Advances in Magnetic Resonance Imaging: How They Are Changing the Management of Prostate Cancer

Association between mpMRI detected tumor apparent diffusion coefficient and 5-year biochemical recurrence risk after radical prostatectomy

PURPOSE

To assess the ability of tumor apparent diffusion coefficient (ADC) values obtained from multiparametric magnetic resonance imaging (mpMRI) to predict the risk of 5-year biochemical recurrence (BCR) after radical prostatectomy (RP).

MATERIALS AND METHODS

This retrospective analysis included 1207 peripheral and 232 non-peripheral zone prostate cancer (PCa) patients who underwent mpMRI before RP (2012-2015), with the outcome of interest being 5-year BCR. ADC was evaluated as a continuous variable and as categories: low (< 850 µm2/s), intermediate (850-1100 µm2/s), and high (> 1100 µm2/s). Kaplan-Meier curves with log-rank testing of BCR-free survival, multivariable Cox proportional hazard regression models were formed to estimate the risk of BCR.

RESULTS

Among the 1439 males with median age 63 (± 7) years, the median follow-up was 59 months, and 306 (25%) patients experienced BCR. Peripheral zone PCa patients with BCR had lower tumor ADC values than those without BCR (874 versus 1025 µm2/s, p < 0.001). Five-year BCR-free survival rates were 52.3%, 74.4%, and 87% for patients in the low, intermediate, and high ADC value categories, respectively (p < 0.0001). Lower ADC was associated with BCR, both as continuously coded variable (HR: 5.35; p < 0.001) and as ADC categories (intermediate versus high ADC-HR: 1.56, p = 0.017; low vs. high ADC-HR; 2.36, p < 0.001). In the non-peripheral zone PCa patients, no association between ADC and BCR was observed.

CONCLUSION

Tumor ADC values and categories were found to be predictive of the 5-year BCR risk after RP in patients with peripheral zone PCa and may serve as a prognostic biomarker.

Prostate magnetic resonance imaging utilization and its relationship with advanced prostate cancer detection

BACKGROUND

The rise in advanced prostate cancer has coincided with increased use of Magnetic Resonance Imaging (MRI), leading to the hypothesis that this increase in surveillance registries is an artifact of more sensitive imaging tools. We assessed the association between regional variation in prostate MRI and advanced prostate cancer diagnoses.

METHODS

We utilized SEER-Medicare data (2004-2015), including men > 65 diagnosed with localized prostate cancer. The predictor variable was the utilization of prostate MRI in each hospital referral region (HRR, representing regional healthcare markets). We compared the proportion of disease recorded as locally advanced or of regional risk group (cT3, cT4, and cN1) which would plausibly have been detected by prostate MRI. We conducted adjusted multivariable analysis and performed correlation analysis with Spearman rank coefficient at the level of the HRR. Sensitivity analysis for years 2011 to 2015 was conducted.

RESULTS

Of 98,921 men diagnosed, 4.01% had locally advanced or regional disease. The median prostate MRI utilization rate was 4.58% (IQR [3.03%, 8.12%]). Adjusted multivariable analysis revealed no statistically significant correlation between MRI utilization and proportion of advanced prostate cancer (aOR = 1.01, 95% CI, [0.99,1.03]) in each region. The correlation between MRI usage and advanced diagnosis was not significant (Spearman Ρ = 0.09, P = 0.4). Sensitivity analysis conducted between 2011 and 2015 showed similar results (aOR = 1.008, 95% CI, [0.989, 1.027]; Spearman Ρ = 0.16, P = 0.1).

CONCLUSIONS

During our study period, HRR-level utilization of MRI was not associated with higher incidences of advanced prostate cancer. This suggests the rising advanced prostate cancer diagnoses observed in this period are unlikely an artifact of greater sensitivity of modern imaging tests, but potentially due to other factors such as changes in screening or risk factors. With increased utilization and evolving techniques in recent years, the association between MRI and advanced prostate cancer detection warrants continued monitoring.

Utility of positive core number on MRI-ultrasound fusion targeted biopsy in combination with PI-RADS scores for predicting unexpected extracapsular extension of clinically localized prostate cancer

OBJECTIVES

To evaluate the utility of magnetic resonance imaging (MRI) and MRI-ultrasound fusion targeted biopsy (TB) for predicting unexpected extracapsular extension (ECE) in clinically localized prostate cancer (CLPC).

METHODS

This study enrolled 89 prostate cancer patients with one or more lesions showing a Prostate Imaging-Reporting and Data System (PI-RADS) score ≥3 but without morphological abnormality in the prostatic capsule on pre-biopsy MRI. All patients underwent TB and systematic biopsy followed by radical prostatectomy (RP). Each lesion was examined by 3-core TB, taking cores from each third of the lesion. The preoperative variables predictive of ECE were explored by referring to RP specimens in the lesion-based analysis.

RESULTS

Overall, 186 lesions, including 81 (43.5%), 73 (39.2%), and 32 (17.2%) with PI-RADS 3, 4, and 5, respectively, were analyzed. One hundred and twenty-two lesions (65.6%) were diagnosed as cancer on TB, and ECE was identified in 33 (17.7%) on the RP specimens. The positive TB core number was ≤2 in 129 lesions (69.4%) and three in 57 lesions (30.6%). On the multivariate analysis, PI-RADS ≥4 (p = 0.049, odds ratio [OR] = 2.39) and three positive cores on TB (p = 0.005, OR = 3.07) were independent predictors of ECE. Lesions with PI-RADS ≥4 and a positive TB core number of 3 had a significantly higher rate of ECE than those with PI-RADS 3 and a positive TB core number ≤2 (37.5% vs. 7.8%, p < 0.001).

CONCLUSIONS

Positive TB core number in combination with PI-RADS scores is helpful to predict unexpected ECE in CLPC.

Role of MRI in diagnosis of prostate cancer and correlation of results with transrectal ultrasound guided biopsy “TRUS”

Background

Prostate cancer is the most common cancer in elderly men, and the second leading cause of cancer-related death in developed countries. For a long time, TRUS is used in screening, diagnosis of prostate lesions. Recently the implementation of multi parametric MRI into a screening program currently seems to be the most promising technique to improve the early detection of prostate cancer.

Results

Thirty Patients were referred from urological outpatient clinics complaining of urological symptoms (dysuria, frequency and urine retention). The study was carried, and the patients were submitted to Ultrasonography, conventional magnetic resonance, diffusion weighted images and MR spectroscopy techniques, these results were correlated with histopathological data. In this study Conventional MRI has moderate sensitivity 81.8% and low specificity 37.3% in diagnosing prostate malignancy. Using of mpMRI combination of diffusion-weighted, Dynamic contrast enhanced and MR spectroscopic imaging is a promising approach for discriminating between benign and malignant lesions in the PZ and increase sensitivity 100% and specificity 96.6% in diagnosing prostate malignancy.

Conclusions

The standard for the definitive diagnosis of prostate cancer is trans-rectal ultrasound biopsy. However, TRUS guided biopsy has a significant sampling error and can miss up to 30% of cancers and may show underestimation of Gleason grade, especially in anteriorly located tumors. It may lead to an increase in complications. MRI has an essential role to play in making safer in diagnosis. It can aid in staging also and surgery or radiation treatment planning. Although T2W MRI has been used widely for diagnosis on the basis of its excellent soft tissue resolution, but its accuracy for the detection and localization of cancer prostate is unsatisfactory. The implementation of multi parametric MRI: MR spectroscopy, Dynamic contrast enhanced and diffusion weighted imaging into a diagnosis program improve the diagnostic performance. These advances are beginning to translate into better treatment selection and more accurate image-guided therapies. In addition, early detection of local recurrence.

Long-term outcomes of prostate intensity-modulated radiation therapy incorporating a simultaneous intra-prostatic MRI-directed boost

Purpose/objectives

This retrospective study demonstrates the long-term outcomes of treating prostate cancer using intensity modulated (IMRT) with incorporation of MRI-directed boost.

Materials/methods

From February 2009 to February 2013, 78 men received image-guided IMRT delivering 77.4 Gy in 44 fractions with simultaneously integrated boost to 81–83 Gy to an MRI-identified lesion. Patients with intermediate-risk or high-risk prostate cancer were recommended to receive 6 and 24–36 months of adjuvant hormonal therapy, respectively.

