Matthew K.H. Hong

Tracking the origins and drivers of subclonal metastatic expansion in prostate cancer

Tumour heterogeneity in primary prostate cancer is a well-established phenomenon. However, how the subclonal diversity of tumours changes during metastasis and progression to lethality is poorly understood. Here we reveal the precise direction of metastatic spread across four lethal prostate cancer patients using whole-genome and ultra-deep targeted sequencing of longitudinally collected primary and metastatic tumours. We find one case of metastatic spread to the surgical bed causing local recurrence, and another case of cross-metastatic site seeding combining with dynamic remoulding of subclonal mixtures in response to therapy. By ultra-deep sequencing end-stage blood, we detect both metastatic and primary tumour clones, even years after removal of the prostate. Analysis of mutations associated with metastasis reveals an enrichment of TP53 mutations, and additional sequencing of metastases from 19 patients demonstrates that acquisition of TP53 mutations is linked with the expansion of subclones with metastatic potential which we can detect in the blood.

Upgrade in Gleason score between prostate biopsies and pathology following radical prostatectomy significantly impacts upon the risk of biochemical recurrence

Study Type – Prognosis (retrospective cohort)

Reducing the risk of false discovery enabling identification of biologically significant genome-wide methylation status using the HumanMethylation450 array

BackgroundThe Illumina HumanMethylation450 BeadChip (HM450K) measures the DNA methylation of 485,512 CpGs in the human genome. The technology relies on hybridization of genomic fragments to probes on the chip. However, certain genomic factors may compromise the ability to measure methylation using the array such as single nucleotide polymorphisms (SNPs), small insertions and deletions (INDELs), repetitive DNA, and regions with reduced genomic complexity. Currently, there is no clear method or pipeline for determining which of the probes on the HM450K bead array should be retained for subsequent analysis in light of these issues.ResultsWe comprehensively assessed the effects of SNPs, INDELs, repeats and bisulfite induced reduced genomic complexity by comparing HM450K bead array results with whole genome bisulfite sequencing. We determined which CpG probes provided accurate or noisy signals. From this, we derived a set of high-quality probes that provide unadulterated measurements of DNA methylation.ConclusionsOur method significantly reduces the risk of false discoveries when using the HM450K bead array, while maximising the power of the array to detect methylation status genome-wide. Additionally, we demonstrate the utility of our method through extraction of biologically relevant epigenetic changes in prostate cancer.

Underestimation of Gleason score at prostate biopsy reflects sampling error in lower volume tumours.

Study Type – Diagnostic (case series)

The ability of prostate-specific antigen (PSA) density to predict an upgrade in Gleason score between initial prostate biopsy and prostatectomy diminishes with increasing tumour grade due to reduced PSA secretion per unit tumour volume.

Study Type – Diagnostic (exploratory cohort)

Positive surgical margins are a risk factor for significant biochemical recurrence only in intermediate‐risk disease

Study Type – Therapy (case series)

Prostate tumour volume is an independent predictor of early biochemical recurrence in a high risk radical prostatectomy subgroup

Aims: To assess if accurately determined tumour volume variables could serve as independent predictors of early biochemical recurrence in high risk prostate cancer patients who underwent radical prostatectomy. Methods: Tumour volume variables were calculated by digital planimetry in 269 prostatectomy specimens of patients with high risk prostate cancer. The associations to biochemical progression of tumour volume and clinicopathological variables, including age, pre-operative prostate specific antigen (PSA) levels, final Gleason score, pathological T stage, and surgical margins, were examined using univariate and multivariate Cox proportional hazards analyses. Results: Median tumour volume was 3.7 ml [interquartile range (IQR) 2.1–6.1 mL] and median follow-up time was 12 months (IQR 6–24 months). Biochemical recurrence occurred in 64 men (24%) during this period, with a median time to recurrence of 7.5 months (IQR 3.0–15.5 months). On univariate analysis all of the tumour volume variables were strongly correlated with the clinicopathological variables, as well as biochemical recurrence (p < 0.001). On multivariate analysis, we found that tumour volume variables served as independent predictors of PSA progression whilst other routinely reported pathological variables did not. Conclusion: Accurately assessing tumour volume in the high risk setting may aid in identifying patients at greatest risk of developing early biochemical recurrence and most in need of adjuvant therapy.

