Accuracy of in-vivo assessment of prostatic volume by MRI and transrectal ultrasonography

Prostate volume prediction on MRI: tools, accuracy and variability

OBJECTIVE

A reliable estimation of prostate volume (PV) is essential to prostate cancer management. The objective of our multi-rater study was to compare intra- and inter-rater variability of PV from manual planimetry and ellipsoid formulas.

METHODS

Forty treatment-naive patients who underwent prostate MRI were selected from a local database. PV and corresponding PSA density (PSAd) were estimated on 3D T2-weighted MRI (3 T) by 7 independent radiologists using the traditional ellipsoid formula (TEF), the newer biproximate ellipsoid formula (BPEF), and the manual planimetry method (MPM) used as ground truth. Intra- and inter-rater variability was calculated using the mixed model-based intraclass correlation coefficient (ICC).

RESULTS

Mean volumes were 67.00 (± 36.61), 66.07 (± 35.03), and 64.77 (± 38.27) cm³ with the TEF, BPEF, and MPM methods, respectively. Both TEF and BPEF overestimated PV relative to MPM, with the former presenting significant differences (+ 1.91 cm³, IQ = [- 0.33 cm³, 5.07 cm³], p val = 0.03). Both intra- (ICC > 0.90) and inter-rater (ICC > 0.90) reproducibility were excellent. MPM had the highest inter-rater reproducibility (ICC = 0.999). Inter-rater PV variation led to discrepancies in classification according to the clinical criterion of PSAd > 0.15 ng/mL for 2 patients (5%), 7 patients (17.5%), and 9 patients (22.5%) when using MPM, TEF, and BPEF, respectively.

CONCLUSION

PV measurements using ellipsoid formulas and MPM are highly reproducible. MPM is a robust method for PV assessment and PSAd calculation, with the lowest variability. TEF showed a high degree of concordance with MPM but a slight overestimation of PV. Precise anatomic landmarks as defined with the BPEF led to a more accurate PV estimation, but also to a higher variability.

KEY POINTS

• Manual planimetry used for prostate volume estimation is robust and reproducible, with the lowest variability between readers. • Ellipsoid formulas are accurate and reproducible but with higher variability between readers. • The traditional ellipsoid formula tends to overestimate prostate volume.

MRI-Based Nomogram of Prostate Maximum Sectional Area and Its Zone Area for Prediction of Prostate Cancer

Objective

To reduce unnecessary prostate biopsies, we designed a magnetic resonance imaging (MRI)-based nomogram prediction model of prostate maximum sectional area (PA) and investigated its zone area for diagnosing prostate cancer (PCa).

Methods

MRI was administered to 691 consecutive patients before prostate biopsies from January 2012 to January 2020. PA, central gland sectional area (CGA), and peripheral zone sectional area (PZA) were measured on axial T2-weighted prostate MRI. Multivariate logistic regression analysis and area under the receiver operating characteristic (ROC) curve were performed to evaluate and integrate the predictors of PCa. Based on multivariate logistic regression coefficients after excluding combinations of collinear variables, three models and nomograms were generated and intercompared by Delong test, calibration curve, and decision curve analysis (DCA).

Results

The positive rate of PCa was 46.74% (323/691). Multivariate analysis revealed that age, PSA, MRI, transCGA, coroPZA, transPA, and transPAI (transverse PZA-to-CGA ratio) were independent predictors of PCa. Compared with no PCa patients, transCGA (AUC = 0.801) was significantly lower and transPAI (AUC = 0.749) was significantly higher in PCa patients. Both of them have a significantly higher AUC than PSA (AUC = 0.714) and PV (AUC = 0.725). Our best predictive model included the factors age, PSA, MRI, transCGA, and coroPZA with the AUC of 0.918 for predicting PCa status. Based on this predictive model, a novel nomogram for predicting PCa was conducted and internally validated (C-index = 0.913).

Conclusions

We found the potential clinical utility of transCGA and transPAI in predicting PCa. Then, we firstly built the nomogram based on PA and its zone area to evaluate its diagnostic efficacy for PCa, which could reduce unnecessary prostate biopsies.

Significance of the prostate central gland and total gland volume ratio in the diagnosis of prostate cancer patients in the prostate specific antigen grey zone

Objective

To explore the significance of the prostate central gland to total gland volume ratio (PVc/PV) in the diagnosis of prostate cancer (PCa) in patients with prostate specific antigen (PSA) levels in the grey zone (4–10 ng/ml).

Methods

This retrospective study enrolled patients that had undergone prostate biopsy. The volume of the prostate and the central prostate gland were measured. The differences in PSA, the ratio of free to total PSA (f/tPSA), PSA density (PSAD) and PVc/PV between the PCa and non-PCa groups were compared. Receiver operating characteristic curve analysis for PCa and clinically significant PCa (csPCa) diagnosis were calculated according to PSA (reference), f/tPSA, PSAD and PVc/PV.

Results

This study enrolled 136 patients. There was no significant difference in PSA and f/tPSA between the PCa and non-PCa groups, while there were significant differences in PSAD and PVc/PV. The area under the curve values of PVc/PV for PCa or csPCa diagnosis were 0.876 and 0.933, respectively; and for PSAD, they were 0.705 and 0.790, respectively. These were significantly different compared with the PSA curve, whereas f/tPSA showed no significant difference from the PSA curve.

Conclusion

PVc/PV could be a predictor of PCa when PSA is between 4–10 ng/ml.

Prostate Benign Diseases

Magnetic resonance imaging (MRI) has been increasingly used in the detection, localization, and staging of prostate cancer. Because of its excellent soft tissue contrast and multiplane imaging, it can be also very useful in the evaluation of benign prostate diseases. Prostatic benign disorders have a high prevalence, vastly represented by benign prostatic hyperplasia and prostatitis. On the contrary, benign prostatic neoplasms are extremely rare, represented by multilocular cystadenoma, leiomyomas, hemangioma, and granular cell tumor, although these uncommon tumors have been most encountered due to widespread use of MRI. Congenital prostatic anomalies are associated with defects in the development of the prostate embryology, including hypoplasia, ectopia, and vascular malformations, abnormalities rarely seen on cross-sectional imaging. Prostatic cysts are the most common development abnormalities and occasionally are related to clinical symptoms, mainly due to infection and hemorrhage. As with prostate cancer, multiparametric MRI is a reliable tool for the diagnosis and management of benign prostatic diseases as well, providing additional information such morphological changes of the prostate, more accurate prostatic measurements, and functional characteristics of nonmalignant prostatic lesions. In this review, we discuss MRI findings of these benign prostatic diseases.

Measurement of Prostate Volume with MRI (A Guide for the Perplexed): Biproximate Method with Analysis of Precision and Accuracy

To review the anatomic basis of prostate boundary selection on T2-weighted magnetic resonance imaging (MRI). To introduce an alternative 3D ellipsoid measuring technique that maximizes precision, report the intra- and inter-observer reliability, and to advocate it's use for research involving multiple observers. We demonstrate prostate boundary anatomy using gross pathology and MRI examples. This provides background for selecting key boundary marks when measuring prostate volume. An alternative ellipsoid volume method is then proposed using these boundaries in an attempt to improve inter-observer precision. An IRB approved retrospective study of 140 patients with elevated serum prostate specific antigen levels and/or abnormal digital rectal examinations was done with T2-weighted MRI applying a new (Biproximate) technique. Measurements were made by 2 examiners, correlated with each other for inter-observer precision and correlated with an expert observer for accuracy. Correlation statistics, linear regression analysis, and tests of means were applied using p ≤ 0.05 as the threshold for significance. Inter-observer correlation (precision) was 0.95 between observers. Correlation between these observers and the expert (accuracy) was 0.94 and 0.97 respectively. Intra-observer correlation for the expert was 0.98. Means for inter-rater reliability and accuracy were all the same (p = 0.001). We conclude that using more precise reproducible landmarks with biproximate technique, precision and accuracy of total prostate volume is found to be demonstrated.

