Formalized prediction of clinically significant prostate cancer: is it possible?

Current state of prostate-specific membrane antigen PET/CT imaging-targeted biopsy techniques for detection of clinically significant prostate cancer

Clinically significant prostate cancer (csPCa) is the focus of clinical diagnosis and treatment of prostate cancer (PCa). The current standard for diagnosing csPCa in men at risk relies on a transrectal (and in some instances transperineal) ultrasound-guided biopsy (TRUS-GB) that is blind to the location of cancer, leading to false-negative csPCa diagnoses. Over the past decade, PSMA PET/CT imaging-targeted prostate biopsy (PSMA PET/CT-TB), which obtains tissue samples from a defined suspicious area, has emerged as a promising solution for improving csPCa detection. Its feasibility and higher csPCa diagnostic value have been reported by a few case reports and studies. The current manuscript will review this latest targeted prostate puncture technology, summarize the existing applications of PSMA PET/CT-TB, including technical considerations, and discuss the advantages and challenges of each technique.

Evaluation of NUF2 and GMNN Expression in Prostate Cancer: Potential Biomarkers for Prostate Cancer Screening

BACKGROUND

Prostate cancer (PC) is one of the most abundant cancers among men, and In Iran, has been responsible for 6% of all deaths from cancer in men. NUF2 and GMNN genes are considered as loci of susceptibility to tumorigenesis in humans. Alterations in expression of these genes have been reported in various malignancies. The aim of our study was to test whether different NUF2 and GMNN expression levels are associated with PC incidence and hence, might be considered as new molecular tools for PC screening.

METHODS

Biopsy samples from 40 PC patients and 41 healthy Iranian men were used to determine the relative gene expression. After RNA extraction and cDNA synthesis, samples were analyzed using TaqMan Quantitative Real time PCR. Patients' background information, included smoking habits and family histories of PC, were recorded. Stages and grades of their PC were classified by the TNM tumor, node, metastasis (TMN) staging system based on standard guidelines.

RESULTS

NUF2 expression did not significantly differ between the groups, while GMNN expression was significantly greater in the PC specimens than in the controls.

CONCLUSION

Regarding the significant role of GMNN in various tumor phenotypes, and its importance in PC progression, the alteration in GMNN expression in PC samples vs. controls indicate that the genetic profiling of this cancer might be considered to personalize therapy for each patient in the future.

Decision models for distinguishing between clinically insignificant and significant tumors in prostate cancer biopsies: an application of Bayes' Theorem to reduce costs and improve outcomes

Prostate cancer is the second leading cause of death from cancer, behind lung cancer, for men in the U. S, with nearly 30,000 deaths per year. A key problem is the difficulty in distinguishing, after biopsy, between significant cancers that should be treated immediately and clinically insignificant tumors that should be monitored by active surveillance. Prostate cancer has been over-treated; a recent European randomized screening trial shows overtreatment rates of 40%. Overtreatment of insignificant tumors reduces quality of life, while delayed treatment of significant cancers increases the incidence of metastatic disease and death. We develop a decision analysis approach based on simulation and probability modeling. For a given prostate volume and number of biopsy needles, our rule is to treat if total length of cancer in needle cores exceeds c, the cutoff value, with active surveillance otherwise, provided pathology is favorable. We determine the optimal cutoff value, c*. There are two misclassification costs: treating a minimal tumor and not treating a small or medium tumor (large tumors were never misclassified in our simulations). Bayes' Theorem is used to predict the probabilities of minimal, small, medium, and large cancers given the total length of cancer found in biopsy cores. A 20 needle biopsy in conjunction with our new decision analysis approach significantly reduces the expected loss associated with a patient in our target population about to undergo a biopsy. Longer needles reduce expected loss. Increasing the number of biopsy cores from the current norm of 10-12 to about 20, in conjunction with our new decision model, should substantially improve the ability to distinguish minimal from significant prostate cancer by minimizing the expected loss from over-treating minimal tumors and delaying treatment of significant cancers.

Characterization of prostate microstructure using water diffusion and NMR relaxation