Results

Median follow-up was 113 months (11–147). There were 18 low-risk, 43 intermediate-risk, and 17 high-risk patients per NCCN risk stratification included in this study. Adjuvant hormonal therapy was utilized in 32 patients (41%). The 10-year biochemical control rate for all patients was 77%. The 10-year biochemical control rates for low-risk, intermediate-risk, and high-risk diseases were 94%, 81%, and 88%, respectively (p = 0.35). The 10-year rates of local control, distant control, and survival were 99%, 88%, and 66%, respectively. Of 25 patients who died, only four (5%) died of prostate cancer. On univariate analysis, T-category and pretreatment PSA level were associated with distant failure rate (p = 0.02). There was no grade =3 genitourinary and gastrointestinal toxicities that persisted at the last follow-up.

Conclusions

This study demonstrated the long-term efficacy of using MRI to define an intra-prostatic lesion for SIB to 81–83Gy while treating the entire prostate gland to 77.4 Gy with IMRT. Our study confirms that modern MRI can be used to locally intensify dose to prostate tumors providing high long-term disease control while maintaining favorable long-term toxicity.

Prostate MRI in Stereotactic Body Radiation Treatment Planning and Delivery for Localized Prostate Cancer

Prostate MRI is increasingly being used to make diagnoses and guide management for patients receiving definitive radiation treatment for prostate cancer. Radiologists should be familiar with the potential uses of prostate MRI in radiation therapy planning and delivery. Radiation therapy is an established option for the definitive treatment of localized prostate cancer. Stereotactic body radiation therapy (SBRT) is an external-beam radiation therapy method used to deliver a high dose of radiation to an extracranial target in the body, often in five or fewer fractions. SBRT is increasingly being used for prostate cancer treatment and has been recognized by the National Comprehensive Cancer Network as an acceptable definitive treatment regimen for low-, intermediate-, and high-risk prostate cancer. MRI is commonly used to aid in prostate radiation therapy. The authors review the uses of prostate MRI in SBRT treatment planning and delivery. Specific topics discussed include the use of prostate MRI for identification of and dose reduction to the membranous and prostatic urethra, which can decrease the risk of acute and late toxicities. MRI is also useful for identification and appropriate dose coverage of the prostate apex and areas of extraprostatic extension or seminal vesicle invasion. In prospective studies, prostate MRI is being validated for identification of and dose intensification to dominant intraprostatic lesions, which potentially can improve oncologic outcomes. It also can be used to evaluate the placement of fiducial markers and hydrogel spacers for radiation therapy planning and delivery. ^©RSNA, 2022.

Convolutional neural network-based reconstruction for acceleration of prostate T2 weighted MR imaging: a retro- and prospective study

OBJECTIVE

The aim of this study was to develop a deep neural network (DNN)-based parallel imaging reconstruction for highly accelerated 2D turbo spin echo (TSE) data in prostate MRI without quality degradation compared to conventional scans.

METHODS

155 participant data were acquired for training and testing. Two DNN models were generated according to the number of acquisitions (NAQ) of input images: DNN-N1 for NAQ = 1 and DNN-N2 for NAQ = 2. In the test data, DNN and TSE images were compared by quantitative error metrics. The visual appropriateness of DNN reconstructions on accelerated scans (DNN-N1 and DNN-N2) and conventional scans (TSE-Conv) was assessed for nine parameters by two radiologists. The lesion detection was evaluated at DNNs and TES-Conv by prostate imaging-reporting and data system.

RESULTS

The scan time was reduced by 71% at NAQ = 1, and 42% at NAQ = 2. Quantitative evaluation demonstrated the better error metrics of DNN images (29-43% lower NRMSE, 4-13% higher structure similarity index, and 2.8-4.8 dB higher peak signal-to-noise ratio; p < 0.001) than TSE images. In the assessment of the visual appropriateness, both radiologists evaluated that DNN-N2 showed better or comparable performance in all parameters compared to TSE-Conv. In the lesion detection, DNN images showed almost perfect agreement (κ > 0.9) scores with TSE-Conv.

CONCLUSIONS

DNN-based reconstruction in highly accelerated prostate TSE imaging showed comparable quality to conventional TSE.

ADVANCES IN KNOWLEDGE

Our framework reduces the scan time by 42% of conventional prostate TSE imaging without sequence modification, revealing great potential for clinical application.

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

The added value of PSMA PET/MR radiomics for prostate cancer staging

PURPOSE

To evaluate the performance of combined PET and multiparametric MRI (mpMRI) radiomics for the group-wise prediction of postsurgical Gleason scores (psGSs) in primary prostate cancer (PCa) patients.

METHODS

Patients with PCa, who underwent [68 Ga]Ga-PSMA-11 PET/MRI followed by radical prostatectomy, were included in this retrospective analysis (n = 101). Patients were grouped by psGS in three categories: ISUP grades 1-3, ISUP grade 4, and ISUP grade 5. mpMRI images included T1-weighted, T2-weighted, and apparent diffusion coefficient (ADC) map. Whole-prostate segmentations were performed on each modality, and image biomarker standardization initiative (IBSI)-compliant radiomic features were extracted. Nine support vector machine (SVM) models were trained: four single-modality radiomic models (PET, T1w, T2w, ADC); three PET + MRI double-modality models (PET + T1w, PET + T2w, PET + ADC), and two baseline models (one with patient data, one image-based) for comparison. A sixfold stratified cross-validation was performed, and balanced accuracies (bAcc) of the predictions of the best-performing models were reported and compared through Student's t-tests. The predictions of the best-performing model were compared against biopsy GS (bGS).

RESULTS

All radiomic models outperformed the baseline models. The best-performing (mean ± stdv [%]) single-modality model was the ADC model (76 ± 6%), although not significantly better (p > 0.05) than other single-modality models (T1w: 72 ± 3%, T2w: 73 ± 2%; PET: 75 ± 5%). The overall best-performing model combined PET + ADC radiomics (82 ± 5%). It significantly outperformed most other double-modality (PET + T1w: 74 ± 5%, p = 0.026; PET + T2w: 71 ± 4%, p = 0.003) and single-modality models (PET: p = 0.042; T1w: p = 0.002; T2w: p = 0.003), except the ADC-only model (p = 0.138). In this initial cohort, the PET + ADC model outperformed bGS overall (82.5% vs 72.4%) in the prediction of psGS.

CONCLUSION

All single- and double-modality models outperformed the baseline models, showing their potential in the prediction of GS, even with an unbalanced cohort. The best-performing model included PET + ADC radiomics, suggesting a complementary value of PSMA-PET and ADC radiomics.

Correlation between FA and ADC, number and length of the periprostatic neurovascular fibers

PURPOSE

Our aim was to explore the relation between FA and ADC, number and length of the periprostatic neurovascular fibers (PNF) by means of 1.5 T Diffusion Tensor Imaging (DTI) imaging through a multivariate linear regression analysis model.

METHODS

For this retrospective study, 56 patients (mean age 63.5 years), who underwent 1.5-T prostate MRI, including DTI, were enrolled between October 2014 and December 2018. Multivariate regression analysis was performed to evaluate the statistically significant correlation between FA values (dependent variable) and ADC, the number and the length of PNF (independent variables), if p-value <0.05. A value of 0.5 indicated poor agreement; 0.5-0.75, moderate agreement; 0.75-0.9, good agreement; 0.61-0.80, good agreement; and 0.9-1.00, excellent agreement.

RESULTS

The overall fit of the multivariate regression model was excellent, with R² value of 0.9445 (R² adjusted 0.9412; p < 0.0001). Multivariate linear regression analysis showed a statistically significant correlation (p < 0.05) for all the three independent variables. The r partial value was -0.9612 for ADC values (p < 0.0001), suggesting a strong negative correlation, 0.4317 for the number of fiber tracts (p < 0.001), suggesting a moderate positive correlation, and -0.306 for the length of the fiber tracts (p < 0.05), suggesting a weak negative correlation.

CONCLUSIONS

Our multivariate linear regression model has demonstrated a statistically significant correlation between FA values of PNF with other DTI parameters, in particular with ADC.

Width of spared neurovascular bundle after robot-assisted laparoscopic prostatectomy in patients with prostate cancer: is it a reliable factor for predicting postoperative sexual outcome?

Purpose

To investigate the relationship between the width of spared neurovascular bundle (NVB) measured during robot-assisted laparoscopic prostatectomy and postoperative sexual outcomes.

