PSA, an outdated biomarker for prostate cancer: In search of a more specific biomarker, citrate takes the spotlight

The prevailing biomarker employed for prostate cancer (PCa) screening and diagnosis is the prostate-specific antigen (PSA). Despite excellent sensitivity, PSA lacks specificity, leading to false positives, unnecessary biopsies and overdiagnosis. Consequently, PSA is increasingly less used by clinicians, thus underscoring the imperative for the identification of new biomarkers. An emerging biomarker in this context is citrate, a molecule secreted by the normal prostate, which has been shown to be inversely correlated with PCa. Here, we discuss about PSA and its usage for PCa diagnosis, its lack of specificity, and the various conditions that can affect its levels. We then provide our vision about what we think would be a valuable addition to our PCa diagnosis toolkit, citrate. We describe the unique citrate metabolic program in the prostate and how this profile is reprogrammed during carcinogenesis. Finally, we summarize the evidence that supports the usage of citrate as a biomarker for PCa diagnosis, as it can be measured in various patient samples and be analyzed by several methods. The unique relationship between citrate and PCa, combined with the stability of citrate levels in other prostate-related conditions and the simplicity of its detection, further accentuates its potential as a biomarker.

Incidence profile of four major cancers among migrants in Australia, 2005-2014

PURPOSE

To compare the incidence profile of four major cancers in Australia by place of birth.

METHODS

In this retrospective population-based cohort study, the analysis included 548,851 residents diagnosed with primary colorectum, lung, female breast, or prostate cancer during 2005-2014. Incidence rate ratio (IRR) and 95% confidence intervals (CI) were calculated for migrant groups relative to Australian-born.

RESULTS

Compared with Australian-born residents, most migrant groups had significantly lower incidence rates for cancers of the colorectum, breast and prostate. The lowest rates of colorectal cancer were among males born in Central America (IRR = 0.46, 95% CI 0.29-0.74) and females born in Central Asia (IRR = 0.38, 95% CI 0.23-0.64). Males born in North-East Asia had the lowest rates of prostate cancer (IRR = 0.40, 95% CI 0.38-0.43) and females born in Central Asia had the lowest rates of breast cancer (IRR = 0.55, 95% CI 0.43-0.70). For lung cancer, several migrant groups had higher rates than Australian-born residents, with the highest rates among those from Melanesia (males IRR = 1.39, 95% CI 1.10-1.76; females IRR = 1.40, 95% CI 1.10-1.78).

CONCLUSIONS

This study describes cancer patterns among Australian migrants, which are potentially helpful in understanding the etiology of these cancers and guiding the implementation of culturally sensitive and safe prevention measures. The lower incidence rates observed for most migrant groups may be maintained with continued emphasis on supporting communities to minimize modifiable risk factors such as smoking and alcohol consumption and participation in organized cancer screening programmes. Additionally, culturally sensitive tobacco control measures should be targeted to migrant communities with high lung cancer incidence rates.

Understanding the diagnosis of prostate cancer

Prostate cancer continues to be the most commonly diagnosed cancer, and the second leading cause of cancer death among Australian men. Prostate-specific antigen testing is personalised (not dichotomous in nature) and its interpretation should take into account the patient's age, symptoms, previous results and medication (eg, 5-α reductase inhibitors such as dutasteride). Multiparametric magnetic resonance imaging of the prostate has been proven to have a 93% sensitivity for detecting clinically significant prostate cancer. It has the potential to decrease unnecessary prostate biopsies by around 27%. International Society of Urological Pathology (ISUP) grade 1 (Gleason score 6) has been shown to have very little, if any, risk of metastasis ISUP grade 1 (Gleason score 3 +3 = 6) and low percentage ISUP grade 2 (Gleason score 3 + 4 [< 10%] = 7) can be offered active surveillance. The goal of active surveillance is to defer treatment but is still curative when required. With better imaging (magnetic resonance imaging and emerging prostate-specific membrane antigen positron emission tomography-computed tomography) and transperineal prostate biopsy, more men can be offered screening after discussion of risks and benefits, knowing that overdiagnosis has been minimised and radical treatment is reserved for only the most aggressive disease.

