Assessment of high-grade prostate cancer risk using prostate cancer biomarkers

INTRODUCTION

To identify patients at risk of high-grade prostate cancer using prostate cancer biomarkers.

MATERIALS AND METHODS

A total of 601 men were screened for prostate cancer in 2012, 2015, and 2016 using prostate cancer biomarkers: prostate health index (phi), 4KScore, and SelectMDx. The first two are blood tests that incorporate several PSA isoforms; SelectMDx measures mRNA levels of homeobox C6 and distal-less homeobox 1 in post-digital rectal examination urine samples. The performance of each biomarker was evaluated using cut off values based on published literature. Gleason Grade Group (GG) ≥ 2 is considered as high-grade prostate cancer.

RESULTS

For patients with PSA < 1.5 ng/mL, none were at risk for GG ≥ 2 cancer based on SelectMDx > 0%, whereas 17.1% were at intermediate to high risk of finding GG ≥ 2 cancer with 4KScore ≥ 7.5%, and 3.5% were at risk of finding any prostate cancer with phi ≥ 36 at biopsy. For cut offs revised for finding men at high risk for GG ≥ 2 cancer at biopsy, only one patient with PSA < 1.5 ng/mL would be at risk with 4KScore ≥ 20% and none with phi ≥ 52.7. For patients with PSA 1.5 to 3.99 ng/mL, 2%, 8%, and 1% were at high risk for finding GG ≥ 2 cancer at biopsy based on phi, 4KScore, and SelectMDx, respectively.

CONCLUSIONS

Men with PSA < 1.5 ng/mL are at very low risk of finding high-grade prostate cancer at biopsy. However, some men with PSA between 1.5 to 3.99 ng/mL may be at intermediate to high risk for high-grade prostate cancer. Thus, primary care physicians could run biomarkers test and refer those with positive biomarker results to a specialist for further evaluation.

The Ratio of the Number of Biopsy Specimens to Prostate Volume (Biopsy Density) Greater Than 1.5 Improves the Prostate Cancer Detection Rate in Men Undergoing Transperineal Biopsy of the Prostate

PURPOSE

We sought to determine the minimum number of transperineal prostate mapping biopsies needed to optimize the prostate cancer detection rate.

MATERIALS AND METHODS

A total of 436 men underwent transperineal prostate mapping biopsy at 2 institutions. Biopsy density was calculated as the ratio of the total number of specimens retrieved (mean 59.4) to prostate volume (mean 44.9 cc). Associations of biopsy density with prostate specific antigen, prostate specific antigen density, cancer diagnosis and the Gleason score were tested by ANOVA and the chi-square test. Regression analysis was done to determine factors associated with a positive transperineal prostate mapping biopsy and Gleason score 7 or higher cancer.

RESULTS

Transperineal prostate mapping biopsy was positive in 299 of 436 men (68.6%). The mean number of positive cores was 7.1 (range 1 to 41) and mean biopsy density was 1.46 (range 0.39 to 3.67). The mean number of cores in positive vs negative transperineal prostate mapping biopsies was 1.61 vs 1.14 (p <0.001). Biopsy density cut points of 0.5 or less, greater than 0.5 to 1.0, greater than 1.0 to 1.5 and greater than 1.5 were associated with positive biopsy in 25%, 37.4%, 70.7% and 84.9% of patients (p <0.001). Dichotomizing biopsy density to 1.5 or less vs greater than 1.5 resulted in a positive biopsy rate of 56.4% vs 84.9% (OR 1.5, 95% CI 1.3-1.7, p <0.001). More Gleason score 6 cancers were diagnosed with higher biopsy density (94 of 158 or 59.5% vs 62 of 141 or 44.9%, p = 0.007). However, the number of positive cores with Gleason score 6 was greater in men with higher biopsy density at 4.9 vs 3.6 (p = 0.036). Prostate specific antigen (p = 0.053) and biopsy density (p = 0.012) were significant on regression analysis for positive transperineal prostate mapping biopsy and Gleason score 7+ disease.

CONCLUSIONS

Biopsy density greater than 1.5 increases the diagnosis of prostate cancer by 1.5 times, detects higher volume Gleason score 6 disease and should be considered the optimal sampling approach when performing transperineal prostate mapping biopsy.

SelectMDx versus Prostate Health Index in the identification of high-grade prostate cancer

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Background: A major clinical challenge is to identify patients at increased risk of high-grade prostate cancer (PCa) (Gleason scores ≥ 7) before biopsy. Thus, we evaluated the clinical utility of SelectMDx and Prostate Health Index (phi) tests for diagnosis of high-grade PCa as compared with transperineal mapping biopsy (TMB) results, where an average of 80 prostate needle biopsies are taken every 5 mm for a diagnostic accuracy of 98%. Methods: 70 patients were selected who had TMB. They were evaluated with both SelectMDx and phi tests from before or after TMB; all had serum and post-digital rectal examination urine samples collected prior to treatment, stored in our biorepository. phi was evaluated using proPSA, free PSA and total PSA in serum. SelectMDx test measured mRNA levels of the HOXC6 and DLX1 in post-DRE urine. Published data shows that phi <27 and SelectMDx score = 0% correlate with patients free of HG PCa. Test results were compared against TMB histopathology data. Multivariate logistic regression (MLS) analyses and receiver operating characteristic (ROC) curves were used to determine diagnostic accuracy. DeLong test was used to determine statistical significance of ROC curves. All analyses were done for diagnosis of any PCa and high-grade PCa. Results: TMB histopathology showed 17/70 patients with no PCa and 22/53 with high-grade PCa. The sensitivity, specificity, positive (PPV) and negative (NPV) predictive values of each test are shown in the table below. Pairwise ROC comparison showed no statistically significant difference in the area under the curve of diagnosing PCa (0.75 vs 0.65) and high-grade PCa (0.71 vs 0.81) by phi and SelectMDx tests respectively. MLS analyses showed phi was significantly better than SelectMDx for diagnosing PCa (β = 0.054; p=0.005) and SelectMDx was significantly better than phi for diagnosing high-grade PCa (β = 8.45; p=0.0002). Conclusions: With high sensitivity and NPV, SelectMDx test is more useful than phi for screening patients at risk of high-grade PCa prior to biopsy. [Table: see text]