Methods

Patients with localized prostate cancer with erectile hardness score ≥2 (N = 105) who underwent NVB-sparing robot-assisted laparoscopic prostatectomy were included. Patients were divided into three groups [first (Q1) vs. second and third (Q2-3) vs. fourth (Q4) quartile] according to width of spared NVB measured with a flexible ruler after prostate removal. Preoperative and postoperative sexual function was evaluated according to erectile hardness score and Expanded Prostate Cancer Index Composite questionnaires.

Results

The proportion of patients with postoperative erectile hardness score ≥2 at postoperative 6 months was as follows: 38.9% (Q1), 48.6% (Q2–3), and 83.3% (Q4) (P = 0.016). The preoperative/postoperative 6-month sexual function score was 40.7/16.9 (Q1), 48.1/19.0 (Q2–3), and 51.2/28.1 (Q4). Postoperative sexual function was significantly associated with preoperative sexual function in Q4 (P = 0.006) and Q2–3 (P = 0.030) but not in Q1. On multivariate analysis, the width of spared NVB was a significant predictor for postoperative 6-month erectile hardness score ≥2. Limitation includes selection bias and short follow-up duration.

Conclusions

Not only the performance but also the degree and quality of NVB sparing thought to be important for postoperative sexual function. Measurement of the width of NVB during surgery could be an easy intraoperative method for assessing the quality of NVB sparing.

Three-dimensional nuclear magnetic resonance spectroscopy: a complementary tool to multiparametric magnetic resonance imaging in the identification of aggressive prostate cancer at 3.0T

Background

The limitations of the assessment of tumor aggressiveness by Prostate Imaging Reporting and Data System (PI-RADS) and biopsies suggest that the diagnostic algorithm could be improved by quantitative measurements in some chosen indications. We assessed the tumor high-risk predictive performance of 3.0 Tesla (3.0T) multiparametric magnetic resonance imaging (mp-MRI) combined with nuclear magnetic resonance spectroscopic sequences (NMR-S) in order to show that the metabolic analysis could bring out an evocative result for the aggressive form of prostate cancer.

Methods

We conducted a retrospective study of 26 patients (mean age, 62.4 years) who had surgery for prostate cancer between 2009 and 2016 after pre-therapeutic assessment with 3.0T mp-MRI and NMR-S. Groups within the intermediate range of the D'Amico risk classification were divided into two categories, low risk (n=20) and high risk (n=6), according to the International Society of Urological Pathology (ISUP) 2-3 limit. Histoprognostic discordances within various risk groups were compared with the corresponding predictive MRI values. The performance of predictive models was assessed based on sensitivity, specificity, and the area under the curve (AUC) of receiver operating characteristic (ROC) curves.

Results

After prostatectomy, histological analysis reclassified 18 patients as high-risk, including 16 who were T3 MRI grade, of whom 13 (81.3%) were found to be pT3. Among the patients who had cT1 or cT2 digital rectal examinations, the T3 MRI factor multiplied by 8.7 [odds ratio (OR), 8.7; 95% confidence interval (CI), 1.3-56.2; P=0.024] the relative risk of being pT3 and by 5.8 (OR, 5.8; 95% CI, 0.95-35.7; P=0.05) the relative risk of being pGleason (pGS) > GS-prostate biopsy. Spectroscopic data showed that the choline concentration was significantly higher (P=0.001) in aggressive disease.

Conclusions

The predictive model of tumor aggressiveness combining mp-MRI plus NMR-S was better than the mp-MRI model alone (AUC, 0.95 vs. 0.86). Information obtained by mp-MRI coupled with spectroscopy may improve the detection of occult aggressive disease, helping in the discrimination of intermediate risks.

Depiction of periprostatic nerve fibers by means of 1.5 T diffusion tensor imaging

PURPOSE

The knowledge of periprostatic nerve fiber (pNF) is still incomplete by means of conventional MRI. The purpose of our study was to demonstrate if DTI imaging is able to depict anatomical features of pNF.

METHODS

For this retrospective study, fifty-six patients (mean age 63.5 years), who underwent 1.5-T prostate MRI, including 32 directions DTI, were enrolled between October 2014 and December 2018. ANOVA test and Student's t-test were performed between the mean values of the number, FA values, and fiber length of pNF between base and mid-gland, mid-gland and apex, base and apex, right and left side, and anterior and posterior face of the prostate. A qualitative analysis was performed to detect the main orientation of pNF through a colorimetric 3D tractographic reconstruction.

RESULTS

The number of pNF showed a decrease from the base (322) to mid-gland (248) and apex (75) (p < 0.05). The FA values were higher at base and mid-gland (0.435 and 0.456) compared to the apex (0.313) (p < 0.05). The length of pNF was higher at apex (13.4 mm) compared to base (11.5 mm) and mid-gland (11.7 mm) (p < 0.05). The number of pNF was higher on the posterior face compared to the anterior face at base (186 vs 137), (p < 0.001). The FA values were higher on the posterior face compared to the anterior face at base (0.452 vs 0.417), mid-gland (0.483 vs 0.429), and apex (0.42 vs 0.382), (p < 0.05). The length of the pNF was higher in the posterior (14.7 mm) than in the anterior face (12 mm) at apex (p < 0.001). The main orientation of pNF was longitudinal in all patients (56/56, 100%).

CONCLUSIONS

DTI imaging has been demonstrated able to depict anatomical features of pNF.

Signal Enhancement of Low Magnetic Field Magnetic Resonance Image Using a Conventional- and Cyclic-Generative Adversarial Network Models With Unpaired Image Sets

In this study, the signal enhancement ratio of low-field magnetic resonance (MR) images was investigated using a deep learning-based algorithm. Unpaired image sets (0.06 Tesla and 1.5 Tesla MR images for different patients) were used in this study following three steps workflow. In the first step, the deformable registration of a 1.5 Tesla MR image into a 0.06 Tesla MR image was performed to ensure that the shapes of the unpaired set matched. In the second step, a cyclic-generative adversarial network (GAN) was used to generate a synthetic MR image of the original 0.06 Tesla MR image based on the deformed or original 1.5 Tesla MR image. Finally, an enhanced 0.06 Tesla MR image could be generated using the conventional-GAN with the deformed or synthetic MR image. The results from the optimized flow and enhanced MR images showed significant signal enhancement of the anatomical view, especially in the nasal septum, inferior nasal choncha, nasopharyngeal fossa, and eye lens. The signal enhancement ratio, signal-to-noise ratio (SNR) and correlation factor between the original and enhanced MR images were analyzed for the evaluation of the image quality. A combined method using conventional- and cyclic-GANs is a promising approach for generating enhanced MR images from low-magnetic-field MR.

Development of an Indian nomogram for predicting extracapsular extension in prostate cancer

Introduction

The aim of our study was to develop a new Indian nomogram to estimate pathologic extracapsular extension (ECE) risk in prostate cancer, by including PI-RADS v1-based magnetic resonance imaging (MRI) ECE risk score to the clinical variables used in the Partin nomogram (PN).

Materials and Methods

We analyzed 273 patients who underwent MRI of prostate and radical prostatectomy (RP). Univariate and multivariate logistic regression analyses were performed to identify predictors of ECE. We calculated the area under the receiver operating characteristic curve (AUC) for three variables used in PN and MRI ECE risk score, and a new nomogram was designed using binary logistic regression. Calibration curves assessed the agreement between the actual ECE risk and the predicted probability of the new nomogram.

Results

Out of 273 patients, 123 patients (45.1) had ECE on MRI, whereas 136 patients (49.8) had ECE on final pathology. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of MRI for predicting ECE were 76.6, 66.9, 70.0, 73.9, and 71.7 (confidence interval 95), respectively. Multivariate logistic regression analyses showed that clinical T-stage (cT), Gleason score (GS), and MRI ECE risk score remained significant. The highest and the lowest values of the AUC for single variables were 0.748 (MRI ECE risk score) and 0.636 (cT stage), respectively, and AUC for PN was 0.67. New nomogram designed using R statistical package has higher predictive accuracy (0.826) compared to PN (0.67) and good calibration.

Conclusions

MRI adds incremental value to PN. A new Indian nomogram can help in the decision-making process of nerve-sparing RP. This nomogram should be used with caution as validation is pending and will require further studies.

Determination of Gleason score discrepancy for risk stratification in magnetic resonance-ultrasound fusion prostate biopsy

BACKGROUND

Magnetic resonance imaging (MRI)-ultrasound (US) fusion biopsy remains challenging and highlights the need towards standardization.

PURPOSE

To characterize the clinical and MRI features of clinically significant prostate cancer (csPCa) with discrepant Gleason score (GS) in MRI-US fusion biopsy.

