Length of capsular contact on prostate MRI as a predictor of extracapsular extension: which is the most optimal sequence?

A pictorial essay of PI-RADS pearls and pitfalls: toward less ambiguity and better practice

Prostate Imaging Reporting and Data System (PI-RADS) was designed to standardize the interpretation of multiparametric magnetic resonance imaging (MRI) of the prostate, aiding in assessing the probability of clinically significant prostate cancer. By providing a structured scoring system, it enables better risk stratification, guiding decisions regarding the need for biopsy and subsequent treatment options. In this article, we explore both the strengths and weaknesses of PI-RADS, offering insights into its updated diagnostic performance and clinical applications, while also addressing potential pitfalls using diverse, representative MRI cases.

Factors associated with pathological up-staging in MRI cT3a prostate cancer - a retrospective study from a high-volume centre

INTRODUCTION

Multiparametric MRI (mpMRI) parameters of pT3a prostate cancer have not been examined in large cohort studies. Therefore, we aimed to identify factors associated with up-staging of mpMRI cT3a in post-operative histopathological confirmation.

METHODS

Retrospective analysis of a prospectively maintained database of a single UK cancer centre. Only cT3a cases who underwent robotic-assisted radical prostatectomy (RARP) were included (N = 383). MRI and specimen histopathology was reviewed independently by expert uro-radiologists and uro-histopathologists, respectively. Factors included age, BMI, prostate-specific antigen (PSA) level, biopsy international society of urological pathology (ISUP) grade, Prostate Imaging Reporting & Data System (PI-RADS®) score, tumour size, tumour coverage of gland (%), gland weight and surgical margins were analysed as predictors of pT3a prostate cancer.

RESULTS

N = 383. Mean age 66 years (58-71), mean BMI 27.1 kg/m2 (25.0-30.0). 314 (82.0%) cases down- unchanged or down-staged, and 69 (18.0%) cases upstaged. PSA level (P = 0.002), PI-RADS score (P < 0.001) and ISUP grade (P < 0.001) are positively associated with upstage categories. ISUP grade ≥3 (OR 5.45, CI 1.88, 9.29, P < 0.002), PI-RADS score ≥4 (OR 3.92, CI 1.88-9.29, P < 0.001) and tumour coverage (OR 1.06, CI 1.05-1.08, P < 0.001) significantly positively associated with upstaging disease, with concurrent decreased probability of downstaging (OR 0.55, 0.14, 0.44, respectively, P < 0.05). Tumour coverage was positively correlated with increasing positive surgical margins (P < 0.05). Capsular contact > 15 mm was very unlikely to be upstaged (OR 0.36, CI 0.21-0.62, P < 0.001), aligning with published results past the widely accepted significant level for extracapsular disease on MRI.

CONCLUSION

The study has identified PSA level, ISUP, PI-RADS score, tumour volume and percentage coverage are key predictive factors in cT3a upstaging. This study uniquely shows tumour coverage percentage as a predictor of cT3a upstaging on mpMRI. ISUP is the strongest predictor, followed by PI-RADS score and tumour coverage of gland. Multi-institutional studies are needed to confirm our findings.

Integration of Multiparameter MRI into Conventional Pretreatment Risk Factors to Predict Positive Surgical Margins After Radical Prostatectomy

INTRODUCTION/BACKGROUND

Positive surgical margins (PSMs) after radical prostatectomy (RP) can increase the risk of biochemical recurrence in prostate cancer (PCa) patients. However, the prediction of the likelihood of PSMs in patients undergoing similar surgical procedures remains a challenge. We aim to develop a predictive model for PSMs in patients undergoing non-nerve-sparing RP.

PATIENTS AND METHODS

In this retrospective study, we analyzed data from PCa patients who underwent minimally invasive non-nerve-sparing RP at our hospital between June 2017 and June 2021. We identified independent risk factors associated with PSMs using clinical and MRI-based parameters in univariate and multivariate logistic regression analyzes. These factors were then used to develop a nomogram for predicting the probability of PSMs. The predictive performance was validated using calibration and receiver operating characteristic curve, area under the curve ,and decision curve analysis.

RESULTS

Multivariate analyzes revealed prostate-specific antigen density, tumor size, tumor location at the apex, tumor contact length, extracapsular extension (ECE) level, and apparent diffusion coefficient value as independent risk factors. A nomogram was developed and validated with high accuracy (C-index = 0.78). Furthermore, we found that 44.2% of patients diagnosed with organ-confined disease had ECE after surgery, and 29.1% of patients with Gleason scores ≤7 had higher pathological scores. Interestingly, the tumor burden calculated from PCa biopsy cores was overestimated when compared to postoperative PCa specimens.

CONCLUSION

We developed a reliable nomogram for predicting the risk of PSMs in PCa patients undergoing non-nerve-sparing RP. The study highlights the importance of incorporating these parameters in personalized surgical management.

