|Year : 2017 | Volume
| Issue : 1 | Page : 104-109
Role of magnetic resonance in evaluation of urinary bladder cancer
Ashraf A Zytoon, Sameh M Azab, Walaa A Abo Samak
Department of Radiodiagnosis, Faculty of Medicine, Menoufia University, Menoufia, Egypt
|Date of Submission||03-Apr-2016|
|Date of Acceptance||26-Jun-2016|
|Date of Web Publication||25-Jul-2017|
Walaa A Abo Samak
Radiodiagnosis Department, Faculty of Medicine, Menoufia University, Shebin El-Kom, El-Menofia
Source of Support: None, Conflict of Interest: None
The aim of this study was to prospectively evaluate the use of MRI as a noninvasive diagnostic tool for staging of bladder tumors using different magnetic resonance (MR) sequences: T2-weighted image (T2WI), diffusion-weighted image (DWI), and precontrast and postcontrast T1-weighted image.
MRI with its superior resolution and supplemented with new emerging sequences is the optimal imaging modality for accurate local staging of bladder cancer, particularly for differentiation between the muscle-invasive and non-muscle-invasive urinary bladder tumors; it is a cornerstone in treatment decision making.
Patients and methods
The study protocol received institutional ethical committee approval, and informed consent was obtained. Between November 2014 and November 2015, 50 consecutive patients (44 men and 6 women; mean age: 64.3 years; range: 44–85 years) who presented with gross hematuria or suspected urinary bladder tumors were enrolled prospectively. All patients underwent MR examination followed by conventional cystoscopy. The patients were evaluated using T2-weighted high-spatial-resolution MRI of the urinary bladder, followed by diffusion-weighted-MRI. Precontrast T1 (with or without fat suppression) and immediate postgadolinium injection were performed if there were no contraindications.
Of all 50 patients, four (8%) were at T1, 12 (24%) were at T2, 23 (46%) were at T3, and 11 (22%) were at T4. The most common symptom was gross hematuria (33 patients; 66%). The overall accuracy of T2WI, DWI, and postcontrast imaging sequences in differentiating stage Tis to T2 tumors from T3 to T4 tumors was 88, 98, and 94%, respectively. DWI has a higher overall accuracy compared with both T2WI and postcontrast T1-weighted image in T staging of bladder cancer.
MRI with new emerging sequences (diffusion-weighted and contrast-enhanced) is highly reliable for accurate local staging of urinary bladder cancer, which is similar to that of conventional cystoscopy. This noninvasive method could be efficiently used for evaluating patients with hematuria of lower urinary tract origin.
Keywords: cystoscopy, diffusion-weighted imaging, hematuria, magnetic resonance imaging
|How to cite this article:|
Zytoon AA, Azab SM, Abo Samak WA. Role of magnetic resonance in evaluation of urinary bladder cancer. Menoufia Med J 2017;30:104-9
|How to cite this URL:|
Zytoon AA, Azab SM, Abo Samak WA. Role of magnetic resonance in evaluation of urinary bladder cancer. Menoufia Med J [serial online] 2017 [cited 2019 Sep 21];30:104-9. Available from: http://www.mmj.eg.net/text.asp?2017/30/1/104/211486
| Introduction|| |
Urinary bladder cancer is one of the most common malignancies of the urinary tract. It is the fourth most common cancer in men and the tenth most common cancer in women. Urinary bladder cancer occurs three to four times more frequently in men than in women .
Bladder neoplasms are classified on the basis of cell type origin as epithelial and nonepithelial (mesenchymal), with over 95% being epithelial . In addition to its cell type, bladder cancer may be described as noninvasive (superficial), non-muscle-invasive, or muscle-invasive .
Squamous cell carcinoma (SCC) varies considerably depending on the geographic location. SCCs account for only 3–7% of bladder cancer in USA and 1% in England, but up to 75% in Egypt .
Bladder cancer may be detected incidentally or because of symptoms. In about 85% of patients, intermittent gross painless hematuria is the most common presenting symptom. Unexplained irritative voiding symptoms such as increased urinary frequency, urgency, or dysuria may also be a sign of bladder cancer, particularly carcinoma in situ (Tis) .