MATERIAL AND METHODS

A total of 400 consecutive patients with suspected cancer lesions who underwent MRI-US fusion biopsy and subsequent prostatectomy were included. In the comparison of biopsy GS with pathology GS, matched lesions were defined as a GS, and discrepant lesions were defined as an upgrade of the GS. Descriptive statistics were used to define clinical characteristics, including age, prostate-specific antigen (PSA), PSA density, and maximal cancer core length (MCCL). Differences between lesions with matched and discrepant GS were determined considering the location and PI-RADS v2 score. A paired comparison of the volumes between the two groups was performed.

RESULTS

There were 130 lesions with discrepant GS in 124 patients. There was no significant difference in the age, PSA, and PSA density between the two groups, except for the MCCL (P = 0.028). The lesions were distributed in the peripheral (n = 88) and transition (n = 42) zones; 33, 50, and 47 lesions were at the apex, mid-gland, and base levels, respectively. PI-RADS scores were as follows: 2 (n = 5), 3 (n = 8), 4 (n = 68), and 5 (n = 39). In comparison with matched lesions, discrepant lesions had significantly smaller multiparametric MRI-measured cancer volumes (P < 0.05).

CONCLUSION

Knowledge of discrepant GS in MRI-US fusion biopsy is important, and a careful approach is needed to reduce this discrepancy.

Local staging of prostate cancer with multiparametric-MRI: accuracy and inter-reader agreement

Background

The accuracy of prostate cancer local staging at the time of diagnosis directly influences patient prognosis and treatment.

Aim

To evaluate the diagnostic performance and interobserver variability of mp-MRI in local staging of prostate cancer, using the histopathologic findings at prostatectomy as the reference standard.

Methods

Fifty patients (mean age 64.4±7.2) with biopsy confirmed prostate cancer were included in this prospective study. All patients were examined with mp-MRI before radical prostatectomy and images were read by three independent radiologists. Sensitivity (Se), specificity (Sp), positive predictive value (PPV), negative predictive value (NPV), and accuracy rate were calculated and compared for all three readers. Interobserver agreement was evaluated using Kappa Cohen coefficient of agreement.

Results

The overall Se, Sp, PPV, NPV and accuracy rates for detecting extraprostatic tumor extension (EPE) ranged between 76.5-94.1%, 45.5-84.9%, 43.8-76.2%, 83.3-96.6% and 58-88%. For evaluation of seminal vesicle invasion (SVI), the overall Se, Sp, PPV, NPV and accuracy rates ranged between 57.1-85.7%, 86.1-97.7%, 40.0-85.7%, 92.5-97.7% and 82-96%, respectively. The overall Kappa Cohen coefficient of agreement varied between 0.349-0.638 for EPE and between 0.507-0.668 for SVI.

Conclusions

Our results showed that 1.5T mp-MRI is a reliable method for local staging of prostate cancer, with good diagnostic performance in detecting EPE and SVI. The overall interobserver agreement rates between readers with the same level of experience in prostate MRI ranged from fair to good in the evaluation of EPE and from moderate to good for the assessment of SVI.

Dosimetric evaluation of synthetic CT generated with GANs for MRI-only proton therapy treatment planning of brain tumors

PURPOSE

The purpose of this study was to address the dosimetric accuracy of synthetic computed tomography (sCT) images of patients with brain tumor generated using a modified generative adversarial network (GAN) method, for their use in magnetic resonance imaging (MRI)-only treatment planning for proton therapy.

METHODS

Dose volume histogram (DVH) analysis was performed on CT and sCT images of patients with brain tumor for plans generated for intensity-modulated proton therapy (IMPT). All plans were robustly optimized using a commercially available treatment planning system (RayStation, from RaySearch Laboratories) and standard robust parameters reported in the literature. The IMPT plan was then used to compute the dose on CT and sCT images for dosimetric comparison, using RayStation analytical (pencil beam) dose algorithm. We used a second, independent Monte Carlo dose calculation engine to recompute the dose on both CT and sCT images to ensure a proper analysis of the dosimetric accuracy of the sCT images.

RESULTS

The results extracted from RayStation showed excellent agreement for most DVH metrics computed on the CT and sCT for the nominal case, with a mean absolute difference below 0.5% (0.3 Gy) of the prescription dose for the clinical target volume (CTV) and below 2% (1.2 Gy) for the organs at risk (OARs) considered. This demonstrates a high dosimetric accuracy for the generated sCT images, especially in the target volume. The metrics obtained from the Monte Carlo doses mostly agreed with the values extracted from RayStation for the nominal and worst-case scenarios (mean difference below 3%).

CONCLUSIONS

This work demonstrated the feasibility of using sCT generated with a GAN-based deep learning method for MRI-only treatment planning of patients with brain tumor in intensity-modulated proton therapy.

MRI ultrasound fusion biopsy in prostate cancer detection: Are randomized clinical trials reproducible in everyday clinical practice?

INTRODUCTION:

The aim of this study was to evaluate the performance of multiparametric magnetic resonance imaging (mpMRI)-ultrasound (US) fusion-targeted biopsies (TB) in men with primary and repeated biopsies comparing the cancer detection rate (CDR) of random biopsies (RB) + TB versus only TB.

METHODS:

The present study is a real-life study on patients with primary and prior negative prostate biopsies with suspicious PCa. A total of 130 men with prostate-specific antigen (PSA) value >2.5 ng/dL and/or abnormal digital rectal examination (DRE) were included in the study and subjected to mpMRI. Patients with >2 previous biopsies and/or with ⩾3 suspected lesions on MRI and/or prostate imaging-reporting and data system (PIRADS) value ⩾4 (n:30 pts) were subjected only to TB on the areas indicated by mpMRI. All the other patients (n:70 pts) were subjected to standard random laterally directed 10-core plus TB on the areas indicated by mpMRI.

RESULTS:

The overall CDR was 53% (53/100). In relation to PIRADS score, the overall CDR was 0, 40% (12/30), 56.83% (29/51), and 84% (11/13) for PIRADS 2, 3, 4, and 5, respectively. According to biopsy modality, CDR for RB + TB was 50% (35/70) and CDR for TB was 60% (18/30) with a p-value of 0.3632.

DISCUSSION:

MRI-US fusion biopsy is associated with a high CDR of clinically significant PCa (csPCa). MRI-US fusion biopsy could be a reasonable approach in patients with previous negative biopsy and high PIRADS score on MRI, to ensure a high CDR of csPCa and to reduce the diagnosis of clinically insignificant tumors.

Transrectal ultrasound-guided prostate biopsy versus combined magnetic resonance imaging-ultrasound fusion and systematic biopsy for prostate cancer detection in routine clinical practice

PURPOSE

The goal of this study was to retrospectively compare systematic ultrasound-guided prostate biopsy (US-PB) and multiparametric magnetic resonance imaging-ultrasound fusion prostate biopsy (MRI-PB) in men undergoing primary or repeated biopsies.

METHODS

A population of 2,200 patients with a prostate-specific antigen (PSA) level >4.0 ng/ dL and/or an abnormal rectal examination was divided into two groups. All patients underwent US-PB (n=1,021) or MRI-PB (n=1,179) between April 2015 and April 2019. Population demographics, including age, PSA level, digital rectal examination results, prostate volume, number of previous negative biopsies, Prostate Imaging Reporting and Data System (PI-RADS) version 2 (V2) score, and biopsy results, were acquired and compared with respect to these variables. Univariate regression analysis of the risk factors for a higher Gleason score (GS) was performed.

RESULTS

The cancer detection rate (CDR) was 23.8% (243 of 1,021) in the US-PB group and 31.3% (399 of 1,179) in the MRI-PB group. Of those, 225 patients (22.0%) in the US-PB group and 374 patients (31.7%) in the MRI-PB group had clinically significant prostate cancer (csPCa). The patients with csPCa in the MRI-PB group included 10 (40%), 50 (62.5%), 184 (94.8%), and 32 (94.1%) patients with PI-RADS V2 scores of 2, 3, 4, and 5, respectively. Of the patients with csPCa, 155 (91.7%) in the US-PB group were diagnosed on the basis of the primary biopsy, compared to 308 (94.4%) in the MRI-PB group. We found the PI-RADS V2 score to be the best predictor of a higher GS.

CONCLUSION

MRI-PB showed a high CDR for csPCa. MRI-PB could be a reasonable approach in patients with high PI-RADS V2 scores at primary biopsy.