Quantitative MRI in the Local Staging of Prostate Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Local staging of prostate cancer (PCa) is important for treatment planning. Radiologist interpretation using qualitative criteria is variable with high specificity but low sensitivity. Quantitative methods may be useful in the diagnosis of extracapsular extension (ECE).

PURPOSE

To assess the performance of quantitative MRI markers for detecting ECE.

STUDY TYPE

Systematic review and meta-analysis.

SUBJECTS

4800 patients from 28 studies with histopathologically confirmed PCa on radical prostatectomy were pooled for meta-analysis. Patients from 46 studies were included for systematic review.

FIELD STRENGTH/SEQUENCE

Diffusion-weighted, T2-weighted, and dynamic contrast-enhanced MRI at 1.5 T or 3 T.

ASSESSMENT

PubMed, Embase, Web of Science, Scopus, and Cochrane databases were searched to identify studies on diagnostic test accuracy or association of any quantitative MRI markers with ECE. Results extracted by two independent reviewers for tumor contact length (TCL) and mean apparent diffusion coefficient (ADC-mean) were pooled for meta-analysis, but not for other quantitative markers including radiomics due to low number of studies available.

STATISTICAL TESTS

Hierarchical summary receiver operating characteristic (HSROC) curves were computed for both TCL and ADC-mean, but summary operating points were computed for TCL only. Heterogeneity was investigated by meta-regression. Results were significant if P ≤ 0.05.

RESULTS

At the 10 mm threshold for TCL, summary sensitivity and specificity were 0.76 [95% confidence interval (CI) 0.71-0.81] and 0.68 [95% CI 0.63-0.73], respectively. At the 15 mm threshold, summary sensitivity and specificity were 0.70 [95% CI 0.53-0.83] and 0.74 [95% CI 0.60-0.84] respectively. The area under the HSROC curves for TCL and ADC-mean were 0.79 and 0.78, respectively. Significant sources of heterogeneity for TCL included timing of MRI relative to biopsy.

DATA CONCLUSION

Both 10 mm and 15 mm thresholds for TCL may be reasonable for clinical use. From comparison of the HSROC curves, ADC-mean may be superior to TCL at higher sensitivities.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Imaging features of the PI-RADS for predicting extraprostatic extension of prostate cancer: systematic review and meta-analysis

OBJECTIVES

To systematically determine the diagnostic performance of each MRI feature of the PI-RADS for predicting extraprostatic extension (EPE) in prostate cancer.

METHODS

A literature search in the MEDLINE and EMBASE databases was conducted to identify original studies reporting the accuracy of each feature on MRI for the dichotomous diagnosis of EPE. The meta-analytic pooled diagnostic odds ratio (DOR), sensitivity, specificity, and their 95% confidence intervals (CIs) were obtained using a bivariate random-effects model.

RESULTS

After screening 1955 studies, 17 studies with a total of 3062 men were included. All six imaging features, i.e., bulging prostatic contour, irregular or spiculated margin, asymmetry or invasion of neurovascular bundle, obliteration of rectoprostatic angle, tumor-capsule interface > 10 mm, and breach of the capsule with evidence of direct tumor extension, were significantly associated with EPE. Breach of the capsule with direct tumor extension demonstrated the highest pooled DOR (15.6, 95% CI [7.7-31.5]) followed by tumor-capsule interface > 10 mm (10.5 [5.4-20.2]), asymmetry or invasion of neurovascular bundle (7.6 [3.8-15.2]), and obliteration of rectoprostatic angle (6.1 [3.8-9.8]). Irregular or spiculated margin showed the lowest pooled DOR (2.3 [1.3-4.2]). Breach of the capsule with direct tumor extension and tumor-capsule interface > 10 mm showed the highest pooled specificity (98.0% [96.2-99.0]) and sensitivity (86.3% [70.0-94.4]), respectively.

CONCLUSIONS

Among the six MRI features of prostate cancer, breach of the capsule with direct tumor extension and tumor-capsule interface > 10 mm were the most predictive of EPE with the highest specificity and sensitivity, respectively.

ACR Appropriateness Criteria® Pretreatment Detection, Surveillance, and Staging of Prostate Cancer: 2022 Update

Prostate cancer is second leading cause of death from malignancy after lung cancer in American men. The primary goal during pretreatment evaluation of prostate cancer is disease detection, localization, establishing disease extent (both local and distant), and evaluating aggressiveness, which are the driving factors of patient outcomes such as recurrence and survival. Prostate cancer is typically diagnosed after the recognizing elevated serum prostate-specific antigen level or abnormal digital rectal examination. Tissue diagnosis is obtained by transrectal ultrasound-guided biopsy or MRI-targeted biopsy, commonly with multiparametric MRI without or with intravenous contrast, which has recently been established as standard of care for detecting, localizing, and assessing local extent of prostate cancer. Although bone scintigraphy and CT are still typically used to detect bone and nodal metastases in patients with intermediate- or high-risk prostate cancer, novel advanced imaging modalities including prostatespecific membrane antigen PET/CT and whole-body MRI are being more frequently utilized for this purpose with improved detection rates. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

MR-based simplified extraprostatic extension evaluation: comparison of performances of different predictive models

OBJECTIVES

To test reproducibility and predictive value of a simplified score for assessment of extraprostatic tumor extension (sEPE grade).

