Carbonic anhydrase IX does not predict ccRCC outcome
medwireNews: Carbonic anhydrase IX (CAIX), a transmembrane protein that regulates neoplastic growth in response to tumoral hypoxia, is not an independent predictor of outcome in patients with clear cell renal cell carcinoma (ccRCC), say US researchers.
"Contrary to other similar but smaller studies, the present follow-up analysis confirmed our initial conclusion that low CAIX expression levels do not independently predict a higher risk of cancer-specific death in patients with ccRCC after multivariable adjustment for relevant prognostic features," say Bradley Leibovich (Mayo Medical School, Rochester, Minnesota) and colleagues.
They note, however, that, although the findings "mitigate the potential of CAIX as purely a prognostic marker, they do not preclude further investigation of CAIX as a diagnostic tool and potential therapeutic target."
The long-term follow-up analysis involved 730 patients with ccRCC who underwent nephrectomy between 1990 and 1999 and were initially assessed in 2007.
The mean CAIX tumor expression was 87%, and 163 (22.3%) tumors had low CAIX expression (≤85%), whereas 567 (77.7%) had high expression (>85%).
At the last follow up, 483 patients had died, including 265 from RCC specifically, and the remaining 247 patients still under observation had a median follow-up of 13.8 years.
On univariate analysis, patients whose tumors had low CAIX expression levels were 62% more likely to die from RCC than patients whose tumors had high CAIX expression. But after taking into account nuclear grade and coagulative tumor necrosis, the difference in death rates was no longer significant between patients with high and low CAIX-expressing tumors.
Even among a subset of 81 patients with metastatic ccRCC, low CAIX expression was not significantly associated with a poor outcome. There was evidence of an increased risk for progression to distant metastases in patients whose tumors contained low versus high levels of CAIX, but again this was no longer significant after adjusting for nuclear grade and coagulative tumor necrosis.
"Based on the present results, we cannot advocate CAIX as an independent prognostic marker for patients with ccRCC," Leibovich et al conclude in BJU International.
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By Lucy Piper, Senior medwireNews Reporter