Objective: To prospectively evaluate the use of MRI for the detecting of bladder tumors and the T- stage using T2W, T1W and diffusion-weighted images (DWI). Material and methods: Twenty-eight consecutive patients (21 men, 7 women; age range, 20 - 82 years; mean age, 62.8 years) suspected of bladder tumors underwent MRI, flexible cystoscopy and transurethral resection (TURB). The presence of bladder tumor was confirmed by histopathology in 21 patients; 18 patients had pTa, one pT1 and two pT2. The images were reviewed by two uroradiologists. They assigned the presence of a bladder tumor and whether the tumor was non-muscle invasive (Ta and T1) or muscle- invasive (T2, T3 or T4). Results: Compared to the histopathological results, the accuracy for identifying a bladder tumor was 60.7% and 53.7% for reviewer A and B, respectively. The sensitivity and specificity were 66.7%/61.9% and 57.1%/42.9%. Positive predictive values were 82.6%/ 76.5%. The overall staging was correct in 47.6%/52.5%, but improved on stage-by-stage up to 50%/66.7%. The agreement between the reviewers was moderate in the detecting, staging and location of the tumor (Kappa = 0.47 - 0.57). Conclusion: A simple MRI using no contrast media, but DWI, cannot replace flexible cystoscopy in the detection of new or recurrent bladder tumors.
Bladder cancer is the most common cancer in the urinary tract and there are approximately 75,000 new cases in the US every year [
A MR examination is painless for the patient and could be an alternative to cystoscopy if the patient, e.g. has radiation injuries, infection or in other ways is not able to undergo cystoscopy. Several studies [
This study was approved by the Local Committee for Health Research Ethics (No. H-2-2011-148) and by the Danish Data Protection Agency. Written and oral informed consent was obtained from all patients who partici- pated in the study.
Patients referred to TURB due to suspicion of first-time or recurrent bladder tumor between August and No- vember 2013 were invited to participate in the study. Exclusion criteria included severe claustrophobia, preg- nancy, magnetic medical implants such as cardiac pacemakers and age <18 years. A total of 32 consecutive pa- tients were enrolled. Four cancelled or did not show for the examination. The remaining 28 patients underwent MR examination before TURB. The study population was composed of 21 men (75%) (mean age, 65 years; range, 43 - 82 years) and seven women (mean age, 56.3 years; range, 30 - 74 years). The patient records were reviewed regarding sex, age, previous surgery, symptoms and urological findings at the first visit. The results of the flexible cystoscopy, the TURB and the pathology reports were noted.
All examinations were performed on a 3T Philips Achieva (Best, the Netherlands) using a 6-channel array coil. The patients were asked to drink approximately 500 ml of water an hour before the examination to ensure a filled bladder. They were scanned in prone position with a small pouch under the lower abdomen to compress the fat surrounding the bladder. Ten minutes before the examination, the patients received 1 ml of Hyoscin-butyl- bromid (Buscopan®, Boehringer Ingelheim, Copenhagen, Denmark) in their deltoid or vastus lateralis muscle. No contrast media and no breath hold were used.
First, T2-weighted (T2W) sequences in the axial, sagittal and coronal planes were obtained (repetition time (TR) msec/echo time (TE) msec, 4700 - 4800/80; matrix, 264 × 176; section thickness 3 mm; field of view (FOV), 21 cm). Then DWI were obtained in the axial plane (TR msec/TE msec, 2100/55; matrix, 180 × 113; section thickness, 3 mm; FOV, 18 cm; b-values sec/mm2, 0, 100, 500, 750, 1000). Lastly, a T1-weighted (T1W) sequence in the axial plane was performed (TR msec/TE msec, 540/10; matrix, 200 × 220; section thickness, 3 mm; FOV, 20 cm). All images were forwarded to PACS (iSite, Phillips, Best, The Netherlands).
The MR images were evaluated individually by two experienced uroradiologists, who only had information re- garding the reason for referral (suspicion of bladder tumor). The detection of a tumor was based on the T2W images and DWI together. The T1W images were used to assess lymph node presence and extravesical tumor mass. A questionnaire was used for the review. The detection and location of the bladder tumor was specified using the following options: 1) right side of the bladder, 2) left side, 3) the trigone, 4) posterior wall, 5) anterior wall and 6) the dome. The presence of high signal intensity (SI) on the DWI was noted for each tumor. For the appearance of the bladder, the options were 1) smooth, 2) trabeculation, and 3) ureterocele. The presence of en- larged lymph nodes and bone-marrow metastasis, and whether they had high SI on DWI, was noted. The staging of the bladder tumor was determined as being Ta-T1 or T2, T3 or T4, thereby dividing the tumor into NMIBT and MIBT using the anatomical criteria used by Takeuchi et al. [
All the patients underwent flexible cystoscopy and MRI. The placement and the appearance of the bladder tumor were noted.