The roles of MRI-based prostate volume and associated zone-adjusted prostate-specific antigen concentrations in predicting prostate cancer and high-risk prostate cancer

Prostate biopsies are frequently performed to screen for prostate cancer (PCa) with complications such as infections and bleeding. To reduce unnecessary biopsies, here we designed an improved predictive model of MRI-based prostate volume and associated zone-adjusted prostate-specific antigen (PSA) concentrations for diagnosing PCa and risk stratification. Multiparametric MRI administered to 422 consecutive patients before initial transrectal ultrasonography-guided 13-core prostate biopsies from January 2012 to March 2018 at Fujian Medical University Union Hospital. Univariate and multivariate logistic regression analyses and determination of the area under the curve (AUC) of the receiver operating characteristic (ROC) curve was performed to evaluate and integrate the predictors of PCa and high-risk prostate cancer (HR-PCa). The detection rates of PCa was 43.84% (185/422). And the detection rates of HR-PCa was 71.35% (132/185) in PCa patients. Multivariate analysis revealed that prostate volume(PV), PSA density(PSAD), transitional zone volume(TZV), PSA density of the transitional zone(PSADTZ), and MR were independent predictors of PCa and HR-PCa. PSA, peripheral zone volume(PZV) and PSA density of the peripheral zone(PSADPZ) were independent predictors of PCa but not HR-PCa. The AUC of our best predictive model including PSA + PV + PSAD + MR + TZV or PSA + PV + PSAD + MR + PZV was 0.906 for PCa. The AUC of the best predictive model of PV + PSAD + MR + TZV was 0.893 for HR-PCa. In conclusion, our results will likely improve the detection rate of prostate cancer, avoiding unnecessary prostate biopsies, and for evaluating risk stratification.

Multiparametric Magnetic Resonance Imaging of the Prostate: Repeatability of Volume and Apparent Diffusion Coefficient Quantification

OBJECTIVES

The aim of this study was to evaluate the repeatability of a region of interest (ROI) volume and mean apparent diffusion coefficient (ADC) in standard-of-care 3 T multiparametric magnetic resonance imaging (mpMRI) of the prostate obtained with the use of endorectal coil.

MATERIALS AND METHODS

This prospective study was Health Insurance Portability and Accountability Act compliant, with institutional review board approval and written informed consent. Men with confirmed or suspected treatment-naive prostate cancer scheduled for mpMRI were offered a repeat mpMRI within 2 weeks. Regions of interest corresponding to the whole prostate gland, the entire peripheral zone (PZ), normal PZ, and suspected tumor ROI (tROI) on axial T2-weighted, dynamic contrast-enhanced subtract, and ADC images were annotated and assessed using Prostate Imaging Reporting and Data System (PI-RADS) v2. Repeatability of the ROI volume for each of the analyzed image types and mean ROI ADC was summarized with repeatability coefficient (RC) and RC%.

RESULTS

A total of 189 subjects were approached to participate in the study. Of 40 patients that gave initial agreement, 15 men underwent 2 mpMRI examinations and completed the study. Peripheral zone tROIs were identified in 11 subjects. Tumor ROI volume was less than 0.5 mL in 8 of 11 subjects. PI-RADS categories were identical between baseline-repeat studies in 11/15 subjects and differed by 1 point in 4/15. Peripheral zone tROI volume RC (RC%) was 233 mm (71%) on axial T2-weighted, 422 mm (112%) on ADC, and 488 mm (119%) on dynamic contrast-enhanced subtract. Apparent diffusion coefficient ROI mean RC (RC%) were 447 × 10 mm/s (42%) in PZ tROI and 471 × 10 mm/s (30%) in normal PZ. Significant difference in repeatability of the tROI volume across series was observed (P < 0.005). The mean ADC RC% was lower than volume RC% for tROI ADC (P < 0.05).

CONCLUSIONS

PI-RADS v2 overall assessment was highly repeatable. Multiparametric magnetic resonance imaging sequences differ in volume measurement repeatability. The mean tROI ADC is more repeatable compared with tROI volume in ADC. Repeatability of prostate ADC is comparable with that in other abdominal organs.

Peripheral zone volume ratio (PZ-ratio) is relevant with biopsy results and can increase the accuracy of current diagnostic modality

The current diagnostic modality of prostate cancer based on prostate specific antigen (PSA) and systematic biopsy is far from ideal in terms of over-diagnosing indolent prostate cancer and missing significant ones. Thus we integrated the peripheral zone volume ratio (PZ-ratio) for diagnostic refinement. This retrospective study included 247 consecutive patients who underwent initial transrectal ultrasound-guided systematic prostate biopsy from April 2014 to November 2015. Prostate volume was determined by semi-automatic contour on axial T2 weighted magnetic resonance imaging (MRI). PZ-ratio was inversely correlated with age (r = −0.36, p <0.0001). Adding PZ-ratio and MRI findings to the current predictive model (age, PSA density, percent-free PSA) significantly increased diagnostic accuracy in all patients (AUC: 0.871 vs. 0.812, p = 0.0059), but not in patient subgroup with PSA 4–10 ng/ml (AUC: 0.863 vs. 0.803, p = 0.12). The new model also significantly reduced the number of unnecessary biopsies while missing less significant cancers at a probability threshold of 25%. PZ-ratio is a potential tool in predicting biopsy results, and when added alone or in combination with MRI findings, the diagnostic accuracy can be further enhanced.

Prostate volume growth rate changes over time: Results from men 18 to 92 years old in a longitudinal community-based study

Previous investigations have shown that changes in total prostate volume (TPV) are highly variable among aging men, and a considerable proportion of aging men have a stable or decreasing prostate size. Although there is an abundance of literature describing prostatic enlargement in association with benign prostatic hyperplasia, less is known about the appropriate age cut-off points for TPV growth rate. In this community-based cohort study, TPV was examined once a year in men who had consecutive health checkup, during a follow-up of 4 years. A total of 5058 men (age 18-92 years old) were included. We applied multiple regression analyses to estimate the correlation between TPV growth rate and age. Overall, 3232 (63.9%) men had prostate growth, and 1826 (36.1%) had a stable or decreased TPV during the study period. The TPV growth rate was correlated negatively with baseline TPV (r=-0.32, P<0.001). Among 2620 men with baseline TPV <15 cm³, the TPV growth rate increased with age (β=0.98, 95% CI: 0.77%-1.18%) only up to 53 years old. Among 2188 men with baseline TPV of 15-33.6 cm³, the TPV growth rate increased with age (β=0.84, 95% CI, 0.66%-1.01%) only up to 61 years old after adjusting for factors of hypertension, obesity, baseline TPV, diabetes mellitus and dyslipidemia. In this longitudinal study, the TPV growth rate increased negatively with baseline TPV, only extending to a certain age and not beyond. Further research is needed to identify the mechanism underlying such differences in prostate growth.

Biopsy Perineural Invasion in Prostate Cancer Patients Who Are Candidates for Active Surveillance by Strict and Expanded Criteria

OBJECTIVE

To evaluate the association of biopsy perineural invasion (PNI) with adverse pathologic findings on radical prostatectomy in patients who would have been candidates for active surveillance (AS).

