Evaluation of magnetic resonance imaging for bladder cancer detection following transurethral resection of bladder tumour (TURBT)

Abstract

Purpose: To evaluate the performance of MRI for detection of bladder cancer following transurethral resection of bladder tumour (TURBT).

Methods: This single-centre retrospective study included forty-one consecutive patients with bladder cancer who underwent bladder MRI after TURBT. Two uroradiologists retrospectively assessed the presence of tumour using bladder MRI with and without DWI (diffusion weighted imaging) using a five-point Likert scale. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated and inter-reader agreement was assessed. Histopathology was used as the reference standard.

Results: 24 out of 41 patients (58.5%) had no residual tumour or Tis (carcinoma in situ) after TURBT. Sensitivity, specificity, PPV and NPV for detection of tumour using T1WI (T1-weighted imaging) and T2WI (T2-weighted imaging) was 50.0%, 54.6%, 21.1%, and 81.8%, respectively and for T1WI, T2WI and DWI combined was 100%, 76.5%, 50.0% and 100%, respectively. Overestimation of tumour was more common than underestimation. MRI showed high accuracy for patients in whom there was no residual tumour (78.9%). Inter-reader agreement for tumour detection improved from fair (κ = 0.54) to moderate (κ = 0.70) when DWI was included.

Conclusion: Non-contrast MRI with DWI showed high sensitivity and relatively high specificity for detection of residual tumour after TURBT. Inter-reader agreement improved from fair to moderate with the addition of DWI. MRI can be useful after TURBT in order to guide further management.

Keywords: Bladder cancer; Diffusion weighted imaging (DWI); Magnetic resonance imaging; Staging; Transurethral resection of bladder tumour (TURBT).

Fig.1

Flow diagram showing patient enrolment

Fig. 2

ROC curves for detection of bladder cancer following TURBT. AUC value of ROC analysis was 0.587 for T1WI and T2WI and 0.890 for T1WI, T2WI and DWI

Fig. 3

Axial T1WI (A), T2WI (B), DWI (C) and ADC map (D) in a 68-year-old male with urothelial carcinoma who underwent MRI after TURBT shows a 5 mm lesion at the anterior bladder wall to the left of the midline close to site of known multifocal tumour seen at TURBT (pT1G3). This lesion was missed on the anatomical sequences (A, B) but the focal hyperintense area at DWI (arrow) and corresponding restricted diffusion on ADC maps (C, D) allowed this to be called with the combined read. Cystectomy confirmed tumour in this location, pTis disease

Fig. 4

Axial T1WI (A), T2WI (B), DWI (C) and ADC map (D) in a 75-year-old male with urothelial carcinoma who underwent MRI after TURBT shows thickening and perivesical stranding at the left posterolateral bladder wall post-TURBT. Based on the anatomical sequences this finding could be interpreted as T3b disease (A, B), however there was no diffusion restriction to suggest residual/recurrence disease (C, D), the staging was therefore organ-confined disease. Cystectomy showed no residual disease.

Fig. 5

Axial T1WI (A), T2WI (B), DWI (C) and ADC map (D) in a 67-year-old male with urothelial carcinoma who underwent MRI after TURBT shows a 9 mm lesion at the right ureteric orifice post-TURBT (G3pTa). Based on the anatomical sequences this finding could be interpreted as residual disease (A, B). Although this was hyperintense at DWI (arrow) there was no diffusion restriction (C, D) as ADC was not low, and therefore this was interpreted as negative for residual/recurrence disease. Serial cystoscopic biopsies showed no evidence of malignancy