The effect of digital rectal exam on the 4Kscore for aggressive prostate cancer

BACKGROUND

The 4Kscore is a new commercially available blood-based diagnostic test which predicts risk for aggressive, clinically significant prostate cancer on prostate biopsy. The 4Kscore is currently restricted to patients who have not had a digital rectal exam (DRE) in the previous 96 h, owing to prior mixed data suggesting that prostate specific antigen (PSA) isoforms may increase by a statistically significant-if not necessarily clinically significant-amount shortly after DRE. Our primary objective was to determine if 4Kscore test results are affected by a preceding DRE.

METHODS

Participants at a Prostate Cancer Awareness Week screening event sponsored by the Prostate Conditions Education Council filled out clinical history questionnaires and had blood samples for 4Kscore testing drawn prior to DRE, then 15-45 min following DRE. Patients with prior cancer diagnosis, 5-alpha reductase inhibitor medication use, or lower urinary tract procedures in the prior 6 months were excluded, resulting in a population of 162 participants for analysis. Values were then compared to determine if there was a significant difference in 4Kscore following DRE.

RESULTS

A statistically significant increase was seen in levels of 3 kallikreins measured (total PSA, free PSA, and intact PSA; median <0.03 ng/mL for all). This resulted in a small but statistically significant decrease in post-DRE 4Kscore (median absolute score decrease 0.43%). Using a 4Kscore cutoff of 7.5% resulted in reclassification of 10 patients (6.2%), nine of whom were "downgraded" from above the cutoff to below.

CONCLUSIONS

If the blood draw for the 4 K score is performed after a screening DRE, there is a statistically significant difference in the 4 K score results, but in the vast majority of cases it would not affect clinical decision making.

Evaluation of prostate cancer risk in men with PSA < 1.5

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Background: Prostate Specific Antigen (PSA) screening remains controversial primarily because of over detection and treatment. There is an unmet clinical need to identify patients at increased risk for high-grade (HG – Gleason Score ≥7) prostate cancer (PCa) since PSA has low sensitivity. Combining PSA with well-validated prostate cancer biomarkers (PCM) can improve risk assessment. We investigated the performance of three PCMs (phi – prostate health index, 4KScore, and SelectMDx) on patients with PSA levels < 1.5 ng/mL that represent a “safe zone” where risk of any PCa is rare Methods: 652 men were screened for PCa during the annual Prostate Cancer Awareness Week at the University of Colorado Hospital. This study was supported by Prostate Condition Education Council and the Schramm Foundation. phi is evaluated using p2PSA, total PSA, and free PSA in serum. Phi < 52.7 suggests absence of HG PCa. 4KScore incorporates four kallikrein protein biomarkers: total PSA, free PSA, intact PSA, human kallikrein protein, and clinical information. A 4KScore < 20% suggests absence of HG PCa. The SelectMDx post-DRE urine test measures mRNA levels of the homeobox C6 and distal-less homeobox 1 biomarkers. SelectMDx score of 0% indicates absence of HG PCa. Results: No patients with a PSA < 1.5 had SelectMDx > 0% and/or phi > 52.7. One patient had a 4KScore of 27%, indicating a risk for HG PCa. For patients with PSA between 1.5-3.99, 2.9% (4/135), 7.4% (4/54), and 2.3% (2/85) had positive phi, 4KScore, and SelectMDx results, respectively. Conclusions: Men with PSA <1.5 ng/mL are at very low risk for HG PCa. Men with PSA between 1.5-3.99 with positive PCM results may be referred for further evaluation. [Table: see text]

Human feasibility study of fluorescence spectroscopy guided optical biopsy needle for prostate cancer diagnosis

