Purpose: Mutations in the fibroblast growth factor receptor 3 (FGFR3) occur in 50% of primary bladder tumors. An FGFR3 mutation is associated with good prognosis, illustrated by significantly lower percentage of patients with progression and disease-specific mortality. FGFR3 mutations are especially prevalent in low grade/stage tumors, with pTa tumors harboring mutations in 85% of the cases. These tumors recur in 70% of patients. Efficient FGFR3 mutation detection for prognostic purposes and for detection of recurrences in urine is an important clinical issue. In this paper, we describe a simple assay for the simultaneous detection of nine different FGFR3 mutations. Experimental Design: The assay consists of one multiplex PCR, followed by extension of primers for each mutation with a labeled dideoxynucleotide. The extended primers are separated by capillary electrophoresis, and the identity of the incorporated nucleotide indicates the presence or absence of a mutation. Results: The assay was found to be more sensitive than single-strand conformation polymorphism analysis. Mutations could still be detected with an input of only 1ng of genomic DNA and in a 20-fold excess of wild-type DNA. Moreover, in urine samples from patients with a mutant tumor, the sensitivity of mutation detection was 62%. Conclusions: We have developed a fast, easy to use assay for the simultaneous detection of FGFR3 mutations, which can be of assistance in clinical decision-making and as an alternative for the follow-up of patients by invasive cystoscopy for the detection of recurrences in urine.Bladder cancer is the fifth most common cancer in the western world with an incidence of 20 new cases per year per 100,000 people in the U.S. (1). Unfortunately, these statistics do not include superficial pTa bladder cancer, which represents the most common type of bladder cancer. In the Netherlands, the incidence of both superficial and invasive bladder cancer is estimated as about 30 new cases per year per 100,000 people. This is in accordance with data from global cancer statistics for the western world (2). Superficial bladder tumors are removed by transurethral resection. However, up to 70% of these patients will develop one or more recurrences, and it has been estimated that 1 in 1,450 people is under surveillance for bladder cancer in the United Kingdom (3). Cystoscopy is an uncomfortable, invasive, and expensive procedure, but currently remains the gold standard for detection of recurrences. Because patients have to be monitored perpetually and have a long-term survival, bladder cancer is the most expensive cancer when calculated on a per patient basis (4).Activating mutations in the fibroblast growth factor receptor 3 (FGFR3) gene have been reported in >50% of primary bladder tumors (5, 6).1 Most of the somatic mutations found in bladder cancer are identical to germ line mutations responsible for skeletal disorders such as thanatophoric dysplasia and achondroplasia (7). It has been reported that FGFR3 mutations are very frequent ...

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