AUA 2019: Role of Diffusion-Weighted MRI in Predicting ≥pT2 and ≥pT3 Upper Tract Urothelial Cancer

Chicago, IL ( Accurate preoperative T staging is crucial for selecting candidates of lymph node dissection and neoadjuvant chemotherapy in upper tract urothelial carcinoma (UTUC) patients. However, image-based clinical T stage is often inconsistent with pathological T stage and clinical understanding is quite common. Apparent diffusion coefficient (ADC) value measure on diffusion-weighted MRI (DW-MRI) is reported to reflect the invasive and proliferative potential of bladder urothelial carcinoma.

The objective of this study was to investigate the role of ADC in predicting >=pathological T2 and >=pathological T3 or positive pathological nodes in UTUC. Furthermore, the authors attempted to construct and internally validate algorithms predicting >=pT2 and >=pT3 or pN+ UTUC incorporating ADC values.

This was a retrospective single-institution study consisting of 58 UTUC patients who underwent MRI/CT scan and then had radical nephroureterectomy (RNU) between 2013 and 2018. The best cut-off ADC values to predict >=pT2 and >=pT3 or pN+ UTUC were determined using partition analysis. Variables predicting worse disease were identified using multivariable logistic regression analysis. In this study, the standardized ADC was measured which is defined as the minimal tumor ADC divided by the mean psoas ADC.

The results demonstrated that of the 58 patients in the study, 16 (28%) were diagnosed with >=clinical stage T3 on CT/MRI. Pathological examination of RNU specimens revealed >=pT2 and >=pT3 or pN+ in 35 (60%) and 31(53%) of patients, respectively. The associations of standard ADC with >=pT2 and >=pT3 or pN+ UTUC is shown in figure 1. The final multivariable models predicting worse disease demonstrated that an ADC <1.145 predicted both >=pT2 and >=pT3 disease. The algorithms predicting >=pT2 and >=pT3 or pN+ disease are shown in figure 2.

In conclusion, a lower ADC value appears to reflect potential invasive UTUC. Algorithms incorporating ADC values, hydronephrosis, and voided urine cytology may improve the accuracy of prediction >=Pt2, and >=pT3 or Pn+ UTUC, compared with standard image-based clinical T stage.

Figure 1 – Association of standardized ADC with >=pT2 and >=pT3 or pN+ UTUC:
AUA2019_of Diffusion-Weighted MRI _1.png

Figure 2 – Algorithms for prediction of disease staging:
AUA2019 of Diffusion Weighted MRI 2


Presented by: Fumitaka Koga Komagome Hospital, Tokyo, Japan

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre @GoldbergHanan at the American Urological Association's 2019 Annual Meeting (AUA 2019), May 3 – 6, 2019 in Chicago, Illinois