Tumor grade and stage are the most important determinants of tumor behavior. When bladder cancer is suspected, the initial workup consists of voided urine cytology, cystoscopy, and radiological evaluation of the upper tracts with computed tomography urography or magnetic resonance urography .
Cystoscopy is a standard method used in the follow-up of patients with a bladder tumor and is recognized for its 90% sensitivity. However, cystoscopy is an invasive method and may require anesthesia, leading to extended periods of application, and aggravate patient compatibility .
| Patients and Methods|| |
The study protocol received institutional ethical committee approval, and informed consent was obtained. Between November 2014 and November 2015, 50 consecutive patients (44 men and 6 women; mean age: 64.3 years; range: 44–85 years) who presented with gross hematuria or suspected urinary bladder tumors were enrolled prospectively. Exclusion criteria included upper urinary tract tumors or stones, a history of urinary tract trauma, contraindications to MRI (e.g., pacemaker or metallic prostheses) or cystoscopy (e.g., unfit for anesthesia or urethral stricture), and refusal to consent to the study. All patients underwent magnetic resonance (MR) examination followed by conventional cystoscopy. The patients were evaluated using T2-weighted high-spatial-resolution MRI of the urinary bladder, followed by diffusion-weighted (DW) MRI. Precontrast T1 (with or without fat suppression) and immediate postgadolinium injection were performed if there were no contraindications.
To moderately distend the bladder, patients were instructed to start drinking water 1 h before the MRI examination. All patients were prohibited from urinating for at least 1 h before examination. In patients with a urethral catheter, 250–400 ml of sterile saline was used to distend the bladder.
Protocol of the magnetic resonance scan of the urinary bladder
Patients were examined with a 1.5-T MRI (Signa Horizon; GE Medical Systems, Milwaukee, Wisconsin, USA). MRI of the pelvis was performed in the axial, sagittal, and coronal planes using a combination of pulse sequences. The study was performed with the patients lying supine with their median sagittal plane perpendicular and coinciding with the midline of the scanner table. The following sequences were performed.
Initially, turbo spin-echo T2-weighted images (T2WIs) in the axial, sagittal, and coronal planes were obtained (repetition time (ms)/echo time (ms): 2250–3500/90–100; bandwidth: 20–83 kHz; matrix: 256 × 256; section thickness: 4–6 mm; intersection gap: 1–2 mm; and field of view: 20 cm).
Thereafter, free-breathing diffusion-weighted images (DWIs) were obtained in the axial plane using a body coil and a monodirectional gradient multisection fast spin-echo echo planar sequence (repetition time (ms)/echo time (ms): 3500–4500/60–70; bandwidth: 142 kHz; matrix: 256 × 256; section thickness: 4–6 mm; intersection gap: 1–2 mm; field of view: 36 cm; signals acquired with b values of 0, 500, and 1000 s/mm 2].
T1-weighted fast field-echo images were obtained using the water-selective excitation technique [repetition time (ms)/echo time (ms): 400–460/10–15; flip angle: 20°; matrix: 256 × 256; section thickness: 4–6 mm; intersection gap: 1–2; field of view: 36 cm; number of sections: 24–27; acquisition time: 26–30 s] before and after administration of 0.2 ml/kg of body weight of gadopentetate dimeglumine Magnevist 1.5-T MRI (Signa Horizon; GE Medical Systems, Milwaukee, Wisconsin, USA).
The data were processed using software (SPSS, version 15; SPSS Inc., Chicago, Illinois, USA), with conventional cystoscopy or the final histopathologic report as the reference standard. We evaluated the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of DW, T2-weighted, and T1-weighted postcontrast MRIs as aids in the identification of bladder tumors and the cause of the hematuria.
Conventional cystoscopy was performed by a urologist (who was blinded to the results of MRI) using a semirigid cystoscope while the patient received spinal anesthesia. In patients treated by means of radical cystectomy, tumor appearance and size were established from the final histologic report; otherwise, tumor appearance and size were established at cystoscopy using a ureteric catheter.
| Results|| |
The male-to-female ratio was 44:6. The incidence was in the age group 44–85 years. In the 50 patients with bladder tumors, 55 lesions were identified with conventional cystoscopy. Forty-five (90%) patients had one lesion and five (10%) patients had two lesions.