METHODS

Using a prospectively populated database of 3084 men who underwent open radical prostatectomy, candidates for AS by strict (Johns Hopkins) and expanded (University of Toronto) criteria were identified. The presence of adverse pathologic features at radical prostatectomy was compared between those men with and without biopsy PNI.

RESULTS

Of 596 men who met strict criteria for AS, 16 (3%) had biopsy PNI. In the strict AS cohort, there were no differences in adverse pathologic features at radical prostatectomy between those with and without PNI. Of 1197 men who were candidates for AS by expanded criteria, 102 (9%) had biopsy PNI. Men with biopsy PNI in the expanded AS cohort were more likely to have extraprostatic extension (P < .001) and pathologic upgrading (P = .01) at prostatectomy. In addition, those with PNI had larger dominant nodules (P < .001), and cancer comprised a greater percentage of their prostate glands (P < .001). There was no difference in the proportion with a positive margin between the 2 groups (P = .77).

CONCLUSION

Biopsy PNI was rare in patients who met strict criteria for AS. Among those men who met expanded criteria, PNI was associated with adverse pathologic findings upon prostatectomy. The presence of biopsy PNI may have a role in further risk stratifying patients who meet expanded criteria for AS.

Robotic Prostatectomy Has a Superior Outcome in Larger Prostates and PSA Density Is a Strong Predictor of Biochemical Recurrence

Objectives. The aims of this study were to compare the outcomes of robotic assisted laparoscopic prostatectomy (RALP) between patients who had larger (≥75 g) and smaller (<75 g) prostates and to evaluate the performance of PSA density (PSAD) in determining the oncological outcome of surgery. Methods and Materials. 344 patients who underwent RALP at a single institution were included in the study. Preoperative risk factors and postoperative, oncological outcomes, erectile function, and continence status were recorded prospectively. Results. During a mean follow-up of 20 months, biochemical recurrence (PSA > 0.2) was observed in 15 patients (4.3%). Prostate size ≥75 g was associated with lower Gleason score on final pathology (P = 0.004) and lower pathological stage (P = 0.02) but an increased length of hospital stay (P = 0.05). PSAD on binary logistic regression independently predicted biochemical recurrence (BCR) when defined as postoperative PSA >0.1 (P = 0.001) and PSA >0.2 (P = 0.039). In both instances PSA was no longer a significant independent predictor. Conclusions. RALP in large prostates (≥75 g, <150 g) is as safe as RALP in smaller prostates and is associated with a lower pathological grade and stage. Higher PSAD is independently associated with BCR and is superior to PSA as a predictor of BCR after RALP.

Accuracy of prostate measurements on MRI with and without an endorectal coil

PURPOSE

To assess accuracy of prostate measurements with and without endorectal coil (ERC).

MATERIALS AND METHODS

Anteroposterior (AP), transverse (TX) and craniocaudal (CC) measurements were recorded from 49 prostate magnetic resonance images (MRIs) done both with and without ERC. Prostate weight was calculated as follows: AP*TX*CC*π/6. Prostate dimensions and weight were obtained from radical prostatectomy pathology report.

RESULTS

After ERC placement, AP decreased by 0.71 cm [95% confidence interval (CI) 0.80-0.61], TX and CC increased by 0.26 cm (95% CI 0.18-0.33) and 0.25 cm (95% CI 0.16-0.35), respectively. Agreement between weight on pathology and MR was excellent: intraclass correlation coefficient (ICC) without ERC=0.96, ICC with ERC=0.90.

CONCLUSION

Although ERC distorts measurements and despite a tendency to underestimate the prostate weight, absolute agreement between prostate weight on pathology and MRI is excellent, both with and without ERC.

Variability in MRI vs. ultrasound measures of prostate volume and its impact on treatment recommendations for favorable-risk prostate cancer patients: a case series

Background

Prostate volume can affect whether patients qualify for brachytherapy (desired size ≥20 mL and ≤60 mL) and/or active surveillance (desired PSA density ≤0.15 for very low risk disease). This study examines variability in prostate volume measurements depending on imaging modality used (ultrasound versus MRI) and volume calculation technique (contouring versus ellipsoid) and quantifies the impact of this variability on treatment recommendations for men with favorable-risk prostate cancer.

Methods

We examined 70 patients who presented consecutively for consideration of brachytherapy for favorable-risk prostate cancer who had volume estimates by three methods: contoured axial ultrasound slices, ultrasound ellipsoid (height × width × length × 0.523) calculation, and endorectal coil MRI (erMRI) ellipsoid calculation.

Results

Average gland size by the contoured ultrasound, ellipsoid ultrasound, and erMRI methods were 33.99, 37.16, and 39.62 mLs, respectively. All pairwise comparisons between methods were statistically significant (all p < 0.015). Of the 66 patients who volumetrically qualified for brachytherapy on ellipsoid ultrasound measures, 22 (33.33%) did not qualify on ellipsoid erMRI or contoured ultrasound measures. 38 patients (54.28%) had PSA density ≤0.15 ng/dl as calculated using ellipsoid ultrasound volumes, compared to 34 (48.57%) and 38 patients (54.28%) using contoured ultrasound and ellipsoid erMRI volumes, respectively.

Conclusions

The ultrasound ellipsoid and erMRI ellipsoid methods appeared to overestimate ultrasound contoured volume by an average of 9.34% and 16.57% respectively. 33.33% of those who qualified for brachytherapy based on ellipsoid ultrasound volume would be disqualified based on ultrasound contoured and/or erMRI ellipsoid volume. As treatment recommendations increasingly rely on estimates of prostate size, clinicians must consider method of volume estimation.

Fully automated prostate segmentation on MRI: comparison with manual segmentation methods and specimen volumes

OBJECTIVE

The objective of our study was to compare calculated prostate volumes derived from tridimensional MR measurements (ellipsoid formula), manual segmentation, and a fully automated segmentation system as validated by actual prostatectomy specimens.

MATERIALS AND METHODS

Ninety-eight consecutive patients (median age, 60.6 years; median prostate-specific antigen [PSA] value, 6.85 ng/mL) underwent triplane T2-weighted MRI on a 3-T magnet with an endorectal coil while undergoing diagnostic workup for prostate cancer. Prostate volume estimates were determined using the formula for ellipsoid volume based on tridimensional measurements, manual segmentation of triplane MRI, and automated segmentation based on normalized gradient fields cross-correlation and graph-search refinement. Estimates of prostate volume based on ellipsoid volume, manual segmentation, and automated segmentation were compared with prostatectomy specimen volumes. Prostate volume estimates were compared using the Pearson correlation coefficient and linear regression analysis. The Dice similarity coefficient was used to quantify spatial agreement between manual segmentation and automated segmentation.

RESULTS

The Pearson correlation coefficient revealed strong positive correlation between prostatectomy specimen volume and prostate volume estimates derived from manual segmentation (R = 0.89-0.91, p < 0.0001) and automated segmentation (R = 0.88-0.91, p < 0.0001). No difference was observed between manual segmentation and automated segmentation. Mean partial and full Dice similarity coefficients of 0.92 and 0.89, respectively, were achieved for axial automated segmentation.

CONCLUSION

Prostate volume estimates obtained with a fully automated 3D segmentation tool based on normalized gradient fields cross-correlation and graph-search refinement can yield highly accurate prostate volume estimates in a clinically relevant time of 10 seconds. This tool will assist in developing a broad range of applications including routine prostate volume estimations, image registration, biopsy guidance, and decision support systems.

