Validity of Parametric MRI Using VIRADS

Bladder Cancer

Our aim in this prospective study is to evaluate the validity of the non-contrast biparametric MRI (bp-MRI), including T2-WI and DWI sequences, and the availability of an alternative to the mp-MRI, for the muscle invasiveness assessment of bladder cancer using VIRAD scoring in both techniques.

Urinary bladder cancer is the second most common neoplasm of the urinary tract worldwide. It accounts for 6-8% of malignancy in men and 2- 3% in women, with the highest incidence rates in North America , Europe and areas with endemic schistosomiasis in Africa and the Middle East.(1) Factors contribute to the development of bladder cancer are: advanced age, male sex, cigarette smoking and parasitic infection with schistosomiasis. Bladder cancer(BC)ranges from unaggressive non-invasive tumor(NMICB) that recur and commit patients to long life surveillance to aggressive and invasive tumors (MICB)with high disease mortality.(2) Knowledge of the clinical, histopathologic, and imaging features of common bladder neoplasms is essential. The first-line imaging tool for assessing bladder lesions is ultrasonography, which may be followed by a computed tomography or magnetic resonance imaging if the origin of the mass is unclear or if distant spread is suspected.(3) Accurate preoperative diagnosis of detrusor muscle invasion of BC is important because non- muscle-invasive (stage T1 or lower) and muscle-invasive (stage T2 or higher) BC are treated differently.Prognosis of the tumor depends mainly on grade ,depths of invasion and the presence of carcinoma insitu(CIS).(4) MRI now become the modality of choice for the local staging of BC , assessment of regional lymph node involvement and the tumor spread to pelvic bones and upper urinary tract.(5) As it has high tissue contrast, multiplanar imaging capabilities, and the ability of tissue characterization.(6) Currently, the multi-parametric magnetic resonance imaging (mp-MRI) is widely used for bladder cancer diagnosis and staging. It consists of the conventional sequence \[T2-weighted anatomic imaging (T2WI)\] and functional MRI techniques \[dynamic contrast-enhanced (DCE) imaging and diffusion-weighted imaging (DWI)\] .(7).With diagnostic accuracy in differentiation between MICB and NMICB was 84% with highest sensitivity 78%.(9) DWI used in mp-MRI is reported as the dominant sequence in evaluating BC muscle invasion .(14) To Avoid contrast material-related complications,the question askesd : Is contrast material important in the local staging of BC ?( 13) So assessing the diagnostic validity of the non contrast biparametric MRI (bpMRI) with that of (mpMRI) based on the Vesicle Imaging-Reporting and Data System (VI-RADS) in predicting muscle invasion by bladder cancer (BCa) is needed.(10). (VIRADS) scoring system was created in 2018 to standardise imaging and reporting of bladder cancer staging with mp- MRI which suggests the likelihood of detruser muscle invasion. Muscle invasion disease carries a worse prognosis and requires radical surgery.(4) VI-RADS provides high diagnostic accuracy to diagnose high grade and muscle invasive bladder cancer.(11) :Prospectively calculated and collected data will be analysed. Computer software: SPSS package 23 Statistical tests: Descriptive statistics will be performed with frequency and cross tabulations for categorical variables. Means and standard deviations will be measured for numerical variables. The chi-square test will be used for comparing independent categorical variables. Monte Carlo simulations will be run for multiple groups if comparisons will not meet the chi-square criteria; Fishers exact test will be used in the comparison of the groups. Students t-test will be used for comparing the numerical data displaying normal distribution; the MannWhitney U-test will be performed for the numerical variables not displaying normal distribution. The P-value will be set at 0.05 and all of the comparisons will be two-tailed.

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