Sensitive allele-specific PCR assay able to detect FGFR3 mutations in tumors and urine from patients with urothelial cell carcinoma of the bladder

The Diagnostic and Prognostic Performance of Urinary FGFR3 Mutation Analysis in Bladder Cancer Surveillance: A Prospective Multicenter Study

OBJECTIVE

To assess the diagnostic and prognostic performance of a noninvasive FGFR3 mutation analysis. After transurethral resection (TUR) of noninvasive bladder transitional cell carcinoma (B-TCC), recurrence occurs in 70% of patients, thus justifying cystoscopic surveillance.

MATERIALS AND METHODS

A prospective multicenter study was carried out with a 2-year follow-up of patients with superficial B-TCC. Urine samples were collected before TUR and then before each cystoscopy during follow-up. Screening for the most prevalent FGFR3 mutations was done using urinary cells. The prognostic significance of an FGFR3 mutation at the time of the initial diagnosis was determined. The performance of the test in diagnosing and/or predicting recurrence during follow-up was assessed by calculating sensitivity and specificity.

RESULTS

Of 191 patients studied, 74 (39%) had a positive analysis before TUR (FGFR3 mutation group). The presence of an FGFR3 mutation at the time of diagnosis was associated with a shorter time to recurrence (P = .02). During follow-up, 68 patients from the FGFR3 mutation group were evaluated. FGFR3 mutation analysis showed a sensitivity of 0.73 and a specificity of 0.87 when compared with the results of cystoscopy. A positive urine test was predictive of recurrence either at the time of the positive result or later during the 2-year follow-up, with a sensitivity of 0.70 and a specificity of 0.87.

CONCLUSION

Among patients with an FGFR3 mutation in the initial tumor, a noninvasive urine test during follow-up can be valuable in diagnosing or predicting subsequent recurrence.

Urinary biomarkers of bladder cancer: an update and future perspectives

Bladder cancer is one of the most prevalent cancers worldwide. Early detection of bladder tumors is critical for improved patient outcomes. The standard method for detection and surveillance of bladder tumors is cystoscopy with urinary cytology. Limitations of cystoscopy and urinary cytology have brought to light the need for more robust diagnostic assays. Ideally, such assays would be applicable to noninvasively obtained, voided urine, and be designed not only for diagnosis, but also for monitoring disease recurrence and response to therapy. Consequently, the development of a noninvasive urine-based assay would be of tremendous benefit to both patients and healthcare systems. This article reports some of the more prominent urine-based biomarkers reported in the literature. In addition, some new technologies that have been used to identify novel urinary biomarkers are highlighted.

A meta-analysis of the relationship between FGFR3 and TP53 mutations in bladder cancer

TP53 and FGFR3 mutations are the most common mutations in bladder cancers. FGFR3 mutations are most frequent in low-grade low-stage tumours, whereas TP53 mutations are most frequent in high-grade high-stage tumours. Several studies have reported FGFR3 and TP53 mutations to be mutually exclusive events, whereas others have reported them to be independent. We carried out a meta-analysis of published findings for FGFR3 and TP53 mutations in bladder cancer (535 tumours, 6 publications) and additional unpublished data for 382 tumours. TP53 and FGFR3 mutations were not independent events for all tumours considered together (OR = 0.25 [0.18-0.37], p = 0.0001) or for pT1 tumours alone (OR = 0.47 [0.28-0.79], p = 0.0009). However, if the analysis was restricted to pTa tumours or to muscle-invasive tumours alone, FGFR3 and TP53 mutations were independent events (OR = 0.56 [0.23-1.36] (p = 0.12) and OR = 0.99 [0.37-2.7] (p = 0.35), respectively). After stratification of the tumours by stage and grade, no dependence was detected in the five tumour groups considered (pTaG1 and pTaG2 together, pTaG3, pT1G2, pT1G3, pT2-4). These differences in findings can be attributed to the putative existence of two different pathways of tumour progression in bladder cancer: the CIS pathway, in which FGFR3 mutations are rare, and the Ta pathway, in which FGFR3 mutations are frequent. TP53 mutations occur at the earliest stage of the CIS pathway, whereas they occur would much later in the Ta pathway, at the T1G3 or muscle-invasive stage.

