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Published on: April 9, 2019
Evaluation of MRI for diagnosis of extraprostatic extension in prostate cancer
Satheesh Krishna1, Christopher S Lim1, Matthew D F McInnes1
1Department of Medical Imaging, Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada.
Purpose:
To assess the ability of magnetic resonance imaging (MRI) to diagnose extraprostatic extension (EPE) in prostate cancer.
Materials And Methods:
With Institutional Review Board (IRB) approval, 149 men with 170 ≥0.5 mL tumors underwent preoperative 3T MRI followed by radical prostatectomy (RP) between 2012-2015. Two blinded radiologists (R1/R2) assessed tumors using Prostate Imaging Reporting and Data System (PI-RADS) v2, subjectively evaluated for the presence of EPE, measured tumor size, and length of capsular contact (LCC). A third blinded radiologist, using MRI-RP-maps, measured whole-lesion: apparent diffusion coefficient (ADC) mean/centile and histogram features. Comparisons were performed using chi-square, logistic regression, and receiver operator characteristic (ROC) analysis.
Results:
The subjective EPE assessment showed high specificity (SPEC = 75.4/91.3% [R1/R2]), low sensitivity (SENS = 43.3/43.6% [R1/R2]), and area-under (AU) ROC curve = 0.67 (confidence interval [CI] 0.61-0.73) R1 and 0.61 (CI 0.53-0.70) R2; (k = 0.33). PI-RADS v2 scores were strongly associated with EPE (P < 0.001 / P = 0.008; R1/R2) with AU-ROC curve = 0.72 (0.64-0.79) R1 and 0.61 (0.53-0.70) R2; (k = 0.44). Tumors with EPE were larger (18.8 ± 7.8 [median 17, range 6-51] vs. 18.8 ± 4.9 [12, 6-28] mm) and had greater LCC (21.1 ± 14.9 [16, 1-85] vs. 13.6 ± 6.1 [11.5, 4-30] mm); P < 0.001 and 0.002, respectively. AU-ROC for size was 0.73 (0.64-0.80) and LCC was 0.69 (0.60-0.76), respectively. Optimal SENS/SPEC for diagnosis of EPE were: size ≥15 mm = 67.7/66.7% and LCC ≥11 mm = 84.9/44.8%. 10th -centile ADC and ADC entropy were both associated with EPE (P = 0.02 and < 0.001), with AU-ROC = 0.56 (0.47-0.65) and 0.76 (0.69-0.83), respectively. Optimal SENS/SPEC for diagnosis of EPE with entropy ≥6.99 was 63.3/75.0%. 25th -centile ADC trended towards being significantly lower with EPE (P = 0.06) with no difference in other ADC metrics (P = 0.25-0.88). Size, LCC, and ADC entropy improved sensitivity but reduced specificity compared with subjective analysis with no difference in overall accuracy (P = 0.38).
Conclusion:
Measurements of tumor size, capsular contact, and ADC entropy improve sensitivity but reduce specificity for diagnosis of EPE compared to subjective assessment.
Level Of Evidence:
3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:176-185.
Insights
Magnetic resonance imaging (MRI) can help diagnose extraprostatic extension (EPE) in prostate cancer. Tumor size, capsular contact, and ADC entropy improve sensitivity but decrease specificity compared to subjective assessment.
Area of Science:
- Radiology
- Oncology
- Medical Imaging
Background:
- Accurate diagnosis of extraprostatic extension (EPE) is crucial for prostate cancer management.
- Magnetic resonance imaging (MRI) is increasingly used for prostate cancer staging.
Purpose of the Study:
- To evaluate the diagnostic performance of 3T MRI in detecting extraprostatic extension (EPE) in prostate cancer.
- To compare the efficacy of subjective assessment, PI-RADS v2, tumor size, length of capsular contact (LCC), and apparent diffusion coefficient (ADC) metrics for EPE diagnosis.
Main Methods:
- 149 men with prostate cancer underwent preoperative 3T MRI before radical prostatectomy.
- Two radiologists subjectively assessed for EPE and measured tumor size and LCC.
- A third radiologist measured whole-lesion ADC metrics.
- Statistical analyses included chi-square, logistic regression, and ROC analysis.
Main Results:
- Subjective EPE assessment showed high specificity but low sensitivity.
- PI-RADS v2 scores were associated with EPE.
- Tumor size and LCC were significantly larger in tumors with EPE.
- ADC entropy showed good diagnostic performance (AU-ROC=0.76).
- Size, LCC, and ADC entropy improved sensitivity but reduced specificity compared to subjective assessment.
Conclusions:
- Measurements of tumor size, LCC, and ADC entropy enhance the sensitivity of MRI for detecting EPE.
- These quantitative MRI features decrease specificity when used for EPE diagnosis.
- Combined quantitative and subjective MRI assessments may optimize EPE detection in prostate cancer.
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