Statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2021; 71 (03) 209-249
• 2 Bose B, Clarke J, Glasbey JC. et al; CROCODILE study group. Catastrophic expenditure and treatment attrition in patients seeking comprehensive colorectal cancer treatment in India: a prospective multicentre study. Lancet Reg Health Southeast Asia 2022;6
• 3 Stitzenberg KB, Barnes E. Advances in rectal cancer surgery. Clin Colorectal Cancer 2022; 21 (01) 55-62
• 4 Cerdan-Santacruz C, São Julião GP, Vailati BB, Corbi L, Habr-Gama A, Perez RO. Watch and wait approach for rectal cancer. J Clin Med 2023; 12 (08) 2873
• 5 Glynne-Jones R, Wyrwicz L, Tiret E. et al; ESMO Guidelines Committee. Rectal cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 2017; 28 (Suppl. 04) iv22-iv40
• 6 Abbas AM, Sheha AM, Salem MN, Altraigey A. Three-dimensional power Doppler ultrasonography in evaluation of adnexal masses. Middle East Fertil Soc J 2017; 22 (04) 241-245
• 7 Engel R, Kudura K, Antwi K. et al. Diagnostic accuracy and treatment benefit of PET/CT in staging of colorectal cancer compared to conventional imaging. Surg Oncol 2024; 57: 102151
• 8 Cerny M, Dunet V, Prior JO. et al. Initial staging of locally advanced rectal cancer and regional lymph nodes: comparison of diffusion-weighted MRI with 18F-FDG-PET/CT. Clin Nucl Med 2016; 41 (04) 289-295
• 9 Klessen C, Rogalla P, Taupitz M. Local staging of rectal cancer: the current role of MRI. Eur Radiol 2007; 17 (02) 379-389
• 10 Ippolito D, Drago SG, Franzesi CT, Fior D, Sironi S. Rectal cancer staging: multidetector-row computed tomography diagnostic accuracy in assessment of mesorectal fascia invasion. World J Gastroenterol 2016; 22 (20) 4891-4900
• 11 Maino C, Vernuccio F, Cannella R. et al. Liver metastases: the role of magnetic resonance imaging. World J Gastroenterol 2023; 29 (36) 5180-5197
• 12 Chan BPH, Patel R, Mbuagbaw L, Thabane L, Yaghoobi M. EUS versus magnetic resonance imaging in staging rectal adenocarcinoma: a diagnostic test accuracy meta-analysis. Gastrointest Endosc 2019; 90 (02) 196-203.e1
• 13 Sinha R, Verma R, Rajesh A, Richards CJ. Diagnostic value of multidetector row CT in rectal cancer staging: comparison of multiplanar and axial images with histopathology. Clin Radiol 2006; 61 (11) 924-931
• 14 Tsili AC, Alexiou G, Naka C, Argyropoulou MI. Imaging of colorectal cancer liver metastases using contrast-enhanced US, multidetector CT, MRI, and FDG PET/CT: a meta-analysis. Acta Radiol 2021; 62 (03) 302-312
• 15 Benson AB, Venook AP, Al-Hawary MM. et al. Rectal Cancer, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology. J Natl Compr Canc Netw 2022; 20 (10) 1139-1167
• 16 Caruso D, Polici M, Bellini D, Laghi A. ESR essentials: imaging in colorectal cancer-practice recommendations by ESGAR. Eur Radiol 2024; 34 (09) 5903-5910
• 17 Al-Sukhni E, Milot L, Fruitman M. et al. Diagnostic accuracy of MRI for assessment of T category, lymph node metastases, and circumferential resection margin involvement in patients with rectal cancer: a systematic review and meta-analysis. Ann Surg Oncol 2012; 19 (07) 2212-2223
• 18 MERCURY Study Group. Diagnostic accuracy of preoperative magnetic resonance imaging in predicting curative resection of rectal cancer: prospective observational study. BMJ 2006; 333 (7572) 779
• 19 Xie H, Zhou X, Zhuo Z, Che S, Xie L, Fu W. Effectiveness of MRI for the assessment of mesorectal fascia involvement in patients with rectal cancer: a systematic review and meta-analysis. Dig Surg 2014; 31 (02) 123-134
• 20 Chandramohan A, Mittal R, Dsouza R. et al. Prognostic significance of MR identified EMVI, tumour deposits, mesorectal nodes and pelvic side wall disease in locally advanced rectal cancer. Colorectal Dis 2022; 24 (04) 428-438
• 21 Bogveradze N, Lambregts DMJ, El Khababi N. et al; MRI rectal study group. The sigmoid take-off as a landmark to distinguish rectal from sigmoid tumours on MRI: reproducibility, pitfalls and potential impact on treatment stratification. Eur J Surg Oncol 2022; 48 (01) 237-244
• 22 Schurink NW, Lambregts DMJ, Beets-Tan RGH. Diffusion-weighted imaging in rectal cancer: current applications and future perspectives. Br J Radiol 2019; 92 (1096) 20180655
• 23 Jhaveri KS, Hosseini-Nik H, Thipphavong S. et al. MRI detection of extramural venous invasion in rectal cancer: correlation with histopathology using elastin stain. AJR Am J Roentgenol 2016; 206 (04) 747-755
• 24 Attenberger UI, Pilz LR, Morelli JN. et al. Multi-parametric MRI of rectal cancer - do quantitative functional MR measurements correlate with radiologic and pathologic tumor stages?. Eur J Radiol 2014; 83 (07) 1036-1043
