








































This is an open access article under the terms of a license that permits non-commercial use, provided the original work is properly cited.  
© 2023 The Authors. Société Internationale d'Urologie Journal, published by the Société Internationale d'Urologie, Canada.

SIUJ  •  Volume 4, Number 4  •  July 2023 SIUJ.ORG

Key Words Competing Interests Article Information

ctDNA, cfDNA, plasma, GU tumors,  
liquid biopsy

None declared. Received on November 23, 2022 
Accepted on April 26, 2023 
This article has been peer reviewed.

Soc Int Urol J. 2023;4(4):338–340

DOI: 10.48083/XTTP6351

In non-muscle-invasive bladder cancer, ctDNA from 
plasma was reported to predict disease recurrence, 
with a high concordance of somatic variants with 
tumor DNA[7]. Molecular profiling of prostate cancer 
using urine and blood revealed a significant associa-
tion between mutation allele frequencies in plasma and 
patients with metastatic prostate cancer[8]. Addition-
ally, while urine exhibited more mutations compared 
to blood, the number of mutations was not found to be 
associated with clinical characteristics of prostate cancer 
patients. However, studies have shown that urine cfDNA 
may be a better source than plasma for early detection  
of and predicting treatment response in bladder cancer 
[9–11]. In patients with bladder cancer, urinary ctDNA 
exhibited a high concordance rate with tumor DNA 
compared to plasma ctDNA[12], highlighting the impor-
tance of urine as a surrogate source of ctDNA for diag-
nosis, disease monitoring, and personalized medicine.

The major challenges associated with using liquid 
biopsies for ctDNA detection include gaps in technology 
development, issues with clinical research methodolo-
gies, and the optimal integration into the clinical work-
flow[13]. The origin of ctDNA circulating in biofluids 
can vary across tissue sources[14], hence, the best source 
of ctDNA for a particular cancer depends heavily on 
the tissue of origin. While plasma has been the most 
universally accessible, extensively studied, and tech-
nologically advanced source for ctDNA detection, the 
challenge for ctDNA detection in plasma is low ctDNA 

Abbreviations 
cfDNA cell-free DNA
ctDNA circulating tumor DNA
GU genitourinary

content (low ctDNA/cf DNA ratio). In recent years, 
urine has shown promising results over plasma as a 
major source of ctDNA for diagnosis and monitoring of 
some GU cancers, especially bladder cancer. Compared 
to plasma, urine is a completely noninvasive source of 
ctDNA, characterized by ease of sampling, a high ratio 
of ctDNA/cfDNA, and high sensitivity for renal cell and 
urothelial carcinomas due to proximity to the tumors. 
However, large volume requirements of urine pose 
challenges for sample storage. Additionally, ctDNA 
yield may depend on time since the previous void, with 
glomerular filtration potentially limiting transrenal 
ctDNA content[15,16]. Seminal fluid may provide a pros-
tate-specific source of cfDNA for prostate cancer, allow-
ing for noninvasive longitudinal sampling at multiple 
time points. Seminal fluid has demonstrated reduced 
DNAse activity[17] and high DNA concentrations[18]. 
However, collecting seminal fluid can be challenging 
after surgical removal of the key organ and/or during 
ongoing androgen deprivation therapy.

Despite some theoretical benefits, urinary and semi-
nal fluid ctDNA assays are less developed than plas-
ma-based ctDNA alternatives. Challenges associated 
with the clinical application of non-plasma–based 
ctDNA detection include the lack of commercial avail-
ability and difficulties in the standardizing pre-analyt-
ical factors. Overall, plasma remains the more validated 
source for clinical applications of liquid biopsies in most 
GU tumors, although urinary ctDNA assays may substi-
tute for plasma assays in bladder cancer.

Acknowledgments
This work was supported by the National Institute 
of Health [R01CA212097 and R01CA250018 to L.W.] 
and by the H. Lee Moffitt Cancer Center & Research 
Institute.

339SIUJ.ORG SIUJ  •  Volume 4, Number 4  •  July 2023338

Benefits of Plasma Over Other Body Fluids for Circulating Tumor DNA Detection in Genitourinary TumorsPRO AND CON — LIQUID BIOPSY

Benefits of Plasma Over Other Body Fluids  
for Circulating Tumor DNA Detection in  
Genitourinary Tumors

Manishkumar S. Patel, Liang Wang

Department of Tumor Biology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, United States

Liquid biopsies have been established as remarkable alternatives to conventional biopsies because of their numerous 
benefits, including early-stage cancer detection, monitoring disease progression, and predicting treatment response 
and survival through a minimally invasive approach[1]. Cell-free DNA (cfDNA) consists of short DNA fragments 
(peak size = 167 bp) released into the bloodstream or other body fluids after cell apoptosis, carrying genome-wide 
DNA from parent cells. Among cfDNA, circulating tumor DNA (ctDNA) is derived from tumor cells and can be 
analyzed from various sources, including blood, urine, saliva, pleural effusions, and cerebrospinal fluid (CSF). 
Plasma-based ctDNA analysis has shown advantages over other biofluids, thanks to standardized blood collection 
and plasma isolation techniques.

Targeted therapies require continuous monitoring and quick analysis of evolving tumor profiles using minimally 
invasive methods. Early cancer diagnosis and early detection of disease recurrence also require easily accessible mate-
rial for genomic analysis, making the detection of ctDNA in body fluids crucial in this process. Generally, ctDNA 
constitutes < 0.01% to 10% of the total cfDNA, a low yield, necessitating sensitive assays for its detection. Challenges 
such as hidden micrometastasis, low DNA-shedding tumors, and the influence of different biological variables like 
mucinous histology contribute to false negatives. All these factors make the detection of ctDNA in body fluids a 
significant challenge for clinical applications.

Although plasma is widely used for ctDNA analysis, serum and other body fluids are also significant components 
of large biorepositories. A recent study demonstrated that variant allele frequency was reduced by approximately half 
in serum when compared to plasma samples[2]. Serum contains higher levels of non-tumor cfDNA, primarily due to 
leukocyte lysis during serum preparation. This can adversely affect the detection of mutations in ctDNA, especially 
the ones with low allele fraction mutations[2]. Overall, plasma minimizes ctDNA dilution and enhances the sensitiv-
ity of ctDNA analysis compared to serum.

For genitourinary (GU) tumors such as prostate, bladder, and renal cancers, the major sources of ctDNA are 
plasma, urine, and seminal fluid. However, blood-based ctDNA analysis is well established for clinical implementa-
tion due to routine blood collection as part of clinical management of patients. Plasma-derived ctDNA enables the 
identification of prognostic, predictive, and response biomarkers in prostate cancer[3]. In a recent study, investigators 
reported an epigenetic classification of renal cell carcinoma (RCC) in patients across all stages of the disease[4]. The 
study demonstrated that urine-based classification was less accurate than plasma; however, technical and compu-
tational optimization could improve urine-based analysis. Another study demonstrated that plasma ctDNA can be 
used for predicting treatment response in metastatic castration-resistant prostate cancer[5]. In metastatic urothelial 
carcinoma, mutation concordance between plasma ctDNA and matched tumor tissue was found to be 83.4%([6]. 

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340 SIUJ  •  Volume 4, Number 4  •  July 2023 SIUJ.ORG

PRO AND CON — LIQUID BIOPSY

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