Combining prostate health index and multiparametric magnetic resonance imaging in the diagnosis of clinically significant prostate cancer in an Asian population

Objective

To evaluate the practicability of combining prostate health index (PHI) and multiparametric magnetic resonance imaging (mpMRI) for the detection of clinically significant prostate cancer (csPC) in an Asian population.

Patients and methods

We prospectively enrolled patients who underwent prostate biopsy due to elevated serum prostate-specific antigen (PSA > 4 ng/mL) and/or abnormal digital rectal examination in a tertiary referral center. Before prostate biopsy, the serum samples were tested for PSA, free PSA, and p2PSA to calculate PHI. Besides, mpMRI was performed using a 3-T scanner and reported in the Prostate Imaging Reporting and Data System version 2 (PI-RADS v2). The diagnostic performance of PHI, mpMRI, and combination of both was assessed.

Result

Among 102 subjects, 39 (38.2%) were diagnosed with PC, including 24 (23.5%) with csPC (Gleason ≥ 7). By the threshold of PI-RADS ≥ 3, the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) to predict csPC were 100%, 44.9%, 35.8%, and 100%, respectively. By the threshold of PHI ≥ 30, the sensitivity, specificity, PPV, and NPV to predict csPC were 91.7%, 43.6%, 33.3%, and 94.4%, respectively. The area under the receiver operator characteristic curve of combining PHI and mpMRI was greater than that of PHI alone (0.873 vs. 0.735, p = 0.002) and mpMRI alone (0.873 vs. 0.830, p = 0.035). If biopsy was restricted to patients with PI-RADS 5 as well as PI-RADS 3 or 4 and PHI ≥ 30, 50% of biopsy could be avoided with one csPC patient being missed.

Conclusion

The combination of PHI and mpMRI had higher accuracy for detection of csPC compared with PHI or mpMRI alone in an Asian population.

Volumetric and Voxel-Wise Analysis of Dominant Intraprostatic Lesions on Multiparametric MRI

Introduction: Multiparametric MR imaging (mpMRI) has shown promising results in the diagnosis and localization of prostate cancer. Furthermore, mpMRI may play an important role in identifying the dominant intraprostatic lesion (DIL) for radiotherapy boost. We sought to investigate the level of correlation between dominant tumor foci contoured on various mpMRI sequences. Methods: mpMRI data from 90 patients with MR-guided biopsy-proven prostate cancer were obtained from the SPIE-AAPM-NCI Prostate MR Classification Challenge. Each case consisted of T2-weighted (T2W), apparent diffusion coefficient (ADC), and K^trans images computed from dynamic contrast-enhanced sequences. All image sets were rigidly co-registered, and the dominant tumor foci were identified and contoured for each MRI sequence. Hausdorff distance (HD), mean distance to agreement (MDA), and Dice and Jaccard coefficients were calculated between the contours for each pair of MRI sequences (i.e., T2 vs. ADC, T2 vs. K^trans, and ADC vs. K^trans). The voxel wise spearman correlation was also obtained between these image pairs. Results: The DILs were located in the anterior fibromuscular stroma, central zone, peripheral zone, and transition zone in 35.2, 5.6, 32.4, and 25.4% of patients, respectively. Gleason grade groups 1-5 represented 29.6, 40.8, 15.5, and 14.1% of the study population, respectively (with group grades 4 and 5 analyzed together). The mean contour volumes for the T2W images, and the ADC and K^trans maps were 2.14 ± 2.1, 2.22 ± 2.2, and 1.84 ± 1.5 mL, respectively. K^trans values were indistinguishable between cancerous regions and the rest of prostatic regions for 19 patients. The Dice coefficient and Jaccard index were 0.74 ± 0.13, 0.60 ± 0.15 for T2W-ADC and 0.61 ± 0.16, 0.46 ± 0.16 for T2W-K^trans. The voxel-based Spearman correlations were 0.20 ± 0.20 for T2W-ADC and 0.13 ± 0.25 for T2W-K^trans. Conclusions: The DIL contoured on T2W images had a high level of agreement with those contoured on ADC maps, but there was little to no quantitative correlation of these results with tumor location and Gleason grade group. Technical hurdles are yet to be solved for precision radiotherapy to target the DILs based on physiological imaging. A Boolean sum volume (BSV) incorporating all available MR sequences may be reasonable in delineating the DIL boost volume.

A Multireader Exploratory Evaluation of Individual Pulse Sequence Cancer Detection on Prostate Multiparametric Magnetic Resonance Imaging (MRI)

RATIONALE AND OBJECTIVES

To determine independent contribution of each prostate multiparametric magnetic resonance imaging (mpMRI) sequence to cancer detection when read in isolation.

MATERIALS AND METHODS

Prostate mpMRI at 3-Tesla with endorectal coil from 45 patients (n = 30 prostatectomy cases, n = 15 controls with negative magnetic resonance imaging [MRI] or biopsy) were retrospectively interpreted. Sequences (T2-weighted [T2W] MRI, diffusion-weighted imaging [DWI], and dynamic contrast-enhanced [DCE] MRI; N = 135) were separately distributed to three radiologists at different institutions. Readers evaluated each sequence blinded to other mpMRI sequences. Findings were correlated to whole-mount pathology. Cancer detection sensitivity, positive predictive value for whole prostate (WP), transition zone, and peripheral zone were evaluated per sequence by reader, with reader concordance measured by index of specific agreement. Cancer detection rates (CDRs) were calculated for combinations of independently read sequences.

RESULTS

44 patients were evaluable (cases median prostate-specific antigen 6.83 [ range 1.95-51.13] ng/mL, age 62 [45-71] years; controls prostate-specific antigen 6.85 [2.4-10.87] ng/mL, age 65.5 [47-71] years). Readers had highest sensitivity on DWI (59%) vs T2W MRI (48%) and DCE (23%) in WP. DWI-only positivity (DWI+/T2W-/DCE-) achieved highest CDR in WP (38%), compared to T2W-only (CDR 24%) and DCE-only (CDR 8%). DWI+/T2W+/DCE- achieved CDR 80%, an added benefit of 56.4% from T2W-only and of 42% from DWI-only (P < .0001). All three sequences interpreted independently positive gave highest CDR of 90%. Reader agreement was moderate (index of specific agreement: T2W = 54%, DWI = 58%, DCE = 33%).

CONCLUSIONS

When prostate mpMRI sequences are interpreted independently by multiple observers, DWI achieves highest sensitivity and CDR in transition zone and peripheral zone. T2W and DCE MRI both add value to detection; mpMRI achieves highest detection sensitivity when all three mpMRI sequences are positive.

Magnetic resonance imaging-transrectal ultrasound fusion image-guided prostate biopsy: Current status of the cancer detection and the prospects of tailor-made medicine of the prostate cancer

Multi-parametric magnetic resonance imaging (mpMRI) has been increasingly used to diagnose clinically significant prostate cancer (csPCa) because of its growing availability and its ability to combine anatomical and functional data. Magnetic resonance imaging (MRI)-transrectal ultrasound (TRUS) fusion imaging provides MRI information with TRUS images for prostate biopsies. This technique combines the superior sensitivity of MRI for targeting suspicious lesions with the practicality and familiarity of TRUS. MRI-TRUS fusion image-guided prostate biopsy is performed with different types of image registration (rigid vs. elastic) and needle tracking methods (electromagnetic tracking vs. mechanical position encoders vs. image-based software tracking). A systematic review and meta-analysis showed that MRI-targeted biopsy detected csPCa at a significantly higher rate than did TRUS-guided biopsy, while it detected significantly fewer cases of insignificant PCas. In addition to the high accuracy of MRI-targeted biopsy for csPCa, localization of csPCa is accurate. The ability to choose the route of biopsy (transperineal vs. transrectal) is required, depending on the patients' risk and the location and size of suspicious lesions on mpMRI. Fusion image-guided prostate biopsy has the potential to allow precise management of prostate cancer, including active surveillance, radical treatment, and focal therapy.

50-Gy Stereotactic Body Radiation Therapy to the Dominant Intraprostatic Nodule: Results From a Phase 1a/b Trial

PURPOSE

Although localized prostate cancer (PCa) is multifocal, the dominant intraprostatic nodule (DIN) is responsible for disease progression after radiation therapy. PCa expresses antigens that could be recognized by the immune system. We therefore hypothesized that stereotactic dose escalation to the DIN is safe, may increase local control, and may initiate tumor-specific immune responses.

