Patterns of Clinical Progression in Radiorecurrent High-risk Prostate Cancer

The Proteogenomics of Prostate Cancer Radioresistance

Prostate cancer is frequently treated with radiotherapy. Unfortunately, aggressive radioresistant relapses can arise, and the molecular underpinnings of radioresistance are unknown. Modern clinical radiotherapy is evolving to deliver higher doses of radiation in fewer fractions (hypofractionation). We therefore analyzed genomic, transcriptomic, and proteomic data to characterize prostate cancer radioresistance in cells treated with both conventionally fractionated and hypofractionated radiotherapy. Independent of fractionation schedule, resistance to radiotherapy involved massive genomic instability and abrogation of DNA mismatch repair. Specific prostate cancer driver genes were modulated at the RNA and protein levels, with distinct protein subcellular responses to radiotherapy. Conventional fractionation led to a far more aggressive biomolecular response than hypofractionation. Testing preclinical candidates identified in cell lines, we revealed POLQ (DNA Polymerase Theta) as a radiosensitizer. POLQ-modulated radioresistance in model systems and was predictive of it in large patient cohorts. The molecular response to radiation is highly multimodal and sheds light on prostate cancer lethality.

SIGNIFICANCE

Radiation is standard of care in prostate cancer. Yet, we have little understanding of its failure. We demonstrate a new paradigm that radioresistance is fractionation specific and identified POLQ as a radioresistance modulator.

Targeting PLOD2 suppresses invasion and metastatic potential in radiorecurrent prostate cancer

Background

Metastatic relapse of prostate cancer after radiotherapy is a significant cause of prostate cancer-related morbidity and mortality. PLOD2 is a mediator of invasion and metastasis that we identified as being upregulated in our highly aggressive radiorecurrent prostate cancer cell line.

Methods

Patient dataset analysis was conducted using a variety of prostate cancer cohorts. Prostate cancer cell lines were treated with siRNA, or the drug PX-478 prior to in vitro invasion, migration, or in vivo chick embryo (CAM) extravasation assay. Protein levels were detected by western blot. For RNA analysis, RNA sequencing was conducted on PLOD2 knockdown cells and validated by qRT-PCR.

Results

PLOD2 is a negative prognostic factor associated with biochemical relapse, driving invasion, migration, and extravasation in radiorecurrent prostate cancer. Mechanistically, HIF1α upregulation drives PLOD2 expression in our radiorecurrent prostate cancer cells, which is effectively inhibited by HIF1α inhibitor PX-478 to reduce invasion, migration, and extravasation. Finally, the long non-coding RNA LNCSRLR acts as a promoter of invasion downstream of PLOD2.

Conclusions

Together, our results demonstrate for the first time the role of PLOD2 in radiorecurrent prostate cancer invasiveness, and point towards its potential as a therapeutic target to reduce metastasis and improve survival outcomes in prostate cancer patients.

Potentiating Salvage Radiotherapy in Radiorecurrent Prostate Cancer Through Anti-CTLA4 Therapy: Implications from a Syngeneic Model

High-risk prostate cancer (PCa) is a leading cause in cancer death and can elicit significant morbidity and mortality. Currently, the salvage of local disease recurrence after radiation therapy (RT) is a major clinical problem. Immune checkpoint inhibitors (ICIs), which enhance immune activation, have demonstrated clinical therapeutic promise in combination with ionizing radiation (IR) in certain advanced cancers. We generated the TRAMP-C2 HF radiorecurrent syngeneic mouse model to evaluate the therapeutic efficacy of ICIs in combination with RT. The administration of anti-PDL1 and/or anti-CTLA4 did not achieve a significant tumor growth delay compared to the control. The combination of IR and anti-PDL1 did not yield additional a growth delay compared to IR and the isotype control. Strikingly, a significant tumor growth delay and complete cure in one-third of the mice were seen with the combination of IR and anti-CTLA4. Immune cells in tumor-draining lymph nodes and tumor-infiltrating lymphocytes from mice treated with IR and anti-CTLA4 demonstrated an upregulation of genes in T-cell functions and enrichment in both CD4+ and CD8+ T-cell populations compared to mice given IR and the isotype control. Taken together, these results indicate enhancement of T-cell response in radiorecurrent PCa by IR and anti-CTLA4.

