[902] Frequency of Somatic Mutations in High Grade Urothelial Carcinomas

O Lin, D Solit, H Al-Ahmadie, A Heguy, N Ishill, VE Reuter, M Millowsky. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: Urothelial carcinoma is a common malignancy with a variable biology and natural history. The majority of patients are initially diagnosed with superficial cancer, however, 20-40% of patients either present with more advanced disease or progress after therapy for early stage disease. Genetic mutations are frequent in urothelial carcinomas and may predict the likelihood of response to targeted therapies. Prior studies have shown that the most common somatic mutations in urothelial carcinomas, independent of grade, are FGFR3, RB1, PIK3CA, CDKN2A and HRAS. In this study, we characterized the frequency of these selected mutations in high grade bladder urothelial carcinomas, which are the ones that might benefit from targeted therapies against these mutations.
Design: Frozen material from 137 cystectomy specimens were retrieved from our institution tumor bank for analysis. All cases represented cases of high grade urothelial carcinoma, superficial and invasive. Only cases with matched pair of tumor and normal tissue were included in this study. DNA was extracted from these specimens and submitted to Sanger Sequencing for FGFR3, RB1, PIK3CA,CDKN2A and HRAS and BRAF. PCR reactions were carried out with 10 ng of whole genome amplified DNA. All putative mutations were confirmed by a second PCR and sequencing reaction, in parallel with amplification and sequencing of matched normal tissue DNA. All traces for mutation calls were manually reviewed.
Results: The observed frequency for each mutation appear in the table below. The majority of patients (60%) did not demonstrate the presence of any of the mutations analyzed. Forty-six (34%) had only one mutation, and nine (7%) had two mutations among the ones evaluated. Among the nine patients with two mutations, three had both BRAF and TP53, two had PIK3CA and TP53, two had both FGFR3 and PIK3CA, one had TP53 and CDKN2A, and one had FGFR3 and BRAF mutations.

Frequency of somatic mutations in high grade urothelial carcinoma
MutationNumber of CasesPercentage (%)

Conclusions: In this cohort, the most common mutations were in TP53, PIK3CA and FGFR3 genes. BRAF mutations can be present in high grade urothelial carcinomas. BRAF and PIK3CA mutations appear mutually exclusive, while TP53 can be present with other somatic mutations. HRAS mutation was not identified in high grade urothelial carcinomas in our series.
Category: Genitourinary (including renal tumors)

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 143, Wednesday Afternoon


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