The locations of the 55 focal bladder lesions on MRIs included the posterior wall (16; 29.1%), the left lateral wall (11; 20.0%), the right lateral wall (8; 14.5%), dome (8; 14.5%), trigone (4; 7.3%), circumferential (5; 9.1%), and the anterior wall (3; 5.5%). The tumor appearance was fungating in 25 (45.5%) bladder lesions, papillary in 14 (25.5%), nodular in 11 (20%), and flat in five (9.0%). The diameter of the lesions ranged from 1 to 12 cm (mean: 4.6 ± 2.7 cm).
The histologic diagnosis was transitional cell carcinoma (TCC) in 30 of 50 (60.0%) patients, SCC in 17 (34.0%), and adenocarcinoma in three (6.0%). As regards MR staging, four (8%) patients were at T1, 12 (24%) patients were at T2, 23 (46%) patients were at T3, and 11 (22%) patients were at T4. The most common symptom was gross hematuria (33 patients; 66%).
Accuracy of T2WI for proper tumor staging was 75.0, 91.1, 78.3, and 81.8% for stages T1, T2, T3, and T4, respectively (P ≤ 0.001, highly significant) [Table 1].
|Table 1 T2-weighted image staging results on a stage-by-stage basis compared with histopathological staging|
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Accuracy of DWI for proper tumor staging was 75.0, 83.3, 95.7, and 100% for stages T1, T2, T3, and T4, respectively (P ≤ 0.001, highly significant) [Table 2].
|Table 2 Diffusion-weighted image staging results on stage-by-stage basis compared with histopathological staging|
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Accuracy of post-contrast-enhanced T1-weighted image for proper tumor staging was 75.0, 100, 88.2, and 71.4% for stages T1, T2, T3, and T4, respectively (P ≤ 0.001, highly significant) [Table 3].
|Table 3 Postcontrast T1-weighted image staging results on a stage-by-stage basis compared with histopathological staging|
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The sensitivity, specificity, and accuracy obtained using DWIs alone or DW plus T2WIs were significantly better than that using T2WIs alone. The sensitivity achieved using T2WI was 85%, whereas that achieved with DWIs alone or DW plus T2WIs together is 100% [Table 4].
|Table 4 Diagnostic accuracy using T2-weighted images and diffusion-weighted images for differentiating stage Tis to T2 tumors from T3 to T4 tumors|
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The sensitivity, specificity, and accuracy obtained using contrast-enhanced MR plus DWIs were significantly better than that obtained using contrast-enhanced MRIs alone. The sensitivity achieved using contrast-enhanced MRIs was 92%, whereas that achieved using DW plus contrast-enhanced MRIs together was 100% [Table 5] and [Figure 1] and [Figure 2].
|Table 5 Diagnostic accuracy using postcontrast T1-weighted images for differentiating Stage Tis to T1 tumors from T2 to T4 tumors|
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|Figure 1: Case no. 1. (a) Axial T2-weighted image (T2WI), (b) sagittal T2WI, and (c) coronal T2WI demonstrate ill-defined mass infiltrating the posterior wall of the urinary bladder (UB) extending to the adjacent part of the left lateral wall measuring 8.5 cm in maximum diameter. It displays low signal intensity in T2WIs. It infiltrates muscular layers of the UB with areas of likely disruption posteriorly and is seen inseparable from the uterine body, cervix, and upper vagina. (d) Diffusion-weighted image shows restricted diffusion with evidence of focal invading the perivesical fat planes along the left posterolateral wall of the UB. (e) Axial postcontrast T1-weighted image shows heterogeneous postcontrast enhancement.|
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|Figure 2: Case no. 2. (a) Axial T2-weighted image (T2WI), (b) sagittal T2WIs demonstrate two irregular nodular masses seen arising from the right posterolateral wall of the urinary bladder (UB) measuring 2.5 and 1.5 cm in maximum diameters, respectively. They display low signal in T2WI with preserved low signal intensity of the outer wall of the UB. (c) Axial postcontrast T1-weighted image shows heterogeneous postcontrast enhancement. (d) diffusion-weighted image shows restricted diffusion with high definition of its margin and no exophytic components.|
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| Discussion|| |
As known, MRI has multiple advantages such as no ionizing radiation, high spatial resolution, and high soft tissue contrast ; DWI has a high level of diagnostic performance in detecting bladder cancer and is comparable to T2WI but with better interobserver agreement. This may be due to the clear contrast visible in DWI; signals of bladder cancer are very bright, whereas images of surrounding tissues appear muted .