Dosimetric effects of bladder and rectal contrast agents in prostate radiotherapy

Background and purpose

Accurate delineation of the target volume and organs at risk (OARs) are vital to ensure systematic errors are small. The use of contrast agents (CAs) in the bladder and rectum may aid contouring and reduce inter and intra-observer variability. The aim of this study was to evaluate the dosimetric effect of the presence of such contrast on the monitor units (MUs), planning target volume (PTV), rectum and bladder.

Materials and methods

The prostate, seminal vesicles, rectum and bladder were contoured by a single observer on ten patients with bladder and rectal contrast. To evaluate the dosimetric effect of the presence of contrast, the density of the ten patients with contrast in the bladder and rectum was virtually changed to 1 g/cm3. A four-field 15 MV conformal radiation therapy technique was applied in which dose volume histograms and MUs were compared using computed tomographic (CT) density and the 1 g/cm3density.

Results

The presence of contrast resulted in a 0·09% (<1 MU) increase in anterior MUs and decrease of 1% (<1 MU) in the posterior beam MUs. Lateral beams were not affected. The PTV and bladder dose increased slightly without contrast. The rectum showed a maximum change of 0·62% dose among the measured dose values. A maximum dose of 0·3 Gy at the 30% volume was also seen.

Conclusions

The dosimetric effect of bladder and rectal CAs on MUs, dose to the PTV and OARs in using this technique was very small. This would not be clinically significant, but only if the extreme limits of dose volume constraints were being reached.

Higher prostate weight is inversely associated with Gleason score upgrading in radical prostatectomy specimens

Background. Protective factors against Gleason upgrading and its impact on outcomes after surgery warrant better definition. Patients and Methods. Consecutive 343 patients were categorized at biopsy (BGS) and prostatectomy (PGS) as Gleason score, ≤6, 7, and ≥8; 94 patients (27.4%) had PSA recurrence, mean followup 80.2 months (median 99). Independent predictors of Gleason upgrading (logistic regression) and disease-free survival (DFS) (Kaplan-Meier, log-rank) were determined. Results. Gleason discordance was 45.7% (37.32% upgrading and 8.45% downgrading). Upgrading risk decreased by 2.4% for each 1 g of prostate weight increment, while it increased by 10.2% for every 1 ng/mL of PSA, 72.0% for every 0.1 unity of PSA density and was 21 times higher for those with BGS 7. Gleason upgrading showed increased clinical stage (P = 0.019), higher tumor extent (P = 0.009), extraprostatic extension (P = 0.04), positive surgical margins (P < 0.001), seminal vesicle invasion (P = 0.003), less “insignificant” tumors (P < 0.001), and also worse DFS, χ² = 4.28, df = 1, P = 0.039. However, when setting the final Gleason score (BGS ≤6 to PGS 7 versus BGS 7 to PGS 7), avoiding allocation bias, DFS impact is not confirmed, χ² = 0.40, df = 1, P = 0.530.Conclusions. Gleason upgrading is substantial and confers worse outcomes. Prostate weight is inversely related to upgrading and its protective effect warrants further evaluation.

Transrectal ultrasound based prostate volume determination: is the frustum algorithm more accurate than planimetry?

PURPOSE

To compare reconstructed volumes calculated via planimetry and frustum algorithms in the context of stepped transrectal ultrasound (US) imaging, and to estimate the reconstruction error for prostate volumes.

METHODS

Prostate contours for 40 permanent implant patients were delineated on magnetic resonance (MR) and transrectal US images by a radiation oncologist. Simulated images of ellipsoid and truncated cone geometrical objects were constructed to determine volume calculation accuracy. Simulation results were used to deduce the algorithm-associated error made when calculating transrectal US prostate volumes.

RESULTS

For imaging without deliberate slice positioning, planimetry reconstruction was mostly accurate while the frustum algorithm underestimated the volume. The discrepancy was mostly due to the end slice reconstruction. For slice positioning that reflected US image acquisition, planimetry overestimated by half the superior slice volume on average while frustum underestimated by half the inferior slice volume. The estimated algorithm errors for prostate contours were 4% and -3%, respectively.

CONCLUSIONS

The planimetry and frustum algorithms offer different interpretations for reconstruction and yield systematic differences in calculated volumes. Both algorithms introduce bias into transrectal US prostate volume determinations that may have clinical implications, planimetry overestimating and frustum underestimating the volume.

Automated computer-derived prostate volumes from MR imaging data: comparison with radiologist-derived MR imaging and pathologic specimen volumes

PURPOSE

To compare prostate gland volume (PV) estimation of automated computer-generated multifeature active shape models (MFAs) performed with 3-T magnetic resonance (MR) imaging with that of other methods of PV assessment, with pathologic specimens as the reference standard.

MATERIALS AND METHODS

All subjects provided written informed consent for this HIPAA-compliant and institutional review board-approved study. Freshly weighed prostatectomy specimens from 91 patients (mean age, 59 years; range, 42-84 years) served as the reference standard. PVs were manually calculated by two independent readers from MR images by using the standard ellipsoid formula. Planimetry PV was calculated from gland areas generated by two independent investigators by using manually drawn regions of interest. Computer-automated assessment of PV with an MFA was determined by the aggregate computer-calculated prostate area over the range of axial T2-weighted prostate MR images. Linear regression, linear mixed-effects models, concordance correlation coefficients, and Bland-Altman limits of agreement were used to compare volume estimation methods.

RESULTS

MFA-derived PVs had the best correlation with pathologic specimen PVs (slope, 0.888). Planimetry derived volumes produced slopes of 0.864 and 0.804 for two independent readers when compared with specimen PVs. Ellipsoid formula-derived PVs had slopes closest to one when compared with planimetry PVs. Manual MR imaging and MFA PV estimates had high concordance correlation coefficients with pathologic specimens.

CONCLUSION

MFAs with axial T2-weighted MR imaging provided an automated and efficient tool with which to assess PV. Both MFAs and MR imaging planimetry require adjustments for optimized PV accuracy when compared with prostatectomy specimens.

The relationship between prostate volume and prostate-specific antigen variability: data from the Baltimore Longitudinal Study of Aging and the Johns Hopkins Active Surveillance Program

Study Type--Prognostic (cohort). Level of Evidence 2b. What's known on the subject? And what does the study add? Previous studies have attempted to characterize the normal biological variability in PSA among men without prostate cancer. These reports suggest that PSA variability is unrelated to age, but there are conflicting data on its association with the baseline PSA level. There are limited published data regarding the effects of prostate volume on PSA variability. A prior study assessing whether prostate volume changes would confound the use of PSA velocity in clinical practice reported that prostate volume changes were not significantly related to PSA changes. This study did not directly address the effect of baseline prostate volume on serial PSA variability. The objective of the current study was to further examine the relationship between prostate volume and PSA variability. Our hypothesis was that larger baseline prostate volume would be associated with increased PSA variability in men without known prostate cancer and in those with suspected small-volume disease. The results of the study suggest that baseline PSA, not prostate volume, is the primary driver of PSA variability in these populations.

OBJECTIVE

• To clarify the relationship between serial prostate-specific antigen (PSA) variability and prostate volume in both cancer-free participants from the Baltimore Longitudinal Study of Aging (BLSA) and patients with low-risk prostate cancer from the Johns Hopkins Active Surveillance Program (AS).

MATERIALS AND METHODS

• In all, 287 men from the BLSA and 131 patients from the AS were included in the analysis, all with at least two PSA measurements and concurrent prostate volume measurements. • PSA variability was calculated in ng/mL per year, and a linear mixed-effects model was used to determine the relative effects of prostate volume, baseline PSA and age on PSA change over time.