METHODS

Sixty-five patients (mean age ± SD, 67 years ± 6.3) treated with radical prostatectomy for prostate cancer who underwent 1.5-Tesla multiparametric magnetic resonance imaging (mpMRI) 6 months before surgery were enrolled. sEPE grade was derived from mpMRI metrics: curvilinear contact length > 15 mm (CCL) and capsular bulging/irregularity. The diameter of the index lesion (dIL) was also measured. Evaluations were independently performed by seven radiologists, and inter-reader agreement was tested by weighted Cohen K coefficient. A nested (two levels) Monte Carlo cross-validation was used. The best cut-off value for dIL was selected by means of the Youden J index to classify values into a binary variable termed dIL*. Logistic regression models based on sEPE grade, dIL, and clinical scores were developed to predict pathologic EPE. Results on validation set were assessed by the main metrics of the receiver operating characteristics curve (ROC) and by decision curve analysis (DCA). Based on our findings, we defined and tested an alternative sEPE grade formulation.

RESULTS

Pathologic EPE was found in 31/65 (48%) patients. Average κ_w was 0.65 (95% CI 0.51-0.79), 0.66 (95% CI 0.48-0.84), 0.67 (95% CI 0.50-0.84), and 0.43 (95% CI 0.22-0.63) for sEPE grading, CLL ≥ 15 mm, dIL*, and capsular bulging/irregularity, respectively. The highest diagnostic yield in predicting EPE was obtained by combining both sEPE grade and dIL*(ROC-AUC 0.81).

CONCLUSIONS

sEPE grade is reproducible and when combined with the dIL* accurately predicts extraprostatic tumor extension.

KEY POINTS

• Simple and reproducible mpMRI semi-quantitative scoring system for extraprostatic tumor extension. • sEPE grade accurately predicts extraprostatic tumor extension regardless of reader expertise. • Accurate pre-operative staging and risk stratification for optimized patient management.

Extraprostatic extension in multiparametric MRI; Is presurgical detection possible?

INTRODUCTION

Extraprostatic extension (EPE) is one of the important factors affecting the prognosis of prostate cancer (PCa). Therefore, preoperative evaluation of the presence of EPE is essential in multiparametric magnetic resonance imaging (mpMRI) examination. However, for the evaluation of mpMRI, objective criteria are needed to detect EPE, especially microscopic EPE.

AIM

To evaluate the efficacy of 1.5T MRI using lesion length (LL) and tumor-capsule contact length (TCL) in detecting EPE in PCa.

METHODS

A total of 110 patients who underwent radical prostatectomy due to PCa were enrolled. Preoperative MR images were evaluated retrospectively by two independent observers who did not know the histopathological results. The observers evaluated LL and TCL. The radiological findings, including lesion location, were verified using histopathological mapping.

RESULTS

Multiparametric MRI examination of the prostate demonstrated low sensitivity (Observer 1; 40.4% and Observer 2; 40.4%) but high specificity (Observer 1; 96.6% and Observer 2; 84.5%), with significant differences for detecting EPE (Observer 1, P < 0.0001; Observer 2, P = 0.003). The increased PI-RADS score correlated positively with the increased EPE rate (P < 0.0001 for both observers). The mean LL and TCL values were statistically significantly higher in patients with EPE than in patients without EPE. The TCL was a significant parameter for EPE, with high sensitivity and low for both observers. For both observes the cutoff value of LL for EPE was 14.5 mm, and the cutoff value of TCL for EPE was 9.5 mm. Histopathological LL value (28 ± 12,3 mm) was higher than radiological LLs (Observer 1; 22,14 ± 10,15 mm and Observer 2; 19,06 ± 8,61).

CONCLUSION

The results revealed that 1.5T MRI demonstrated low sensitivity and high specificity in detecting EPE. The LL and TCL may be indirectly beneficial in detecting EPE. Considering the radiological underestimation of LL may be helpful before PCa surgery.

The role of MRI in prostate cancer: current and future directions

There has been an increasing role of magnetic resonance imaging (MRI) in the management of prostate cancer. MRI already plays an essential role in the detection and staging, with the introduction of functional MRI sequences. Recent advancements in radiomics and artificial intelligence are being tested to potentially improve detection, assessment of aggressiveness, and provide usefulness as a prognostic marker. MRI can improve pretreatment risk stratification and therefore selection of and follow-up of patients for active surveillance. MRI can also assist in guiding targeted biopsy, treatment planning and follow-up after treatment to assess local recurrence. MRI has gained importance in the evaluation of metastatic disease with emerging technology including whole-body MRI and integrated positron emission tomography/MRI, allowing for not only better detection but also quantification. The main goal of this article is to review the most recent advances on MRI in prostate cancer and provide insights into its potential clinical roles from the radiologist's perspective. In each of the sections, specific roles of MRI tailored to each clinical setting are discussed along with its strengths and weakness including already established material related to MRI and the introduction of recent advancements on MRI.