A Systematic Review of the Efficacy and Toxicity of Brachytherapy Boost Combined with External Beam Radiotherapy for Nonmetastatic Prostate Cancer

CONTEXT

The optimum use of brachytherapy (BT) combined with external beam radiotherapy (EBRT) for localised/locally advanced prostate cancer (PCa) remains uncertain.

OBJECTIVE

To perform a systematic review to determine the benefits and harms of EBRT-BT.

EVIDENCE ACQUISITION

Ovid MEDLINE, Embase, and EBM Reviews-Cochrane Central Register of Controlled Trials databases were systematically searched for studies published between January 1, 2000 and June 7, 2022, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. Eligible studies compared low- or high-dose-rate EBRT-BT against EBRT ± androgen deprivation therapy (ADT) and/or radical prostatectomy (RP) ± postoperative radiotherapy (RP ± EBRT). The main outcomes were biochemical progression-free survival (bPFS), severe late genitourinary (GU)/gastrointestinal toxicity, metastasis-free survival (MFS), cancer-specific survival (CSS), and overall survival (OS), at/beyond 5 yr. Risk of bias was assessed and confounding assessment was performed. A meta-analysis was performed for randomised controlled trials (RCTs).

EVIDENCE SYNTHESIS

Seventy-three studies were included (two RCTs, seven prospective studies, and 64 retrospective studies). Most studies included participants with intermediate-or high-risk PCa. Most studies, including both RCTs, used ADT with EBRT-BT. Generally, EBRT-BT was associated with improved bPFS compared with EBRT, but similar MFS, CSS, and OS. A meta-analysis of the two RCTs showed superior bPFS with EBRT-BT (estimated fixed-effect hazard ratio [HR] 0.54 [95% confidence interval {CI} 0.40-0.72], p < 0.001), with absolute improvements in bPFS at 5-6 yr of 4.9-16%. However, no difference was seen for MFS (HR 0.84 [95% CI 0.53-1.28], p = 0.4) or OS (HR 0.87 [95% CI 0.63-1.19], p = 0.4). Fewer studies examined RP ± EBRT. There is an increased risk of severe late GU toxicity, especially with low-dose-rate EBRT-BT, with some evidence of increased prevalence of severe GU toxicity at 5-6 yr of 6.4-7% across the two RCTs.

CONCLUSIONS

EBRT-BT can be considered for unfavourable intermediate/high-risk localised/locally advanced PCa in patients with good urinary function, although the strength of this recommendation based on the European Association of Urology guideline methodology is weak given that it is based on improvements in biochemical control.

PATIENT SUMMARY

We found good evidence that radiotherapy combined with brachytherapy keeps prostate cancer controlled for longer, but it could lead to worse urinary side effects than radiotherapy without brachytherapy, and its impact on cancer spread and patient survival is less clear.

Recurrent Gleason Score 6 Prostate Cancer After Radiotherapy or Ablation: Should We Observe Them All? Results from a Large Multicenter Salvage Radical Prostatectomy Consortium

BACKGROUND

Salvage radical prostatectomy (sRP) yields poor functional outcomes and relatively high complication rates. Gleason score (GS) 6 prostate cancer (PCa) has genetic and clinical features showing little, if not absent, metastatic potential. However, the behavior of GS 6 PCa recurring after previous PCa treatment including radiotherapy and/or ablation has not been investigated.

OBJECTIVE

To evaluate the oncological outcomes of sRP for radio- and/or ablation-recurrent GS 6 PCa.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective data of sRP for recurrent PCa after local nonsurgical treatment were collected from 14 tertiary referral centers from 2000 to 2021.

INTERVENTION

Prostate biopsy before sRP and sRP.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

A survival analysis was performed for pre-sRP biopsy and sRP-proven GS 6. Concordance between PCa at pre-sRP biopsy and sRP histology was assessed.

RESULTS AND LIMITATIONS

We included GS 6 recurrent PCa at pre-sRP biopsy (n = 142) and at sRP (n = 50), as two cohorts. The majority had primary radiotherapy and/or brachytherapy (83.8% of GS 6 patients at pre-sRP biopsy; 78% of GS 6 patients at sRP) and whole-gland treatments (91% biopsy; 85.1% sRP). Biopsy GS 6 10-yr metastasis, cancer-specific survival (CSS), and overall survival (OS) were 79% (95% confidence interval [CI] 61-89%), 98% (95-99%), and 89% (78-95%), respectively. Upgrading at sRP was 69%, 35.5% had a pT3 stage, and 13.4% had positive nodes. The sRP GS 6 10-yr metastasis-free survival, CSS, and OS were 100%, 100%, and 90% (95% CI 58-98%) respectively; pT3 and pN1 disease were found in 12% and 0%, respectively. Overall complications, high-grade complications, and severe incontinence were experienced by >50%, >10%, and >15% of men, respectively (in both the biopsy and the sRP cohorts). Limitations include the retrospective nature of the study and absence of a centralized pathological review.