In the current study, 50 patients were examined by means of MR examination. The cystoscopy/biopsy was considered as a standard reference. The sensitivity, specificity, PPV, NPV, and accuracy of DW-MRI for detecting urinary bladder carcinoma were 100, 94, 97, 100, and 98%, respectively.
In a study carried out by Abou-El-Ghar et al. on 130 patients with hematuria, cystoscopy was considered as a standard reference. The sensitivity, specificity, PPV, NPV, and accuracy of DW-MRI were 98.5, 93.3, 100, 92.3, and 97%, respectively. The authors found excellent agreement between DW-MRI and conventional cystoscopy. Reviewers could identify almost all bladder lesions and missed only two lesions that were less than 4 mm in diameter.
El-Assmy et al.  studied the feasibility of using DW-MRI in bladder cancer follow-up after transurethral resection of the prostate. In 47 patients, cystoscopy identified 34 bladder lesions in 24 patients, and in the remaining 23 the bladder looked normal. The sensitivity, specificity, accuracy, PPV, and NPV of DW-MRI for identifying bladder tumors were 91.6% (22/24), 91.3% (21/23), 91.5% (43/47), 91.6% (22/24), and 91.3% (21/23), respectively.
With respect to results of histological examination of the transurethral endoscopic biopsy taken in our study from 50 patients, about 60% had TCC, 34% had SCC, and 6% had adenocarcinoma. These results are in agreement with those of Gandrup et al. , who reported that more than 70% of bladder cancers are TCCs.
In our study, 14 patients had pathologic lymph node involvement, of whom 10 (20%) were staged as N1, three (6%) were staged as N2, and one (2%) was staged as N3. Among the findings, 36/50 (72%) patients were free of lymph node involvement.
In our study, 13/50 (26%) patients were staged as M1 showing metastasis to the bone, liver, prostate, and peritoneal spaces. The most common metastasis in our study was to the bone, representing aggressive high-grade tumors at the time of presentation. Among the findings, 37/50 (74%) patients were staged as Mx as distant metastasis could not be assessed.
In our study, the accuracy of gadolinium-enhanced MR study was 94% in differentiating superficial from invasive tumors, which was slightly better than that in previous reports. The overall staging accuracy was 97% when contrast-enhanced and DWIs were used together.
However, Tekes et al.  reported that the accuracy was as low as 62% and overstaging was the most common error (32%), but they found that T staging accuracy improved up to 85% in differentiating superficial from invasive tumors.
Takeuchi et al.  reported that the tumor and submucosa were of similar signal intensity in 60% of the dynamic contrast-enhanced findings, and submucosal linear enhancement (SLE) was difficult to recognize in these cases. Thus, contrast-enhanced images might have limitations for use to correctly distinguish T1 tumors with intact SLE from T2 tumors with disrupted SLE. DWI could reduce overstaging because of its good contrast resolution.
Hayashi et al.  used an endorectal coil, using the criterion of SLE. Intact SLE adjacent to a tumor was regarded as indicative of stage T1 or lower. When the SLE was disrupted by a tumor but there was no infiltration into the perivesical fat, it was considered to be stage T2. The diagnostic accuracy of the study was 87% when differentiating between T1 or lower tumors and T2 or higher tumors, and the overall accuracy for staging bladder tumors was 83%.
We agree with the authors with regard to these two issues that could explain the improvement in our study as regards the accuracy for differentiating T2 or lower tumors from T3 and higher tumors, being slightly shifted from 94 to 97% when using contrast-enhanced MRI and DW-MRI, respectively.
| Conclusion|| |
For the radiological evaluation of urinary bladder carcinoma, MRI is a valuable imaging modality due to high tissue contrast, no radiation exposure, multiplanar imaging capabilities, and the possibility of tissue characterization. DW-MRI has advantages such as short acquisition time and high contrast resolution between tumors and normal tissue.
MRI has high reliability for the diagnosis of bladder tumors, which is similar to that of conventional cystoscopy. This noninvasive method could be efficiently used for evaluation of patients with hematuria of lower urinary tract origin.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]