Current prostate biopsy cores have a very low diagnostic yield. These biopsies often fail to diagnose prostate cancer since 90% of cores are histopathologically classified as benign. The concentrations of endogenous fluorophores in prostate tissue vary with disease states. Thus, fluorescence spectroscopy could be utilized to quantify these variations for identification of malignant lesions. We investigated clinical feasibility of a 14 gauge (1.98 mm) optical biopsy needle guided by fluorescence spectroscopy for real-time in vivo prostate cancer diagnosis. Built-in optical sensor has 8×100μm fibers for tissue excitation and a single 200μm fiber to collect spectral data. Custom-made fluorometer has 2 light-emitting diodes at 290 and 340 nm and a spectrometer. User interface for fluorometer operation and data collection was developed using LabView software. Each spectral data acquisition required ~2 seconds. The in vivo biopsies were performed during radical retropubic prostatectomy surgery on the exposed prostate with blood flow to the gland intact. A tissue biopsy core was obtained from each biopsy site after acquisition of spectral data. Above procedure was repeated ex vivo after surgical excision of the prostate. Biopsy cores were histopathologically classified as either benign or malignant and correlated with corresponding spectral data. Partial Least Square analysis was performed to determine diagnostically significant principal components as potential classifiers. A linear support vector machine and leave-one-out cross validation method was employed for tissue classification. Thirteen patients were consented to the study. Histopathological analysis found cancer in 29/208 in vivo and 51/224 ex vivo viable biopsy cores. Study results show 72% sensitivity, 66% specificity, and 93% negative predictive value for in vivo and 75%, 80%, and 93%, respectively, for ex vivo malignant versus benign prostatic tissue classification. Optical biopsy needle has a very high negative predictive value to indicate benign tissue while sufficient sensitivity for targeting areas suspicious for cancer within the prostate gland. Hence, the optical biopsy needle can increase the diagnostic yield of prostate biopsies with consequent improvement in patient care.

Diffuse reflectance spectroscopy can differentiate high grade and low grade prostatic carcinoma

Prostate tumors are graded by the revised Gleason Score (GS) which is the sum of the two predominant Gleason grades present ranging from 6-10. GS 6 cancer exclusively with Gleason grade 3 is designated as low grade (LG) and correlates with better clinical prognosis for patients. GS >7 cancer with at least one of the Gleason grades 4 and 5 is designated as HG indicate worse prognosis for patients. Current transrectal ultrasound guided prostate biopsies often fail to correctly diagnose HG prostate cancer due to sampling errors. Diffuse reflectance spectra (DRS) of biological tissue depend on tissue morphology and architecture. Thus, DRS could potentially differentiate between HG and LG prostatic carcinoma. A 15-gauge optical biopsy needle was prototyped to take prostate biopsies after measuring DRS with a laboratory fluorometer. This needle has an optical sensor that utilizes 8×100 μm optical fibers for tissue excitation and a single 200 μm central optical fiber to measure DRS. Tissue biopsy cores were obtained from 20 surgically excised prostates using this needle after measuring DRS at 5 nm intervals between 500-700 nm wavelengths. Tissue within a measurement window was histopathologically classified as either benign, LG, or HG and correlated with DRS. Partial least square analysis of DRS identified principal components (PC) as potential classifiers. Statistically significant PCs (p<;0.05) were tested for their ability to classify biopsy tissue using support vector machine and leave-one-out cross validation method. There were 29 HG and 49 LG cancers among 187 biopsy cores included in the study. Study results show 76% sensitivity, 80% specificity, 93% negative predictive value, and 50% positive predictive value for HG versus benign, and 76%, 73%, 84%, and 63%, for HG versus LG prostate tissue classification. DRS failed to diagnose 7/29 (24%) HG cancers. This study demonstrated that an optical biopsy needle guided by DRS has sufficient accuracy to differentiate HG from LG carcinoma and benign tissue. It may allow precise targeting of HG prostate cancer providing more accurate assessment of the disease and improvement in patient care.

Diagnosis of prostatic carcinoma on multiparametric magnetic resonance imaging using shearlet transform

This paper presents a method to diagnose prostate cancer on multiparametric magnetic resonance imaging (Mp-MRI) using the shearlet transform. The objective is classification of benign and malignant regions on transverse relaxation time weighted (T2W), dynamic contrast enhanced (DCE), and apparent diffusion coefficient (ADC) images. Compared with conventional wavelet filters, shearlet has inherent directional sensitivity, which makes it suitable for characterizing small contours of cancer cells. By applying a multi-scale decomposition, the shearlet transform captures visual information provided by edges detected at different orientations and multiple scales in each region of interest (ROI) of the images. ROIs are represented by histograms of shearlet coefficients (HSC) and then used as features in Support Vector Machines (SVM) to classify ROIs as benign or malignant. Experimental results show that our method can recognize carcinoma in T2W, DCE, and ADC with overall sensitivity of 92%, 100%, and 89%, respectively. Hence, application of shearlet transform may further increase utility of Mp-MRI for prostate cancer diagnosis.

Systematic diagnosis of prostate cancer using an optical biopsy needle adjunct with fluorescence spectroscopy

Transrectal ultrasound guided prostate biopsies often fail to diagnose prostate cancer with 90% of cores reported as benign. Thus, it is desirable to target prostate cancer lesions while reducing the sampling of benign tissue. The concentrations of natural fluorophores in prostate tissue fluctuate with disease states. Hence, fluorescence spectroscopy could be used to quantify these fluctuations to identify prostate cancer. An optical biopsy needle with a light sensitive optical probe at the tip of the inner needle was developed to take prostate biopsies after measuring tissue fluorescence with a laboratory fluorometer. The optical probe consists of eight 100 μm fibers for tissue excitation and a single 200 μm fiber to capture fluorescence spectra. Random biopsy cores were taken from 20 surgically excised prostates after measuring fluorescence spectra of tissue between 295-550nm for several excitations between 280-350nm. Each biopsy core was histopathologically classified and correlated with corresponding spectra. Prostate biopsies were grouped into benign or malignant based on the histological findings. Out of 187 biopsy cores, 109 were benign and 78 were malignant. Partial least square analysis of tissue spectra was performed to identify diagnostically significant principal components as potential classifiers. A linear support vector machine and leave-one-out cross validation method was employed for tissue classification. Study results show 86% sensitivity, 87% specificity, 90% negative predictive value, and 83% positive predictive value for benign versus malignant prostate tissue classification. This study demonstrates potential clinical applications of fluorescence spectroscopy guided optical biopsy needle for prostate cancer diagnosis with the consequent improvement of patient care.