CONCLUSIONS

GS 6 sRP-proven PCa recurring after nonsurgical primary treatment has almost no metastatic potential, while patients experience relevant morbidity of the procedure. However, a significant proportion of GS 6 cases at pre-sRP biopsy are upgraded at sRP. In the idea not to overtreat, efforts should be made to improve the diagnostic accuracy of pre-sRP biopsy.

PATIENT SUMMARY

We investigated the oncological results of salvage radical prostatectomy for recurrent prostate cancer of Gleason score (GS) 6 category. We found a very low malignant potential of GS 6 confirmed at salvage radical prostatectomy despite surgical complications being relatively high. Nonetheless, biopsy GS 6 was frequently upgraded and had less optimal oncological control. Overtreatment for recurrent GS 6 after nonsurgical first-line treatment should be avoided, and efforts should be made to increase the diagnostic accuracy of biopsies for recurrent disease.

Diagnostic Performance of 68Ga-PSMA-11 PET/CT Versus Multiparametric MRI for Detection of Intraprostatic Radiorecurrent Prostate Cancer

For men with prostate cancer who develop biochemical failure after radiotherapy, European guidelines recommend reimaging with 68Ga-PSMA-11 PET/CT and multiparametric MRI (mpMRI). However, the accuracy of 68Ga-PSMA-11 PET/CT for detecting intraprostatic recurrences is unclear, both with and without mpMRI. Methods: A single-center retrospective study of a series of patients investigated for radiorecurrence between 2016 and 2022 is described. All patients underwent 68Ga-PSMA-11 PET/CT, mpMRI, and prostate biopsy. PET/CT images were interpreted independently by 2 expert readers masked to other imaging and clinical data. The primary outcome was the diagnostic accuracy of PET/CT versus mpMRI and of PET/CT with mpMRI together versus mpMRI alone. The secondary outcome was the proportion of cancers missed by mpMRI but detected by PET/CT. Diagnostic accuracy analysis was performed at the prostate hemigland level using cluster bootstrapping. Results: Thirty-five men (70 hemiglands) were included. Cancer was confirmed by biopsy in 43 of 70 hemiglands (61%). PET/CT sensitivity and negative predictive values (NPVs) were 0.89 (95% CI, 0.78-0.98) and 0.79 (95% CI, 0.62-0.95), respectively, which were not significantly different from results by MRI (sensitivity of 0.72; 95% CI, 0.61-0.83; P = 0.1) (NPV of 0.59; 95% CI, 0.41-0.75; P = 0.07). Specificity and positive predictive values were not significantly different. When PET/CT and MRI were used together, the sensitivity was 0.98 (95% CI, 0.92-1.00) and NPV was 0.93 (95% CI, 0.75-1.00), both significantly higher than MRI alone (P = 0.003 and P < 0.001, respectively). Specificity and positive predictive values remained not significantly different. MRI missed 12 of 43 cancers (28%; 95% CI, 17%-43%), of which 11 of 12 (92%; 95% CI, 62%-100%) were detected by PET/CT. Conclusion: For detecting intraprostatic radiorecurrence, 68Ga-PSMA-11 PET/CT has high sensitivity that is not significantly different from mpMRI. When 68Ga-PSMA-11 PET/CT and mpMRI were used together, the results conferred a significantly greater sensitivity and NPV than with mpMRI alone. 68Ga-PSMA-11 PET/CT may therefore be a useful tool in the diagnosis of localized radiorecurrence.

The Role of Multiparametric MRI and MRI-targeted Biopsy in the Diagnosis of Radiorecurrent Prostate Cancer: An Analysis from the FORECAST Trial

BACKGROUND

The role of multiparametric magnetic resonance imaging (MRI) for detecting recurrent prostate cancer after radiotherapy is unclear.

OBJECTIVE

To evaluate MRI and MRI-targeted biopsies for detecting intraprostatic cancer recurrence and planning for salvage focal ablation.