Targeting mutant fibroblast growth factor receptors in cancer

Fibroblast growth factor receptors (FGFRs) play diverse roles in the control of cell proliferation, cell differentiation, angiogenesis and development. Activating the mutations of FGFRs in the germline has long been known to cause a variety of skeletal developmental disorders, but it is only recently that a similar spectrum of somatic FGFR mutations has been associated with human cancers. Many of these somatic mutations are gain-of-function and oncogenic and create dependencies in tumor cell lines harboring such mutations. A combination of knockdown studies and pharmaceutical inhibition in preclinical models has further substantiated genomically altered FGFR as a therapeutic target in cancer, and the oncology community is responding with clinical trials evaluating multikinase inhibitors with anti-FGFR activity and a new generation of specific pan-FGFR inhibitors.

Biomarkers in bladder cancer

Detailed molecular insights into bladder cancer biology might allow more detailed prognostication and optimization of treatment with the objective of improving patient outcome and quality of life. However, in bladder cancer research the search for biomarkers has been called into question and has even obtained notoriety. It is unlikely that any single marker will be able to improve prognostication for patients with bladder cancer above and beyond grade and stage, but a combination of multiple independent markers might more precisely predict the outcome. From a previous review, we identified seven biomarkers to study within the setting of the Bladder Cancer Prognosis Programme (BCPP), a 5-year multicentre programme of research based at the University of Birmingham and funded by Cancer Research UK, investigating their effectiveness in predicting recurrence and progression. As part of the ongoing quality-assurance process for BCPP we present an updated review of our selected biomarkers, as well as highlighting other recent important developments in bladder cancer research.

Novel therapeutic targets in bladder cancer: mutation and expression of FGF receptors

Bladder cancer presents several challenges in clinical management. For the large group of noninvasive tumors, key problems are the development of multiple recurrences that require long-term surveillance and a lack of effective therapies to prevent recurrence. For the smaller group of poor prognosis patients with invasive disease, novel therapies are urgently needed. The identification of mutations of FGF receptor 3 (FGFR3) in most noninvasive bladder tumors and the recent finding of overexpression of this receptor not only in superficial tumors but also in many invasive bladder cancers has generated optimism that therapies targeting this receptor tyrosine kinase may have major application in the treatment of urothelial cancers. There is little information on the other members of this receptor family apart from FGFR2, which is implicated as a tumor suppressor. Recent preclinical evaluations of FGFR3 as a therapeutic target have provided a strong impetus for the development of targeted agents for clinical use.

Role of FGFR3 in urothelial cell carcinoma: biomarker and potential therapeutic target

Although non-invasive bladder tumours (pTa) are the most common group of bladder tumours at presentation, there has until recently been relatively little information on their molecular biology. Thus it was of great interest when mutations in the FGF receptor 3 (FGFR3) were identified in bladder tumours and it became apparent that these were most common in tumours of low grade and stage. Since the initial description of activating mutations of FGFR3, there have been numerous studies confirming the frequency and spectrum of these mutations in bladder cancers of all grades and stages. Mutation screening techniques have evolved and improved. FGFR3 mutation has been assessed as a predictive biomarker in tumour tissues and as a diagnostic biomarker in urine. Efforts have been made to understand the function of FGFR3 in urothelial and other cells. Although our understanding of FGFR3 function is incomplete, it is already apparent that this may represent an important therapeutic target not only in non-invasive bladder cancer but also in a significant number of invasive tumours. This review summarises the current state of knowledge of this interesting receptor in urothelial carcinoma (UC).