In prostate (PCa) and colorectal (CRC) cancer, there is a need to improve patient stratification techniques that aid diagnostic and prognostic decision-making. To fulfill this unmet clinical need,... Show moreIn prostate (PCa) and colorectal (CRC) cancer, there is a need to improve patient stratification techniques that aid diagnostic and prognostic decision-making. To fulfill this unmet clinical need, the measurement of disease-related biological parameters known as “biomarkers” from biofluids is an approach with the potential to develop noninvasive tests as well as achieve greater clinical accuracy and personalized medicine. Thus, this thesis focused on developing a better understanding of biomarkers relevant to PCa and CRC as well as advancing analytical methodology and achieving methodological advancements for the purpose of biomarker discovery. In chapters two and three, a large diversity of prostate-specific antigen (PSA) cleaved and non-cleaved proteoforms (PCa) with different N-glycosylation patterns were determined in urine and seminal fluid using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS), some of which are relevant for PCa patient stratification. In addition, the data processing workflow was improved in chapter three in order to enable larger studies of intact proteoforms to be performed. Furthermore, chapter four developed a reversed phase-liquid chromatography (RPLC)-MS method whereby it was possible to determine sialic acid linkages and positional isomers in released N-glycans following fluorescent labeling and sialic acid derivatization. This method was applied in chapter five to study serum N-glycosylation profiles in CRC and it was demonstrated that specific N-glycan isomers are implicated in the disease and differences between histological types were eradicated following surgery. Show less
The relation between prostate-specific antigen (PSA) and other relevant prebiopsy information is often combined in a risk calculator (RC). If the setting for RC use differs from that in which it... Show moreThe relation between prostate-specific antigen (PSA) and other relevant prebiopsy information is often combined in a risk calculator (RC). If the setting for RC use differs from that in which it was developed, there is a risk of making clinical decisions based on incorrect estimates of the absolute risk. The ERSPC-MRI RC predicts clinically significant prostate cancer (csPC; Gleason >= 3 + 4) on targeted and systematic biopsy using information on PSA, digital rectal examination, prostate volume, age, previous negative biopsy, and Prostate Imaging-Recording and Data System score. This calculator was developed on a clinical cohort of 961 men (2012-2017) with a csPC prevalence of 36%. Discrimination was good (area under the receiver operating characteristic curve 0.84). With the increasing use of multiparametric magnetic resonance imaging, we foresee that this RC will also be used for men with a lower a priori likelihood of PC. We investigated the effect of such a scenario on individual risk predictions. A small update of the intercept for the calculator can restore the accuracy to support decision-making with locally valid risk estimates.Patient summary: Decisions on who to refer for a prostate biopsy with its risk of sepsis and overdiagnosis require more than a prostate-specific antigen test. A prediction tool may take other relevant prebiopsy information into account, but may need to be updated to contemporary center-specific settings to provide accurate estimates of the risk of having prostate cancer. (C) 2019 Published by Elsevier B.V. on behalf of European Association of Urology. Show less
Early detection of prostate cancer may lead to the overdiagnosis and overtreatment of patients as well as missing significant cancers. The current diagnostic approach uses elevated serum... Show moreEarly detection of prostate cancer may lead to the overdiagnosis and overtreatment of patients as well as missing significant cancers. The current diagnostic approach uses elevated serum concentrations of prostate-specific antigen (PSA) as an indicator of risk. However, this test has been widely criticized as it shows poor specificity and sensitivity. In order to improve early detection and diagnosis, several studies have investigated whether different PSA proteoforms are correlated to prostate cancer. Until now, studies and methodologies for the comprehensive characterization of PSA proteoforms from biofluids are scarce. For this purpose, we developed an intact protein assay to analyze PSA by capillary electrophoresis-electrospray ionization-mass spectrometry after affinity purification from patients? urine. Here, we determined six proteolytic cleavage variants. In regard to glycosylation, tri-, di-, mono- and non-sialylated complex-type N-glycans were found on non-cleaved PSA, as well as the non-glycosylated variant. The performance of the intact protein assay was assessed using a pooled sample, obtaining an inter-day variability of 15%. Furthermore, urinary patient samples were analyzed by intact protein analysis and a bottom-up approach (glycopeptide analysis). This combined approach revealed complimentary information on both levels, demonstrating the benefit of using two orthogonal techniques to provide a thorough profile of urinary PSA.Significance: The detection of clinically relevant prostate cancer requires a more specific and sensitive biomarker and, in this case, several PSA proteoforms may be able to aid or improve the current PSA test. However, a comprehensive analysis of the intact PSA proteoform profile is still lacking. This study investigated the PSA proteoforms present in urine and, in particular, determined the relative contribution of cleaved PSA and noncleaved PSA forms to the total glycosylation profile. Importantly, intact protein analysis did not require further sample treatment before being measured by CE-ESI-MS. Furthermore, its glycosylation was also assessed in a bottom-up approach to provide complementary information. Overall, these results represent an important basis for future characterization and biomarker studies. Show less
Background: Since the introduction of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging, isolated local recurrence after radical prostatectomy (RP) can be... Show moreBackground: Since the introduction of prostate-specific membrane antigen (PSMA) positron emission tomography (PET) imaging, isolated local recurrence after radical prostatectomy (RP) can be delineated accurately.Objective: To describe and evaluate surgical technique, biochemical response, and therapy-free survival (TFS) after salvage surgery in patients with local recurrence in the seminal vesicle bed.Design, setting, and participants: We retrospectively assessed 40 patients treated with open salvage surgery in two centres (11/2014-02/2020). All patients presented with biochemical recurrence (BCR) after RP with a singular local recurrence at PSMA PET imaging. Thirty-three (82.5%) patients received previous salvage radiation therapy.Surgical procedure: Open salvage surgery with PSMA radioguidance.Measurements: Prostate-specific antigen (PSA) nadir and percentage of patients with complete biochemical response (cBR) without further treatment (PSA < 0.2 ng/ml) after 6-16 wk were assessed. BCR-free survival and TFS were calculated using Kaplan-Meier estimates. Clavien-Dindo complications were evaluated.Results and limitations: Prior to salvage surgery, median PSA was 0.9 ng/ml (interquartile range [IQR]: 0.5-1.7 ng/ml). Postoperatively, median PSA nadir was 0.1 ng/ml (IQR: 0-0.4 ng/ml). In 31 (77.5%) patients, cBR was observed. During the median follow-up of 24.4 months, 22 (55.0%) patients experienced BCR and 12 (30.0%) received further therapy. At 1 yr of follow-up, BCR-free survival rate was 62.2% and TFS rate was 88.3%. Three (7.5%) Clavien-Dindo grade III complications were observed. The main limitations are the retrospective design, short follow-up, and lack of a control group.Conclusions: Salvage surgery of local recurrence within the seminal vesicle bed is feasible. It may present an opportunity in selected, locally recurrent patients to prolong BCR-free survival and increase TFS. Further studies are needed to confirm our findings.Patient summary: We looked at the outcomes from prostate cancer patients with locally recurrent disease after radical prostatectomy and radiotherapy. We found that surgery in well-selected patients may be an opportunity to prolong treatment-free survival. (C) 2020 European Association of Urology. Published by Elsevier B.V. All rights reserved. Show less
Cremers, R.; Asperen, C. van; Kil, P.; Vasen, H.; Wiersma, T.; Oort, I. van; Kiemeney, L. 2012
