T-staging of rectal cancer: accuracy of 3.0 Tesla MRI compared with 1.5 Tesla

Factors affecting the restaging accuracy of magnetic resonance imaging after preoperative chemoradiation in patients with rectal cancer

PURPOSES

We evaluated patient or tumor factors associated with the preoperative restaging accuracy of magnetic resonance imaging (MRI) for determining T and N stages as well as circumferential resection margin (CRM) involvement after chemoradiation (CRT) in patients with locally advanced rectal cancer.

METHODS

Seventy-seven patients with rectal cancer that were treated with preoperative CRT (50.4 Gy) followed by radical resection were included. Post-CRT MRI was performed approximately 4 weeks after preoperative CRT.

RESULTS

The median tumor distance from the anal verge was 6 cm, 48 (62%) of which were anterior and 29 (38%) posterior. The median tumor diameter was 3 cm. A stage-by-stage comparison showed that correct staging occurred in 62%, 43%, and 86% of patients for T staging, N staging, and CRM prediction, respectively. Shorter distance to the anal verge (<5 cm), smaller tumor diameter (<1 cm), and anterior tumor location were associated with incorrect T staging. There were no significant variables in terms of N staging accuracy. Shorter tumor distance and anterior tumor location were associated with incorrect CRM prediction.

CONCLUSIONS

Our findings suggest that specific tumor factors such as small, distal, or anterior rectal tumors are closely associated with the accuracy of MRI after preoperative CRT.

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.

T staging of rectal cancer: accuracy of diffusion-weighted imaging compared with T2-weighted imaging on 3.0 tesla MRI

OBJECTIVE

To evaluate the performance of diffusion-weighted imaging (DWI) in the T staging of primary rectal cancer compared with T2-weighted (T2W) fast spin-echo imaging using 3.0 tesla magnetic resonance imaging (MRI).

METHODS

In total, 46 consecutive patients with rectal cancer who underwent MRI examination before surgery were included in the study. The diagnostic accuracy, sensitivity and specificity of DWI and T2W imaging (T2WI) for T staging of the tumors were evaluated, and interobserver agreement between the two radiologists was calculated.

RESULTS

The diagnostic accuracies of DWI and T2WI for the T staging of rectal cancer were 73.9% and 71.7%, respectively. The sensitivity and specificity of DWI were 90.0% and 88.9% for diagnosing T1 tumors, 64.3% and 87.5% for T2 tumors, 77.8% and 89.3% for T3 tumors and 50.0% and 97.6% for T4 tumors, respectively; while the sensitivity and specificity of T2WI were 80.0% and 91.7% for T1 tumors, 64.3% and 78.1% for T2 tumors, 77.8% and 89.3% for T3 tumors and 50.0% and 100% for T4 tumors, respectively. There were no significant differences in the diagnostic accuracy, sensitivity or specificity between DWI and T2WI no matter what kind of T stage was concerned (P > 0.05). The interobserver agreement was 0.74 for DWI and 0.63 for T2WI.

CONCLUSIONS

DWI can be applied as a useful tool for evaluating the T staging of rectal cancer. The interobserver agreement obtained by using DWI is better than that obtained by using T2WI.

Is there a benefit in using magnetic resonance imaging in the prediction of preoperative neoadjuvant therapy response in locally advanced rectal cancer?

OBJECTIVE

This meta-analysis aimed to evaluate the accuracy of magnetic resonance imaging (MRI) in predicting responses in patients with locally advanced rectal cancer after preoperative neoadjuvant therapy.

METHODS

Articles in English language relating to the accuracy of MRI for this utility were retrieved. Methodological quality was assessed by Quality Assessment of Diagnostic Accuracy Studies tool. Pooled estimation and subgroup analysis data were obtained by statistical analysis.

RESULTS

Fourteen studies involved 751 pathologically confirmed patients met the inclusion criteria. Methodological quality was relatively high. To predict histopathological response in locally advanced rectal cancer by MRI, the pooled sensitivity and specificity were 0.78 [95 % confidence intervals (CI), 0.65, 0.87] and 0.81 (95 % CI, 0.72, 0.87), respectively. Positive likelihood ratio and negative likelihood ratio were 4.1 (95 %CI, 2.9, 5.8) and 0.27 (95 % CI, 0.17, 0.43), respectively. Subgroup analysis showing that imaging was performed at 3.0 T MRI devices had higher pooled sensitivity (0.92, 95 % CI, 0.84, 1.00) than the subgroup of MRI with ≤1.5 T (0.68, 95 % CI, 0.53, 0.82) (p < 0.05).The sensitivity and specificity of T2-weighted imaging (T2WI) with diffusion-weighted imaging (DWI) were 0.92 (95 % CI, 0.81, 1.00) and 0.75 (95 % CI, 0.54, 0.95); those of T2WI alone were 0.64 (95 % CI, 0.47, 0.82) and 0.88 (95 % CI, 0.81, 0.94) (p > 0.05).

CONCLUSION

This meta-analysis indicates that MRI is an accurate tool in predicting pathologic response after preoperative therapy in patients with locally advanced rectal cancer. It is suggested to perform MRI by 3.0 T devices, which might be sensitive to identify responder. The addition of DWI to T2WI showed a non-significant improvement in sensitivity, which deserves further investigation.

Stage and size using magnetic resonance imaging and endosonography in neoadjuvantly-treated rectal cancer

AIM: To assess the stage and size of rectal tumours using 1.5 Tesla (1.5T) magnetic resonance imaging (MRI) and three-dimensional (3D) endosonography (ERUS).

