SAN FRANCISCO—Active surveillance of small renal masses (SRMs) may be an appropriate approach for many patients, especially older individuals and those with comorbidities that would complicate treatment or reduce life expectancy, according to Michael Jewett, MD, of Princess Margaret Hospital and the University of Toronto.

Studies show that most SRMs grow very slowly and rarely progress to metastases, Dr. Jewett said. Thus, treatment often can be delayed.

In an oral presentation, Dr. Jewett said the incidence of renal cell carcinoma (RCC) has increased by 2% every year for the past 20 years in North America. The trend is due largely to the incidental detection of SRMs, defined as masses 4 cm in diameter or less. Patients with these masses traditionally have been treated with surgery or more recently, ablation, but these approaches may not always be necessary, he said. In his opinion, SRMs are being overtreated.

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When clinicians identify asymptomatic masses, they should first order a biopsy to determine if they are malignant “because at least 20% of these are benign.”

“The usual practice is to assume that a newly diagnosed small renal mass is a cancer without doing a biopsy,” he said. “Use of biopsy is increasing, so that is good.”

Small observational studies have shown that most SRMs grow slowly and few metastasize. In a prospective Canadian active surveillance study of SRMs, researchers found that biopsy-proven small RCC tumors have a growth rate of less than 1 mm a year (J Urol. 2009;181[suppl.]:320).  Researchers analyzed 87 biopsied lesions (54 RCC, 11 benign, and 22 non-diagnostic). Less than 2% of SRMs progressed to metastases.

Investigators presented findings here at the 2010 Genitourinary Cancers Symposium.