RESULTS

• In a model with prostate volume, age and baseline PSA, there was no significant relationship between prostate volume and PSA variability (BLSA, P= 0.57; AS, P= 0.49). • Only baseline PSA showed a significant relationship to PSA yearly variability (PSAYV) (P < 0.001). Specifically, a one unit higher baseline PSA (ng/mL) corresponded on average to 0.09 and 0.06 ng/mL per year higher PSAYV in the BLSA and AS populations, respectively.

CONCLUSIONS

• The results of the present study suggest that the primary driver of PSA variability is the baseline PSA level, rather than prostate volume. • Clinicians might consider the baseline PSA level to help predict the expected variability in serial PSA measurements.

Prostate size as a predictor of Gleason score upgrading in patients with low risk prostate cancer

PURPOSE

Gleason score upgrading between biopsy and surgical pathological specimens occurs in 30% to 50% of cases. Predicting upgrading in men with low risk prostate cancer may be particularly important since high grade disease influences management decisions and impacts prognosis. We determined whether prostate size predicts Gleason score upgrading in patients with low risk prostate cancer.

MATERIALS AND METHODS

A total of 1,251 consecutive patients with D'Amico low risk disease and complete data available underwent radical prostatectomy at our institution between January 2000 and June 2008. Patients were divided into 3 groups by pathological Gleason score, including no, minor (3 + 4 = 7) and major (4 + 3 = 7 or greater) Gleason score upgrading. We developed bivariate and multivariate models to determine whether prostate size was an important predictor of upgrading while controlling for clinical and biopsy characteristics.

RESULTS

Of 1,251 cases 387 (31.0%) were upgraded, including 324 (26%) and 63 (5%) with minor and major upgrading, respectively. As expected, Gleason score upgrading was associated with worse pathological and cancer control outcomes. On multivariate analysis smaller prostate size was an independent predictor of any and major upgrading (OR 0.58, 95% CI 0.48-0.69, p <0.01 and OR 0.67, 95% CI 0.49-0.96, p = 0.03, respectively). Men with prostate volume at the 25th percentile (36 cm(3)) were 50% more likely to experience upgrading than men with prostate volume at the 75th percentile (58 cm(3)).

CONCLUSIONS

Of low risk cases 31% were upgraded at final pathology. Smaller prostate size predicts Gleason score upgrading in men with clinically low risk prostate cancer. This is important information when counseling patients on management and prognosis.

Image fusion techniques in permanent seed implantation

Over the last twenty years major software and hardware developments in brachytherapy treatment planning, intraoperative navigation and dose delivery have been made. Image-guided brachytherapy has emerged as the ultimate conformal radiation therapy, allowing precise dose deposition on small volumes under direct image visualization. In this process imaging plays a central role and novel imaging techniques are being developed (PET, MRI-MRS and power Doppler US imaging are among them), creating a new paradigm (dose-guided brachytherapy), where imaging is used to map the exact coordinates of the tumour cells, and to guide applicator insertion to the correct position. Each of these modalities has limitations providing all of the physical and geometric information required for the brachytherapy workflow. Therefore, image fusion can be used as a solution in order to take full advantage of the information from each modality in treatment planning, intraoperative navigation, dose delivery, verification and follow-up of interstitial irradiation. Image fusion, understood as the visualization of any morphological volume (i.e. US, CT, MRI) together with an additional second morphological volume (i.e. CT, MRI) or functional dataset (functional MRI, SPECT, PET), is a well known method for treatment planning, verification and follow-up of interstitial irradiation. The term image fusion is used when multiple patient image datasets are registered and overlaid or merged to provide additional information. Fused images may be created from multiple images from the same imaging modality taken at different moments (multi-temporal approach), or by combining information from multiple modalities. Quality means that the fused images should provide additional information to the brachytherapy process (diagnosis and staging, treatment planning, intraoperative imaging, treatment delivery and follow-up) that cannot be obtained in other ways. In this review I will focus on the role of image fusion for permanent seed implantation.

Prostate volume changes over time: results from the Baltimore Longitudinal Study of Aging

PURPOSE

According to a 1944 publication by Swyer benign prostatic hyperplasia develops in some men after age 45 with further prostatic growth whereas in other men prostate size remains stable or decreases with advancing age. Although there is an abundance of literature describing prostatic enlargement in association with benign prostatic hyperplasia, less is known about the phenomenon of prostate atrophy.

MATERIALS AND METHODS

In the Baltimore Longitudinal Study of Aging serial pelvic magnetic resonance imaging was performed in men without prostate cancer beginning in 1993. From this population we retrospectively identified 278 men with 2 or more magnetic resonance imaging determined prostate volume measurements to examine differential growth rates in a cohort of community men over time.

RESULTS

Median age was 58 years and median prostate size was 28 cc at study entry. At a median followup of 4.3 years prostate size increased in 61.9% and remained stable or decreased in 38.1% of men. The median rate of volume change was 0.6 cc per year (range -9.9 to 62.1), corresponding to a median growth rate of 2.5% per year (range -29.2 to 176.4%). During followup 64.6% of men with an initial prostate size less than 40 cc had prostate growth compared to only 50.9% of men with an initial prostate size of 40 cc or greater.

CONCLUSIONS

These results suggest that changes in prostate size are highly variable among aging men. Although benign prostatic hyperplasia is common, a considerable proportion of aging men have a stable or decreasing prostate size. Further research is needed to identify the underlying mechanism for such differences in prostate growth.

Does prostate growth confound prostate specific antigen velocity? Data from the Baltimore longitudinal study of aging

PURPOSE

Although prostate specific antigen velocity was proposed to increase the specificity of prostate specific antigen-based screening, there are little published data on the effect of differential prostate growth on prostate specific antigen velocity. If a patient presents with rising prostate specific antigen over a year or more, it would be useful to know whether such a change in prostate specific antigen could be explained by prostate growth. Thus, we investigated the relationship between changes in prostate size and prostate specific antigen changes in a large cohort of men without prostate cancer.

MATERIALS AND METHODS

We identified 242 men without prostate cancer from the Baltimore Longitudinal Study of Aging who had 2 or greater serial pelvic magnetic resonance imaging studies and contemporaneous prostate specific antigen measurements. In this population we used the t test, correlation coefficients, and regression analysis to examine the relationship between prostate specific antigen changes and prostate volume changes, as assessed by magnetic resonance imaging.

RESULTS

The mean age was 55 years. During 4.2 years of median followup, the median rate of volume change was 0.6 cc per year (range -9.9 to 11.8), and the median prostate specific antigen change was 0.03 ng/ml per year. There was no correlation between prostate specific antigen changes and prostate growth, as measured in cc per year (r = -0.01, p = 0.9) or the percent change per year (r = 0.07, p = 0.3). On multivariate analysis, there was no significant relationship between changes in prostate volume and prostate specific antigen changes.

CONCLUSIONS

Our data suggest that volume increases alone do not cause a high prostate specific antigen velocity. Despite growth rates as high as 10 cc per year, prostate specific antigen velocity was less than 0.1 ng/ml per year in most men without prostate cancer. Thus, differential rates of prostatic growth should not confound the use of prostate specific antigen velocity for prostate cancer detection and prognostication.

The potential role of prebiopsy magnetic resonance imaging combined with prostate-specific antigen density in the detection of prostate cancer

AIM

Two-thirds of patients with a gray-zone prostate-specific antigen (PSA) level undergo unnecessary biopsy. Sensitivity is not yet sufficient to permit the use of modified PSA parameters or magnetic resonance (MR) imaging alone for prostate cancer screening. Thus, we evaluated the combination of MR imaging and PSA density (PSAD) for specificity and sensitivity.

