Published online Oct 30, 2023.
https://doi.org/10.4111/icu.20230120
Accuracy of Vesical Imaging-Reporting and Data System for muscle-invasive bladder cancer detection from multiparametric magnetic resonance imaging
,1
Chatwadee Limpaiboon,2
Satit Siriboonrid,1
Nattapong Binsri,1
Sarayut Kanjanatarayon,1
Weerayut Wiriyabanditkul,1
and Vittaya Jiraanankul1
Abstract
Purpose
The Vesical Imaging-Reporting and Data System (VI-RADS) was used to distinguish the invasive nature of bladder masses before surgery. These imaging criteria can be used to carefully select patients who are candidates for repeat transurethral resection of bladder tumor (Re-TUR-BT). One-third of patients are understage at the time of Re-TUR-BT. This study aimed to evaluate the discrimination accuracy of VI-RADS between non-muscle-invasive bladder cancer and muscle-invasive bladder cancer.
Materials and Methods
Patients with a bladder mass identified by cystoscopy who were assigned for TUR-BT were offered multiparametric magnetic resonance imaging (mpMRI) for VI-RADS. TUR-BT reports were compared with preoperative VI-RADS scores to evaluate the accuracy of discrimination of the muscle-invasive nature of the bladder mass.
Results
A total of 58 bladder tumor lesions were included, 13 with muscle-invasive bladder cancer and 45 with non-muscle-invasive bladder cancer. Sensitivity and specificity were 92.3% and 86.7%, respectively, when a VI-RADS cutoff of 4 or more was used to define muscle-invasive bladder cancer. Positive predictive value and negative predictive value were 66.7% and 97.5%, with an accuracy of 87.9%. The area under the receiver operating characteristic curve was 0.932 (95% confidence interval, 0.874–0.989), and the empirical optimal cutpoint from the Youden method was 3.
Conclusions
VI-RADS is an accurate tool for correctly differentiating muscle-invasive bladder cancer from non-muscle-invasive bladder cancer. We found a cutpoint of VI-RADS 1–3 vs. 4–5 to have the highest specificity and accuracy for the discrimination of non-muscle-invasive from muscle-invasive bladder cancer.
Graphical Abstract
INTRODUCTION
Bladder cancer is one of the most prevalent genitourinary cancers and progresses and spreads rapidly. It may result in disability or, perhaps, death. The estimated incidence rates of bladder cancer in Thailand are 4.2 and 1.3 per 100,000 population in males and females, respectively [1]. The most frequent clinical manifestation of this cancer is gross hematuria, which can be a late manifestation of the course of the disease; the tumor may already have spread to any layer of the bladder. About 20% to 30% of patients will present with muscle-invasive bladder cancer at the initial presentation [2].
Conventional investigation involving urine cytology or cystoscopy is performed to identify and confirm a bladder lesion in preparation for surgery. Transurethral resection of the bladder tumor (TUR-BT) is performed to collect the bladder mass for therapeutic purposes and to investigate the invasiveness of the bladder mass to the muscle layer via pathology report, which determines the next course of treatment. A statement based on solid evidence agrees that it is important to include the detrusor muscle in the tissue sample during TUR-BT. This is because if the detrusor muscle is missing, there is a risk of understaging of the bladder tumor and increased risk for residual disease [3]. Final pathology findings may reveal understaging in 33% of bladder tumors that underwent repeat transurethral resection of bladder tumor (Re-TUR-BT), especially in high-grade tumors [4]. Other research has also shown that the detrusor muscle plays an important role. In a study involving pT1 high-grade bladder cancer, the investigators found that if the detrusor muscle is missing, the chance of the cancer progressing to muscle-invasive bladder cancer is higher. Thus, it is important to pay attention to the detrusor muscle in these cases [5].
In the current guideline from the European Association of Urology (EAU) for non-muscle-invasive bladder cancer, a repeat resection is recommended only for pTa/pT1 high-grade bladder cancer cases when the detrusor muscle is absent [6]. For pTa low-grade bladder cancer, the absence of the detrusor muscle during the initial TUR-BT does not impact tumor recurrence, and no further attention is required [7].
