Tumor contact lenght with the capsule vs arc-dimension-ratio for predicting extraprostatic extension of prostate cancer
Number:28ESURABS0007
Type:Scientific Electronic Presentation
Authors: Lorenzo Vassallo, Mirella Fasciano, Gisella Lingua, Federica Groppo Marchisio, Alberto Talenti
Keywords:mpMRI, prostate cancer, staging, extra-capsular.
SECTIONS
Objectives

To compare the diagnostic performance of tumor curvilinear contact length with the capsule (TCL) with that of arc-dimension ratio (tumor curvilinear contact length with the capsule divided by tumor dimension) for predicting extraprostatic extension (EPE) of prostate cancer (PCa) on multiparametric MRI (mpMRI) and to determine a threshold value to apply in clinical practice.  

Material and methods

BACKGROUND

Extraprostatic extension (EPE) is one of the most important prognostic factors for prostate cancer and it is associated with adverse oncological outcomes such as post-treatment biochemical recurrence, development of metastasis, and decreased survival. Recognition of the presence of EPE is critical in patients treated with radical prostatectomy (RP) (e.g., whether to perform nerve-sparing procedures) and treatment planning for patients who undergo radiotherapy [1,2]. 

Multiparametric magnetic resonance imaging (mp-MRI) has been widely utilized for the detection, local staging, and treatment planning in patients with prostate cancer. However, the accuracy of mp-MRI in determining EPE has been variable among studies. This may stem from the fact that EPE evaluation on MRI has traditionally been based on the subjective assessment...

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Figure 1. Graphical examples showing how the readers quantified capsule contact length (curvilinear line), tumor dimension (straight line), and their ratio (arc-dimension ratio). Each feature was measured on the image where it demonstrated greatest value, and not necessarily recorded on the same image. T2-weighted images of a 58-year-old (a) show capsule contact lengths of 32 mm, tumor dimension of 28 mm, and hence arc-dimension ratio of 1.14 (32/28).
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.

TCL and arc-dimension ratio were significantly different between the two groups (p<0.001).

The optimal cut-off for TCL in predicting EPE 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 specificity of 84% (Figure 2).

The optimal cut-off for arc-dimension ratio was 1.02, which yielded an area under the ROC curve of 84.6% (95% CI:75.6-93.6%), corresponding to a sensitivity of 86% and specificity of 82% (Figure 3).

Figure 2. The optimal cut-off for TCL in predicting EPE 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 specificity of 84%.
Figure 3. The optimal cut-off for arc-dimension ratio was 1.02, which yielded an area under the ROC curve of 84.6% (95% CI:75.6-93.6%), corresponding to a sensitivity of 86% and specificity of 82%.
Conclusions

In patients with prostate cancer and no frank signs of EPE, TCL and arc-dimension ratio were both useful predictors of EPE; arc-dimension ratio provided better performance than TCL. We recommended using 16.5 mm as a cut-off point for TCL and 1.02 for arc-dimension ratio (Figure 4 and 5).

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, in previous study TCL had greater inter-reader reproducibility, while arc-dimension-ratio relatively lower reproducibility compared with other quantitative measures, probably because of its nature as ratio of two variables,

Further studies, possibly multicentric, are required to confirm our preliminary results in a...

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Figure 4.T2-weighted image (a), diffusion weighted image (b = 2000 s/mm2)(b), and apparent diffusion coefficient (ADC) map (c) of pre-operative prostate magnetic resonance imaging of a 63-year-old male. The index lesion was categorized as score 5 on second version of Prostate Imaging Reporting and Data System standards owing to its size (15 mm). ADC value recorded 725 mm2/s. The lesion showed capsular bulging, capsular contact length of 25 mm, and thus arc-dimension ratio of 1.66 was assigned for this lesion, all of which are above the thresholds of each imaging parameter for extraprostatic extension (EPE). The lesion was confirmed as stage pT3a with EPE.
Figure 5.T2-weighted image (a), diffusion weighted image (b = 2000 s/mm2)(b), and apparent diffusion coefficient (ADC) map (c) of pre-operative prostate magnetic resonance imaging of a 59-year-old male. The index lesion was categorized as score 5 on second version of Prostate Imaging Reporting and Data System standards owing to its size (16 mm). ADC value recorded 689 mm2/s. The lesion showed mild capsular bulging, capsular contact length of 15 mm, and thus arc-dimension ratio of 0.93 was assigned for this lesion, capsular contact lenght was above the threshold for EPE, while arc-dimension-ratio was below. At pathology the lesion was confirmed as stage pT2 without EPE.