Evaluation of risk of muscle invasion, perivesical and/or lymph node affectation by diffusion-weighted magnetic nuclear resonance in the patient who is a candidate for radical cystectomy.

INTRODUCTION

Preoperative staging of bladder cancer using imaging methods has serious limitations. The accuracy of the abdominal diffusion-weighted magnetic resonance (DW-MRI) to predict residual muscle invasion, perivesical and/or lymph node affectation in the cystectomy specimen is evaluated.

MATERIAL AND METHODS

A prospective study was performed on 20 patients with high grade muscle invasive bladder cancer who received transurethral resection of the bladder (TURB) in a period of <1 month. The DW-MRI was performed before the radical cystectomy and the radiologist predicted muscle invasion, extravesical affectation and lymph node affectation, being blind to the histopathological study. Sensitivity (S), specificity (sp), positive predictive value (PPV), negative predictive value (NPV) and accuracy (Ac) of the test were analyzed. The medians of the apparent diffusion coefficient (ADC) value (Mann-Whitney) were compared and the ROC curves study for DW-MRI and ADC was carried out.

RESULTS

Distribution by categories was: pT0 1(5%), pT1 6(30%), pT2 2(10%), pT3 8(40%) and pT4 3(15%). There was agreement in the T-pT assignment in 17(85%). In 7(35%) there was lymph node affectation (pN1-2). Consistency of the DW-MRI for muscle affectation was k=.89 (CI .67-1; S=1.0, Sp=,86, PPV=.93, NPV=1.0, Ac=.95), for perivesical fat affectation k=.6 (CI .25-.95; S=.8, Sp=.8, PPV=.8, NPV=.8, Ac=.8) and for lymph node affectation k=.89 (CI .67-1; S=.86, Sp=1.0, PPV=1.0, NPV=.93, Ac=.95). Mean value of ADC was greater in G2 tumors (OMS1987) compared to G3 (p=.08). Evaluation of DW-MRI imaging and ADC numerical value showed equivalent areas under the curve for muscle (.93 and .9; Z=.7), fat (.8 and .91; Z=.31) and lymph node (.93 and .97; Z=.36) affectation, respectively.

CONCLUSIONS

DW-MRI allows for good pre-operative evaluation of the patient who is a candidate for cystectomy, especially for the prediction of muscle (<pT2 vs ≥pT2) and/or lymph node (N0 vs N1-2) affectation. Both are key points to choice the therapeutic attitude after the bladder TURB. Furthermore, the ADC coefficient also predicts tumor differentiation grade.