The new Vesical Imaging-Reporting and Data System (VI-RADS) was introduced as a way to differentiate the muscle invasiveness of a bladder mass. The imaging criteria claim to have a high sensitivity and specificity for detecting muscle-invasive bladder cancer; however, it has not yet been generally verified as the investigation of choice [8]. The imaging criteria can be used to carefully select patients who are candidates for Re-TUR-BT [9]. Some multi-institutional studies are ongoing to validate the scoring system [10]. One-third of patients at the time of Re-TUR-BT are understaged as mentioned. In the future, validation of this tool for evaluating the muscle invasiveness of bladder cancer could significantly alter this limitation.
MATERIALS AND METHODS
1. Patient population
This was an experimental study conducted over the period of January to December 2021 in the urology Division of Urology, Department of Surgery at Phramongkutklao Hospital. The study was approved by an ethics committee (approval number: IRBRTA 1241/2021) and the institutional review board, Royal Thai Army Medical Department. Participants were recruited from the urology outpatient clinic among patients who were diagnosed with a bladder mass by cystoscopy and who underwent routine preoperative evaluation of whether they were candidates for TUR-BT or radical cystectomy. Patients were assigned for multiparametric magnetic resonance imaging (mpMRI) for VI-RADS evaluation. The inclusion criteria consisted of the presence of a detectable bladder mass on both cystoscopy and mpMRI, as well as thorough histological examination of the mass following TUR-BT. Furthermore, patients were excluded if they had undergone other treatments such as neoadjuvant chemotherapy or radiation prior to TUR-BT and exhibited contraindications for mpMRI, such as impaired renal function or diagnosed claustrophobic disorders. Cases where the histological analysis of the bladder mass indicated it to be benign were also subject to exclusion from our study.
2. mpMRI examination
The examination was performed with a 1.5 T magnet (Philip Ingenia). The pelvic imaging protocol focuses on the bladder. The standard VI-RADS protocol was used, as follows: thin-slice 3-mm two-dimensional T2-weighted sequences in the axial, coronal, and sagittal planes; axial diffusion-weighted imaging (DWI); and axial dynamic contrast-enhanced imaging (DCE) with the temporal resolution of DCE 30 seconds in 2 minutes after a single injection of Gadovist at 0.1 mmol/kg at a rate of 3 mL/s (Fig. 1) (b-values for DWI and apparent diffusion coefficient (ADC) were 0, 50, 400, 800, and 1,200) [11]. Antispasmodic drugs were given 30 minutes beforehand. Patients voided 1 to 2 hours before imaging, and then drank 500 to 1,000 mL of water 30 minutes before the examination.
Fig. 1
Summary schematic representation of VI-RADS scoring. VI-RADS, Vesical Imaging-Reporting and Data System; SC, structural category; SI, signal intensity; DCE, dynamic contrast-enhanced imaging; DWI, diffusion-weighted imaging.
3. Interpretation of VI-RADS
One competent radiologist alone reviewed all mpMRI results. This radiologist had 10 years of experience of advanced diagnostic body imaging. The radiologist was uninformed of the patient’s clinical and medical history, as well as their cystoscopy results. The radiologist examined each patient’s bladder lesion and evaluated the VI-RADS per lesion using T2-weighted imaging, DWI, and DCE. If the patient had multiple lesions, each lesion was checked. The images of each VI-RADS score are shown in Fig. 2.
Fig. 2
Images of VI-RADS scores. Images is a case courtesy of Dr. Chatwadee Limpaiboon, Department of Radiology, Phramongkutklao Hospital, Thailand. VI-RADS, Vesical Imaging-Reporting and Data System; T2W, T2-weighted imaging; DWI, diffusion-weighted imaging; DCE, dynamic contrast-enhanced imaging; ADC, apparent diffusion coefficient.
4. Histopathologic evaluation
All patients underwent monopolar TUR-BT within 8 weeks of mpMRI results at Phramongkutklao Hospital’s Division of Urology, Department of Surgery. An experienced pathologist examined the tissue to determine whether it was muscle-invasive. If the patient met the Re-TUR-BT criteria, having a high-grade tumor without the presence of detrusor muscle in the specimen, he or she underwent Re-TUR-BT within 6 weeks, according to the guidelines.
