Surveillance may be viable for small renal masses

Key Points

Washington-Surgical treatment for small renal masses may be cautiously delayed in select patients with significant competing risks for mortality, according to a study from Fox Chase Cancer Center, Philadelphia.

This observation contains the proviso that these patients should be followed closely with serial imaging to identify growth kinetics that might signal a need for intervention.

"The growth of many small renal masses, as a whole, is slow, and the risk of metastases in the near term is low, approximately 2% at 2 to 3 years in selected patients," said first author Marc Smaldone, MD, a urologic oncology fellow at Fox Chase. "Our pooled analysis noted that no tumor smaller than 3 cm or tumors that demonstrated zero growth over time metastasized.

However, surveillance remains a viable option that will allow patients with cardiovascular, pulmonary, and other diseases to have these treated before definitive treatment of the renal cancer is pursued.

Patient age associated with progression

The authors identified several factors associated with progression to metastases when compared to patients that did not progress. Among those factors associated with a risk of progression were age (mean, 75.1 years; p<.03), an initial maximum tumor diameter of 4.3 cm or greater (p<.001), an initial estimated tumor volume of 66.3 cm³ or greater (p<.001), a linear growth rate of 0.80 cm/year (p<.001), and a volumetric growth rate of 27.1 cm³ /year (p<.001).

The study was initiated after observations from small studies suggested that a significant proportion of patients with small renal masses could have more indolent disease.

"Despite a lack of level I evidence, these data [from smaller studies] are provocative. The idea that active surveillance may be an option in select patients with small renal masses has generated considerable interest," said Dr. Smaldone, who worked on the study with Robert G. Uzzo, MD, and colleagues.

The authors pursued this interest by performing a systematic review of all studies with a continuing observation of small renal masses. They narrowed 105 articles down to 18 studies suitable for systematic review. These comprised 880 patients with 936 renal masses. At a mean of 40 months, 18 patients (2%) progressed to metastatic disease.

Six of the 18 studies met criteria for pooled analysis. These studies encompassed 259 patients with 284 small renal masses. Of these masses, 65 (23%) displayed no growth during the observation period and none of these lesions progressed to metastases.

"It is important to note that all patients who progressed had positive growth rates over time, and all tumors were larger than 3 cm when metastasis was detected," said Dr. Smaldone.

"Pathologic data were available for half of the patients who progressed and of these, the majority were high-grade disease," he added.

Dr. Smaldone said it was clear that the majority of small renal masses exhibit slow growth and that the risk of short-term metastatic progression is low.

On the other hand, the data indicate that those patients who progressed exhibited growth kinetics suggestive of more aggressive tumor biology, he added.

"In fact," said Dr. Smaldone, "if it was not for their advanced age and contraindications for invasive therapy, the majority of these patients would not be chosen for active surveillance."

He noted that linear and volumetric growth rates were perhaps the most reliable available triggers for intervention.

"Ultimately, lesions that exhibit positive growth rates over time may select for early intervention, and masses that demonstrate zero or negative growth over time may be candidates for prolonged surveillance," Dr. Smaldone said.

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