Current Opinion on the Use of Magnetic Resonance Imaging in Staging Prostate Cancer: A Narrative Review

Accurate staging is critical for treatment planning and prognosis in men with prostate Cancer. Prostate magnetic imaging resonance (MRI) may aid in the staging evaluation by verifying organ-confined status, assessing the status of the pelvic lymph nodes, and establishing the local extent of the tumor in patients being considered for therapy. MRI has a high specificity for diagnosing extracapsular extension, and therefore may impact the decision to perform nerve sparing prostatectomy, along with seminal vesicle invasion and lymph node metastases; however, its sensitivity remains limited. Current guidelines vary significantly regarding endorsing the use of MRI for staging locoregional disease. For high-risk prostate cancer, most guidelines recommend cross sectional imaging, including MRI, to evaluate for more extensive disease that may merit change in radiation field, extended androgen deprivation therapy, or guiding surgical planning. Although MRI offers reasonable performance characteristics to evaluate bone metastases, guidelines continue to support the use of bone scintigraphy. Emerging imaging technologies, including coupling positron emission tomography (PET) with MRI, have the potential to improve the accuracy of prostate cancer staging with the use of novel radiotracers.

The Quantitative Assessment of Using Multiparametric MRI for Prediction of Extraprostatic Extension in Patients Undergoing Radical Prostatectomy: A Systematic Review and Meta-Analysis

PURPOSE

To investigate the diagnostic performance of using quantitative assessment with multiparametric MRI (mpMRI) for prediction of extraprostatic extension (EPE) in patients with prostate cancer (PCa).

METHODS

We performed a computerized search of MEDLINE, Embase, Cochrane Library, Web of Science, and Google Scholar from inception until July 31, 2021. Summary estimates of sensitivity and specificity were pooled with the bivariate model, and quality assessment of included studies was performed with the Quality Assessment of Diagnostic Accuracy Studies-2. We plotted forest plots to graphically present the results. Multiple subgroup analyses and meta-regression were performed to explore the variate clinical settings and heterogeneity.

RESULTS

A total of 23 studies with 3,931 participants were included. The pooled sensitivity and specificity for length of capsular contact (LCC) were 0.79 (95% CI 0.75-0.83) and 0.77 (95% CI 0.73-0.80), for apparent diffusion coefficient (ADC) were 0.71 (95% CI 0.50-0.86) and 0.71 (95% CI 059-0.81), for tumor size were 0.62 (95% CI 0.57-0.67) and 0.75 (95% CI 0.67-0.82), and for tumor volume were 0.77 (95% CI 0.68-0.84) and 0.72 (95% CI 0.56-0.83), respectively. Substantial heterogeneity was presented among included studies, and meta-regression showed that publication year (≤2017 vs. >2017) was the significant factor in studies using LCC as the quantitative assessment (P=0.02).

CONCLUSION

Four quantitative assessments of LCC, ADC, tumor size, and tumor volume showed moderate to high diagnostic performance of predicting EPE. However, the optimal cutoff threshold varied widely among studies and needs further investigation to establish.

Comparison of biparametric versus multiparametric prostate MRI for the detection of extracapsular extension and seminal vesicle invasion in biopsy naïve patients

PURPOSE

To compare biparametric MRI (bpMRI) with multiparametric MRI (mpMRI) staging accuracy in assessing extracapsular extension (ECE) and seminal vesicle invasion (SVI).

METHOD

Biopsy-naïve patients undergoing 3 T-MRI before radical prostatectomy for clinically significant prostate cancer were included in this single-centre retrospective study. Two uroradiologists separately evaluated bpMRI and mpMRI for presence of ECE and SVI using a 5-point Likert scale (1: ECE/SVI highly unlikely, 5: ECE/SVI highly likely).

RESULTS

110 men of median age 63 years and PSA 8.5 ng/mL were included. ECE and SVI was confirmed histologically in 71/110 (64.5 %) and 18/110 (16.4 %) patients, respectively. Sensitivity and specificity of bpMRI versus mpMRI for predicting ECE was 59.1 % and 87.2 % versus 66.2 % and 84.6 %, respectively. For SVI detection, the sensitivity and specificity for bpMRI versus mpMRI was 66.7 % and 92.4 % versus 83.3 % and 97.8 %, respectively. At an optimal cut-off Likert score ≥3 for ECE prediction, mpMRI area under the receiver operating curve (AUC) was 0.80 (95 % confidence interval (CI) 0.72-0.87) versus 0.78 (95 % CI 0.69-0.86) for bpMRI (p = 0.52) and for SVI, mpMRI AUC was 0.91 (95 % CI 0.84-0.96) versus 0.86 (95 % CI 0.78-0.92) for bpMRI (p = 0.02), respectively. Inter-reader agreement for both ECE and SVI prediction was substantial, with a marginally higher k-value for mpMRI (k range, 0.67-0.75) than bpMRI (k range, 0.65-0.69).

