ADC ratio and tumor contact length with the capsule as predictors of extracapsular extension of prostate cancer on mpMRI
Number:27ESURABS0016
Type:Scientific Electronic Presentation
Authors: Lorenzo Vassallo, Mirella Fasciano, Andrea Cerutti
Keywords:ADC RATIO - Prostate Cancer - MRI - Extracapsular
SECTIONS
Objectives

Tumor contact lenght (TCL) with the capsule, defined as the length of prostate tumor in contact with the capsule, has been proposed as an independent and reproducible predictor of extracapsular extension (ECE) of prostate cancer (PCa). LCC showed improved accuracy in predicting ECE compared to the previously reported qualitative MRI findings of bulging or irregularity of the capsule. However, its adoption in clinical practice has been slow for several reasons. Prior studies have been based on small numbers of patients and have assessed LCC using different thresholds (6–20 mm) using various MRI sequences (i.e., T2WI, ADC, or dynamic contrast-enhanced).

However, the thresholds suggested by previous studies show a large variability. This variability in TCL measurement leads to disagreement on the selection of the proper threshold to use in clinical practice and for...

...read more


Material and methods

We retrospectively analyzed 112 patients who underwent preoperative mpMRI and radical prostatectomy for PCa between October 2017 and December 2020.

Images were acquired under fasting conditions with a 1.5 T scanner (Optima MR450w, GE Healthcare, Milwaukee, Illinois, USA) using a 32-channel phased-array coil combined with air-inflated endorectal coil (Medrad, Indianola, Pa). Imaging protocol included three orthogonal T2w sequences, axial Diffusion Weighted Imaging (DWI) and Dynamic Contrast Enhanced (DCE) which was triggered to start simultaneously with the power injection of 0.1 mmol/kg gadobutrol(Gadovist, Bayer Schering, Berlin, Germany) through a peripheral line at 0.7 mL/s, followed by infusion of 20 cc normal saline at the same rate. Axial DWI was acquired at b-values of 0, 1000 and 2000 s/mm2. The average time to complete the whole MRI examination was 40...

...read more

Figure 1. Example of patient with frank breach of prostate capsule at axial-T2-weighted MRI (A) and at diffusion-weighted-imaging (B) excluded from the study.
Figure 2. Example of patient with overt seminal vesicle invasion at axial-T2-weighted MRI (A), at ADC map (B) and at sagittal-T2-weighted MRI (C) excluded from the study.

Results

41 patients were excluded from the study. Mean participants age was 66.8 (range years 55.2 - 78.5), median prostate-specific antigen was 7.3 ng/mL (range, 3.2-21.9 ng/mL) and median prostate volume was 52.2 ml (range, 36.5 - 80.4 mL).

In 71 men we found 87 PCa, 45 with ECE and 42 without.

The optimal cutoff for ADC ratio in predicting ECE was 0.46, which yielded an area under the ROC curve of 69% (95% CI: 57.8%-80.3%), corresponding to a sensitivity of 55% and a specificity of 78% (Figure 3). The optimal cutoff for TCL was 16.5 mm, which yielded an area under the ROC curve of 82.5% (95% CI: 73.8%-91.3%), corresponding to a sensitivity of 71% and a specificity of 84% (Figure 4). Combining the two criteria improved the diagnostic performance, yielding an area under the ROC curve of 84.6% (95% CI: 76.4%-92.8%), corresponding to a sensitivity of 79% and a specificity of...

...read more

Figure 3. The optimal cutoff for ADC ratio in predicting ECE was 0.46, which yielded an area under the ROC curve of 69% (95% CI: 57.8%-80.3%), corresponding to a sensitivity of 55% and a specificity of 78%.
Figure 4. The optimal cutoff for TCL was 16.5 mm, which yielded an area under the ROC curve of 82.5% (95% CI: 73.8%-91.3%), corresponding to a sensitivity of 71% and a specificity of 84%.

Conclusions

In patients with prostate cancer and no frank signs of ECE, ADC ratio and TCL were useful predictors of ECE and the best results were obtained when both the values were used in combination (Figure 6).

Our study has several limitation. First it is a retrospective study with a small number of patients. In addition mpMRI were analyzed by a single reader, who however had over 7 years of experience in interpreting prostate MRI. Inter-reader agreement was not evaluated, however previous studies showed that ADC and TCL had greater inter-reader reproducibility.

Further studies, possibly multicentric, are required to confirm our preliminary results in a larger series of patients.

Figure 6. Patient with a lesion in the posterior lateral section of right peripheral zone at prostate mid-gland. The lesion showed a TCL of 11 mm with ADC ratio of 0.38: at radical prostatectomy patologist identified ECE suggesting the importance of using both the values in combination to improve the performance.