• 25 Detering R, van Oostendorp SE, Meyer VM. et al; Dutch ColoRectal Audit Group*. MRI cT1-2 rectal cancer staging accuracy: a population-based study. Br J Surg 2020; 107 (10) 1372-1382
• 26 Reginelli A, Clemente A, Sangiovanni A. et al. Endorectal ultrasound and magnetic resonance imaging for rectal cancer staging: a modern multimodality approach. J Clin Med 2021; 10 (04) 641
• 27 Riihimäki M, Hemminki A, Sundquist J, Hemminki K. Patterns of metastasis in colon and rectal cancer. Sci Rep 2016; 6 (01) 29765
• 28 Cohen R, Platell CF. Metachronous colorectal cancer metastasis: who, what, when and what to do about it. J Surg Oncol 2024; 129 (01) 71-77
• 29 O'Leary MP, Parrish AB, Tom CM, MacLaughlin BW, Petrie BA. Staging Rectal cancer: the utility of chest radiograph and chest computed tomography. Am Surg 2016; 82 (10) 1005-1008
• 30 Shenoy-Bhangle A, Baliyan V, Kordbacheh H, Guimaraes AR, Kambadakone A. Diffusion weighted magnetic resonance imaging of liver: principles, clinical applications and recent updates. World J Hepatol 2017; 9 (26) 1081-1091
• 31 Chen MZ, Zhang X, Mui M, Kong JCH, Heriot AG, Ellis-Clark J. Retrospective audit: utility of PET scan in routine preoperative rectal cancer staging. ANZ J Surg 2023; 93 (03) 617-621
• 32 Folkesson J, Birgisson H, Pahlman L, Cedermark B, Glimelius B, Gunnarsson U. Swedish Rectal Cancer Trial: long lasting benefits from radiotherapy on survival and local recurrence rate. J Clin Oncol 2005; 23 (24) 5644-5650
• 33 Secerov Ermenc A, Segedin B. The role of MRI and PET/CT in radiotherapy target volume determination in gastrointestinal cancers-review of the literature. Cancers (Basel) 2023; 15 (11) 2967
• 34 De Pietro S, Di Martino G, Caroprese M. et al. The role of MRI in radiotherapy planning: a narrative review “from head to toe”. Insights Imaging 2024; 15 (01) 255
• 35 Ryan JE, Warrier SK, Lynch AC, Ramsay RG, Phillips WA, Heriot AG. Predicting pathological complete response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer: a systematic review. Colorectal Dis 2016; 18 (03) 234-246
• 36 Patel UB, Blomqvist LK, Taylor F. et al. MRI after treatment of locally advanced rectal cancer: how to report tumor response–the MERCURY experience. AJR Am J Roentgenol 2012; 199 (04) W486-95
• 37 Bates DDB, Golia Pernicka JS, Fuqua III JL. et al. Diagnostic accuracy of b800 and b1500 DWI-MRI of the pelvis to detect residual rectal adenocarcinoma: a multi-reader study. Abdom Radiol (NY) 2020; 45 (02) 293-300
• 38 Nougaret S, Rousset P, Lambregts DMJ. et al. MRI restaging of rectal cancer: the RAC (Response-Anal canal-CRM) analysis joint consensus guidelines of the GRERCAR and GRECCAR groups. Diagn Interv Imaging 2023; 104 (7-8): 311-322
• 39 Lu QY, Guan Z, Zhang XY. et al. Contrast-enhanced MRI for T restaging of locally advanced rectal cancer following neoadjuvant chemotherapy and radiation therapy. Radiology 2022; 305 (02) 364-372
• 40 Battersby NJ, Dattani M, Rao S. et al. A rectal cancer feasibility study with an embedded phase III trial design assessing magnetic resonance tumour regression grade (mrTRG) as a novel biomarker to stratify management by good and poor response to chemoradiotherapy (TRIGGER): study protocol for a randomised controlled trial. Trials 2017; 18 (01) 394
• 41 Korngold EK, Moreno C, Kim DH. et al; Expert Panel on Gastrointestinal Imaging. ACR Appropriateness Criteria® staging of colorectal cancer: 2021 update. J Am Coll Radiol 2022; 19 (5S): S208-S222
• 42 Murcia Duréndez MJ, Frutos Esteban L, Luján J. et al. The value of 18F-FDG PET/CT for assessing the response to neoadjuvant therapy in locally advanced rectal cancer. Eur J Nucl Med Mol Imaging 2013; 40 (01) 91-97
• 43 Yuval JB, Patil S, Gangai N. et al. MRI assessment of rectal cancer response to neoadjuvant therapy: a multireader study. Eur Radiol 2023; 33 (08) 5761-5768
• 44 Park S, Park HS, Jang S. et al. Utility of abbreviated MRI in the post-treatment evaluation of rectal cancer. Acta Radiol 2024; 65 (07) 689-699
• 45 Nors J, Iversen LH, Erichsen R, Gotschalck KA, Andersen CL. Incidence of recurrence and time to recurrence in stage I to III colorectal cancer: a nationwide Danish cohort study. JAMA Oncol 2024; 10 (01) 54-62
• 46 Swartjes H, van Rees JM, van Erning FN. et al. Locally recurrent rectal cancer: toward a second chance at cure? A population-based, retrospective cohort study. Ann Surg Oncol 2023; 30 (07) 3915-3924
• 47 Jayaprakasam VS, Alvarez J, Omer DM, Gollub MJ, Smith JJ, Petkovska I. Watch-and-wait approach to rectal cancer: the role of imaging. Radiology 2023; 307 (01) e221529
• 48 Byun HK, Koom WS. A practical review of watch-and-wait approach in rectal cancer. Radiat Oncol J 2023; 41 (01) 4-11

Publication History

Article published online:
02 April 2025