Ethnic minorities (African American and Hispanic) males prefer prostate cryoablation as aggressive treatment of localized prostate cancer

INTRODUCTION

Our safety net hospital offers minimally invasive, traditional open and perineal radical prostatectomies, as well as radiation therapy and medical oncological services when appropriate. Historically, only few African American and Hispanic patients elected surgical procedures due to unknown reasons. Interestingly, after initiation of the prostate cryoablation program (Whole Gland) in 2003 at Denver Health Medical Center (DHMC) we noticed a trend towards cryotherapy in these specific patient populations for the treatment of localized prostate cancer. We analyzed the profile of ethnic minority men evaluated for localized prostate cancer and evaluated the associated factors in the decision making for the treatment of localized prostate cancer.

MATERIALS AND METHODS

A retrospective review of 524 patients seen for prostate cancer from January 2003 to January 2012 in our safety net hospital was conducted. The treatment selected by the patient after oncologic consultation was then recorded. The health insurance status, demographic data, and personal statements of reasons for elected procedure were obtained. A multivariate logistic regression for associated factors influencing treatment decisions was then formed. Patients were categorized by using the D'Amico risk stratification criteria.

RESULTS

The insurance status revealed that only 1% of African American patients had private health insurance versus 5% Hispanic and 26% of Caucasians. African American men were at higher D'Amico risk with more positive metastasis evaluation yet were less likely to undergo surgery and instead often elected for radiation therapy. Conversely, Hispanic and Caucasian men often elected cryoablation and radical prostatectomy for their treatment. Referrals for surgery were primarily Caucasian males with private health insurance. Most minority patients had indigent health coverage. Statistical analysis further revealed that age, marital status, indigent enrollment, D'Amico risk, and the option of cryoablation may influence patient's selection for surgical management of localized prostate cancer.

CONCLUSION

Many factors influence treatment selection including race, age, marital status, enrollment in an indigent program, and a high D'Amico risk. The less invasive nature of cryoablation appeared to influence patients' opinion regarding surgery for the treatment of localized prostate cancer, especially in African American men.

Anterior tumors of the prostate: diagnosis and significance

INTRODUCTION

Prostate biopsies are usually taken from the peripheral rather than anterior region of the prostate. Consequently, tumors originating from the anterior apical region and transition zones may be under-sampled. We examined whether addition of transrectal anterior biopsy (TAB) would improve efficacy of prostate biopsies.

MATERIALS AND METHODS

Simulations of TAB and sextant biopsy (SB) were performed using computer models of 86 autopsy prostates (AP) and 40 radical prostatectomy (RP) specimens. TAB was obtained bilaterally from apex, mid, and base regions by advancing the biopsy needle 5 mm-35 mm beyond the prostatic capsule. A phase I clinical trial with 114 patients was conducted to determine the performance of an extended biopsy protocol consisting of TAB, SB, and laterally-directed biopsy (LDB).

RESULTS

The overall cancer detection rates of SB and TAB were 33% and 55% for AP series (p = 0.00003); 60% and 88% for RP series (p = 0.006). Alternatively, SB + bilateral apical TAB and SB + bilateral mid TAB had cancer detection rates of 45% and 42% for AP series; 80% and 78% for RP series. The extended biopsy protocol detected cancer in 33% (38/114) of patients with 29, 25, and 15 diagnosed by SB, LDB, and bilateral apical TAB, respectively. Patients diagnosed by bilateral apical TAB versus SB (p = 0.01) and LDB (p = 0.02) were statistically significant. Without bilateral apical TAB, the overall cancer detection rate decreased to 30% (34/114).

CONCLUSIONS

Inclusion of bilateral TAB from apical region for first time and repeat prostate biopsies may increase diagnosis of prostate cancer. The clinical significance of these findings needs further investigations and clinical follow up.

Clinical-pathologic correlation between transperineal mapping biopsies of the prostate and three-dimensional reconstruction of prostatectomy specimens

BACKGROUND

Extended transrectal ultrasound guided biopsies (TRUSB) of the prostate may not accurately convey true morphometric information and Gleason score (GS) of prostate cancer (PCa) and the clinical use of template-guided (5-mm grid) transperineal mapping biopsies (TPMBs) remains controversial.

METHODS

We correlated the clinical-pathologic results of 1,403 TPMB cores obtained from 25 men diagnosed with PCa with 64 cancer lesions found in their corresponding radical prostatectomy (RP) specimens. Special computer models of three-dimensional, whole-mounted radical prostatectomy (3D-WMRP) specimens were generated and used as gold standard to determine tumor morphometric data. Between-sample rates of upgrade and downgrade (highest GS and a novel cumulative GS) and upstage and downstage (laterality) were determined. Lesions ≥ 0.5 cm(3) or GS ≥ 7 were considered clinically significant.

