Carbonic anhydrase IX (CA IX) expression and outcome after radiotherapy for muscle-invasive bladder cancer

Aims: Carbonic anhydrase IX (CA IX) expression has been described as an endogenous marker of hypoxia in solid neoplasms. Furthermore, CA IX expression has been associated with an aggressive phenotype and resistance to radiotherapy (RT). Here we assess the prognostic significance of CA IX expression in patients with muscle-invasive bladder cancer treated with RT. Methods and Materials: A standard immunohistochemistry technique was used to demonstrate CA IX expression in 110 muscle-invasive bladder tumours treated with RT. Clinico-pathological data was obtained from medical casenotes. Results: CA IX immunostaining was detected in 89 (~81%) patients. Staining was predominantly membranous, with areas of concurrent cytoplasmic and nuclear staining and was abundant in luminal and perinecrotic areas. No significant correlation was demonstrated between overall CA IX status and initial response to RT, five-year bladder cancer-specific survival or time to local recurrence. Conclusions: The distribution of CA IX expression in paraffin-embedded tissue sections seen in this series is consistent with previous studies in bladder cancer but does not provide significant prognostic information with respect to response to RT at 3 months and disease-specific survival following radical RT.