For many pathologies, early structural tissue changes occur at the cellular level, on the scale of micrometers or tens of micrometers. Magnetic resonance imaging (MRI) is a powerful non-invasive imaging tool used for medical diagnosis, but its clinical hardware is incapable of reaching the cellular length scale directly. In spite of this limitation, microscopic tissue changes in pathology can potentially be captured indirectly, from macroscopic imaging characteristics, by studying water diffusion. Here we focus on water diffusion and NMR relaxation in the human prostate, a highly heterogeneous organ at the cellular level. We present a physical picture of water diffusion and NMR relaxation in the prostate tissue, that is comprised of a densely-packed cellular compartment (composed of stroma and epithelium), and a luminal compartment with almost unrestricted water diffusion. Transverse NMR relaxation is used to identify fast and slow T ₂ components, corresponding to these tissue compartments, and to disentangle the luminal and cellular compartment contributions to the temporal evolution of the overall water diffusion coefficient. Diffusion in the luminal compartment falls into the short-time surface-to-volume (S/V) limit, indicating that only a small fraction of water molecules has time to encounter the luminal walls of healthy tissue; from the S/V ratio, the average lumen diameter averaged over three young healthy subjects is measured to be 217.7±188.7 μm. Conversely, the diffusion in the cellular compartment is highly restricted and anisotropic, consistent with the fibrous character of the stromal tissue. Diffusion transverse to these fibers is well described by the random permeable barrier model (RPBM), as confirmed by the dynamical exponent ϑ = 1/2 for approaching the long-time limit of diffusion, and the corresponding structural exponent p = -1 in histology. The RPBM-derived fiber diameter and membrane permeability were 19.8±8.1 μm and 0.044±0.045 μm/ms, respectively, in agreement with known values from tissue histology and membrane biophysics. Lastly, we revisited 38 prostate cancer cases from a recently published study, and found the same dynamical exponent ϑ = 1/2 of diffusion in tumors and benign regions. Our results suggest that a multi-parametric MRI acquisition combined with biophysical modeling may be a powerful non-invasive complement to prostate cancer grading, potentially foregoing biopsies.

Development of a new nomogram to predict insignificant prostate cancer in patients undergoing radical prostatectomy

OBJECTIVE

The aim of this study was to develop a nomogram to predict the probability of insignificant prostate cancer.

MATERIALS AND METHODS

A retrospective analysis was conducted of patients who underwent radical prostatectomy at a Korean hospital between January 2005 and December 2014. Patients with pathologically insignificant prostate cancer were defined as having organ-confined disease with tumor volume less than 0.5 cm³ without Gleason scores of 4 or 5. Multivariable logistic regression analysis with a stepwise selection was used to model the relationship between preoperative characteristics and insignificant prostate cancer, and a nomogram to predict the probability of insignificant prostate cancer was created. Receiver operating characteristics (ROC) analysis was performed to assess the predictive value of the model.

RESULTS

The final study population consisted of 1343 patients. Among these patients, insignificant prostate cancer was confirmed in 188 men (14.0%) at the time of prostatectomy. Six independent predictors of insignificant prostate cancer were identified: number of positive cores (p < 0.001), maximal single core tumor involvement (p < 0.001), biopsy Gleason score (p < 0.001), prostate volume (p = 0.024), patient age (p < 0.001) and prostate-specific antigen density (p < 0.001) in the multivariable model. A nomogram to predict insignificant prostate cancer was developed using these six preoperative characteristics. The area under the ROC curve for nomogram predictions was 0.87.

CONCLUSION

The nomogram developed in this paper identifies the probability of insignificant prostate cancer and gives providers more information to guide their clinical decisions.

Evidence that selenium binding protein 1 is a tumor suppressor in prostate cancer

Selenium-Binding Protein 1 (SBP1, SELENBP1, hSP56) is a selenium-associated protein shown to be at lower levels in tumors, and its lower levels are frequently predictive of a poor clinical outcome. Distinguishing indolent from aggressive prostate cancer is a major challenge in disease management. Associations between SBP1 levels, tumor grade, and disease recurrence following prostatectomy were investigated by duplex immunofluorescence imaging using a tissue microarray containing tissue from 202 prostate cancer patients who experienced biochemical (PSA) recurrence after prostatectomy and 202 matched control patients whose cancer did not recur. Samples were matched by age, ethnicity, pathological stage and Gleason grade, and images were quantified using the Vectra multispectral imaging system. Fluorescent labels were targeted for SBP1 and cytokeratins 8/18 to restrict scoring to tumor cells, and cell-by-cell quantification of SBP1 in the nucleus and cytoplasm was performed. Nuclear SBP1 levels and the nuclear to cytoplasm ratio were inversely associated with tumor grade using linear regression analysis. Following classification of samples into quartiles based on the SBP1 levels among controls, tumors in the lowest quartile were more than twice as likely to recur compared to those in any other quartile. Inducible ectopic SBP1 expression reduced the ability of HCT-116 human tumor cells to grow in soft agar, a measure of transformation, without affecting proliferation. Cells expressing SBP1 also demonstrated a robust induction in the phosphorylation of the p53 tumor suppressor at serine 15. These data indicate that loss of SBP1 may play an independent contributing role in prostate cancer progression and its levels might be useful in distinguishing indolent from aggressive disease.