METHODS

During the period April 2004 through March 2006, 185 patients with a PSA level of 4.0-10.0 ng/mL underwent MR imaging and transrectal ultrasonography-guided 8-core biopsy (systemic sextant biopsy of the peripheral zone plus two cores of transition zone). All MR images were interpreted prospectively by two radiologists. An image was considered positive for prostate cancer if any feature indicated a cancerous lesion. Receiver operating characteristic (ROC) curves were used to compare the usefulness of the PSA level, PSAD and PSA transitional zone density (PSATZ) for the detection of prostate cancer.

RESULTS

Of the 185 patients, 62 had prostate cancer. Sensitivity and specificity of the axial T2-weighted MR imaging findings for cancer detection were 79.0% and 59.4%, respectively. The area under the ROC curve was 0.590 for the PSA level, 0.718 for PSAD and 0.695 for PSATZ. MR imaging findings and PSAD were shown by multivariate analysis to be statistically significant independent predictors of prostate cancer (P < 0.001). With a PSAD cut-off value of 0.111, sensitivity was 96.8%, but specificity was 19.5%. Combining MR imaging findings with PSAD increased the specificity to 40% and retained 95% sensitivity.

CONCLUSION

MR imaging findings combined with PSAD provide high sensitivity and improve the specificity for the early detection of prostate cancer.

MR-guided prostate interventions

In this article the current issues of diagnosis and detection of prostate cancer are reviewed. The limitations for current techniques are highlighted and some possible solutions with MR imaging and MR-guided biopsy approaches are reviewed. There are several different biopsy approaches under investigation. These include transperineal open magnet approaches to closed-bore 1.5T transrectal biopsies. The imaging, image processing, and tracking methods are also discussed. In the arena of therapy, MR guidance has been used in conjunction with radiation methods, either brachytherapy or external delivery. The principles of the radiation treatment, the toxicities, and use of images are outlined. The future role of imaging and image-guided interventions lie with providing a noninvasive surrogate for cancer surveillance or monitoring treatment response. The shift to minimally invasive focal therapies has already begun and will be very exciting when MR-guided focused ultrasound surgery reaches its full potential.

Transperineal Ultrasound for Measurement of Prostate Volume: Validation Against Transrectal Ultrasound

PURPOSE

We evaluated the transperineal ultrasound method to measure total and central prostate volume compared with the standard transrectal ultrasound.

MATERIALS AND METHODS

Healthy men without prostate disease underwent transperineal and transrectal ultrasound at a single session to calculate total and central prostate volume by the ellipsoidal formula from maximal measured dimensions. Reproducibility within and between methods was evaluated by ICC, CV and Bland-Altman plots.

RESULTS

In 13 men measured on 3 occasions within 2 weeks transperineal and transrectal ultrasound had high within method (ICC 0.92 and 0.97, and CV 7.2% and 5.1%, respectively) and between method (ICC 0.98 and CV 5.4%) agreement. Agreement for central prostate volume was good but it was lower within method (ICC 0.74 and 0.73, and CV 20.5% and 20.3%, respectively) and between method (ICC 0.85 and CV 19.7%). Transperineal ultrasound bias was -2.7% for total and -8.9% for central prostate volume. Of 287 healthy men the methods highly correlated for total prostate volume in 245 (ICC 0.92, 95% CI 0.90 to 0.94) and for central prostate volume in 217 (ICC 0.87, 95% CI 0.83 to 0.90). Transperineal ultrasound had minimal bias for total prostate volume (-3.7%, mean -1.0 ml, 95% CI -1.7 to -0.2 ml) and no bias for central prostate volume (-3.0%, mean bias 0.10 ml, 95% CI -0.3 to 0.5 ml). Transperineal ultrasound was more acceptable but it had a higher technical failure rate for total and central prostate volume (13.6% vs 1.4% and 23.7% vs 3.5%, respectively).

CONCLUSIONS

Transperineal ultrasound provides an accurate, less invasive and more acceptable alternative but with a higher technical failure rate than transrectal ultrasound, especially for central prostate volume. By trading off acceptability for the failure rate transperineal ultrasound may enhance the feasibility of valid studies requiring repeat prostate volume measurement in asymptomatic men.

Evaluation of magnetic resonance imaging-based prostate-specific antigen density of the prostate in the diagnosis of prostate cancer

OBJECTIVES

We evaluated prostate-specific antigen (PSA) density of the prostatic volume (PSAD) estimated using transrectal ultrasonography (TRUS; TRUS-based PSAD), magnetic resonance imaging (MRI; MRI-based PSAD), and PSA density of the transition zone (TZ) volume (PSATZD) estimated using MRI (MRI-based PSATZD) in the diagnosis of prostate cancer (PCa).

METHODS

One hundred and twenty patients, who were suspected to have PCa based on PSA, ranged between 4.1 and 20.0 ng/mL were enrolled in this study.

RESULTS

The prostatic volume estimated using TRUS was smaller than the volume estimated using MRI by 11.4% in the patients with PSA levels ranging 4.1-20.0 ng/mL, 7.2% in those 4.1-10.0 ng/mL, and 15.7% in those 10.1-20.0 ng/mL, respectively. PSA levels were correlated with the prostatic volume estimated using TRUS and MRI, and TZ volume estimated using MRI in the patients without PCa; however, the level was not correlated with them in the patients with PCa. The area under the receiver operating characteristic curve of MRI-based PSAD was higher than that of TRUS-based PSAD; however, there was no statistical difference. Stepwise logistic regression analysis for the prediction of PCa by using PSA-related parameters confirmed that MRI-based PSATZD was the most significant predictor in patients with PSA levels in the range of 4.1-20.0 ng/mL (P < 0.001), the range of 4.1-10.0 ng/mL (P = 0.002), and the range of 10.1-20.0 ng/mL (P < 0.001), respectively.

CONCLUSIONS

The prostatic volume estimated using TRUS was smaller than the volume estimated using MRI. MRI-based PSATZD is the most significant predictor in the four parameters.

An adaptive off-line procedure for radiotherapy of prostate cancer

PURPOSE

To determine the planning target volume (PTV) margin for an adaptive radiotherapy procedure that uses five computed tomography (CT) scans to calculate an average prostate position and rectum shape. To evaluate alternative methods to determine an average rectum based on a single delineation.

METHODS AND MATERIALS

Repeat CT scans (8-13) of 19 patients were used. The contoured prostates of the first four scans were matched on the planning CT (pCT) prostate contours. With the resulting translations and rotations the average prostate position was determined. An average rectum was obtained by either averaging the coordinates of corresponding points on the rectal walls or by selecting the "best" rectum or transforming the pCT rectum. Dose distributions were calculated for various expanded average prostates. The remaining CT scans were used to determine the dose received by prostate and rectum during treatment.

RESULTS

For the prostate of the pCT scan and a 10-mm margin, all patients received more than 95% of the prescribed dose to 95% of the prostate. For the average prostate, a margin of 7 mm was needed to obtain a similar result (average PTV reduction 30%). The average rectum overestimated the mean dose to the rectum by 0.4 +/- 1.6 Gy, which was better than the pCT rectum (2.1 +/- 3.0 Gy) and the alternative average rectums (1.0 +/- 2.6 Gy and 1.4 +/- 3.2 Gy).

CONCLUSIONS

Our adaptive procedure allows for reduction of the PTV margin to 7 mm without decreasing prostate coverage during treatment. For accurate estimation of the rectum dose, rectums need to be delineated and averaged over multiple scans.