PATIENTS AND METHODS

Patients with localized PCa were treated with stereotactic extreme hypofractionated doses of 36.25 Gy in 5 fractions to the whole prostate while simultaneously escalating doses to the magnetic resonance image-visible DIN (45 Gy, 47.5 Gy, and 50 Gy in 5 fractions). The phase 1a part was designed to determine the recommended phase 1b dose in a "3 + 3" cohort-based, dose-escalation design. The primary endpoint was dose-limiting toxicities defined as ≥grade 3 gastrointestinal (GI) or genitourinary (GU) toxicity (or both) by National Cancer Institute Common Terminology Criteria for Adverse Events (version 4) up to 90 days after the first radiation fraction. The secondary endpoints were prostate-specific antigen kinetics, quality of life (QoL), and blood immunologic responses.

RESULTS

Nine patients were treated in phase 1a. No dose-limiting toxicities were observed at either level, and therefore the maximum tolerated dose was not reached. Further characterization of tolerability, efficacy, and immunologic outcomes was conducted in the subsequent 11 patients irradiated at the highest dose level (50 Gy) in the phase 1b expansion cohort. Toxicity was 45% and 25% for grades 1 and 2 GU, and 20% and 5% for grades 1 and 2 GI, respectively. No grade 3 or worse toxicity was reported. The average (±standard error of the mean) of the QoL assessments at baseline and at 3-month posttreatment were 0.8 (±0.8) and 3.5 (±1.5) for the bowel (mean difference, 2.7; 95% confidence interval, 0.1-5), and 6.4 (±0.8) and 7.27 (±0.9) for the International Prostate Symptom Score (mean difference, 0.87; 95% confidence interval, 0.3-1.9), respectively. A subset of patients developed antigen-specific immune responses against prostate-specific membrane antigen (n = 2), prostatic acid phosphatase (n = 1), prostate stem cell antigen (n = 4), and prostate-specific antigen (n = 2).

CONCLUSIONS

Irradiation of the whole prostate with 36.25 Gy in 5 fractions and dose escalation to 50 Gy to the DIN was tolerable and determined as the recommended phase 1b dose. This treatment has promising antitumor activity, which will be confirmed by the ongoing phase 2 part. Preliminary QoL analysis showed minimal impact in GU, GI, and sexual domains. Stereotactic irradiation induced antigen-specific immune responses in a subset of patients.

Magnetic Resonance Imaging only Workflow for Radiotherapy Simulation and Planning in Prostate Cancer

Magnetic resonance imaging (MRI) is often combined with computed tomography (CT) in prostate radiotherapy to optimise delineation of the target and organs-at-risk (OAR) while maintaining accurate dose calculation. Such a dual-modality workflow requires two separate imaging sessions, and it has some fundamental and logistical drawbacks. Due to the availability of new MRI hardware and software solutions, CT examinations can be omitted for prostate radiotherapy simulations. All information for treatment planning, including electron density maps and bony anatomy, can nowadays be obtained with MRI. Such an MRI-only simulation workflow reduces delineation ambiguities, eases planning logistics, and improves patient comfort; however, careful validation of the complete MRI-only workflow is warranted. The first institutes are now adopting this MRI-only workflow for prostate radiotherapy. In this article, we will review technology and workflow requirements for an MRI-only prostate simulation workflow.

Diagnostic accuracy of multiparametric magnetic resonance imaging in detecting extracapsular extension in intermediate and high - risk prostate cancer

OBJECTIVES

To evaluate the diagnostic performance of preoperative multiparametric magnetic resonance imaging (mp-MRI) as a predictor of extracapsular extension (ECE) and unfavorable Gleason score (GS) in patients with intermediate and high-risk prostate cancer (PCa).

MATERIALS AND METHODS

Patients with clinically localized PCa who underwent radical prostatectomy (RP) and had preoperative mp-MRI between May-2011 and December-2013. Mp-MRI was evaluated according to the European Society of Urogenital Radiology MRI prostate guidelines by two different readers. Histopathological RP results were the standard reference.

RESULTS

79 patients were included; mean age was 61 and median preoperative prostate-specific antigen (PSA) 7.0. On MRI, 28% patients had ECE evidenced in the mp-MRI, 5% seminal vesicle invasion (SVI) and 4% lymph node involvement (LNI). At RP, 39.2% had ECE, 26.6% SVI and 12.8% LNI. Sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of mp-MRI for ECE were 54.9%, 90.9%, 76%, 81% and 74.1% respectively; for SVI values were 19.1%, 100%, 77.3%, 100% and 76.1% respectively and for LNI 20%, 98.4%, 86.7%, 66.7% and 88.7%.

CONCLUSIONS

Major surgical decisions are made with digital rectal exam (DRE) and ultrasound studies before the use of Mp-MRI. This imaging study contributes to rule out gross extraprostatic extension (ECE, SVI, LNI) without competing with pathological studies. The specificity and NPV are reasonable to decide surgical approach. A highly experienced radiology team is needed to provide accurate estimations of tumor extension and aggressiveness.

MRI-only based radiation therapy of prostate cancer: workflow and early clinical experience

BACKGROUND

Magnetic resonance imaging (MRI) is the most comprehensive imaging modality for radiation therapy (RT) target delineation of most soft tissue tumors including prostate cancer. We have earlier presented step by step the MRI-only based workflow for RT planning and image guidance for localized prostate cancer. In this study we present early clinical experiences of MRI-only based planning.

MATERIAL AND METHODS

We have analyzed the technical planning workflow of the first 200 patients having received MRI-only planned radiation therapy for localized prostate cancer in Helsinki University Hospital Cancer center. Early prostate specific antigen (PSA) results were analyzed from n = 125 MRI-only patients (n = 25 RT only, n = 100 hormone treatment + RT) and were compared with the corresponding computed tomography (CT) planned patient group.

RESULTS

Technically the MRI-only planning procedure was suitable for 92% of the patients, only 8% of the patients required supplemental CT imaging. Early PSA response in the MRI-only planned group showed similar treatment results compared with the CT planned group and with an equal toxicity level.

CONCLUSION

Based on this retrospective study, MRI-only planning procedure is an effective and safe way to perform RT for localized prostate cancer. It is suitable for the majority of the patients.

Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule: a systematic review

Radiation therapy (RT) is a curative treatment option for localized prostate cancer. Prostate irradiation with focal dose escalation to the intraprostatic dominant nodule (IDN) is an emerging treatment option that involves the prophylactic irradiation of the whole prostate while increasing RT doses to the visible prostatic tumor. Because of the lack of large multicentre trials, a systematic review was performed in an attempt to get an overview on the feasibility and efficacy of focal dose escalation to the IDN.

A bibliographic search for articles in English, which were listed in MEDLINE from 2000 to 2016 to identify publications on RT with focal directed boost to the IDN, was performed. The review was completed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines.

Twenty-two articles describing 1,378 patients treated with RT using focal boost were identified and fulfilled the selection criteria. Intensity-modulated radiation therapy (IMRT) was used in 720 patients (52.3%), volumetric modulated arc therapy was used in 45 patients (3.3%), stereotactic body radiation therapy (SBRT) in 113 patients (8.2%), and low–dose rate and high–dose rate brachytherapy (BT) were used in 305 patients (22.1%) and 195 patients (14.1%), respectively. Use of androgen deprivation therapy varied substantially among series. Biochemical disease-free survival at 5 years was reported for a cohort of 812 (58.9%) patients. The combined median biochemical disease-free survival for this group of patients was 85% (range: 78.8–100%; 95% confidence interval: 77.1–82.7%).

The average occurrence of grade III or worse gastrointestinal and genitourinary late toxicity was, respectively, 2.5% and 3.1% for intensity-modulated RT boost, 10% and 6% for stereotactic body RT, 6% and 2% for low–dose rate BT, and 4% and 4.3% for high–dose rate BT.

This review shows encouraging results for focal dose escalation to the IDN with acceptable short- to medium-term side effects and biochemical disease control rates. However, owing to the heterogeneity of patient population and the short follow-up, the results should be interpreted with caution. Considering that the clinical endpoint in the studies was biochemical recurrence, the use and duration of androgen deprivation therapy administration should be carefully considered before driving definitive conclusions. Randomized trials with long-term follow-up are needed before this technique can be generally recommended.

Quantitative parameters in dynamic contrast-enhanced magnetic resonance imaging for the detection and characterization of prostate cancer

Objectives

to assess the diagnostic accuracy of quantitative parameters of DCE-MRI in multi-parametric MRI (mpMRI) in comparison to the histopathology (including Gleason grade) of prostate cancer.