Untangling the association between prostate-specific antigen and diabetes: a systematic review and meta-analysis

Objectives

Several studies have shown an inverse association between diabetes mellitus and prostate cancer (PCa). Some researchers suggest that this relationship is due to reduced PCa detection in diabetics due to lower prostate-specific antigen (PSA) levels compared to non-diabetics. Our objective is to analyze the impact of diabetes on PSA in asymptomatic men without known prostate pathology and without prior prostate intervention.

Methods

We searched Medline (via PubMed), Embase and Scopus. We included studies that reported the relationship between serum PSA levels and diabetes or diabetes treatment in asymptomatic adult men without known prostate pathology, and without prior prostate intervention. Pooled mean differences were compared between diabetics and non-diabetics.

Results

Of 2,392 screened abstracts, thirteen studies met the inclusion criteria and 8 (62%) reported appropriate measures that could be included in a meta-analysis. Eleven (85%) examined the influence of diabetes on PSA levels and 8 (62%) evaluated the influence of diabetes treatments on PSA levels. Overall diabetics had a significantly lower PSA level compared to non-diabetics (mean difference: -0.07 ng/mL; 95% CI -0.10, -0.04).

Conclusions

Diabetes and related factors (such as disease duration, severity and treatment) were significantly associated with lower PSA levels among asymptomatic men, yet differences were small and are unlikely to influence PCa detection in a screening setting.

Age-specific reference ranges of prostate-specific antigen in the elderly of Amirkola: A population-based study

Objective

To determine the age-specific reference ranges of prostate-specific antigen (PSA) in the older men in the city of Amirkola.

Methods

This cross-sectional study is a part of Amirkola Health and Ageing Project (AHAP) which has been conducted as a cohort study since 2011 in Amirkola, a city in northern Iran. The demographic information of all men aged 60 and older were collected through questionnaires and interviews and the PSA measurements were performed using ELISA and Diametra kit. The acquired data were analyzed afterwards.

Results

A number of 837 elderly men with a mean age of 69.99±7.72 years participated in this study. The serum PSA level (95th percentile) was determined to be 0.9 (0–4.89) ng/mL in the age group of 60–64 years, 1.1 (0–4.88) ng/mL in the age group of 65–69 years, 0.93 (0–9.01) ng/mL in the age group of 70–74 years, 1.3 (0–7.95) ng/mL in the age group of 75–79 years, 1.9 (0–11.98 ng/mL) in the age group of 80–84 years, and 1.45 (0–33.17) ng/mL in the 85 and older group. The serum PSA level was significantly correlated with age (p=0.000).

Conclusion

This study indicated that there is a direct correlation between the age and serum PSA levels. The use of age-specific reference range could guide clinicians on the incidence of prostate cancer in this population and perhaps reduce the number of unnecessary tests in this population group.

Survival outcomes in elderly men undergoing radical prostatectomy in Australia

BACKGROUND

To investigate the outcomes of patients older than 75 years of age in Victoria undergoing radical prostatectomy for prostate cancer.

METHODS

Data on all men undergoing radical prostatectomy in Victoria between 1 January 2004 and 31 December 2014 were obtained from the Victorian Cancer Registry. Tumour characteristics including Gleason grade, stage of disease and cause of death were obtained. Statistical analysis was performed using chi-squared test, Cox proportional hazards method and Kaplan-Meier analysis.

RESULTS

A total of 14 686 men underwent radical prostatectomy during the defined period, with a median follow-up of 58 months. Of these, 332 were men over the age of 75. All parameters are comparisons between patients >75 years of age and men <75 years of age. Men >75 years had a higher proportion of Gleason grade ≥8 disease (16.6% versus 11.4%, P < 0.001) but had similar stage of disease. Men >75 years had lower rates of 5- and 10-year overall survival (67.3% versus 96.3% and 27.7% versus 89.1%) and lower rates of 5- and 10-year prostate cancer-specific survival (96.2% versus 99.3% and 94.3% versus 97.4%), respectively. Age was an independent risk factor for prostate cancer specific and overall mortality on multivariate analysis (hazard ratio 1.49, 95% confidence interval 1.32-1.68; P < 0.001 and hazard ratio 4.26, 95% confidence interval 2.15-8.42; P < 0.001), when adjusted for stage and grade.

CONCLUSION

Older men undergoing radical prostatectomy in Victoria had higher-grade disease but similar stage. Age was an independent risk factor for worse prostate cancer-specific and overall survival.