METHODS: In this study, patients were recruited in a phase I/II trial of neoadjuvant chemotherapy for biopsy-proven rectal cancer planned for surgical resection with or without preoperative radiotherapy. The feasibility and accuracy of 1.5T MRI and 3D ERUS were compared with the histopathology of the fixed surgical specimen (pathology) to determine the stage and size of the rectal cancer before and after neoadjuvant chemotherapy. A Philips Intera 1.5T with a cardiac 5-channel synergy surface coil was used for the MRI, and a B-K Medical Falcon 2101 EXL 3D-Probe was used at 13 MHz for the ERUS. Our hypothesis was that the staging accuracy would be the same when using MRI, ERUS and a combination of MRI and ERUS. For the combination, MRI was chosen for the assessment of the lymph nodes, and ERUS was chosen for the assessment of perirectal tissue penetration. The stage was dichotomised into stage I and stage II or greater. The size was measured as the supero-inferior length and the maximal transaxial area of the tumour.

RESULTS: The staging feasibility was 37 of 37 for the MRI and 29 of 36 for the ERUS, with stenosis as a limiting factor. Complete sets of investigations were available in 18 patients for size and 23 patients for stage. The stage accuracy by MRI, ERUS and the combination of MRI and ERUS was 0.65, 0.70 and 0.74, respectively, before chemotherapy and 0.65, 0.78 and 0.83, respectively, after chemotherapy. The improvement of the post-chemotherapy staging using the combination of MRI and ERUS compared with the staging using MRI alone was significant (P = 0.046). The post-chemotherapy understaging frequency by MRI, ERUS and the combination of MRI and ERUS was 0.18, 0.14 and 0.045, respectively, and these differences were non-significant. The measurements of the supero-inferior length by ERUS compared with MRI were within 1.96 standard deviations of the difference between the methods (18 mm) for tumours smaller than 50 mm. The agreement with pathology was within 1.96 standard deviations of the difference between imaging and pathology for all tumours with MRI (15 mm) and for tumours that did not exceed 50 mm with ERUS (22 mm). Tumours exceeding 50 mm in length could not be reliably measured by ERUS due to the limit in the length of each recording.

CONCLUSION: MRI is preferable to use when assessing the size of large or stenotic rectal tumours. However, staging accuracy is improved by combining MRI with ERUS.

Magnetic resonance imaging of rectal cancer

Optimal treatment decisions for patients with rectal cancer are based on knowledge of tumor characteristics and prognostic features and any initial treatment must aim to reduce the risk of both local and distant recurrence. The radiologist has become an increasingly important part of multidisciplinary team managing rectal cancer. The primary goal of MRI staging of rectal tumors is to identify prognostic factors in order to offer patients a tailored treatment based on individual risks. Restaging of rectal tumors using MRI after chemoradiation therapy is becoming more relevant issue, since further tailoring of treatment is increasingly being considered after the treatment.

MRI after treatment of locally advanced rectal cancer: how to report tumor response--the MERCURY experience

OBJECTIVE

The Magnetic Resonance Imaging and Rectal Cancer European Equivalence (MERCURY) Study validated the use of MRI for posttreatment staging and its correlation with survival outcomes. As a consequence, reassessment of MRI scans after preoperative therapy has implications for surgical planning, the timing of surgery, sphincter preservation, deferral of surgery for good responders, and development of further preoperative treatments for radiologically identified poor responders.

CONCLUSION

In this article we report a validated systematic approach to the interpretation of MR images of patients with rectal cancer after chemoradiation.

Imaging paradigms in assessment of rectal carcinoma: loco-regional and distant staging

The role of imaging in the management of rectal malignancy has progressively evolved and undergone several paradigm shifts. Unlike a few decades ago when the role of a radiologist was restricted at defining the longitudinal extent of the tumour with barium enema, recent advances in imaging techniques permit highly accurate locoregional and distant staging of the disease as well as prognostication on those who are likely to have a postoperative recurrence. Computed tomography (CT) has always been the mainstay of imaging when evaluating for distant metastasis, with the advent of positron emission tomography/CT improving its specificity. In rectal malignancy, it is the local extent of the disease that often influences the surgical decision making and need for neoadjuvant therapy. Although endoscopic ultrasound has been the traditional technique for determining the depth of tumour invasion, over the last decade magnetic resonance imaging (MRI) has emerged as a very effective tool for accurate T-staging. This review intends to address the status of various imaging modalities and their advantages and limitations in detection, pretreatment staging, and assessment of therapeutic efficacy in rectal cancer, with emphasis on MRI of high spatial resolution.

Rectal imaging: part 1, High-resolution MRI of carcinoma of the rectum at 3 T

OBJECTIVE

MRI is currently the imaging modality of choice for the detection, characterization, and staging of rectal cancer. A variety of examinations have been used for preoperative staging of rectal cancer, including digital rectal examination, endorectal (endoscopic) ultrasound, CT, and MRI. Endoscopic ultrasound is the imaging modality of choice for small and small superficial tumors. MRI is superior to CT for assessing invasion to adjacent organs and structures, especially low tumors that carry a high risk of recurrence.

CONCLUSION

High-resolution MRI is an accurate and sensitive imaging method delineating tumoral margins, mesorectal involvement, nodes, and distant metastasis. In this article, we will review the utility of rectal MRI in local staging, preoperative evaluation, and surgical planning. MRI at 3 T can accurately delineate the mesorectal fascia involvement, which is one of the main decision points in planning treatment.