CONCLUSIONS

Diagnostic performance of bpMRI and mpMRI was comparable for detection of ECE, however, mpMRI with contrast was superior for SVI detection and improved the inter-reader agreement.

Quantitative Prostate MRI

Prostate MRI is reported in clinical practice using the Prostate Imaging and Data Reporting System (PI-RADS). PI-RADS aims to standardize, as much as possible, the acquisition, interpretation, reporting, and ultimately the performance of prostate MRI. PI-RADS relies upon mainly subjective analysis of MR imaging findings, with very few incorporated quantitative features. The shortcomings of PI-RADS are mainly: low-to-moderate interobserver agreement and modest accuracy for detection of clinically significant tumors in the transition zone. The use of a more quantitative analysis of prostate MR imaging findings is therefore of interest. Quantitative MR imaging features including: tumor size and volume, tumor length of capsular contact, tumor apparent diffusion coefficient (ADC) metrics, tumor T₁ and T₂ relaxation times, tumor shape, and texture analyses have all shown value for improving characterization of observations detected on prostate MRI and for differentiating between tumors by their pathological grade and stage. Quantitative analysis may therefore improve diagnostic accuracy for detection of cancer and could be a noninvasive means to predict patient prognosis and guide management. Since quantitative analysis of prostate MRI is less dependent on an individual users' assessment, it could also improve interobserver agreement. Semi- and fully automated analysis of quantitative (radiomic) MRI features using artificial neural networks represent the next step in quantitative prostate MRI and are now being actively studied. Validation, through high-quality multicenter studies assessing diagnostic accuracy for clinically significant prostate cancer detection, in the domain of quantitative prostate MRI is needed. This article reviews advances in quantitative prostate MRI, highlighting the strengths and limitations of existing and emerging techniques, as well as discussing opportunities and challenges for evaluation of prostate MRI in clinical practice when using quantitative assessment. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 2.

Extraprostatic Tumor Extension: Comparison of Preoperative Multiparametric MRI Criteria and Histopathologic Correlation after Radical Prostatectomy

Background There are no standardized and well-validated criteria for assessing the risk of extraprostatic extension (EPE) of prostate cancer at preoperative multiparametric MRI. Purpose To compare diagnostic performance, intra- and interreader agreement, and correlations of MRI-based criteria for assessment of EPE after radical prostatectomy, including EPE grade, European Society of Urogenital Radiology (ESUR) score, Likert scale, and capsular contact length (CCL). Materials and Methods This retrospective study included consecutive men who underwent MRI and radical prostatectomy between July 2016 and March 2017. Two genitourinary radiologists independently estimated the probability of EPE by using four MRI-based scoring methods. The diagnostic accuracies and intra- and interobserver agreement were evaluated with area under the receiver operating characteristic curve (AUC) and κ statistics, respectively. Correlations between MRI-based score and histologic extent of EPE were analyzed by using the Spearman correlation coefficient (ρ). Results A total of 301 men (mean age ± standard deviation, 65 years ± 7) were evaluated. A total of 129 (42.9%) men had EPE. The AUC ranges of EPE grade, ESUR score, Likert scale, and CCL for assessment of EPE were 0.77-0.81, 0.79-0.81, 0.78-0.79, and 0.78-0.85, respectively, for the two readers. The Likert scale showed lower sensitivity (68.2% [88 of 129] for reader 1, 72.1% [93 of 129] for reader 2) than did EPE grade (77.5% [100 of 129] for reader 1, 79.8% [103 of 129] for reader 2; P ≤ .04). Intra- and interreader agreement were substantial (κ range, 0.61-0.74) for the four methods, with ESUR score showing the lowest values (κ = 0.61 and κ = 0.63, respectively). EPE grade showed highest correlation with histologic extent of EPE (ρ = 0.53 and ρ = 0.55 for circumferential length; ρ = 0.42 and ρ = 0.55 for radial length for readers 1 and 2, respectively; P < .001). Conclusion Extraprostatic extension (EPE) grade, European Society of Urogenital Radiology score, Likert scale, and capsular contact length showed good overall diagnostic performance; however, the EPE grade resulted in more reliable performance and had the highest correlation with histologic EPE extent. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Padhani and Petralia in this issue.

Prediction of extraprostatic extension by MRI tumor contact length: difference between anterior and posterior prostate cancer

BACKGROUND

Tumor contact length (TCL) is defined as the extent of contact between prostate cancer and the prostatic capsule, and its predictive value for microscopic extraprostatic extension (EPE) has been reported. However, the impact of the zonal origin (anterior or posterior tumor) of the tumor on the diagnosis of EPE is controversial.