Patients and methods

150 men with suspected prostate cancer (abnormal digital rectum examination and or elevated prostate-specific antigen) received pre-biopsy 3T mpMRI and were recruited into peer-reviewed, protocol-based prospective study. The DCE-MRI quantitative parameters (K^trans (influx transfer constant) and k_ep (efflux rate constant)) of the cancerous and normal areas were recorded using four different kinetic models employing Olea Sphere (Olea Medical, La Ciotat, France). The correlation between these parameters and the histopathology of the lesions (biopsy and in a sub-cohort 41 radical prostatectomy specimen) was assessed.

Results

The quantitative parameters showed a significant difference between non-cancerous (benign) and cancerous lesions (Gleason score≥3+3) in the prostate gland. The cut-off values for prostate cancer differentiation were: K^trans (0.205 min⁻¹) and k_ep (0.665 min⁻¹) in the extended Tofts model (ET) and K^trans(0.205 min⁻¹ and k_ep (0.63 min⁻¹) in the Lawrence and Lee delay (LD) models respectively. The mean K^trans value also showed a difference between low-grade cancer (Gleason score=3+3) and high-grade cancer (Gleason score ≥ 3+4). With the addition of DCE-MRI quantitative parameters, the sensitivity of the PIRAD scoring system was increased from 56.6% to 92.1% (K^trans_ET), 93.1% (k_ep_ET), 91.0%, (K^trans_LD) and 89.4% (k_ep_LD).

Conclusion

Quantitative DCE-MRI parameters improved the diagnostic performance of conventional MRI in distinguishing normal and prostate cancers, including characterization of grade of cancers. The ET and LD models in post-image processing analysis provided better cut-off values for prostate cancer differentiation than the other quantitative DCE-MRI parameters.

Evaluation of periprostatic neurovascular fibers before and after radical prostatectomy by means of 1.5 T MRI diffusion tensor imaging

OBJECTIVE

To evaluate if diffusion tensor imaging (DTI) is able to detect changes of periprostatic neurovascular fibers (PNFs) before and after radical prostatectomy (RP), and if these changes are related to post-surgical urinary incontinence and erectile dysfunction.

METHODS

22 patients (mean age 62.6 years) with biopsy-proven prostate cancer underwent 1.5 T DTI before and after RP. The number, fractional anisotropy (FA) values and length of PNFs before and after RP were compared using Student's t-test. Each patient filled out two questionnaires before and after RP, one for the evaluation of urinary continence (ICIQ-SF) and one for the evaluation of erectile function (IIEF-5). The ratios of the number, FA values and length of PNFs before and after RP (DTI B-A RATIOs) and the ratios between the scores obtained before and after RP for both ICIQ-SF and IIEF-2 (ICIQ-SF B-A RATIOs and IIEF-2 B-A RATIOs) were calculated to perform the Kendall's τ-test between them.

RESULTS

There was a statistically significant decrease of the number of PNFs after RP at base, midgland, and apex (p < 0.01) and of FA values at midgland (p < 0.05), with positive statistically significant correlation between the DTI B-A RATIOs of the number of PNFs and IIEF-2 B-A RATIOs (p < 0.05, ρ = 0.47).

CONCLUSION

DTI was able to detect that the decrease of the number of the PNFs after RP was statistically related to the post-surgical erectile dysfunction (p < 0.05). Advances in knowledge: This work demonstrates that: (1) 1.5 T MRI DTI is able to detect the decrease of the number and of the FA of PNFs after prostatectomy; (2) the decrease of the number of PNFs after prostatectomy is related with the post-surgical erectile dysfunction; (3) 1.5 T MRI DTI has demonstrated to be a reproducible technique in detecting the changes of the PNFs induced by RP, with high interobserver agreement.

Adjuvant Versus Early Salvage Radiation Therapy Following Radical Prostatectomy for Men with Localized Prostate Cancer

Radical prostatectomy (RP) is now the most common definitive treatment for high-risk prostate cancer. Unfortunately, many men will have residual microscopic disease after surgery alone. Despite level 1 evidence supporting the use of adjuvant radiation therapy (ART), <10% of men with adverse pathology (positive margins or T3 disease) receive ART in the USA. Early salvage radiation therapy (eSRT) at the time of biochemical recurrence has been proposed as an alternative strategy despite the lack of published randomized trials to support this approach. Multiple randomized trials are ongoing or recently completed to compare ART to eSRT, but given the long natural history of prostate cancer, long-term oncologic outcomes from these trials will not be reported for several years. In this review, we discuss the shifting trends in the diagnosis of high-risk prostate cancer given a decline in PSA screening, use of RP for high-risk disease, and compare and contrast the retrospective and randomized evidence regarding ART and SRT.

Association of multiparametric MRI quantitative imaging features with prostate cancer gene expression in MRI-targeted prostate biopsies

Standard clinicopathological variables are inadequate for optimal management of prostate cancer patients. While genomic classifiers have improved patient risk classification, the multifocality and heterogeneity of prostate cancer can confound pre-treatment assessment. The objective was to investigate the association of multiparametric (mp)MRI quantitative features with prostate cancer risk gene expression profiles in mpMRI-guided biopsies tissues.Global gene expression profiles were generated from 17 mpMRI-directed diagnostic prostate biopsies using an Affimetrix platform. Spatially distinct imaging areas ('habitats') were identified on MRI/3D-Ultrasound fusion. Radiomic features were extracted from biopsy regions and normal appearing tissues. We correlated 49 radiomic features with three clinically available gene signatures associated with adverse outcome. The signatures contain genes that are over-expressed in aggressive prostate cancers and genes that are under-expressed in aggressive prostate cancers. There were significant correlations between these genes and quantitative imaging features, indicating the presence of prostate cancer prognostic signal in the radiomic features. Strong associations were also found between the radiomic features and significantly expressed genes. Gene ontology analysis identified specific radiomic features associated with immune/inflammatory response, metabolism, cell and biological adhesion. To our knowledge, this is the first study to correlate radiogenomic parameters with prostate cancer in men with MRI-guided biopsy.

Feasibility of MR-only proton dose calculations for prostate cancer radiotherapy using a commercial pseudo-CT generation method

A magnetic resonance (MR)-only radiotherapy workflow can reduce cost, radiation exposure and uncertainties introduced by CT-MRI registration. A crucial prerequisite is generating the so called pseudo-CT (pCT) images for accurate dose calculation and planning. Many pCT generation methods have been proposed in the scope of photon radiotherapy. This work aims at verifying for the first time whether a commercially available photon-oriented pCT generation method can be employed for accurate intensity-modulated proton therapy (IMPT) dose calculation. A retrospective study was conducted on ten prostate cancer patients. For pCT generation from MR images, a commercial solution for creating bulk-assigned pCTs, called MR for Attenuation Correction (MRCAT), was employed. The assigned pseudo-Hounsfield Unit (HU) values were adapted to yield an increased agreement to the reference CT in terms of proton range. Internal air cavities were copied from the CT to minimise inter-scan differences. CT- and MRCAT-based dose calculations for opposing beam IMPT plans were compared by gamma analysis and evaluation of clinically relevant target and organ at risk dose volume histogram (DVH) parameters. The proton range in beam's eye view (BEV) was compared using single field uniform dose (SFUD) plans. On average, a [Formula: see text] mm) gamma pass rate of 98.4% was obtained using a [Formula: see text] dose threshold after adaptation of the pseudo-HU values. Mean differences between CT- and MRCAT-based dose in the DVH parameters were below 1 Gy ([Formula: see text]). The median proton range difference was [Formula: see text] mm, with on average 96% of all BEV dose profiles showing a range agreement better than 3 mm. Results suggest that accurate MR-based proton dose calculation using an automatic commercial bulk-assignment pCT generation method, originally designed for photon radiotherapy, is feasible following adaptation of the assigned pseudo-HU values.

MRI/US fusion-guided biopsy: performing exclusively targeted biopsies for the early detection of prostate cancer

PURPOSE

The aim of this study was to validate the role of MR/Ultrasound Fusion-Guided Targeted Biopsy as a first diagnostic modality in subjects with clinical suspicion of prostate cancer (PCa).

MATERIALS AND METHODS

108 men (age range 46-78 years) with clinical suspicion for PCa (PSA > 4 ng/mL) underwent multiparametric MRI of the prostate (mpMRI) and, when suspicious lesion were found (according to the PIRADSv2 scoring system), targeted biopsy was performed. All patients without significant alteration patterns at mpMRI have been referred for follow-up at 1 year.