Enhanced Detection of Cancer Biomarkers in Blood-Borne Extracellular Vesicles Using Nanodroplets and Focused Ultrasound

The feasibility of personalized medicine approaches will be greatly improved by the development of noninvasive methods to interrogate tumor biology. Extracellular vesicles shed by solid tumors into the bloodstream have been under recent investigation as a source of tumor-derived biomarkers such as proteins and nucleic acids. We report here an approach using submicrometer perfluorobutane nanodroplets and focused ultrasound to enhance the release of extracellular vesicles from specific locations in tumors into the blood. The released extracellular vesicles were enumerated and characterized using micro flow cytometry. Only in the presence of nanodroplets could ultrasound release appreciable levels of tumor-derived vesicles into the blood. Sonication of HT1080-GFP tumors did not increase the number of circulating tumor cells or the metastatic burden in the tumor-bearing embryos. A variety of biological molecules were successfully detected in tumor-derived extracellular vesicles, including cancer-associated proteins, mRNAs, and miRNAs. Sonication of xenograft HT1080 fibrosarcoma tumors released extracellular vesicles that contained detectable RAC1 mRNA with the highly tumorigenic N92I mutation known to exist in HT1080 cells. Deep sequencing serum samples of embryos with sonicated tumors allowed the identification of an additional 13 known heterozygous mutations in HT1080 cells. Applying ultrasound to HT1080 tumors increased tumor-derived DNA in the serum by two orders of magnitude. This work is the first demonstration of enhanced extracellular vesicle release by ultrasound stimulation and suggests that nanodroplets/ultrasound offers promise for genetic profiling of tumor phenotype and aggressiveness by stimulating the release of extracellular vesicles. Cancer Res; 77(1); 3-13. ©2016 AACR.

Australian patterns of prostate cancer care: Are they evolving?

Background

Approaches to prostate cancer (PCa) care have changed in recent years out of concern for overdiagnosis and overtreatment. Despite these changes, many patients continue to undergo some form of curative treatment and with a growing perception among multidisciplinary clinicians that more aggressive treatments are being favored. This study examines patterns of PCa care in Australia, focusing on current rates of screening and aggressive interventions that consist of high-dose-rate (HDR) brachytherapy and pelvic lymph node dissection (PLND).

Methods

Health services data were used to assess Australian men undergoing PCa screening and treatment from 2001 to 2014. Age-specific rates of prostate-specific antigen (PSA) screening were calculated. Ratios of radical prostatectomy (RP) with PLND to RP without PLND, and HDR brachytherapy to low-dose-rate (LDR) brachytherapy were determined by state jurisdictions.

Results

From 2008, the rate of PSA screening trended downward significantly with year for all age ranges (P < 0.02) except men aged ≥ 85 (P = 0.56). PLND rates for 2008–2014 were lower than rates for 2001–2007 across all states and territories. From 2008 to 2014, PLND was performed ≥ 2.7 times more frequently in New South Wales and the Australian Capital Territory than in other jurisdictions. Since 2007, brachytherapy practice across Australia has evolved towards a relatively low use of HDR brachytherapy (ratio of HDR to LDR brachytherapy < 0.5 for all jurisdictions except the Australian Capital Territory).

Conclusion

Rates of PLND and HDR brachytherapy for PCa have declined in Australia, providing evidence for the effect of stage migration due to widespread PSA screening. Currently, PSA screening rates remain high among older men, which may expose them to unnecessary investigations and treatment-related morbidity.

Prostate cancer screening in Primary Health Care: the current state of affairs

This study aims to examine the current practice of General practitioners (GPs)/primary care physicians in opportunistic screening for prostate cancer (PC) by digital rectal examination(DRE) and Prostate Specific Antigen(PSA) testing and identify any difference in screening practice. Printed copies and/or electronic versions of a survey was distributed amongst 438 GPs throughout Australia in 2012. Statistical analyses (Wilcoxon rank-sum test, Fisher's exact test or Pearson chi-square test)were performed by outcomes and GP characteristics.There were a total of 149 responses received (34%), with similar gender distribution in rural and metropolitan settings. 74% GPs believed PSA testing was at least 'somewhat effective' in reducing PC mortality with annual PSA screening being conducted by more GPs in the metropolitan setting compared to the rural GPs (35% vs 18.4%), while 25% of rural GPs would not advocate routine PSA screening. When examining the concordance between DRE and PSA testing by gender of GP, the male GPs reported performing PSA testing more frequently than DRE in patients between ages 40 to 69 (p = 0.011). Urology Society guidelines (77.2%) and College of GPs (73.2%) recommendations for PC screening were thought to be at least 'somewhat useful'. Although reference ranges for PSA tests were felt to be useful, the majority (65.8%) found it easier to refer to an urologist due to the disagreements in guidelines. In conclusion, the current guidelines for PSA screening appear to cause more confusion due to their conflicting advice, leaving GPs to formulate their own practice methods, calling for an urgent need for uniform collaborative guidelines.