The specimens were reviewed by an uropathologist for the diagnosis including the pT staging and grading. The tumors were graded using the WHO 2004 classification [
The statistical analyses were performed using the software “R” and the Statistical Package for Social Sciences, version 20 (SPSS, Chicago, Illinois, USA). In the evaluation of the two reviewers’ performance in identifying, staging and locating bladder tumors, kappa statistics were applied. A Kappa value less than 0.20 was poor, 0.21 - 0.40 fair, 0.41 - 0.60 moderate, 0.61 - 0.80 good and 0.81 - 1 was considered excellent.
The reason for the referral and the distribution among the pathology stages is shown in
The left image shows high signal intensity (SI) in the tumor (white arrow) on the DWI sequence. The right image shows the corresponding ADC map showing the tumor with low SI (black arrow). The area for measuring the ADC value is also shown. The region of interest (ROI) was placed in the darkest section of the tumor area. Histopathological examination revealed a pT2 tumor
An example of how a pTa tumor appears on axial T2W, DWI and ADC-map. The left image shows a T2W image, the middle an ADC map and the right a DWI. This tumor did not have high SI on DWI
. Symptoms grouped by pathology stage.
Symptoms | Benign conditions/Normal No. (%) | NMIBT (pTa, pT1) No. (%) | MIBT (pT2-pT4) No. (%) |
---|---|---|---|
Macroscopic hematuria | 1 (3.5) | 5 (17.9) | 1 (3.5) |
Microscopic hematuria | 2 (7) | - | - |
Recurrent bladder cancer | 3 (10.7) | 12 (42.9) | 1 (3.5) |
Incidental finding | - | 1 (3.5) | - |
Nocturia | 1 (3.5) | 1 (3.5) | - |
Total | 7 (25) | 18 (64.3) | 3 (10.7) |
Of the identified tumors, 15 had a high SI on the DWI (b = 1000 sec/mm2). Two tumors did not have high SI: one was a small pTa tumor; the other was a small papilloma with a minimal area of invasion of lamina propria (pT1) and the finding of CIS. Both tumors were recurrent cancers.
The mean and standard deviations of the ADC values (×10−3 mm2/sec) were as follows: carcinomas (n = 15), 1.89 ± 0.53, the peripherical zone of the prostate (n = 11), 2.70 ± 0.66 and the transition zone of the prostate (n = 11), 2.10 ± 0.48. There was a statistically significant difference between ADC values of the bladder compared to the peripherical (p = 0.023) and central zone of the prostate (p = 0.02), respectively.
Both reviewers staged 13 patients to have non-muscle invasive (Ta/T1) and four muscle invasive tumors (T2 or T3). Both reviewers staged one tumor as being T2, but histopathology revealed it to be a biopsy sample of the detrusor muscle with necrotic tissue and no malignancy. The overall staging was 47.6%/52.4%, but improved on stage-to-stage performance up to 66.6% (
The accuracy of reviewer A was 60.7% and for reviewer B 53.8%. The sensitivity for detecting tumors were 66.7%/61.9% for reviewer A and B, respectively. The specificity was 57.1%/42.9%, the positive predictive val- ue (PPV) 82.6%/76.5% and the negative predictive value (NPV) 36.4%/27.3% for reviewer A and B, respec- tively.
The agreement between the readers was moderate in both identifying a tumor (kappa = 0.57), the placement (kappa = 0.47) and staging (kappa = 0.53).
The distribution of identified tumors based on pathology stage appears in
Studies have reported sensitivities between 40% - 100% (
The left bar in each category of pathology represents Re- viewer A and the right bar Reviewer B. The figure illustrates the findings of the MR examinations and the distribution of histopa- thology. The most overlooked tumor was the non-invasive papillo- ma (pTa)
. Comparison between the two readers in staging of bladder tumors.