DESIGN, SETTING, AND PARTICIPANTS

FOcal RECurrent Assessment and Salvage Treatment (FORECAST; NCT01883128) was a prospective cohort diagnostic study that recruited 181 patients with suspected radiorecurrence at six UK centres (2014 to 2018); 144 were included here.

INTERVENTION

All patients underwent MRI with 5 mm transperineal template mapping biopsies; 84 had additional MRI-targeted biopsies. MRI scans with Likert scores of 3 to 5 were deemed suspicious.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

First, the diagnostic accuracy of MRI was calculated. Second, the pathological characteristics of MRI-detected and MRI-undetected tumours were compared using the Wilcoxon rank sum test and chi-square test for trend. Third, four biopsy strategies involving an MRI-targeted biopsy alone and with systematic biopsies of one to two other quadrants were studied. Fisher's exact test was used to compare MRI-targeted biopsy alone with the best other strategy for the number of patients with missed cancer and the number of patients with cancer harbouring additional tumours in unsampled quadrants. Analyses focused primarily on detecting cancer of any grade or length. Last, eligibility for focal therapy was evaluated for men with localised (≤T3bN0M0) radiorecurrent disease.

RESULTS AND LIMITATIONS

Of 144 patients, 111 (77%) had cancer detected on biopsy. MRI sensitivity and specificity at the patient level were 0.95 (95% confidence interval [CI] 0.92 to 0.99) and 0.21 (95% CI 0.07 to 0.35), respectively. At the prostate quadrant level, 258/576 (45%) quadrants had cancer detected on biopsy. Sensitivity and specificity were 0.66 (95% CI 0.59 to 0.73) and 0.54 (95% CI 0.46 to 0.62), respectively. At the quadrant level, compared with MRI-undetected tumours, MRI-detected tumours had longer maximum cancer core length (median difference 3 mm [7 vs 4 mm]; 95% CI 1 to 4 mm, p < 0.001) and a higher grade group (p = 0.002). Of the 84 men who also underwent an MRI-targeted biopsy, 73 (87%) had recurrent cancer diagnosed. Performing an MRI-targeted biopsy alone missed cancer in 5/73 patients (7%; 95% CI 3 to 15%); with additional systematic sampling of the other ipsilateral and contralateral posterior quadrants (strategy 4), 2/73 patients (3%; 95% CI 0 to 10%) would have had cancer missed (difference 4%; 95% CI -3 to 11%, p = 0.4). If an MRI-targeted biopsy alone was performed, 43/73 (59%; 95% CI 47 to 69%) patients with cancer would have harboured undetected additional tumours in unsampled quadrants. This reduced but only to 7/73 patients (10%; 95% CI 4 to 19%) with strategy 4 (difference 49%; 95% CI 36 to 62%, p < 0.0001). Of 73 patients, 43 (59%; 95% CI 47 to 69%) had localised radiorecurrent cancer suitable for a form of focal ablation.

CONCLUSIONS

For patients with recurrent prostate cancer after radiotherapy, MRI and MRI-targeted biopsy, with or without perilesional sampling, will diagnose cancer in the majority where present. MRI-undetected cancers, defined as Likert scores of 1 to 2, were found to be smaller and of lower grade. However, if salvage focal ablation is planned, an MRI-targeted biopsy alone is insufficient for prostate mapping; approximately three of five patients with recurrent cancer found on an MRI-targeted biopsy alone harboured further tumours in unsampled quadrants. Systematic sampling of the whole gland should be considered in addition to an MRI-targeted biopsy to capture both MRI-detected and MRI-undetected disease.

PATIENT SUMMARY

After radiotherapy, magnetic resonance imaging (MRI) is accurate for detecting recurrent prostate cancer, with missed cancer being smaller and of lower grade. Targeting a biopsy to suspicious areas on MRI results in a diagnosis of cancer in most patients. However, for every five men who have recurrent cancer, this targeted approach would miss cancers elsewhere in the prostate in three of these men. If further focal treatment of the prostate is planned, random biopsies covering the whole prostate in addition to targeted biopsies should be considered so that tumours are not missed.

Definitions of "Cure" After Low-Dose-Rate Brachytherapy in Low- and Intermediate-Risk Prostate Cancer: Phoenix or Surgical?

Purpose

The aim of this study was to compare a surgical with a Phoenix-derived definition of cure at 4 years after treatment by ¹²⁵J low-dose-rate brachytherapy (LDR-BT) in patients with low- and intermediate-risk prostate cancer.

