# FGFR3 alterations (bladder cancer)

Source: https://onco.cc/terms/fgfr3/  
OnCo record `fgfr3` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

FGFR3 is a growth-receptor gene mutated or fused in about a fifth of advanced bladder cancers and most low-grade early ones. It is the only targetable biomarker in bladder cancer so far.

## Summary

FGFR3 is a growth-receptor gene altered by point mutation or fusion in a substantial share of advanced bladder cancers and in most low-grade early ones, and it is so far the only targetable biomarker in this disease. The alterations include the S249C, R248C and Y373C point mutations and the FGFR3-TACC3 fusion, and they define luminal-papillary tumours that tend to be less immune-infiltrated. Erdafitinib is approved for FGFR3-altered disease after immunotherapy on the strength of the THOR trial. Testing is by NGS on tissue or on urine and ctDNA. The term is referenced from the Bladder & urothelial cancer and Urethral cancer entries, from Erdafitinib and THOR, and it sits alongside the FGFR2 target record.

## Fields

- Kind: Term
- Last checked: 2026-09-07

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Fibroblast_growth_factor_receptor_3
- ClinicalTrials.gov NCT03390504: THOR: https://clinicaltrials.gov/study/NCT03390504

## Connected records

- cancers: [Bladder & urothelial cancer](https://onco.cc/cancers/urothelial/), [Urethral cancer](https://onco.cc/cancers/urethral/), [Urothelial carcinoma of the urethra](https://onco.cc/cancers/urethral-urothelial-carcinoma/)
- targets: [FGFR2](https://onco.cc/targets/fgfr2/)
- drugs: [Erdafitinib](https://onco.cc/drugs/erdafitinib/)
- trials: [THOR](https://onco.cc/trials/thor/)
- biomarkers: [FGFR3 alteration (mutation or fusion)](https://onco.cc/biomarkers/fgfr3-alteration/)

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JSON: https://onco.cc/api/v1/entities/fgfr3.json