Prostate Volume Measured Preoperatively Predicts for Organ-Confined Disease in Men with Clinically Localized Prostate Cancer

OBJECTIVES

Imaging-measured prostate volumes are different between patients with confined and extraprostatic prostate cancer. The purpose of this study was to determine whether the prostate volume measured by magnetic resonance imaging (MRI) or transrectal ultrasonography (TRUS) was of incremental predictive value for organ-confined prostate cancer after considering preoperative prostate-specific antigen level, biopsy Gleason score, and clinical stage.

METHODS

We retrospectively reviewed 1071 and 1201 consecutive patients who had undergone MRI or TRUS prostate volume measurement from 1983 to 2003. We controlled for other factors such as biopsy-derived Gleason score, preoperative serum prostate-specific antigen level, and clinical stage. Two statistical models, one incorporating MRI data and one TRUS data, were developed to predict for organ-confined prostate cancer. The models were subjected to bootstrapping by resampling 200 times to reduce bias when estimating the areas under the receiver operating characteristic curve.

RESULTS

In both statistical models, preoperative prostate-specific antigen (P <0.001), biopsy Gleason score (P <0.001), and clinical stage (P <0.001) were significant predictors for organ-confined prostate cancer. The MRI volume (P <0.001) and TRUS volume (P <0.001) were incremental predictors in their respective models. However, the area under the receiver operating characteristic curve increase was 1% and 2% for TRUS and MRI, respectively.

CONCLUSIONS

The preoperative volume of the prostate measured by either MRI or TRUS can be used to predict for organ-confined prostate cancer. However, the value of adding the prostate volume as a variable on its own to the prediction model is limited.

MRI-based PSA density and PSA density of the transitional zone compared with PSA alone: correlation with prostate cancer Gleason score

OBJECTIVES

The tumor Gleason score is an important prognostic factor in prostate cancer (PCA). This retrospective study analyzes whether serum prostate-specific antigen (PSA), or magnetic resonance imaging (MRI)-based PSA density of the entire prostate (PSAD) or the prostatic transitional zone (PSAT) distinguishes between PCA of Gleason scores 6 or lower (G6-) and 7 or higher (G7+).

MATERIALS AND METHODS

Total prostate and transitional zone volumes were planimetrically determined in axial, T2-weighted fast spin echo (FSE) MRI images of the prostate in 61 patients with previously untreated PCA. Automated standardized microparticle enzyme immuno-assay (EIAs) measured PSA.

RESULTS

Thirty patients had G6- and 31 patients had G7+. PSA values ranged from 1.0 to 57.2 ng/mL. Assignment to G6- or G7+, respectively, was correct in 49 of 61 (80%) cases (odds ratio [OR], 17.1; 95% confidence interval [CI], 4.8-61.5) for PSA above the optimal cutoff level of 10.35 ng/mL, 48 cases (79%; OR, 13.7; 95% CI, 4.0-46.8) for PSAD above the optimal cutoff level of 0.23 ng/mL/cm, and 45 cases (74%; OR, 6.9; 95% CI, 2.2-21.3) for PSAT above the optimal cutoff level of 0.38 ng/mL/cm (no significant differences, McNemar test).

CONCLUSIONS

In patients with biopsy-proven PCA, serum PSA level alone and MRI-based PSAD and PSAT help distinguish between G6- and G7+. PSAD and PSAT do not improve the level of confidence at which this discrimination is made.

A magnetic resonance imaging study of prostate deformation relative to implanted gold fiducial markers

PURPOSE

To describe prostate deformation during radiotherapy and determine the margins required to account for prostate deformation after setup to intraprostatic fiducial markers (FM).

METHODS AND MATERIALS

Twenty-five patients with T1c-T2c prostate cancer had three gold FMs implanted. The patients presented with a full bladder and empty rectum for two axial magnetic resonance imaging (MRI) scans using a gradient recalled echo (GRE) sequence capable of imaging the FMs. The MRIs were done at the time of radiotherapy (RT) planning and a randomly assigned fraction. A single observer contoured the prostate surfaces. They were entered into a finite element model and aligned using the centroid of the three FMs.

RESULTS

During RT, the prostate volume decreased by 0.5%/fraction (p = 0.03) and the FMs in-migrated by 0.05 mm/fraction (p < 0.05). Prostate deformation was unrelated to differential bladder and bowel filling, but was related to a transurethral resection of the prostate (TURP) (p = 0.003). The standard deviation for systematic uncertainty of prostate surface contouring was 0.8 mm and for FM centroid localization was 0.4 mm. The standard deviation of random interfraction prostate deformation was 1.5 mm and for FM centroid variability was 1.1 mm. These uncertainties from prostate deformation can be incorporated into a margin recipe to determine the total margins required for RT.

CONCLUSIONS

During RT, the prostate exhibited: volume decrease, deformation, and in-migration of FMs. Patients with TURPs were prone to prostate deformation.

Metabolic factors associated with benign prostatic hyperplasia

CONTEXT

Benign prostatic hyperplasia poses a significant public health problem, but its etiology remains unclear. Obesity and associated abnormalities in glucose homeostasis may play a role in benign prostatic hyperplasia development by influencing prostate growth.

OBJECTIVE

The objective of this study was to determine whether obesity, fasting plasma glucose concentration, and diabetes are associated with radiologically determined prostate enlargement, an objective measure of benign prostatic hyperplasia.

DESIGN

This study was a cross-sectional analysis with robust variance estimates to account for multiple measures over time in the same individuals.

SETTING

This prospective cohort study was composed of community volunteers.

PATIENTS

Patients studied were 422 adult men enrolled in The Baltimore Longitudinal Study of Aging.

MAIN OUTCOME MEASUREMENTS

Total prostate volume as determined by pelvic magnetic resonance imaging was measured.

RESULTS

Among 422 participants, 91 (21.6%) had prostate enlargement (defined as total prostate volume >/= 40 cc) at first visit. Compared with men of normal weight [body mass index (BMI) < 25 kg/m(2)], the age-adjusted odds ratio (OR) for prostate enlargement for overweight men (BMI, 25-29.9 kg/m(2)) was 1.41 (95% CI, 0.84-2.37), for obese men (BMI, 30-34 kg/m(2)) was 1.27 (95% CI, 0.68-2.39), and for severely obese men (BMI >/= 35 kg/m(2)) was 3.52 (95% CI, 1.45-8.56) (P = 0.01). Men with elevated fasting glucose (>110 mg/dl) were more likely to have an enlarged prostate than men with normal fasting glucose (

CONCLUSIONS

Obesity, elevated fasting plasma glucose, and diabetes are risk factors for benign prostatic hyperplasia.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Aged, 80 and over
• Black People
• Blood Glucose/analysis
• Body Mass Index
• Cohort Studies
• Cross-Sectional Studies
• Diabetes Complications
• Ethnicity
• Humans
• Longitudinal Studies
• Male
• Middle Aged
• Obesity/complications
• Odds Ratio
• Prospective Studies
• Prostate/pathology
• Prostatic Hyperplasia/etiology
• Prostatic Hyperplasia/metabolism
• Prostatic Hyperplasia/pathology
• Testosterone/blood
• Urologic Diseases/etiology
• Waist-Hip Ratio
• White People

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Grants

• Z01 AG000015-49 Intramural NIH HHS

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Affiliation(s)

J Kellogg Parsons Division of Urology, University of California San Diego, 200 West Arbor Drive, San Diego, California 21287, USA.
H Ballentine Carter
Alan W Partin
B Gwen Windham
E Jeffrey Metter
Luigi Ferrucci
Patricia Landis
Elizabeth A Platz

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Automated localization of implanted seeds in 3D TRUS images used for prostate brachytherapy

An algorithm has been developed in this paper to localize implanted radioactive seeds in 3D ultrasound images for a dynamic intraoperative brachytherapy procedure. Segmentation of the seeds is difficult, due to their small size in relatively low quality of transrectal ultrasound (TRUS) images. In this paper, intraoperative seed segmentation in 3D TRUS images is achieved by performing a subtraction of the image before the needle has been inserted, and the image after the seeds have been implanted. The seeds are searched in a "local" space determined by the needle position and orientation information, which are obtained from a needle segmentation algorithm. To test this approach, 3D TRUS images of the agar and chicken tissue phantoms were obtained. Within these phantoms, dummy seeds were implanted. The seed locations determined by the seed segmentation algorithm were compared with those obtained from a volumetric cone-beam flat-panel micro-CT scanner and human observers. Evaluation of the algorithm showed that the rms error in determining the seed locations using the seed segmentation algorithm was 0.98 mm in agar phantoms and 1.02 mm in chicken phantoms.