Methods and Materials

A total of 427 evaluable men with low-risk (62.8%) and intermediate-risk (37.2%) prostate cancer were treated with LDR-BT (160 Gy). Cure was defined at 4 years either as not having experienced a biochemical recurrence by the Phoenix definition, or by a surgical definition, using a posttreatment prostate-specific antigen of ≤0.2 ng/mL. Biochemical recurrence-free survival (BRFS), metastasis-free survival (MFS), and cancer-specific survival were calculated at 5 and 10 years using the Kaplan-Meier method. Standard diagnostic test evaluations were used to compare both definitions with regard to later metastatic failure or cancer-specific death.

Results

At 48 months, 427 patients were evaluable with a Phoenix-defined and 327 with a surgical-defined cure. At 5 and 10 years BRFS was 97.4% and 89% and MFS was 99.5% and 96.3% in the Phoenix-defined cure cohort, and BRFS was 98.2% and 92.7% and MFS was 100% and 99.4% in the surgical-defined cure cohort. Specificity for cure was 100% for both definitions. Sensitivity was 97.4% for the Phoenix and 96.3% for the surgical definition. The positive predictive value was 100% for both, whereas the negative predictive value was 29% for the Phoenix and 7.7% for the surgical definition. Accuracies of a correct prediction of cure were 94.8% and 96.3% for the Phoenix and the surgical definition, respectively.

Conclusions

Both definitions are useful for a reliable assessment of cure after LDR-BT in patients with low-risk and intermediate-risk prostate cancer. Cured patients might follow a less stringent follow-up schedule from 4 years onward, whereas patients not achieving cure at 4 years should be monitored for an extended time.

MRI-guided focal or integrated boost high dose rate brachytherapy for recurrent prostate cancer

Background and purpose

Locally recurrent prostate cancer after radiotherapy merits an effective salvage strategy that mitigates the risk of adverse events. We report outcomes of a cohort enrolled across two institutions investigating MRI-guided tumor-targeted salvage high dose rate brachytherapy (HDR-BT).

Materials and methods

Analysis of a prospective cohort of 88 patients treated across two institutions with MRI-guided salvage HDR-BT to visible local recurrence after radiotherapy (RT). Tumor target dose ranged from 22-26 Gy, using either an integrated boost (ibBT) or focal technique (fBT), delivered in two implants over a median of 7 days. Outcome metrics included cancer control and toxicity (CTCAE). Quality of life (QoL-EPIC) was analyzed in a subset.

Results

At a median follow-up of 35 months (6 -134), 3 and 5-year failure-free survival (FFS) outcomes were 67% and 49%, respectively. At 5 years, fBT was associated with a 17% cumulative incidence of local failure (LF) outside the GTV (vs. 7.8% ibBT, p=0.14), while LF within the GTV occurred in 13% (vs. 16% ibBT, p=0.81). Predictors of LF outside fBT volumes included pre-salvage PSA>7 ng/mL (p=0.03) and interval since RT less than 5 years (p=0.04). No attributable grade 3 events occurred, and ibBT was associated with a higher rate of grade 2 toxicity (p<0.001), and trend towards a larger reduction in QoL sexual domain score (p=0.07), compared to fBT.

Conclusion

A tumor-targeted HDR-BT salvage approach achieved favorable cancer control outcomes. While a fBT was associated with less toxicity, it may be best suited to a subgroup with lower PSA at later recurrence. Tumor targeted dose escalation may be warranted.

Genomic Features of Lung-Recurrent Hormone-Sensitive Prostate Cancer

PURPOSE

Pulmonary involvement is rare in metastatic hormone-sensitive prostate cancer (mHSPC) that recurs after treatment for localized disease. Guidelines recommend intensive systemic therapy, similar to patients with liver metastases, but some lung-recurrent mHSPC may have good outcomes. Genomic features of lung metastases may clarify disease aggression, but are poorly understood since lung biopsy is rarely performed. We present a comparative assessment of genomic drivers and heterogeneity in metachronous prostate tumors and lung metastases.

METHODS

We leveraged a prospective functional imaging study of 208 biochemically recurrent prostate cancers to identify 10 patients with lung-recurrent mHSPC. Histologic diagnosis was attained via thoracic surgery or fine-needle lung biopsy. We retrieved clinical data and performed multiregion sampling of primary tumors and metastases. Targeted and/or whole-exome sequencing was applied to 46 primary and 32 metastatic foci.