METHODS

We retrospectively analyzed the records of 233 consecutive patients who underwent preoperative MRI and radical prostatectomy. We designated their tumors as anterior or posterior, and evaluated the correlation between the TCL measured by MRI and microscopic EPE in the radical prostatectomy specimen. Then, we created the predicted probability curves for EPE versus TCL for anterior and posterior prostate cancer.

RESULTS

There were 109 patients (47%) with an anterior tumor and 124 patients (53%) with a posterior tumor. Postoperative pathological analysis confirmed pT3 in 18 patients (17%) with an anterior tumor and in 53 patients (43%) with a posterior tumor. Multivariate analysis demonstrated that the zonal origin of the tumor was an independent predictive factor for EPE. We developed separate probability curves of EPE versus TCL for anterior and posterior prostate cancer, which revealed that anterior tumors were less likely to invade the extraprostatic tissues. Among patients whose TCL was 10-20 mm, 9/32 patients (28%) with an anterior tumor had EPE compared with 24/45 patients (53%) with a posterior tumor (p = 0.036). The decision curve of this EPE predictive model had high clinical efficacy.

CONCLUSIONS

Our results indicate that anterior tumors have more favorable pathological characteristics than posterior tumors with the same TCL measured by MRI. We constructed two separate predicted probability curves for EPE after discriminating anterior and posterior tumors, which will be useful for decision making in clinical practice.

Can Extraprostatic Extension Be Predicted by Tumor-Capsule Contact Length in Prostate Cancer? Relationship With International Society of Urological Pathology Grade Groups

OBJECTIVE. The objective of our study was to evaluate the relationship between the tumor-capsule contact length, defined as tumor contact length (TCL), and extraprostatic extension (EPE) using the MRI-based TCL measurements and the real TCL measurements from pathology and to determine whether the International Society of Urological Pathology (ISUP) grade group of the tumors influenced this relationship. MATERIALS AND METHODS. In this retrospective study, we reviewed prostate multiparametric MRI (mpMRI) studies performed between 2012 and 2018 of 1576 patients and found that 134 patients also underwent radical prostatectomy (RP) after mpMRI. Finally, 86 patients with index lesions in contact with the prostate capsule in RP specimens were enrolled in the study. ROC analysis was used to evaluate the cutoff values of TCLs measured at pathology and TCLs measured on MRI in terms of EPE according to ISUP grade groups. RESULTS. There was no statistically significant cutoff value for pathology-based TCL measurements in individual ISUP grade groups and subgroups. Although not statistically significant, pathology-based TCL cutoff values decreased (from 21.0 to 11.0 mm) as ISUP grade group increased in terms of EPE positivity. When the relationship between MRI-based TCL measurements and EPE was considered, statistically significant cutoff values (range, 14.5-16.6 mm) could be determined in many groups and subgroups with low ISUP grades (sensitivity, 66.7-100%; specificity, 52.8-93.0%; p = 0.006-0.042). However, no statistically significant cutoff value was found for high ISUP grades. CONCLUSION. ISUP grade groups may have an effect on the TCL-EPE relationship. When the MRI-based TCL and EPE relationship is evaluated independent of ISUP grade group, a cutoff value around 15-16 mm may be usable to predict EPE.

Multiparametric MRI - local staging of prostate cancer and beyond

Background Accurate local staging is critical for treatment planning and prognosis in patients with prostate cancer (PCa). The primary aim is to differentiate between organ-confined and locally advanced disease with the latter carrying a worse clinical prognosis. Multiparametric MRI (mpMRI) is the imaging modality of choice for the local staging of PCa and has an incremental value in assessing pelvic nodal disease and bone involvement. It has shown superior performance compared to traditional staging based on clinical nomograms, and provides additional information on the site and extent of disease. MRI has a high specificity for diagnosing extracapsular extension (ECE), seminal vesicle invasion (SVI) and lymph node (LN) metastases, however, sensitivity remains poor. As a result, extended pelvic LN dissection remains the gold standard for assessing pelvic nodal involvement, and there has been recent progress in developing advanced imaging techniques for more distal staging. Conclusions T2W-weighted imaging is the cornerstone for local staging of PCa. Imaging at 3T and incorporating both diffusion weighted and dynamic contrast enhanced imaging can further increase accuracy. "Next generation" imaging including whole body MRI and PET-MRI imaging using prostate specific membrane antigen (68Ga-PSMA), has shown promising for assessment of LN and bone involvement as compared to the traditional work-up using bone scintigraphy and body CT.

