Investigations in a variety of tumor types have demonstrated that circulating tumor cells are present in the peripheral blood of patients, even those with what is thought to be otherwise localized disease, and can be prognostic of outcome.
In this prospective study reported by Gilbert and colleagues, the value of carbonic anhydrase IX (CA-9) expression in peripheral blood, as a surrogate marker of circulating tumor cells detected through an RT-PCR assay, is examined in 41 patients with clinically organ confined renal tumors prior to surgical extirpation.
Forty one patients had peripheral blood collected and assayed for CA-9 expression prior to surgical therapy. Median follow-up was 4.3 years and median patient age was 71 years. Pathologic analysis of the surgical specimens demonstrated 87.8% with renal cell carcinoma (RCC), 7.3% with oncocytoma, and 4.9% with angiomyolipoma. Of patients with RCC, 77.8% were clear cell, 16.7% were papillary, and 5.5% were chromophobe. Of the 41 patients, 68.3% were CA-9 negative in their peripheral blood, whereas 31.7% were CA-9 positive. Of the 13 patients that were CA-9 positive, 84.6% were clear cell RCC, 7.7% were chromophobe RCC, and 7.7% were oncocytoma. The 5 year disease free survival for patients that were CA-9 negative was 88.1% versus 39.5% in those that were CA-9 positive (p=0.048). Of the 28 patients that were CA-9 negative, 7.1% of patients demonstrated a tumor recurrence in follow-up. Of the 13 patients that were CA-9 positive, 30.8% demonstrated a tumor recurrence in follow-up.
This study suggests that assays of peripheral blood for CA-9 may be prognostic in patients with otherwise localized renal tumors. The significance of expression of CA-9 in benign tumor entities such as oncocytoma remains unclear. Clearly, establishment of this assay as a marker of prognosis in RCC awaits further, larger prospective studies.
Written by Christopher G. Wood, MD - UroToday
Gilbert SM, et al., Urology 67(5): 942-945, 2006