RESULTS

91/108 patients showed on the mpMRI highly suspicious lesions (PIRADS 4 and 5); the remaining 17/108 patients revealed no significant alteration consistent with PCa (PIRADS 3). Among the first group of patients, 58/91 proved to be positive for PCa on the pathology report: 24 patients had a Gleason Score (GS) 6 (3 + 3); 18 patients GS 7 of which 7 (3 + 4) and 11 (4 + 3); 14 patients GS 8 (4 + 4); two patients GS 9 (5 + 4); 33 proved to be negative. Overall cancer detection rate (CDR) was 63%. However, the CDR rises significantly, up to 77%, after the 53 initial consecutive biopsies that were performed (p < 0,05) and thus identified as part of the learning curve. Patients of the second group (17/108) have been followed with serial PSA assessments, clinical reevaluation, and follow-up mpMRI.

CONCLUSION

Performing exclusively targeted MR/Ultrasound Fusion-Guided biopsies for the diagnosis of PCa in patients with suspicious PSA levels (> 4 ng/mL) increases the detection rate of clinically significant cancer, changing both the therapeutic options and the prognosis.

Development and comparison of a Chinese nomogram adding multi-parametric MRI information for predicting extracapsular extension of prostate cancer

PURPOSE

To improve the performation of a nomogram for predicting side-specific extracapsular extension (SS-ECE).

RESULTS

One hundred and ninety-six patients (55.5%) had ECE on final pathology. Bilateral and unilateral ECE rate was 13.9% (49/353) and 41.6% (147/353), respectively. The mean age was 65.9 years and the mean serum prostate specific antigen (PSA) was 15.0 ng/ml. Based on multivariate logistic regression analysis, clinical stage (cStage), PSA, Gleason sum, percentage of positive cores, and ECE risk score were significant predictors of ECE. The current nomogram had higher predictive accuracy (0.851) and superior calibration. According to the decision curve analysis (DCA) results, the updated nomogram demonstrated a high net benefit across a wide range of threshold probabilities.

MATERIALS AND METHODS

We studied 353 patients with cStage T1c-T3 prostate cancer underwent radical prostatectomy. The candidate predictors associated with ECE were cStage, PSA, Gleason sum, percentage of positive cores, maximum cancer percentage and ECE risk score from multi-parametric magnetic resonance imaging (MP-MRI). The receiver operating characteristic (ROC) analysis was performed and an updated nomogram was constructed. The DCA was performed to test the predictive ability of the nomogram. In addition, the validation and calibration of the Memorial Sloan-Kettering cancer center (MSKCC) nomograms were performed in the current subjects.

CONCLUSIONS

Predictors, including cStage, PSA, Gleason sum, percentage of positive cores, maximum cancer percentage, and ECE risk score, were combined to construct a SS-ECE prediction nomogram. And the current nomogram might help urologists in decision-making process of preserving or resecting neurovascular bundles preoperatively.

Analysis of histological findings obtained combining US/mp-MRI fusion-guided biopsies with systematic US biopsies: mp-MRI role in prostate cancer detection and false negative

AIMS AND OBJECTIVES

To evaluate the diagnostic accuracy of mp-MRI correlating US/mp-MRI fusion-guided biopsy with systematic random US-guided biopsy in prostate cancer diagnosis.

MATERIALS AND METHODS

137 suspected prostatic abnormalities were identified on mp-MRI (1.5T) in 96 patients and classified according to PI-RADS score v2. All target lesions underwent US/mp-MRI fusion biopsy and prostatic sampling was completed by US-guided systematic random 12-core biopsies. Histological analysis and Gleason score were established for all the samples, both target lesions defined by mp-MRI, and random biopsies. PI-RADS score was correlated with the histological results, divided in three groups (benign tissue, atypia and carcinoma) and with Gleason groups, divided in four categories considering the new Grading system of the ISUP 2014, using t test. Multivariate analysis was used to correlate PI-RADS and Gleason categories to PSA level and abnormalities axial diameter. When the random core biopsies showed carcinoma (mp-MRI false-negatives), PSA value and lesions Gleason median value were compared with those of carcinomas identified by mp-MRI (true-positives), using t test.

RESULTS

There was statistically significant difference between PI-RADS score in carcinoma, atypia and benign lesions groups (4.41, 3.61 and 3.24, respectively) and between PI-RADS score in Gleason < 7 group and Gleason > 7 group (4.14 and 4.79, respectively). mp-MRI performance was more accurate for lesions > 15 mm and in patients with PSA > 6 ng/ml. In systematic sampling, 130 (11.25%) mp-MRI false-negative were identified. There was no statistic difference in Gleason median value (7.0 vs 7.06) between this group and the mp-MRI true-positives, but a significant lower PSA median value was demonstrated (7.08 vs 7.53 ng/ml).

CONCLUSION

mp-MRI remains the imaging modality of choice to identify PCa lesions. Integrating US-guided random sampling with US/mp-MRI fusion target lesions sampling, 3.49% of false-negative were identified.

Retrospective comparison of direct in-bore magnetic resonance imaging (MRI)-guided biopsy and fusion-guided biopsy in patients with MRI lesions which are likely or highly likely to be clinically significant prostate cancer

Purpose

To compare clinically significant prostate cancer (csPCa) detection rates between magnetic resonance imaging (MRI)–transrectal ultrasound (TRUS) fusion-guided prostate biopsy (FGB) and direct in-bore MRI-guided biopsy (MRGB).

Methods

We performed a comparison of csPCa detection rates between FGB and MRGB. Included patients had (1) at least one prior negative TRUS biopsy; (2) a Prostate Imaging Reporting and Data System (PI-RADS) 4 or 5 lesion and (3) a lesion size of ≥8 mm measured in at least one direction. We considered a Gleason score ≥7 being csPCa. Descriptive statistics with 95% confidence intervals (CI) were used to determine any differences.

Results

We included 51 patients with FGB (59 PI-RADS 4 and 41% PI-RADS 5) and 227 patients with MRGB (34 PI-RADS 4 and 66% PI-RADS 5). Included patients had a median age of 69 years (IQR, 65–72) and a median PSA level of 11.0 ng/ml (IQR, 7.4–15.1) and a median age of 67 years (IQR, 61–70), the median PSA 12.8 ng/ml (IQR, 9.1–19.0) within the FGB and the MRGB group, respectively. Detection rates of csPCA did not differ significantly between FGB and MRGB, 49 vs. 61%, respectively.

Conclusion

We did not detect significant differences between FGB and MRGB in the detection of csPCa. The differences in detection ratios between both biopsy techniques are narrow with an increasing lesion size. This study warrants further studies to optimize selection of best biopsy modality.

Multiparametric magnetic resonance imaging of the prostate-a basic tutorial

Prostate cancer is the second most common cause of cancer related death in the United States and the most commonly diagnosed malignancy in men. In general, prostate cancer is slow growing, though there is a broad spectrum of disease that may be indolent, or aggressive and rapidly progressive. Screening for prostate is controversial and complicated by lack of specificity and over diagnosis of clinically insignificant cancer. Imaging has played a role in diagnosis of prostate cancer, primarily through systemic transrectal ultrasound (TRUS) guided biopsy. While TRUS guided biopsy radically changed prostate cancer diagnosis, it still remains limited by low resolution, poor tissue characterization, relatively low sensitivity and positive predictive value. Advances in multiparametric magnetic resonance imaging (mpMRI) have allowed more accurate detection, localization, and staging as well as aiding in the role of active surveillance (AS). The use of mpMRI for the evaluation of prostate cancer has increased dramatically and this trend is likely to continue as the technique is rapidly improving and its applications expand. The purpose of this article is to review the basic principles of mpMRI of the prostate and its clinical applications, which will be reviewed in greater detail in subsequent chapters of this issue.

Multiparametric MR Imaging for Detection and Locoregional Staging of Prostate Cancer

Detection and staging of prostate cancer (PCa) based on digital rectal examination, prostate-specific antigen levels, and systematic transrectal ultrasound-guided biopsies show notorious limitations in light of the current needs of PCa management. Multiparametric magnetic resonance imaging (mpMRI) has emerged as a useful noninvasive imaging technique for detection, staging, assessment of aggressiveness, and treatment monitoring of PCa, combining anatomic high-resolution T2-weighted images with functional techniques, such as diffusion-weighted imaging and dynamic contrast enhancement evaluation. In this article, the authors review the technical aspects and the current clinical role of mpMRI for detection and locoregional staging of PCa.