Apparent diffusion coefficient in extraprostatic extension of prostate cancer: a systematic review and diagnostic meta-analysis

Objective: To evaluate the diagnostic performance of apparent diffusion coefficient (ADC) for local staging of prostate cancer. Methods: Databases of Web of Science, MEDLINE (Ovid and PubMed), Cochrane Library, EMBASE, and Google Scholar were searched up to May 31, 2018, with language restricted to English. All studies concerning multiparametric magnet resonance imaging (mpMRI) with ADC for detection of extracapsular extension (ECE, T3a) and/or extraprostatic extension (EPE, overall stage of T3) were identified by two reviewers independently, and quality of included studies was evaluated using Quality Assessment of Diagnostic Accuracy Studies-2 tool. True positive, false positive, false negative and true negative of each study were extracted to reconstruct the 2×2 tables for evaluating diagnostic accuracy. Summary estimates of sensitivity, specificity, and corresponding 95% CIs were calculated with bivariate model and hierarchical summary receiver operating characteristic model, then presented in forest plots. Multiple subgroup analyses and meta-regression were performed, and publication bias was evaluated with Deeks funnel. Results: A total of 18 studies were included, with 6 involved ECE and 12 for EPE. Pooled sensitivity was 80.5% (95% CI 76.5-83.9%) with specificity of 69.1% (95% CI 62.3-75.2%). Multiple subgroup analyses showed that if ADC and length of capsular contact are regarded as independent predictors, pooled sensitivity was 85% (95% CI 77-90%) and 81.1% (95% CI 76.0-85.3%), with specificity of 70.8% (95% CI 56.3-82.0%) and 66.6% (95% CI 57.6-74.5%), respectively. Meta-regression demonstrated that there was no substantially significant difference in types of coil, magnet field strength (1.5T versus 3.0T), and analysis method (per-lesion versus per-patient). Conclusion: By introducing ADC to MRI, we could obtain favorable sensitivity for diagnostic performance of EPE, but with a little decreased specificity.

Defining the incremental value of 3D T2-weighted imaging in the assessment of prostate cancer extracapsular extension

Objectives

To assess the added value of 3D T2-weighted imaging (T2WI) over conventional 2D T2WI in diagnosing extracapsular extension (ECE).

Methods

Seventy-five patients undergoing 3-T MRI before radical prostatectomy were included. PI-RADS ≥ 4 lesions were assessed for ECE on 2D T2W images using a 5-point Likert scale (1 = no ECE, 5 = definite ECE) and the length of tumour prostatic capsular contact. A second read using 3D T2W images and reformats evaluated ECE and the maximal 3D capsular contact length and surface.

Results

One hundred six lesions were identified at MRI. ECE was confirmed by histology in 54% (57/106) of lesions and 64% (48/75) of patients. Sensitivity and specificity for 3D T2 reads were 75.4% versus 64.9% (p = 0.058), respectively, and 83.7% versus 85.7% (p = 0.705) for 2D T2 reads, respectively. 3D T2W reads showed significantly higher mean subjective Likert scores of 3.7 ± 1.4 versus 3.3 ± 1.4 (p = 0.001) in ECE-positive lesions and lower mean Likert score of 1.5 ± 1 versus 1.6 ± 0.9 (p = 0.27) in ECE-negative lesions compared with 2D T2W reads. 3D contact significantly increased sensitivity from 59.6 to 73.7% (p = 0.03), whilst maintaining the same specificity of 87.8% (p = 1). High-grade group tumours (≥ Gleason 4 + 3) showed significantly higher ECE prevalence than low-grade tumours (88% versus 44%, p < 0.001) and a positive predictive value (PPV) for ECE of 90.9% with ≥ 5 mm of contact versus PPV of 90.4% at ≥ 12.5 mm for lower grade tumours.

Conclusions

3D T2WI significantly increases sensitivity and confidence in calling ECE. The capsular contact length threshold differed between low- and high-grade cancers.

Key Points

• 3D capsular contact length and 3D surface contact significantly increased sensitivity in diagnosing ECE.

• 3D T2W reads significantly increased reader confidence in calling ECE.

• Thresholds for capsular contact length differed between low-grade and high-grade cancers.

Electronic supplementary material

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Contribution of Radiology to Staging of Prostate Cancer

Accurate tumor detection and establishment of disease extent are important for optimal management of prostate cancer. Disease stage, beginning with identification of the index prostate lesion, followed by primary tumor, lymph node, and distant metastasis evaluation, provide crucial clinical information that not only have prognostic and predictive value, but guide patient management. A wide array of radiological imaging modalities including ultrasound, computed tomography, and magnetic resonance imaging have been used for the purpose of prostate cancer staging with variable diagnostic performance. Especially, the last years have seen remarkable technological advances in magnetic resonance imaging technology, enabling referring clinicians and radiologists to obtain even more valuable data regarding staging of prostate cancer. Marked improvements have been seen in detection of the index prostate lesion and evaluation of extraprostatic extension while further improvements are still needed in identifying metastatic lymph nodes. Novel approaches such as whole-body MRI are emerging for more accurate and reproducible assessment of bone metastasis. Post-treatment assessment of prostate cancer using radiological imaging is a topic with rapidly changing clinical context and special consideration is needed for the biochemical setting, that is, the relatively high serum prostate-specific antigen levels in studies assessing the value of radiological imaging for post-treatment assessment and emerging therapeutic approaches such as early salvage radiation therapy. The scope of this review is to provide the reader insight into the various ways radiology contribute to staging of prostate cancer in the context of both primary staging and post-treatment assessment. The strengths and limitations of each imaging modality are highlighted as well as topics that warrant future research.