RESULTS

From 64 separate 3D-WMRP lesions, 25 had significant volume (mean 1.13 cm(3)) and 39 were insignificant (mean 0.09 cm(3)) (P < 0.0001); 18/64 lesions were missed by TPMB, but only one was clinically significant with GS-8 (0.02 cm(3)). When comparing the cumulative GS of TPMB versus RP, 72% (n = 18) had identical scores, 12% (n = 3) were upgraded, and only 16% (n = 4) were downgraded. Laterality of TPMB and RP was strongly correlated, 80% same laterality, 4% were up-staged, and 16% down-staged.

CONCLUSIONS

Our clinical-pathology correlation showed very high accuracy of TPMB with a 5-mm grid template to detect clinically significant PCa lesions as compared with 3D-WMRP, providing physicians and patients with a reliable assessment of grade and stage of disease and the opportunity to choose the most appropriate therapeutic options.

Optimization of prostate cancer diagnosis by increasing the number of core biopsies based on gland volume

In this prospective, non-randomized phase-I clinical trial, we comparatively studied the performance of six laterally-directed biopsies or the modified fan-shaped biopsies (MFSB), midline sextant biopsies (MB), and transition zone biopsies (TZB) and examine their prostate cancer (PCa) detection rates. A total of 114 patients received combinations of MFSB, MB, and TZB based on prostate gland volume: those ≤15 cc received 8 biopsies; those >15 cc but ≤ 50 cc received 14 biopsies; and those >50 cc received 20 biopsies. The mean prostate-specific antigen (PSA) level, Gleason score, and prostate volume were 8.0 ng/ml, 6.4, and 47 cc, respectively. PCa detection rate of the MB was 25% while the MFSB was 22%. The overall PCa detection rate was 33.3% with all biopsies. PCa and high-grade prostatic intraepithelial neoplasia (HG-PIN) detection rates decrease as the size of the prostate increases. PCa detection rates were 50.0% for volumes ≤19.9 cc and volumes of >50 cc had a detection rate of 25.8%. PSA levels of <3.0 had PCa detection rates of 15% which increased to 58% with PSA levels >9.0. In a multivariate analysis, only TZB was significant for PCa diagnosed by PSA (β=7.4, p<0.01). Our study showed that it is important to perform both the lateral MFSB and the MB to improve overall PCa detections rates. Thus, we recommend performing MB, MFSB, and TZB based on prostate volume, as follows: 8 biopsies for ≤15 cc; 14 for those >15 cc but ≤50 cc, and 14-20 for those >50 cc.

Digital quantification of five high-grade prostate cancer patterns, including the cribriform pattern, and their association with adverse outcome

Proper grading of the cribriform prostate cancer pattern has not previously been supported by outcome-based evidence. Among 153 men who underwent radical prostatectomy, 76 with prostate-specific antigen (PSA) failure (≥0.2 ng/mL [0.2 μg/L]) were matched to 77 without failure. Frequencies of high-grade patterns included fused small acini, 83.7%; papillary, 52.3%; large cribriform, 37.9%; small (≤12 lumens) cribriform, 17.0%; and individual cells, 22.9%. A cribriform pattern was present in 61% (46/76) of failures but 16% (12/77) of nonfailures (P < .0001). Multivariate analysis showed the cribriform pattern had the highest odds ratio for PSA failure, 5.89 (95% confidence interval, 2.53-13.70; P < .0001). The presence of both large and small cribriform patterns was significantly linked to failure. The cumulative odds ratio of failure per added square millimeter of cribriform pattern was 1.173 (P = .008), higher than for any other pattern. All 8 men with a cribriform area sum of 25 mm(2) or more had failure (range, 33-930). Regrading cribriform cancer as Gleason 5 improved the grade association with failure, although half of all cases with individual cells also had a cribriform pattern, precluding a precise determination of the independent importance of the latter. The cribriform pattern has particularly adverse implications for outcome.

Image registration accuracy of a 3-dimensional transrectal ultrasound-guided prostate biopsy system

OBJECTIVE

For a follow-up prostate biopsy procedure, it is useful to know the previous biopsy locations in anatomic relation to the current transrectal ultrasound (TRUS) scan. The goal of this study was to validate the performance of a 3-dimensional TRUS-guided prostate biopsy system that can accurately relocate previous biopsy sites.

METHODS

To correlate biopsy locations from a sequence of visits by a patient, the prostate surface data obtained from a previous visit needs to be registered to the follow-up visits. Two interpolation methods, thin-plate spline (TPS) and elastic warping (EW), were tested for registration of the TRUS prostate image to follow-up scans. We validated our biopsy system using a custom-built phantom. Beads were embedded inside the phantom and were located in each TRUS scan. We recorded the locations of the beads before and after pressures were applied to the phantom and then compared them with computer-estimated positions to measure performance.

RESULTS

In our experiments, before system processing, the mean target registration error (TRE) +/- SD was 6.4 +/- 4.5 mm (range, 3-13 mm). After registration and TPS interpolation, the TRE was 5.0 +/- 1.03 mm (range, 2-8 mm). After registration and EW interpolation, the TRE was 2.7 +/- 0.99 mm (range, 1-4 mm). Elastic warping was significantly better than the TPS in most cases (P < .0011). For clinical applications, EW can be implemented on a graphics processing unit with an execution time of less than 2.5 seconds.

