Prediagnostic genetic stratification for aggressive prostate cancer—is the puzzle for genetic variants gaining shape?

Introduction

Population-based screening for prostate cancer (PCa) using prostate-specific antigen (PSA) has shown to reduce the cancer-specific mortality but was associated with a high rate of overdiagnosis (1). The reason for this is the high prevalence of PCa (2). Thus, 27 men had to be diagnosed with PCa in order to prevent 1 PCa-specific death in the cited mass screening trial. It is important to recognize, that the mentioned screening study was a population-based trial (= every eligible participant providing consent was tested). There was no risk-stratification intended prior to PSA-testing. A PSA cut-off was the only trigger for biopsy irrespective of risk factors. In addition, conditions increasing the PSA-value such as benign prostate enlargement were not considered in the study protocol. The value of PSA screening is higher among individuals defined by particular characteristics, such as family history of PCa, ethnicity, increasing age, or genetic factors. Therefore, a prediagnostic information on the future risk for aggressive PCa might be of important clinical value in order to stratify individuals at risk. In an attempt to categorize men according to their future risk profile, efforts have been made including baseline PSA-values at younger age (3), family history (4) and single nucleotide polymorphism in the kallikrein 6 region (since PSA is a member of the kallikrein-family) (5).

Recently, a new study was published in the British Medical Journal. The authors aimed to identify men who might be at risk for PCa development and therefore would be candidates for a more focused (and earlier) PCa screening. More than 200,000 single nucleotide polymorphism (SNP) were analyzed in a development set by performing a stepwise regression framework in order to calculate the individual genetic risk. This yielded 54 SNP that were incorporated in a risk model. Clinical data was obtained from 31,747 men of the international “Prostate Cancer Association Group to Investigate Cancer Associated Alterations in the Genome” (PRACTICAL), which is a collaborative group of researchers investigating the inherited risk of PCa. Aggressive PCa was defined as Gleason Score ≥7, cT3/cT4 disease, PSA ≥10 ng/mL or cN1/cM1-disease). Finally, the model was tested in a validation set of 6,411 men from the ProtecT-Study (6) [1,583 men with an PCa, 632 with aggressive PCa, 220 with very aggressive PCa all diagnosed by transrectal ultrasound biopsy (TRUS) and 4,828 controls]. ProtecT assigned 1,643 men with localized PCa to active monitoring, surgery or radiation therapy. The authors conclude that the “polygenic hazard scores can be used for personalized genetic risk estimates that can predict for age at onset for aggressive PCa”. Any effort to minimize overdiagnosis should be welcomed with open arms. However, a few questions remain:

Is the polygenic hazard scores safe? Does it reduce the unnecessary biopsy? Does is help preventing overdiagnosis? And finally: Does the polygenic hazard scores reduce PCa-specific mortality? Any combination variants might be used for risk prediction in order to improve screening for lethal disease. However, although there is a plethora of research on SNP`s for aggressive cancer (7-10), the puzzle for genetic variants is still not gaining shape for clinical purposes.

Conclusions

The variable clinical course of aggressive PCa makes the risk prediction difficult. “Proceed with caution!” (11) or in other words “publish these data with care” is one of the dictums standing for the current scientific situation. It is debatable, whether adding more SNPs will help preventing unnecessary biopsies, overdiagnosis or even death from PCa in the future.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned and reviewed by the Section Editor Peng Zhang (Department of Urology, Zhongnan Hospital of Wuhan University, Wuhan, China).

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/tcr.2018.07.05). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Schroder FH, Hugosson J, Roobol MJ, et al. Screening and prostate cancer mortality: results of the European Randomised Study of Screening for Prostate Cancer (ERSPC) at 13 years of follow-up. Lancet 2014;384:2027-35. [Crossref] [PubMed]
2. Jahn JL, Giovannucci EL, Stampfer MJ. The high prevalence of undiagnosed prostate cancer at autopsy: implications for epidemiology and treatment of prostate cancer in the Prostate-specific Antigen-era. Int J Cancer 2015;137:2795-802. [Crossref] [PubMed]
3. Vickers AJ, Ulmert D, Sjoberg DD, et al. Strategy for detection of prostate cancer based on relation between prostate specific antigen at age 40-55 and long term risk of metastasis: case-control study. BMJ 2013;346:f2023. [Crossref] [PubMed]
4. Randazzo M, Muller A, Carlsson S, et al. A positive family history as a risk factor for prostate cancer in a population-based study with organised prostate-specific antigen screening: results of the Swiss European Randomised Study of Screening for Prostate Cancer (ERSPC, Aarau). BJU Int 2016;117:576-83. [Crossref] [PubMed]
5. Briollais L, Ozcelik H, Xu J, et al. Germline Mutations in the Kallikrein 6 Region and Predisposition for Aggressive Prostate Cancer. J Natl Cancer Inst 2017;109: [Crossref] [PubMed]
6. Hamdy FC, Donovan JL, Lane JA, et al. 10-Year Outcomes after Monitoring, Surgery, or Radiotherapy for Localized Prostate Cancer. N Engl J Med 2016;375:1415-24. [Crossref] [PubMed]
7. Zheng SL, Sun J, Wiklund F, et al. Cumulative association of five genetic variants with prostate cancer. N Engl J Med 2008;358:910-9. [Crossref] [PubMed]
8. Zhang P, Xia JH, Zhu J, et al. High-throughput screening of prostate cancer risk loci by single nucleotide polymorphisms sequencing. Nat Commun 2018;9:2022. [Crossref] [PubMed]
9. Van den Broeck T, Joniau S, Clinckemalie L, et al. The role of single nucleotide polymorphisms in predicting prostate cancer risk and therapeutic decision making. Biomed Res Int 2014;2014:627510 [Crossref] [PubMed]
10. Thibodeau SN, French AJ, McDonnell SK, et al. Identification of candidate genes for prostate cancer-risk SNPs utilizing a normal prostate tissue eQTL data set. Nat Commun 2015;6:8653. [Crossref] [PubMed]
11. Tosoian JJ, Antonarakis ES. Molecular heterogeneity of localized prostate cancer: more different than alike. Transl Cancer Res 2017;6:S47-50. [Crossref] [PubMed]