5. Statistical analysis
SPSS version 19 (IBM Corp.) was used to gather the data, and statistical analysis was also performed. The final pathology results indicated whether the bladder mass was muscle-invasive, and the participants were separated into two groups accordingly. We used a chi-square test to compare the frequency distributions of the VI-RADS score and the risk factors for bladder cancer, such as urinalysis results, mass type, urine pH, and urine cytology. We then used linear correlation analysis to describe the relationship between the pathological stage for each VI-RADS score and the pathological stage with each risk factor. The diagnostic performance of the VI-RADS score was evaluated by analyzing the receiver operating characteristic (ROC) curve and the area under the curve. Sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were also evaluated. Values of p<0.05 indicated statistical significance.
RESULTS
A total of 37 individuals underwent mpMRI and TUR-BT. After we applied the exclusion criteria, 35 individuals (31 males and 4 females) with a total of 58 bladder lesions were included in the study. The participants’ demographic data are shown in Table 1.
Table 1
Demographic data of the study population
To determine whether any other characteristic was associated with the muscle invasiveness of the detected mass, characteristics such as underlying disease and urine analysis findings were analyzed after the participants were divided into two categories: those with muscle-invasive and those with non-muscle-invasive disease. The correlations of the factors with muscle-invasive bladder cancer are shown in Table 2. The pathology results from TUR-BT were non-muscle-invasive bladder cancer in 45 lesions (77.6%) and muscle-invasive bladder cancer in 13 (22.4%). The risk factors associated with the development of muscle-invasive bladder cancer included urine white blood cell (WBC) and red blood cell (RBC) counts of more than 100 per high-power field (hpf), a greater dimension of bladder mass, a VI-RADS score surpassing 3, and urine cytology outcomes indicating the presence of atypical cells.
Table 2
Factors studied for correlation with muscle-invasive bladder cancer
A radiologist also assigned a VI-RADS score, with a score of 1 indicating that muscle invasion is highly unlikely (24 lesions), a score of 2 indicating that muscle invasion is unlikely (13 lesions), a score of 3 indicating that muscle invasion is questionable (3 lesions), a score of 4 indicating that muscle invasion is likely (14 lesions), and a score of 5 (4 lesions). For VI-RADS scores of 3, 4, and 5, respectively, 33%, 64%, and 75% of muscle-invasive masses were found in each category (none of the samples with a VI-RADS score of 1 or 2 were muscle-invasive bladder cancer) (Fig. 3). A final VI-RADS score of 3 was the empirical cutpoint for detecting muscle-invasive bladder cancer using Youden’s index. We discovered that the VI-RADS score of 3 had 100% sensitivity, 82.2% specificity, and 86.2% accuracy. A VI-RADS score of 4 had 92.3% sensitivity, 86.7% specificity, and 87.9% accuracy. Table 3 also shows the positive and negative predictive values. The area under the ROC curve was 0.932, and the ROC curve analysis is summarized in Fig. 4.
Fig. 3
Distribution of Vesical Imaging-Reporting and Data System (VI-RADS) score within the population according to histologic study of bladder mass.
Fig. 4
Receiver operating characteristic (ROC) curve of the Vesical Imaging-Reporting and Data System (VI-RADS). CI, confidence interval.