CONCLUSIONS

Elastic warping interpolation yields more accurate results than the TPS for registration of TRUS prostate images. Experimental results indicate potential for clinical application of this method.

Adaptation of a 3D prostate cancer atlas for transrectal ultrasound guided target-specific biopsy

Due to lack of imaging modalities to identify prostate cancer in vivo, current TRUS guided prostate biopsies are taken randomly. Consequently, many important cancers are missed during initial biopsies. The purpose of this study was to determine the potential clinical utility of a high-speed registration algorithm for a 3D prostate cancer atlas. This 3D prostate cancer atlas provides voxel-level likelihood of cancer and optimized biopsy locations on a template space (Zhan et al 2007). The atlas was constructed from 158 expert annotated, 3D reconstructed radical prostatectomy specimens outlined for cancers (Shen et al 2004). For successful clinical implementation, the prostate atlas needs to be registered to each patient's TRUS image with high registration accuracy in a time-efficient manner. This is implemented in a two-step procedure, the segmentation of the prostate gland from a patient's TRUS image followed by the registration of the prostate atlas. We have developed a fast registration algorithm suitable for clinical applications of this prostate cancer atlas. The registration algorithm was implemented on a graphical processing unit (GPU) to meet the critical processing speed requirements for atlas guided biopsy. A color overlay of the atlas superposed on the TRUS image was presented to help pick statistically likely regions known to harbor cancer. We validated our fast registration algorithm using computer simulations of two optimized 7- and 12-core biopsy protocols to maximize the overall detection rate. Using a GPU, patient's TRUS image segmentation and atlas registration took less than 12 s. The prostate cancer atlas guided 7- and 12-core biopsy protocols had cancer detection rates of 84.81% and 89.87% respectively when validated on the same set of data. Whereas the sextant biopsy approach without the utility of 3D cancer atlas detected only 70.5% of the cancers using the same histology data. We estimate 10-20% increase in prostate cancer detection rates when TRUS guided biopsies are assisted by the 3D prostate cancer atlas compared to the current standard of care. The fast registration algorithm we have developed can easily be adapted for clinical applications for the improved diagnosis of prostate cancer.

Three-dimensional sonography with needle tracking: role in diagnosis and treatment of prostate cancer

OBJECTIVE

Image-guided prostate biopsy has become routine in medical diagnosis. Although it improves biopsy outcome, it mostly operates in 2 dimensions, therefore lacking presentation of information in the complete 3-dimensional (3D) space. Because prostatic carcinomas are nonuniformly distributed within the prostate gland, it is crucial to accurately guide the needles toward clinically important locations within the 3D volume for both diagnosis and treatment.

METHODS

We reviewed the uses of 3D image-guided needle procedures in prostate cancer diagnosis and cancer therapy as well as their advantages, work flow, and future directions.

RESULTS

Guided procedures for the prostate rely on accurate 3D target identification and needle navigation. This 3D approach has potential for better disease diagnosis and therapy. Additionally, when fusing together different imaging modalities and cancer probability maps obtained from a population of interest, physicians can potentially place biopsy needles and other interventional devices more accurately and efficiently by better targeting regions that are likely to host cancerous tissue.

CONCLUSIONS

With the information from anatomic, metabolic, functional, biochemical, and biomechanical statuses of different regions of the entire gland, prostate cancers will be better diagnosed and treated with improved work flow.

Three different strategies for real-time prostate capsule volume computation from 3-D end-fire transrectal ultrasound

estimation of prostate capsule volume via segmentation of the prostate from 3-D ultrasound volumetric ultrasound images is a valuable clinical tool, especially during biopsy. Normally, a physician traces the boundaries of the prostate manually, but this process is tedious, laborious, and subject to errors. The prostate capsule edge is computed using three different strategies: (a) least square approach, (b) level set approach, and (c) Discrete Dynamic Contour approach. (a) In the least square method, edge points are defined by searching for the optimal edge based on the average signal characteristics. These edge points constitute an initial curve which is later refined; (b) Level set approach. The images are modeled as piece-wise constant, and the energy functional is defined and minimized. This method is also automated; and (c) The Discrete Dynamic Contour (DDC). A trained user selects several points in the first image and an initial contour is obtained by a model based initialization. Based on this initialization condition, the contour is deformed automatically to better fit the image. This method is semi-automatic. The three methods were tested on database consisting of 15 prostate phantom volumes acquired using a Philips ultrasound machine using an end-fire TRUS. The ground truth (GT) is developed by tracing the boundary of prostate on a slice-by-slice basis. The mean volumes using the least square, level set and DDC techniques were 15.84 cc, 15.55 cc and 16.33 cc, respectively. We validated the methods by calculating the volume with GT and we got an average volume of 15.

Clinical staging of prostate cancer: a computer-simulated study of transperineal prostate biopsy

OBJECTIVE

To identify the precise location of prostate cancer within the gland and thus possibly permit more aggressive therapy of the lesion, while potentially sparing the noncancerous gland from ablative therapy.