BXL628, A Novel Vitamin D3 Analog Arrests Prostate Growth in Patients with Benign Prostatic Hyperplasia: A Randomized Clinical Trial

OBJECTIVE

To evaluate the effect of BXL628, a vitamin D3 analog, on prostate volume in patients with benign prostatic hyperplasia (BPH).

METHODS

We conducted a phase II, double blind, randomized, placebo controlled, clinical study. Patients eligible were aged>or=50 years, had a diagnosis of BPH and a prostate volume>or=40 ml. Eligible patients were randomized and given either BXL628 150 mcg daily or placebo for 12 weeks. All randomized patients underwent at baseline and at the end of study pelvic MRI to measure prostatic volume, uroflowmetry (Qmax), American Urological Association Symptom Index (AUASI), serum PSA, testosterone, dihydrotestosterone and luteizing hormone.

RESULTS

A total of 119 patients were randomized: 57 patients to BXL628 and 62 to placebo. The percentage change of prostate volume at 12 week was -2.90 in the BXL628 group vs. +4.32 in the placebo group (p-value<0.0001). The estimated difference between treatments (BXL628 minus placebo) was -7.22% (95% confidence limit -9.27 to -5.18). Considering Qmax, mean change vs. baseline was -0.30 in BXL628 vs. +1.50 in the placebo group: this finding was not statistically significant. The mean change of the AUASI total score at final visit vs. baseline was -1.77 in the BXL628 group vs. -3.45 in the placebo group (p=not significant).

CONCLUSION

BXL628 was able to arrest prostate growth within 12 weeks in men aged>or=50 years with prostatic volume>or=40 ml. Its unprecedented mechanism of action may offer a new opportunity for the treatment of BPH.

Assessing prostate volume by magnetic resonance imaging: a comparison of different measurement approaches for organ volume analysis

OBJECTIVES

We sought to evaluate the capabilities of different magnetic resonance imaging (MRI)-based methodologies for measuring prostate volume.

MATERIALS AND METHODS

Twenty-four male beagles with benign prostatic hyperplasia were enrolled in a drug trial and imaged at 5 time points. A total of 120 prostate volumes were determined by MRI-based semiautomated segmentation. For planimetric assessment, 8 diameter locations were determined in the axial and coronal plane of the MRI slice with maximum extension of the prostate. Thirteen calculation models based on these diameters were determined by comparison to the reference volume and evaluated during treatment.

RESULTS

The segmented MRI prostate volume significantly correlated with post necropsy volume. The best diameter-based model also worked very well for monitoring prostate volume of dogs under treatment.

CONCLUSIONS

MRI-based segmentation is highly accurate in assessing prostate volume. Diameter-based measurements are closely correlated to the segmented prostate volume and are feasible to monitor therapy.

MR and CT image fusion for postimplant analysis in permanent prostate seed implants

PURPOSE

To compare the outcome of two different image-based postimplant dosimetry methods in permanent seed implantation.

METHODS AND MATERIALS

Between October 1999 and October 2002, 150 patients with low-risk prostate carcinoma were treated with (125)I and (103)Pd in our institution. A CT-MRI image fusion protocol was used in 21 consecutive patients treated with exclusive brachytherapy. The accuracy and reproducibility of the method was calculated, and then the CT-based dosimetry was compared with the CT-MRI-based dosimetry using the dose-volume histogram (DVH) related parameters recommended by the American Brachytherapy Society and the American Association of Physicists in Medicine.

RESULTS

Our method for CT-MRI image fusion was accurate and reproducible (median shift <1 mm). Differences in prostate volume were found, depending on the image modality used. Quality assurance DVH-related parameters strongly depended on the image modality (CT vs. CT-MRI): V(100) = 82% vs. 88%, p < 0.05. D(90) = 96% vs. 115%, p < 0.05. Those results depend on the institutional implant technique and reflect the importance of lowering inter- and intraobserver discrepancies when outlining prostate and organs at risk for postimplant dosimetry.

CONCLUSIONS

Computed tomography-MRI fused images allow accurate determination of prostate size, significantly improving the dosimetric evaluation based on DVH analysis. This provides a consistent method to judge a prostate seed implant's quality.

Reduction of dose delivered to the rectum and bulb of the penis using MRI delineation for radiotherapy of the prostate

PURPOSE

The prostate volume delineated on MRI is smaller than on CT. The purpose of this study was to determine the influence of MRI- vs. CT-based prostate delineation using multiple observers on the dose to the target and organs at risk during external beam radiotherapy.

MATERIALS AND METHODS

CT and MRI scans of the pelvic region were made of 18 patients and matched three-dimensionally on the bony anatomy. Three observers delineated the prostate using both modalities. A fourth observer delineated the rectal wall and the bulb of the penis. The planning treatment volume (PTV) was generated from the delineated prostates with a margin of 10 mm in three-dimensions. A three-field treatment plan with a prescribed dose of 78 Gy to the International Commission on Radiation Units and Measurements point was automatically generated from each PTV. Dose-volume histograms were calculated of all PTVs, rectal walls, and penile bulbs. The equivalent uniform dose was calculated for the rectal wall using a volume exponent (n = 0.12).

RESULTS

The equivalent uniform dose of the CT rectal wall in plans based on the CT-delineated prostate was, on average, 5.1 Gy (SEM 0.5) greater than in the plans based on the MRI-delineated prostate. For the MRI rectal wall, this difference was 3.6 Gy (SEM 0.4). Allowing for the same equivalent uniform dose to the CT rectal wall, the prescribed dose to the PTV could be raised from 78 to 85 Gy when using the MRI-delineated prostate for treatment planning. The mean dose to the bulb of the penis was 11.6 Gy (SEM 1.8) lower for plans based on the MRI-delineated prostate. The mean coverage (volume of the PTV receiving > or =95% of the prescribed dose) was 99.9% for both modalities. The interobserver coverage (coverage of the PTV by a treatment plan designed for the PTV delineated by another observer in the same modality) was 97% for both modalities. The MRI rectum was significantly more ventrally localized than the CT rectum, probably because of the rounded tabletop and no knee support on the MRI scanner.

CONCLUSIONS

The dose delivered to the rectal wall and bulb of the penis is significantly reduced with treatment plans based on the MRI-delineated prostate compared with the CT-delineated prostate, allowing a dose escalation of 2.0-7.0 Gy for the same rectal wall dose. The interobserver coverage was the same for CT and MRI delineation of the prostate. A statistically significant difference in position between the CT- and MRI-delineated rectum was observed, probably owing to a different tabletop and use of knee support.