RESULTS

Unusually for mHSPC, all patients remained alive despite a median follow-up of 11.5 years. Several patients experienced long-term freedom from systemic treatment. The genomic landscape of lung-recurrent mHSPC was typical of curable prostate cancer with frequent PTEN, SPOP, and chromosome 8p alterations, and there were no deleterious TP53 and DNA damage repair gene mutations that characterize aggressive prostate cancer. Despite a long median time to recurrence (76.8 months), copy number alterations and clonal mutations were highly conserved between metastatic and primary foci, consistent with intrapatient homogeneity and limited genomic evolution.

CONCLUSION

In this retrospective hypothesis-generating study, we observed indolent genomic etiology in selected lung-recurrent mHSPC, cautioning against grouping these patients together with liver or bone-predominant mHSPC. Although our data do not generalize to all patients with lung metastases, the results encourage prospective efforts to stratify lung-recurrent mHSPC by genomic features.

Value of Targeted Biopsies and Combined PSMA PET/CT and mp-MRI Imaging in Locally Recurrent Prostate Cancer after Primary Radiotherapy

Simple Summary

After primary radiotherapy for prostate cancer, patients may develop an isolated local recurrence. The diagnostic workup of these recurrences guides decision making for potential focal salvage treatments. The aim of this study was to determine the positive predictive value (PPV) of combined multiparametric (mp) MRI and prostate specific membrane antigen (PSMA) PET/CT imaging in this setting, with histological conformation using MR-guided targeted biopsies. In 41 patients counseled for focal salvage high dose rate (HDR) brachytherapy, a PPV of 97.6% was found for combined mp-MRI and PSMA PET/CT. Therefore, biopsies can safely be omitted in these patients.

Abstract

Radiorecurrent prostate cancer is conventionally confirmed using systematic and/or targeted biopsies. The availability of multiparametric (mp) MRI and prostate specific membrane antigen (PSMA) PET/CT has increased diagnostic accuracy. The objective was to determine the positive predictive value (PPV) of combined mp-MRI and PSMA PET/CT and whether pathology verification with MR-targeted biopsies remains necessary for patients with radiorecurrent prostate cancer. Patients with locally recurrent prostate cancer who were referred for 19 Gy single-dose MRI-guided focal salvage high dose rate (HDR) brachytherapy between 2015 and 2018 were included in the current analysis. Patients were selected if they underwent pre-biopsy mp-MRI and PSMA PET/CT. Based on these images, lesions suspect for isolated tumor recurrence were transperineally biopsied using transrectal ultrasound fused with MRI. A total of 41 patients were identified from the database who underwent cognitive targeted (n = 7) or MRI/PSMA-transrectal ultrasound (TRUS) fused targeted (n = 34) biopsies. A total of 40 (97.6%) patients had positive biopsies for recurrent cancer. Five patients initially had negative biopsies (all MRI/PSMA-TRUS fusion targeted), four of whom recurrence was confirmed after a re-biopsy. One (2.4%) patient refused re-biopsy, leading to a positive predictive value (PPV) for combined imaging of 97.6%. Biopsies can therefore safely be withheld when the results of the combined mp-MRI and PSMA PET/CT are conclusive, avoiding an unnecessary invasive and burdensome procedure.

Proteomic discovery of non-invasive biomarkers of localized prostate cancer using mass spectrometry

Prostate cancer is the second most frequently diagnosed non-skin cancer in men worldwide. Patient outcomes are remarkably heterogeneous and the best existing clinical prognostic tools such as International Society of Urological Pathology Grade Group, pretreatment serum PSA concentration and T-category, do not accurately predict disease outcome for individual patients. Thus, patients newly diagnosed with prostate cancer are often overtreated or undertreated, reducing quality of life and increasing disease-specific mortality. Biomarkers that can improve the risk stratification of these patients are, therefore, urgently needed. The ideal biomarker in this setting will be non-invasive and affordable, enabling longitudinal evaluation of disease status. Prostatic secretions, urine and blood can be sources of biomarker discovery, validation and clinical implementation, and mass spectrometry can be used to detect and quantify proteins in these fluids. Protein biomarkers currently in use for diagnosis, prognosis and relapse-monitoring of localized prostate cancer in fluids remain centred around PSA and its variants, and opportunities exist for clinically validating novel and complimentary candidate protein biomarkers and deploying them into the clinic.