MATERIALS AND METHODS

Three-dimensional "solid" computer models were reconstructed for 86 autopsy specimens and 20 stage T1c radical prostatectomy specimens. Transperineal biopsies were simulated for grid sizes of 5-mm (method A) and 10-mm (method B) with an 18 G, 23-mm long biopsy needle. One or two biopsies per grid point were obtained for a total of 12-108 biopsies, depending on the size of the prostate. Clinically threatening cancers were defined as having volumes of > or = 0.5 mL or Gleason sum > or = 7.

RESULTS

Method A detected significantly more carcinomas than method B in both the autopsy and prostatectomy specimens (autopsy, 72 vs 51; prostatectomy, 50 vs 32, both P < 0.001). Method A also detected more clinically threatening cancers found at autopsy (38/40 vs 31/40, P = 0.008). Among autopsy patients with negative sextant biopsies whose disease was localized to one side, method A detected 72% and method B detected 29-43% (P < 0.001).

CONCLUSIONS

The results of this computer simulation show that 5- and 10-mm grid biopsies detect three-quarters and a third, respectively, at autopsy, of patients with the disease localized to one side of the prostate, which may be useful when planning highly selective ablative treatments in the future.

Biomorphometric analysis of human prostatic carcinoma by using three-dimensional computer models

Advances in the detection of carcinoma of the prostate during the last 15 years have accounted for a sharp increase and then an abrupt decrease in the incidence of the disease. A more recent decline in its mortality rates has been variously interpreted as either the success of early detection and improved treatment or lead-time bias. The recently reported Prostate Cancer Prevention Trial had an overall detection rate that approached the 30%-40% prevalence rates reported in autopsy series in which men died of other causes. However, the prognostic information that can be obtained from prostate cancer found on biopsy is limited. Three-dimensional computer modeling is one technique that allows multiple studies on "immortal" prostates to test methods of biopsy sampling accuracy and to assist in the determination of the disease's severity. Computer modeling can assess detection rates and assesses tumor multifocality and heterogeneity. It can provide a more accurate representation of tumor volume, aiding in therapeutic decision making, and can assess sampling errors of various biopsy methods. It has been shown to be superior to wire-frame technique by immortalizing the original shape and dimensions of the surgically excised prostate gland. Moreover, our 3-dimensional computer modeling system improves upon other systems: It is more than a simple extension of the planimetric technique, and it is able to demarcate clearly the boundaries of Gleason grades just 1 grade apart.

Laterally directed biopsies detect more clinically threatening prostate cancer: computer simulated results

BACKGROUND

The purpose of this study was to determine, whether a modified fan-shaped biopsy (MFSB) technique which utilizes six laterally directed biopsies would lead to higher detection rates of clinically threatening prostatic carcinoma than the six random systematic core biopsy (SRSCB) method.

METHODS

We reconstructed 3-dimensional solid computer models of 86 autopsy prostates and 40 radical prostatatectomy specimens. Simulations of SRSCB and MFSB were then performed using the same biopsy sites except that the biopsy probe was rotated 45 degrees toward posterolateral peripheral zone for MFSB. When the Gleason sum was less than 7, clinically threatening cancers were defined as having a tumor volume > or =0.25 cc or > or =0.5 cc.

RESULTS

When the cut off volume was 0.25 cc, MFSB detected significantly more threatening carcinomas in autopsy prostates than did SRSCB (P < 0.0082). This was also true for the surgical prostates (P < 0.0047) as well as for a sub-group of non-palpable carcinomas (P < 0.0047). When the cut off volume was increased to 0.5 cc, MFSB detected significantly more threatening carcinomas in the radical series (P < 0.0047) and for the non-palpable carcinomas (P < 0.0082), but not in the autopsy series.

CONCLUSIONS

The MFSB technique, which utilizes laterally directed biopsies, appears to be an effective approach to improve the detection of clinically threatening prostatic carcinoma.

Aberrant HOXC expression accompanies the malignant phenotype in human prostate

Dysregulation of HOX gene expression has been implicated as a factor in malignancies for a number of years. However, no consensus has emerged regarding specific causative genes. Using a degenerate reverse transcription-PCR technique, we show up-regulation of genes from the HOXC cluster in malignant prostate cell lines and lymph node metastases. When relative expression levels of the four HOX clusters were examined, lymph node metastases and cell lines derived from lymph node metastases exhibited very similar patterns, patterns distinct from those in benign cells or malignant cell lines derived from other tumor sites. Specific reverse transcription-PCR for HOXC4, HOXC5, HOXC6, and HOXC8 confirmed overexpression of these genes in malignant cell lines and lymph node metastases. Laser capture microdissection and examination of paired tumor/normal prostate epithelial cells also indicated overexpression of these HOXC genes in primary tumor cells. Our data indicate a possible link between expression of HOXC genes and malignancy in prostate cells. Overexpression of HOXC8 in LNCaP prostate cancer cells suppressed transactivation by androgen receptors. We speculate that HOXC overexpression may predispose tumor cells to androgen independence by necessitating adaptation to diminished androgen signaling.

Detection of abnormal E-cadherin expression by simulated prostate biopsy

PURPOSE

Sampling error is an inherent problem of prostate biopsy. Consequently the determination of whether a given carcinoma is clinically significant based on biopsy results is problematic. We assess the dimensions of sampling error and, thereby, provide insight into the potential value of prognostic markers applied to needle biopsies.