Nanowire analysis of cancer-testis antigens as biomarkers of aggressive prostate cancer

OBJECTIVE

To demonstrate the ability of the nCounter Analysis System, a nanowire technology, to sensitively and accurately detect cancer-testis antigens (CTAs) in men with prostate cancer and correlate them with disease parameters. The clinical implementation of novel biomarkers is necessary to provide for individual disease treatment planning for men with prostate cancer. The CTAs, as cancer-associated biomarkers that may correlate with aggressive disease, have the potential to play an important role.

METHODS

Formalin-fixed, paraffin embedded samples were used from men undergoing radical prostatectomy for prostate cancer. The expression of CTAs along with control genes was measured from formalin-fixed, paraffin-embedded prostate cancer tissues using real-time polymerase chain reaction and the nCounter assay.

RESULTS

Using a nanowire-based assay, ribonucleic acid (RNA) expression levels of the CTAs CSAG2 and NOL4 were found to be significantly higher in men with Gleason score (GS) 8-10 disease than those with GS ≤4+3 disease. On the contrary, the RNA expression level of PAGE4 was lower in men with GS 8-10 disease than those with GS ≤6 group. This study demonstrates that CTAs can be detected with a nanostring assay that is translatable and that a set of CTAs correlates with the clinical characteristics of the disease.

CONCLUSION

CTAs represent unique, cancer-associated biomarkers with potential utility in the clinic. The nCounter nanowire technology provides an opportunity to evaluate this panel of CTAs associated with aggressive prostate cancer in a multi-institutional fashion.

Configuration and validation of a novel prostate disease nomogram predicting prostate biopsy outcome: A prospective study correlating clinical indicators among Filipino adult males with elevated PSA level

Objective

To configure and validate a novel prostate disease nomogram providing prostate biopsy outcome probabilities from a prospective study correlating clinical indicators and diagnostic parameters among Filipino adult male with elevated serum total prostate specific antigen (PSA) level.

Methods

All men with an elevated serum total PSA underwent initial prostate biopsy at our institution from January 2011 to August 2014 were included. Clinical indicators, diagnostic parameters, which include PSA level and PSA-derivatives, were collected as predictive factors for biopsy outcome. Multiple logistic-regression analysis involving a backward elimination selection procedure was used to select independent predictors. A nomogram was developed to calculate the probability of the biopsy outcomes. External validation of the nomogram was performed using separate data set from another center for determination of sensitivity and specificity. A receiver-operating characteristic (ROC) curve was used to assess the accuracy in predicting differential biopsy outcome.

Results

Total of 552 patients was included. One hundred and ninety-one (34.6%) patients had benign prostatic hyperplasia, and 165 (29.9%) had chronic prostatitis. The remaining 196 (35.5%) patients had prostate adenocarcinoma. The significant independent variables used to predict biopsy outcome were age, family history of prostate cancer, prior antibiotic intake, PSA level, PSA-density, PSA-velocity, echogenic findings on ultrasound, and DRE status. The areas under the receiver-operating characteristic curve for prostate cancer using PSA alone and the nomogram were 0.688 and 0.804, respectively.

Conclusion

The nomogram configured based on routinely available clinical parameters, provides high predictive accuracy with good performance characteristics in predicting the prostate biopsy outcome such as presence of prostate cancer, high Gleason prostate cancer, benign prostatic hyperplasia, and chronic prostatitis.

Limited ability of existing nomograms to predict outcomes in men undergoing active surveillance for prostate cancer

OBJECTIVE

To assess the ability of current nomograms to predict disease progression at repeat biopsy or at delayed radical prostatectomy (RP) in a prospectively accrued cohort of patients managed by active surveillance (AS).

MATERIALS AND METHODS

A total of 273 patients meeting low-risk criteria who were managed by AS and who underwent multiple biopsies and/or delayed RP were included in the study. The Kattan (base, medium and full), Steyerberg, Nakanishi and Chun nomograms were used to calculate the likelihood of indolent disease ('nomogram probability') as well as to predict 'biopsy progression' by grade or volume, 'surgical progression' by grade or stage, or 'any progression' on repeat biopsy or surgery. We evaluated the associations between each nomogram probability and each progression outcome using logistic regression with (area under the receiver-operating characteristic curve (AUC) values and decision curve analysis.

RESULTS

The nomogram probabilities of indolent disease were lower in patients with biopsy progression (P < 0.01) and any progression on repeat biopsy or surgical pathology (P < 0.05). In regression analyses, nomograms showed a modest ability to predict biopsy progression, adjusted for total number of biopsies (AUC range 0.52-0.67) and any progression (AUC range 0.52-0.70). Decision curve analyses showed that all the nomograms, except for the Kattan base model, have similar value in predicting biopsy progression and any progression. Nomogram probabilities were not associated with surgical progression in a subgroup of 58 men who underwent delayed RP.

