Tumor Size Predicts Synchronous Metastatic Renal Cell Carcinoma: Implications For Surveillance Of Small Renal Masses

July 2, 2007 – 2:36 pm | posted in Urology / Nephrology

UroToday.com- The biggest risk in active surveillance paradigms for incidental renal masses is not that a tumor might grow but rather that a tumor might metastasize, thus rendering a potentially curable patient incurable. In the retrospective series on active surveillance that have been published metastatic progression and disease specific mortality from renal cell carcinoma (RCC) is, thankfully, a rare event. Here, Kunkle and colleagues out of Fox Chase Cancer Center examine the incidence of synchronous metastatic disease as a function of tumor size, trying to gain insight as to at what size a malignant renal tumor might gain metastatic potential.

The authors identified 110 patients that presented with biopsy proven synchronous metastatic disease from a primary renal cell carcinoma and compared them to 250 patients with localized disease. Of these, 87.2% had clear cell histology. Primary tumor size was larger for patients with synchronous metastases (median 8.0 cm (range 2.2-20)) when compared to those with localized RCC (median 4.5 cm (range 0.3-17.5)) (p<0.001). The probability of presenting with synchronous metastatic disease increased with increasing tumor size (p<0.0001). The authors noted that no tumor < 2 cm presented with metastases and <5% of tumors that presented with metastases were ? 3 cm. The risk of presenting with a synchronous metastasis increased 22% for every one centimeter increase in tumor size. A doubling of risk of presenting with a synchronous metastasis occurred with a 3.5 cm increase in tumor size.

The authors conclude that tumor size can be predictive of biologic potential in RCC and that tumors less than 3 cm rarely if ever metastasize. Increased tumor size was associated with an increased risk of metastatic progression, which should have implications for those being observed on an active surveillance protocol. These data also demonstrate the considerable overlap in tumor size between biologically aggressive tumors that present with synchronous metastases and those without. A take home message should also be that the biology of RCC is unpredictable and patients that are placed on active surveillance protocols should only be those that either can’t tolerate or refuse tumor resection/ablation.

Kunkle DA, Crispen PL, Li T, Uzzo RG

J Urol 177(5):1692-1697, May 2007.
doi:10.1016/j.juro.2007.01.029

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