Small kidney tumors have an aggressive potential and should be treated, according to the results of a large multicenter study.

“Many clinicians regard small renal cell cancer as having a benign biologic behavior. Nonoperative surveillance protocols are often being used in patients with small renal tumors,” wrote S. Steffens and colleagues. “The aim of this large retrospective multicenter study was to evaluate the prevalence of locally advanced growth and distant metastases in patients with small renal cell carcinomas following surgery.”

The investigation included 2,197 patients with renal cell carcinoma (RCC) of 4 cm or smaller in maximal tumor diameter and complete patient and tumor specific characteristics from six centers in Germany between 1990 and 2011.

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The risk of presenting nodal disease or distant metastasis increased insignificantly with rising tumor diameters. After a mean follow-up of more than 5 years, the tumor-associated death rates were 6.5% in the subgroup whose tumor diameter was 2 cm or less, 7.6% in those with a tumor diameter of 2 to 3 cm, and 8.4% in those with tumor diameters of 3 to 4 cm. Kaplan-Meier 5-year cancer specific survival (CSS) rates did not differ significantly: 93.3%, 92.1%, and 92.8%, respectively.

Patients with no lymphatic or distant metastasis at the time of diagnosis or surgery had a 5-year cancer specific death rate of 5.8%. The 5-year cancer related death rate was significantly higher among the 75 patients with nodal or distant involvement at the time of surgery (P <.001).

In conclusion, the authors stressed that lymph node and distant metastases occur even in small RCCs: “These results have significant implications since the rate of patients diagnosed with small renal masses is increasing and nonoperative surveillance protocols are currently being used in patients with small renal tumors,” wrote the study authors.

This study was presented at the 28th Annual European Association of Urology Congress, which was held in Milan, Italy, March 15-19, 2013.