CONCLUSIONS

Existing nomograms have only modest accuracy in predicting the outcomes of patients undergoing AS. Improvements to existing nomograms should be made before they are implemented in clinical practice and used to select patients for AS.

MicroRNA-4723 inhibits prostate cancer growth through inactivation of the Abelson family of nonreceptor protein tyrosine kinases

The Abelson (c-Abl) proto-oncogene encodes a highly conserved nonreceptor protein tyrosine kinase that plays a role in cell proliferation, differentiation, apoptosis and cell adhesion. c-Abl represents a specific anti-cancer target in prostate cancer as aberrant activity of this kinase has been implicated in the stimulation of prostate cancer growth and progression. However, the mechanism of regulation of c-Abl is not known. Here we report that Abl kinases are regulated by a novel microRNA, miR-4723, in prostate cancer. Expression profiling of miR-4723 expression in a cohort of prostate cancer clinical specimens showed that miR-4723 expression is widely attenuated in prostate cancer. Low miR-4723 expression was significantly correlated with poor survival outcome and our analyses suggest that miR-4723 has significant potential as a disease biomarker for diagnosis and prognosis in prostate cancer. To evaluate the functional significance of decreased miR-4723 expression in prostate cancer, miR-4723 was overexpressed in prostate cancer cell lines followed by functional assays. miR-4723 overexpression led to significant decreases in cell growth, clonability, invasion and migration. Importantly, miR-4723 expression led to dramatic induction of apoptosis in prostate cancer cell lines suggesting that miR-4723 is a pro-apoptotic miRNA regulating prostate carcinogenesis. Analysis of putative miR-4723 targets showed that miR-4723 targets integrin alpha 3 and Methyl CpG binding protein in addition to Abl1 and Abl2 kinases. Further, we found that the expression of Abl kinase is inversely correlated with miR-4723 expression in prostate cancer clinical specimens. Also, Abl1 knockdown partially phenocopies miR-4723 reexpression in prostate cancer cells suggesting that Abl is a functionally relevant target of miR-4723 in prostate cancer. In conclusion, we have identified a novel microRNA that mediates regulation of Abl kinases in prostate cancer. This study suggests that miR-4723 may be an attractive target for therapeutic intervention in prostate cancer.

Transperineal biopsy of the prostate--is this the future?

Transperineal prostate biopsy is re-emerging after decades of being an underused alternative to transrectal biopsy guided by transrectal ultrasonography (TRUS). Factors driving this change include possible improved cancer detection rates, improved sampling of the anteroapical regions of the prostate, a reduced risk of false negative results and a reduced risk of underestimating disease volume and grade. The increasing incidence of antimicrobial resistance and patients with diabetes mellitus who are at high risk of sepsis also favours transperineal biopsy as a sterile alternative to standard TRUS-guided biopsy. Factors limiting its use include increased time, training and financial constraints as well as the need for high-grade anaesthesia. Furthermore, the necessary equipment for transperineal biopsy is not widely available. However, the expansion of transperineal biopsy has been propagated by the increase in multiparametric MRI-guided biopsies, which often use the transperineal approach. Used with MRI imaging, transperineal biopsy has led to improvements in cancer detection rates, more-accurate grading of cancer severity and reduced risk of diagnosing clinically insignificant disease. Targeted biopsy under MRI guidance can reduce the number of cores required, reducing the risk of complications from needle biopsy.

Activation of abl family kinases in solid tumors

Although c-Abl and Arg non-receptor tyrosine kinases are well known for driving leukemia development, their role in solid tumors has not been appreciated until recently. Accumulating evidence now indicates that c-Abl and/or Arg are activated in some solid tumor cell lines via unique mechanisms that do not involve gene mutation/translocation, and c-Abl/Arg activation promotes matrix degradation, invasion, proliferation, tumorigenesis, and/or metastasis, depending on the tumor type. However, some data suggest that c-Abl also may suppress invasion, proliferation, and tumorigenesis in certain cell contexts. Thus, c-Abl/Arg may serve as molecular switches that suppress proliferation and invasion in response to some stimuli (e.g., ephrins) or when inactive/regulated, or as promote invasion and proliferation in response to other signals (e.g., activated growth factor receptors, loss of inhibitor expression), which induce sustained activation. Clearly, more data are required to determine the extent and prevalence of c-Abl/Arg activation in primary tumors and during progression, and additional animal studies are needed to substantiate in vitro findings. Furthermore, c-Abl/Arg inhibitors have been used in numerous solid tumor clinical trials; however, none of these trials were restricted to patients whose tumors expressed highly activated c-Abl/Arg (targeted trial). Targeted trials are critical for determining whether c-Abl/Arg inhibitors can be effective treatment options for patients whose tumors are driven by c-Abl/Arg.