Pathology | Correctly staged | Overstaged | Understaged | ||||
---|---|---|---|---|---|---|---|
Reviewer A | Reviewer B | Reviewer A | Reviewer B | Reviewer A | Reviewer B | ||
Normal/Benign | % | 66.7 | 50 | 33.3 | 50 | - | - |
No. | 4/6 | 3/6 | 2/6 | 3/6 | - | - | |
pTa-pT1 | % | 61.1 | 50 | 11 | 11 | 38.9 | 44.4 |
No. | 11/18 | 9/18 | 2/18 | 2/18 | 7/18 | 8/18 | |
pT2 | % | 50 | 100 | 50 | 0 | - | - |
No. | 1/2 | 2/2 | 1/2 | 0 | - | - | |
Overall | % | 52.4 | 47.6 | 14.3 | 14.3 | 33.3a | 38.1 |
No. | 11/21 | 10/21 | 3/21 | 3/21 | 7/21a | 8/21 |
aThe tumor was not identified on MRI.
study was retrospective, had a smaller number of patients included and MRI was performed after biopsies. Our population included 21 patients with carcinoma and 64.3% of these were pTa tumors. This is a high percentage of low stage tumors. Compared with other studies (
Correct staging of the bladder tumors is crucial for the correct choice of treatment. Our results show that in approximately 50% of the patients the staging was correct. It improved up to 66% when differentiating between NMIBT
. A summarized table of MR studies and bladder tumor detection.
Author | Study type | Tesla | MR type | No pt. | Statisticsa (%) | ADC (×10−3 mm2/sec) |
---|---|---|---|---|---|---|
Present study | Prospective | 3 | T2W, T1W, DWI | 28 | Sens: 61.9 - 66.7 Spec: 42.9 - 57.1 | 1.89 ± 0.53 |
Wu et al. [9] 2013 | Prospective | 3 | T2, DWI | 362 | T2 + DWI: Sens: 89 - 94 Spec: 93 - 100 Accuracy: 92 - 98 | - |
Kobayashi et al. [7] 2011 | Prospective | 1.5 | T2, DW | 104 | DWI sens: 91.3 - 92.0 T2 sens: 89.4 - 91.0 | 0.39 - 2.07 |
Avcu et al. [8] 2011 | Prospective | 1.5 | T2, DWI | 63 patients + 20 healthy controls | Sens: 100.0 Spec: 76.5 PPV: 92.0 NPV: 100.0 Accuracy: 93.7 | 1.07 ± 0.26 |
Abou-El-Ghar et al. [10] 2009 | Prospective | 1.5 | T2, DWI | 130 | Sens: 98.1 Spec: 92.3 PPV: 100 NPV: 92.3 Accuracy: 97 | - |
Watanabe et al. [15] 2009 | Retrospective | 1.5 | T1, T2, DW, Contrast series | 18 | T1W + T2W + DWI: Sens: 40.0 Spec: 93.0 | - |
El-Assmy et al. [12] 2008 | Prospective | 1.5 | T2, DWI | 43 | Sens: 100.0 PPV: 100.0 | 1.40 ± 0.51 |
El-Assmy et al. [11] 2009 | Prospective | 1.5 | T2, DWI | 106 | DWI: Sens: 98.1, PPV: 100 T2: Sens: 96.2 PPV: 100 | - |
Matsuki et al. [6] 2007b | Retrospective | 1.5 | DWI | 15 | Sens: 100.0 Spec: 100.0b | 1.18 ± 0.21 |
aSens: Sensitivity; Spec: Specificity; PPV: positive predictive value; NPV: negative predictive value; bMR performed after biopsy.
and MIBT (
The mean ADC value in our study was higher than other studies (
In a study by Tekes et al. [
In a recent study by El-Assmy [
Limitations of the study were the small numbers of patients, and that the distribution of the T-stages was un- even with a large number of pTa-pT1 and a small numbers of pT2.
We were not able to establish the radiologic-cystoscopy correlation regarding location of the bladder because the urologists did not use a standard questionnaire during cystoscopy, but instead described the location by words. The strength is that we prospectively and consecutively included patients in a population with many re- current bladder tumors with low T-stages which have not been done before; previous studies have been retros- pective or have had a population with higher T-stage tumors.
The literature mentioned in this paper show that the accuracy of both detection and staging of the bladder tu- mors increases when adding DWI, but even more when adding contrast-media series. Our study was performed on a limited group of patients who underwent an easy-to-perform MRI without contrast media, but with T1W, T2W and DWI sequences, thereby making the examination easier, quicker and without potential adverse effects to the contrast media. However, the study results show low sensitivity, specificity and accuracy and are not adequate to start using MRI of the bladder in the work-up of patients with suspected bladder tumors. More stu- dies are needed in order to determine if this kind of MRI of the bladder is feasible in the work-up of patients suspected for bladder tumors in a population with a high percentage of pTa and pT1 stage tumors.
In conclusion, our results show that MRI performed on a 3-Tesla scanner using only T2W, T1W and DWI can- not be used as an alternative to flexible cystoscopy in the detecting and staging of bladder tumors.