MATERIALS AND METHODS

We constructed 3-dimensional computer models of 21 prostatectomy specimens, including outlines of carcinomas, regions of abnormal E-cadherin expression and individual Gleason patterns. The 6 random systematic core biopsy technique and modifications were simulated using a computer algorithm.

RESULTS

In 6 of 21 cases the area of abnormal E-cadherin expression and/or high grade carcinoma was not sampled on 6 random systematic core biopsy. The areas missed were either small or inconsistently under sampled regions of the prostate. Modifying the placement of biopsy needles improved the detection of these features. In addition, percent tumor in the needle appeared to be well correlated to percent tumor in the prostate (r = 0.891, r2 = 0.642).

CONCLUSIONS

To avoid underestimating the aggressiveness of prostatic carcinoma at least 6 biopsies should be taken from each patient. A more extensive sampling is probably not warranted in all patients but it may prove useful in those in whom extent of disease is unclear or whose general health makes treatment decisions difficult. A reliable estimate of tumor volume in the prostatectomy specimen can be made based on relative amount of tumor in the biopsy specimen on an individual basis.

Morphological analysis and classification of latent prostate cancer using a 3-dimensional computer algorithm: analysis of tumor volume, grade, tumor doubling time and life expectancy

PURPOSE

We estimate the potential clinical significance of prostate cancers found at autopsy provided the individual had lived to the projected lifespan based on life expectancy tables.

MATERIALS AND METHODS

We used 3-dimensional computer models of 59 autopsy prostates that contained clinically undetected carcinoma to determine tumor volumes. Using doubling times of 2, 3, 4 and 6 years, carcinoma volumes at autopsy were extrapolated through patient projected lifespans. The carcinomas were then classified as clinically insignificant or significant according to Mayo Clinic criteria.

RESULTS

In 13 patients less than 60 years old, using doubling times of 2, 3, 4 and 6 years, clinically significant tumors were identified in 13 (100%), 10 (77%), 7 (54%) and 7 (54%), respectively. In 46 patients 60 years old or greater significant tumors were identified in 32 (70%), 22 (48%), 21 (46%) and 18 (39%), respectively. A statistical difference (p <0.0001) was found between the mean tumor volume (0.20 +/- 0.10 cc) of 43 organ confined carcinomas and the mean tumor volume (3.26 +/- 3.58 cc) of 16 extracapsular tumors. No capsule perforation was found in tumors with Gleason sums of 4 or less. However, capsule perforation was present in 8 of 31 tumors (25.8%) with Gleason sums of 5 or 6, and 8 of 11 tumors (72.7%) with Gleason scores of 7 or 8.

CONCLUSIONS

Prostatic carcinomas that remain clinically insignificant throughout life are likely to have doubling times greater than 4 years. The subset of carcinomas that emerge as clinically significant are likely to have doubling times less than 3 years. Therefore, an accurate method to measure doubling time at diagnosis could, provide an objective indicator to guide clinical management.

Computer modeling of prostate biopsy: tumor size and location--not clinical significance--determine cancer detection

PURPOSE

Sampling error is an inherent problem of prostate biopsy, and the determination of clinical significance based on biopsy results is problematic. We quantify the dimensions of these problems by computer simulation.

MATERIALS AND METHODS

We constructed 3-dimensional solid computer models of 59 autopsy prostates containing clinically undetected prostate cancer, and performed simulations of the standard prostate biopsy method.

RESULTS

Biopsy simulation detected 19 tumors from the 59 prostates, the majority of which were in the most accessible portion of the prostate, the posterior peripheral zone. Using 0.5 cc or greater tumor volume or less than 0.5 cc and Gleason sum 7 or greater as criteria of significance, the model detected 58% (11 of 19) significant tumors and 20% (8 of 40) insignificant tumors. With 0.25 cc or greater tumor volume or less than 0.25 cc and Gleason sum 7 or greater as criteria 15 of 29 significant (52%) and 4 of 30 insignificant (13%) tumors were detected. Among significant tumors defined by either volume criterion there was a statistical difference between detected and undetected tumors in terms of mean tumor volume and mean ratio of tumor volume-to-prostate volume. Among insignificant tumors defined by either criterion there was no such difference.

CONCLUSIONS

As much as 20 to 40% of currently detected prostate cancer may be histologically insignificant, as 4 of 19 cancers were detected when 0.25 cc was used as volume determinant of clinical significance and 8 of 19 were detected when 0.5 cc volume was used. These tumors are detected randomly. On the other hand, perhaps only one-half to three-fourths of clinically significant prostate cancers are being detected, and then only because the volume and anatomic location make them hard to miss.

A 3-D reconstruction algorithm for interpolation and extrapolation of planar cross sectional data

A three dimensional (3-D) reconstruction algorithm utilizing both linear interpolation and linear extrapolation was developed for the study of human prostatic cancer. The algorithm was validated by comparing the volumes and shapes of original to reconstructed objects. Synthetic objects of known geometry and wax models with shapes characteristic of prostatic carcinomas were assessed with standard planimetry and by the digital interpolation-extrapolation method. Volume and multifocality measurements obtained by reconstructing excised prostate glands using histologic maps obtained from whole-mount sections were tested. The new algorithm provided greater accuracy in determining tumor volumes than conventional methods. This model provides a basis for mathematical analysis of prostate cancer lesions.