Paraneoplastic syndromes in prostate cancer.

Prostate cancer is the second most common urological malignancy to be associated with paraneoplastic syndromes after renal cell carcinoma. These syndromes tend to occur in the setting of late stage and aggressive tumors with poor overall outcomes. Recognition of these syndromes is clinically important as it might lead to the detection of underlying malignancy and impact on the treatment options available. The literature features around 100 cases of paraneoplastic syndromes associated with prostate cancer and these include endocrine manifestations, neurological entities, dermatological conditions, and other syndromes. Over 70% of cases document the syndrome as the initial clinical manifestation of prostate cancer, while in just under 20% the syndrome was an initial sign of disease progression to the castrate-resistant state. The vast majority of cases involved advanced metastatic malignancy. The syndromes generally resolve upon institution of treatment for the underlying prostate cancer, but some syndromes require specific therapies. Some syndromes are associated with serum markers that are readily detectable and demonstration of these putative markers within prostate cancer tissue at an individual level would firmly link the paraneoplastic syndrome with its underlying prostatic malignancy. The causes of paraneoplastic syndromes in prostate cancer are incompletely understood, and further research into their biology might shed more light on the complex molecular mechanisms that underpin prostate cancer and its lethal potential.

Haemostasis in neurosurgery: What is the evidence for gelatin-thrombin matrix sealant?

Strict intra-operative haemostasis is essential in the practice of neurosurgery. Over the last century, haemostatic methods have advanced significantly and the modern surgeon is now faced with an array of haemostatic agents, each with subtly different qualities and proven in different contexts with various levels of evidence. The popularity of endoscopic and laparoscopic procedures in other surgical specialties has encouraged the introduction of novel agents to achieve haemostasis where conventional methods have proven difficult. These agents are beginning to find a role in routine use for surgery in both the elective and emergent settings. This article reviews the mechanisms of different haemostasis methods and the current evidence for their use in neurosurgery, with a focus on the more recently introduced gelatin-thrombin matrix sealant (Floseal [Baxter, Hayward, CA, USA]).

Curated microRNAs in urine and blood fail to validate as predictive biomarkers for high-risk prostate cancer.

Purpose The purpose of this study was to determine if microRNA profiling of urine and plasma at radical prostatectomy can distinguish potentially lethal from indolent prostate cancer. Materials and Methods A panel of microRNAs was profiled in the plasma of 70 patients and the urine of 33 patients collected prior to radical prostatectomy. Expression of microRNAs was correlated to the clinical endpoints at a follow-up time of 3.9 years to identify microRNAs that may predict clinical response after radical prostatectomy. A machine learning approach was applied to test the predictive ability of all microRNAs profiled in urine, plasma, and a combination of both, and global performance assessed using the area under the receiver operator characteristic curve (AUC). Validation of urinary expression of miRNAs was performed on a further independent cohort of 36 patients. Results The best predictor in plasma using eight miRs yielded only moderate predictive performance (AUC = 0.62). The best predictor of high-risk disease was achieved using miR-16, miR-21 and miR-222 measured in urine (AUC = 0.75). This combination of three microRNAs in urine was a better predictor of high-risk disease than any individual microRNA. Using a different methodology we found that this set of miRNAs was unable to predict high-volume, high-grade disease. Conclusions Our initial findings suggested that plasma and urinary profiling of microRNAs at radical prostatectomy may allow prognostication of prostate cancer behaviour. However we found that the microRNA expression signature failed to validate in an independent cohort of patients using a different platform for PCR. This highlights the need for independent validation patient cohorts and suggests that urinary microRNA signatures at radical prostatectomy may not be a robust way to predict the course of clinical disease after definitive treatment for prostate cancer.