Table 3
Accuracy of each VI-RADS score for detecting muscle-invasive bladder mass
DISCUSSION
We gathered the data in this study prospectively as patients received a new diagnosis in the outpatient department, underwent cystoscopy, and subsequently underwent mpMRI to determine whether the mass was muscle-invasive or non-muscle-invasive. A large section of the sampled bladder masses were given a low grade (VI-RADS scores of 1 and 2), whereas a small portion of the sampled bladder masses were assigned a high grade (VI-RADS scores of 3 to 5). We found the VI-RADS score to have high sensitivity, high specificity, and high accuracy. Several studies have set the muscle-invasive bladder cancer cutpoint at 3 or 4, depending on the literature [12, 13]. In our research, we discovered that the sensitivity, specificity, and accuracy were 100%, 82.5%, and 86.21%, respectively, at a cutpoint of 3. Sensitivity, specificity, and accuracy were 92.3%, 86.7%, and 87.9% at a cutpoint of 4. Regarding bladder cancer, we need to detect all muscle-invasive bladder cancer because of its high morbidity and mortality. In our opinion, we advise adopting 4 as a cutpoint because of the higher specificity and accuracy. Even with the lower sensitivity of the cutpoint of 4 compared with the cutpoint of 3, the tool accurately shows that the risk for muscle invasiveness is higher. The ROC curve indicates favorable outcomes for this diagnostic tool and establishes VI-RADS greater than 3 as the ideal criterion to detect muscle-invasive bladder cancer.
In this study, we found that urine WBC and RBC counts of more than 100 per hpf, a greater dimension of bladder mass, a VI-RADS score of more than 3, as well as urine cytology outcomes indicating the presence of atypical cells were risk factors for muscle-invasive bladder cancer. But because of the small number of cases of non-muscle-invasive bladder cancer, we need more study cases to evaluate the risk factors for muscle-invasive disease.
A limitation of our study was that there was only one radiologist, and as such, there was no interobserver variability. The radiologist involved in this study had more than 10 years of radiological experience as well as 5 years of experience reading mpMRI findings. In addition, to identify the risk factors for the muscle-invasive nature of bladder masses, we had a limited sample of high-grade VI-RADS patients (scores of 3 to 5) and a small number of patients with muscle-invasive disease. This suggests that additional research may be necessary to verify the VI-RADS. Also, we used only one MRI model (Philip Ingenia 1.5 Tesla). All the masses were excised by TUR-BT because the patient who was selected to undergo radical cystectomy had been given neoadjuvant chemotherapy prior to the surgery and thus was eliminated from the study. In recent years, Thailand has not employed the VI-RADS grading system much, and there have been few studies on this subject. We encourage the use of this diagnostic technique as a predictor of muscle-invasive bladder cancer after finding a bladder mass because only a small number of radiologists are skilled in interpreting mpMRI findings in this area. This can aid in clinical decision-making regarding the bladder mass type. As the VI-RADS score is thoroughly validated, we anticipate that it will be able to help physicians decide whether to do a VI-RADS score with merely a bladder biopsy or, if muscle-invasive nature is shown, to proceed directly to radical treatment rather than TUR-BT. In addition, the VI-RADS score can be used in place of TUR-BT if the bladder mass determined by TUR-BT is unclear.
CONCLUSIONS
The VI-RADS is an accurate tool to correctly differentiate muscle-invasive bladder cancer from non-muscle-invasive bladder cancer. We found a cutpoint of VI-RADS of 1–3 vs. 4–5 to have the highest performance for the discrimination of non-muscle-invasive from muscle-invasive disease.
CONFLICTS OF INTEREST:The authors have nothing to disclose.
FUNDING:This work was financially supported by Department of Surgery, Phramongkutklao Hospital, Thailand.
AUTHORS’ CONTRIBUTIONS:
Research conception and design: Chatwadee Limpaiboon and Vittaya Jiraanankul.
Data acquisition: Chayanon Jai-ua, Sarayut Kanjanatarayon, and Weerayut Wiriyabanditkul.
Statistical analysis: Chayanon Jai-ua and Vittaya Jiraanankul.
Data analysis and interpretation: Chayanon Jai-ua, Chatwadee Limpaiboon, and Vittaya Jiraanankul.
Drafting of the manuscript: Chayanon Jai-ua.
Critical revision of the manuscript: Satit Siriboonrid, Nattapong Binsri, and Vittaya Jiraanankul.
Obtaining funding: Chayanon Jai-ua.
Supervision: Vittaya Jiraanankul.
Approval of the final manuscript: all authors.
ACKNOWLEDGMENTS
The authors are grateful to the Department of Radiology, Phramongkutklao Hospital, Thailand who participated in this study.
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