Evaluation of the most optimal multiparametric magnetic resonance imaging sequence for determining pathological length of capsular contact

OBJECTIVES

To assess the most optimal multi-parametric magnetic resonance imaging sequence (Mp-MRI) in determining pathological length of capsular contact (LCC) for the diagnosis of prostate cancer extraprostatic extension (EPE).

METHODS

105 patients with prostate cancer who underwent Mp-MRI of prostate prior to radical prostatectomy were enrolled in this retrospective study. LCC was determined from T2-weighted images (T2WI), Apparent Diffusion Coefficient (ADC) map, dynamic contrast-enhanced MRI (DCE-MRI) separately by two blinded radiologists. The LCCs in patients with and without EPE were compared with Mann Whitney-U test. The relationship between pathological LCC and the LCC that was measured from each Mp-MRI sequences were calculated by using Spearman test. The ability of all individual Mp-MRI sequences in determining pathological LCC was calculated by drawing receiver operator characteristic (ROC) curves. The diagnostic accuracy of LCC based on each MRI sequences for EPE diagnosis was also calculated with ROC curve analysis.

RESULTS

The patients with EPE had longer median LCC than patients without EPE for each Mp-MRI sequences and for both readers. In addition, the LCC showed a broader overlapping between patients with and without EPE on ADC map (reader-1, p = 0.01; reader-2, p = 0.01) when compared with T2WI (reader-1, p = 0.002; reader-2, p = 0.001) and DCE-MRI (reader-1, p = 0.001; reader-2, p = 0.001). LCC based on DCE-MRI showed the strongest correlation with pathological LCC. The area under the curve (AUC) based on LCC was higher when using the DCE-MRI (reader-1: 0.874, p = 0.030; reader-2: 0.862, p = 0.02) than when using T2WI and ADC map in predicting pathological LCC for both readers. While the LCC based on ADC map showed poor diagnostic accuracy, LCC based on T2WI and DCE-MRI had fair diagnostic accuracy for EPE diagnosis.

CONCLUSION

The contact between prostate tumor and capsule seems to be a useful and objective parameter for evaluating the EPE of prostate cancer with Mp-MRI. More specifically, LCC based on DCE-MRI has highest correlation with pathological LCC and has better ability to predict pathological LCC when compared with other Mp-MRI sequences. However, the performance of LCC based on T2WI and DCE-MRI was similar for EPE diagnosis. It seems measurement of LCC from DCE-MRI and measurement of LCC from T2WI does not show any difference in clinical EPE assessment.

Diagnostic Utility of a Likert Scale Versus Qualitative Descriptors and Length of Capsular Contact for Determining Extraprostatic Tumor Extension at Multiparametric Prostate MRI

OBJECTIVE

The purpose of this study is to determine the reproducibility and diagnostic performance of a Likert scale in comparison with the European Society of Urogenital Radiology (ESUR) criteria and tumor-pseudocapsule contact length (TCL) for the detection of extraprostatic extension (EPE) at multiparametric MRI.

MATERIALS AND METHODS

This was a retrospective review of all men who underwent multiparametric MRI followed by prostatectomy between November 2015 and July 2016. Multiparametric 3-T MRI studies with an endorectal coil were independently reviewed by five readers who assigned the likelihood of EPE using a 1-5 Likert score, ESUR criteria, and TCL (> 10 mm). EPE outcome (absent or present) for the index lesion at whole-mount histopathologic analysis was the standard of reference. Odds ratios (ORs) and areas under the ROC curve (A_z) were used for diagnostic accuracy. The interreader agreement was determined using a weighted kappa coefficient. A p < 0.05 was considered significant.

RESULTS

Eighty men met the eligibility criteria. At univariate analysis, the Likert score showed the strongest association (OR, 1.8) with EPE, followed by prostate-specific antigen level (OR, 1.7), ESUR score (OR, 1.6), and index lesion size (OR, 1.2). At multivariable analysis, higher Likert score (OR, 1.8) and prostate-specific antigen level (OR, 1.6-1.7) were independent predictors of EPE. The A_z value for Likert scores was statistically significantly higher (0.79) than that for TCL (0.74; p < 0.01), but not statistically significantly higher than the value for ESUR scores (0.77; p = 0.17). Interreader agreement with Likert (κ = 0.52) and ESUR scores (κ = 0.55) was moderate and slightly superior to that for TCL (κ = 0.43). Except for TCL among inexperienced readers (κ = 0.34), reader experience did not affect interreader agreement.

CONCLUSION

A Likert score conveying the degree of suspicion at multiparametric MRI is a stronger predictor of EPE than is either ESUR score or TCL and may facilitate informed decision making, patient counseling, and treatment planning.