Prostate cancer: measuring PSA

Population screening with prostate-specific antigen (PSA) for detection of prostate cancer is a topic associated with ongoing dissent and confusion within the oncology and wider medical community. The PSA blood test has been used in various stages of prostate cancer management, including screening and the assessment of future risk of prostate cancer development, detection of recurrent disease after local therapy and in the management of advanced disease. However, PSA-based decision-making in prostate cancer has significant shortcomings. This review will summarise the evidence and current recommendations for the use of PSA in detection and management of prostate cancer.

The relationship between solar UV exposure, serum vitamin D levels and serum prostate-specific antigen levels, in men from New South Wales, Australia: the CHAMP study

PURPOSE

We aim to determine the relationship between season, personal solar UV exposure, serum 25(OH)D and 1,25(OH)2D and serum prostate-specific antigen (PSA) levels.

METHODS

Questionnaire data and blood samples were collected at baseline from participants of the Concord Health and Ageing in Men Project (n = 1,705), aged 70 and above. They were grouped as men 'free of prostate disease' for those with no record of having prostate cancer, benign prostatic hyperplasia, or prostatitis and with serum PSA levels below 20 ng/mL, and 'with prostate disease' for those with a record of either of these diseases or with serum PSA levels 20 ng/mL or above. Personal solar UV exposure (sUV) was estimated from recalled hours of outdoor exposure and weighted against ambient solar UV radiation. Sera were analysed to determine levels of PSA, 25(OH)D and 1,25(OH)2D, and analysed using multiple regression, adjusting for age, BMI and region of birth.

RESULTS

The association between sUV and serum PSA levels was conditional upon season (p interaction = 0.04). There was no direct association between serum PSA and 25(OH)D in both groups of men. There was a positive association between serum PSA and 1,25(OH)2D in men with prostate disease (mean = 110.6 pmol/L; p heterogeneity = 0.03), but there was no such association in men free of prostate disease (mean = 109.3 pmol/L; p heterogeneity = 0.8).

CONCLUSION

The association between PSA and sUV may only be evident at low solar UV irradiance, and this effect may be independent of serum vitamin D levels.

Population-based analysis of prostate-specific antigen (PSA) screening in younger men (<55 years) in Australia

OBJECTIVE

To analyse the trends in opportunistic PSA screening in Australia, focusing on younger men (<55 years of age), to examine the effects of this screening on transrectal ultrasonography (TRUS)-guided biopsy rates and to determine the nature of prostate cancers (PCas) being detected.

SUBJECTS AND METHODS

All men who received an opportunistic screening PSA test and TRUS-guided biopsy between 2001 and 2008 in Australia were analysed using data from the Australian Cancer registry (Australian Institute of Health and Welfare) and Medicare databases. The Victorian cancer registry was used to obtain Gleason scores. Age-standardized and age-specific rates were calculated, along with the incidence of PCa, and correlated with Gleason scores.

RESULTS

A total 5 174 031 PSA tests detected 128 167 PCas in the period 2001-2008. During this period, PSA testing increased by 146% (a mean of 4629 tests per 100 000 men annually), with 80 and 59% increases in the rates of TRUS-guided biopsy and incidence of PCa, respectively. The highest increases in PSA screening occurred in men <55 years old and up to 1101 men had to be screened to detect one incident case of PCa (0.01%). Screening resulted in two thirds of men aged <55 years receiving a negative TRUS biopsy. There was no correlation with Gleason >7 tumours in patients aged <55 years.

CONCLUSION

Despite the ongoing controversy about the merits of PCa screening, there was an increase in PSA testing, especially in men <55 years old, leading to a modestly higher incidence of PCa in Australia. Overall, PSA screening was associated with high rates of negative TRUS-biopsy and the detection of low/intermediate grade PCa among younger patients.