Active Surveillance for Small Renal Masses -- More Details

Some Don't Need Treatment

Nick Mulcahy

May 16, 2011

May 16, 2011 (Washington, DC) — For patients who have small renal masses and who are not good candidates for surgery, active surveillance is a low-risk management option — for a few years at the very least — according to a study presented here at the American Urological Association (AUA) 2011 Annual Scientific Meeting.

The study was a systematic review of 18 natural history studies of patients with small renal masses that may or may not be malignancies.

The study authors found that among 880 patients with small masses, only 2.1% had their masses metastasize during observation periods, and the tumor spread took place, on average, at about 40 months.

A pooled analysis of 6 of the studies indicated that 259 patients with the masses, who had an average follow-up of 33.5 months, had a mean linear growth rate of 0.31 cm/year, which is a "very slow rate," said lead author Marc Smaldone, MD, a urologic oncology fellow at Fox Chase Cancer Center in Philadelphia, Pennsylvania, who spoke at the meeting press briefing.

Dr. Robert Uzzo

The combination of the low rate of metastases and the slow rate of growth of these masses should give confidence to clinicians who employ active surveillance with patients, suggested senior author Robert Uzzo, MD, also from Fox Chase, where this avant garde research is being conducted. This study is an update of their 2006 study, which looked at data from only about 200 patients, he said.

"These data will allow clinicians to say to an elderly or infirm patient: 'You probably are not going to die from this'," Dr. Uzzo said during the press briefing. Nonetheless, there is an outstanding caveat, he said: "We don't have long-term data."

Incidentally discovered small renal masses are increasingly common as more people undergo abdominal imaging, said Dr. Smaldone.

The situation is akin to what happened with prostate cancer, said Dr. Uzzo. But instead of prostate-specific antigen tests, computed tomography, magnetic resonance imaging, and ultrasound are used, he told Medscape Medical News, explaining that detection methods have caused a rapid increase in the number of cancers, but that many will be indolent.

Since 1982, there has been an astounding 244% increase in the detection of small renal masses, said James McKiernan, MD, from Columbia University in New York City, who attended the press briefing but was not involved with the study.

However, small renal masses and early-stage prostate cancer are not entirely analogous in terms of their clinical evaluation, said Jeffrey Holzbeierlein, MD, from the University of Kansas in Kansas City, who moderated the briefing.

When small renal masses are detected, only their size is predictive of their aggressiveness, he said. With prostate cancer, clinicians stratify risk using multiple measures: PSA scores, Gleason scores from biopsied tissue, and digital rectal exam results, Dr. Holzbeierlein added.

Currently, small renal masses are not regularly biopsied, noted Dr. Uzzo, because "80% to 90%" will turn out to be cancers. However, with more and more masses being detected, there is a "new trend to biopsy," he said.

Until small renal masses can be more definitively characterized, active surveillance is currently limited to elderly and infirm patients who are not candidates for surgery, according to all of the experts. In these patients, "the risks of treatment may be higher than the risk of any cancer," said Dr. Smaldone.

Active surveillance for small renal masses is not limited to academic medical centers, said Dr. Uzzo, adding that "a steady 3% to 5%" of all such masses are being watched rather than treated in community-based practices.

Tumor Spread Is Delayed Event

Active surveillance has been an option in the AUA guidelines for the management of stage 1 kidney cancer since 2009, said Dr. Smaldone. Nonetheless, "we don't have a good idea how quickly these tumors grow and which metastasize," he said, explaining the ongoing need for data.

In their systematic review of 880 patients, the study authors compared progressors, whose tumors metastasized, with nonprogressors; significant trends in the progression cohort were revealed for increased age (75.1 vs 66.6 years; P = .03), initial tumor size (4.3 vs 2.3 cm; P < .001), volume (66.3 vs 15.1 cm3; P < .001), linear growth rate (0.8 vs 0.3 cm/year; P = .001), and volumetric growth rate (27.1 vs 6.2 cm3/year; P < .001).

The authors note that the progression/metastases occurred at a mean of 40.2 months, and make several other observations about the progressors.

"Tumor spread under active surveillance is an uncommon and delayed event. All patients who developed metastatic disease had positive growth rates, which suggests that even tumors that are highly aggressive should show some evidence of malignant potential prior to progression. Also, all tumors were greater than 3 cm at the time metastases were detected," said Dr. Smaldone.

From the smaller sample of the pooled analysis, the authors reported that 23% (n = 65) of the 259 patients had zero growth while under radiographic surveillance. None of these small renal masses, 88% of which were malignant, progressed to metastases.

Partients with "lesions that exhibit zero growth over time may represent a population appropriate for prolonged active surveillance, while positive growth rates self-select for delayed intervention," Dr. Smaldone and his colleagues write in their study abstract.

At a mean of 30.5 months, 45% (n = 129) of the patients in the pooled analysis received delayed treatment because of growth.

This study was funded by the Kidney Cancer Keystone Program. The authors have disclosed no relevant financial relationships.

American Urological Association (AUA) 2011 Annual Scientific Meeting: Abstract 1663. Presented May 15, 2011.


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