Practice Update

COMMENT

By David J McConkey

PhD

on-muscle invasive bladder cancer

(NMIBC) does not usually progress

to become muscle-invasive and

lethal, but 50% to 70% of tumors recur,

necessitating that patients undergo reg-

ular lifelong surveillance with cystoscopy

complemented with urine cytology and

biopsy. As a consequence, clinical man-

agement of NMIBC is costlier than it is for

any other cancer. Cystoscopy is a relatively

inefficient means of detecting cancer, as

it has been estimated that only one of

seven cystoscopies result in the detec-

tion of recurrences.

The development of

more specific, less costly, and less intrusive

monitoring approaches is a major priority

for ongoing research.

Recent studies have demonstrated that

cancer-associated mutations and other

DNA alterations can be detected in body

fluids.

2–4

Strategies to detect these alter-

ations in so-called “liquid biopsies” from

blood and urine collected from patients

with bladder cancer are being devel-

oped aggressively to monitor subclinical

systemic disease and to identify candi-

date targets for therapeutic intervention.

Approximately 70% of NMIBCs contain

activating mutations in the type-3 recep-

tor for fibroblast growth factors (FGFR3),

making it an extremely attractive biomarker

for cancer surveillance. Indeed, past stud-

ies established FGFR3 mutations can be

detected in the urine in a majority of cases

and that assays designed to measure them

may out-perform urine cytology

and that

adding other prevalent mutations such as

PIK3CA5 might increase assay sensitivity.

Importantly, mutant FGFR3 and PIK3CA

also serve as therapeutic targets,

so these

same assays could prove to be useful in

assigning patients to specific therapies.

In a paper recently published in

European

Urology

, Christensen and colleagues iden-

tified mutations in FGFR3 and/or PIK3CA

in primary tumors from two retrospective

cohorts, one consisting of 363 NMIBCs

and the other consisting of 468 MIBCs from

patients undergoing radical cystectomy.

They then used digital droplet PCR to meas-

ure the same mutations in urine and plasma

from subsets of these patients (25 NMIBCs

and 31 MIBCs). Overall, the presence of

FGFR3 and/or PIK3CAmutations in the urine

(tumor DNA, or tDNA) was associated with

the presence of tumor as determined by

cystoscopy, tumor size >3 cm, and higher

EORTC risk score in patients with NMIBC;

however, plasma tDNAwas only detected in

patients at the time of progression tomuscle

Liquid biopsy analysis of FGFR3 and

PIK3CA hotspot mutations for disease

surveillance in bladder cancer

European Association of Urology

Take-home message

•

Cell-free tumor DNA in liquid biopsies (urine supernatant and plasma) may have bio-

marker potential. In this study, urine was evaluated for the presence of established

bladder cancer gene mutations (FGFR3 and PIK3CA) to assess their prognostic

ability in patients undergoing disease surveillance. Tumor DNA from two patient

cohorts (non-muscle invasive bladder cancer [NMIBC] patients, n = 363; bladder

cancer patients undergoing cystectomy, n = 468) was screened using droplet

digital PCR assays. High levels of tumor DNA were associated with later disease

progression in NMIBC. High levels of tumor DNA in plasma samples were associ-

ated with recurrence in the cystectomy cohort.

•

Urine and plasma from patients with bladder cancer might be used to understand

disease biology and predict progression and metastasis using mutation assays.

Abstract

BACKGROUND

Disease surveillance in patients

with bladder cancer is important for early diag-

nosis of progression and metastasis and for

optimised treatment.

OBJECTIVE

To develop urine and plasma assays

for disease surveillance for patients with FGFR3

and PIK3CA tumour mutations.

DESIGN, SETTING, AND PARTICIPANTS

Droplet dig-

ital polymerase chain reaction (ddPCR) assays

were developed and tumour DNA from two

patient cohorts was screened for FGFR3 and

PIK3CA hotspot mutations. One cohort included

363 patients with non-muscle-invasive bladder

cancer (NMIBC). The other cohort included 468

patients with bladder cancer undergoing radi-

cal cystectomy (Cx). Urine supernatants (NMIBC

n=216, Cx n=27) and plasma samples (NMIBC

n=39, Cx n=27) from patients harbouring muta-

tions were subsequently screened using ddPCR

assays.

OUTCOME MEASUREMENTS AND STATISTICAL ANAL-

YSIS

Progression-free survival, recurrence-free

survival, and overall survival were measured.

Fisher’s exact test, the Wilcoxon rank-sum test

and Cox regression analysis were applied.

RESULTS AND LIMITATIONS

In total, 36% of the

NMIBC patients (129/363) and 11% of the Cx

patients (44/403) harboured at least one FGFR3

or PIK3CA mutation. Screening of DNA from

serial urine supernatants from the NMIBC cohort

revealed that high levels of tumour DNA (tDNA)

were associated with later disease progression

in NMIBC (p=0.003). Furthermore, high levels of

tDNA in plasma samples were associated with

recurrence in the Cx cohort (p=0.016). A positive

correlation between tDNA levels in urine and

plasma was observed (correlation coefficient

0.6). The retrospective study design and low

volumes of plasma available for analysis were

limitations of the study.

CONCLUSIONS

Increased levels of FGFR3 and

PIK3CA mutated DNA in urine and plasma are

indicative of later progression and metastasis

in bladder cancer.

PATIENT SUMMARY

Urine and plasma from patients

with bladder cancer may be monitored for

diagnosis of progression and metastasis using

mutation assays.

Liquid biopsy analysis of FGFR3 and PIK3CA

hotspot mutations for disease surveillance in

bladder cancer.

Eur Urol

2017 Jun 01;71(6)961-

969, E Christensen, K Birkenkamp-Demtröder,

I Nordentoft, et al.

This study represents

another important step

forward in the integration of

genomics into the routine

clinical management of

patients with bladder cancer.

GENITOURINARY

PRACTICEUPDATE ONCOLOGY