Active Surveillance for Small Renal Masses Is Non-Inferior to Primary Intervention

Active Surveillance for Small Renal Masses Is Non-Inferior to Primary Intervention

Mr. Ridwan Alam
Active surveillance appears to be a safe option in the intermediate term for carefully selected patients who present with small renal masses (SRMs) less than 4.0 cm in diameter, according to data from DISSRM, a prospective registry study (Abstract 430).

“Do we really need to treat all patients with SRMs?” asked Ridwan Alam, a medical student at Johns Hopkins University School of Medicine, during a General Session on diagnosis and treatment of local renal cancer on Feb. 18. He noted that 20% to 40% of SRMs turn out to be benign on final pathology, and that percentage decreases with decreasing tumor size. “Less than 20% of SRMs have a potentially aggressive pathology,” he added, and SRMs generally have a very low metastatic potential.

That means there is likely substantial overtreatment of these tumors. Most studies on active surveillance (AS) in this patient population have been retrospective, and AS remains underutilized; various guidelines offer AS as a suitable or reasonable option, which likely reflects the lack of strong data, Mr. Alam said.

The DISSRM registry opened in 2009 and included patients age 18 years or older who had an SRM no more than 4.0 cm in size and a clinical stage of T1a.

Importantly, patients in the registry chose for themselves to undergo AS or primary intervention, after counseling. Patients were offered biopsy at enrollment, but it was not required; all patients in the AS group underwent axial imaging (CT or MRI) at enrollment, with follow-up imaging every 6 to 12 months. Intervention was recommended upon evidence of progression, which was defined as a growth rate of more than 0.5 cm/year, a tumor diameter greater than 4.0 cm, or metastatic disease. The investigators designed this a non-inferiority trial to compare results with historical data on primary intervention.

A total of 615 patients was included in this analysis, approximately evenly split between primary intervention (298 patients, 48.5%) and AS (317 patients, 51.5%). Of the patients in the AS group, 45 (14.2%) crossed over to delayed intervention. The median follow-up period was 3.0 years, and 23% of the cohort was observed for 5 years or more. Those who selected AS, compared with those who selected primary intervention, tended to be older (70.8 years vs. 61.8 years; p < 0.001), had worse health in terms of both Eastern Cooperative Oncology Group and Charlson comorbidity scores (Carlson score of 0 in 43.5% of patients in AS group vs. 60.1% of patients in the primary intervention group; p < 0.001), and had smaller tumors (1.8 cm diameter vs. 2.5 cm; p < 0.001).

Mr. Alam described the median growth as being “very low,” at 0.09 cm/year. Thirty-three patients (20.8%) experienced tumor growth greater than 0.5 cm/year; the remaining 79.2% of patients experienced no growth at all or very slow growth. Mr. Alam noted that the variability in growth rates was highest in the first year and then decreased, which he said could be a mathematical artifact.

Panelists discuss the DISSRM prospective registry study.
The cancer-specific survival was very similar after 7 years: 100% with AS and 98.9% with primary intervention (p = 0.3). Overall survival was significantly worse with AS, however, than with primary intervention (62.8% vs. 85.1%; p = 0.001), which likely reflected the older age and poorer health of patients in the AS group. On multivariable analysis, age was a significant predictor of all-cause mortality (hazard ratio 1.06, 95% CI [1.02, 1.10]; p = 0.003), as was Eastern Cooperative Oncology Group score. There was no difference in mental health measures between the AS and intervention groups.

Mr. Alam noted that there was no metastatic disease seen among patients in the AS group, including those who experienced progression on the basis of predefined criteria. “We [may] want to rethink our idea of progression, looking at persistent versus interval growth,” he said.

On the basis of these results that showed non-inferiority to primary intervention, “we can conclude that AS for SRMs is safe,” said Mr. Alam. The researchers also have developed a DISSRM score to help select patients who are candidates for AS; it still requires validation in other cohorts.

During a panel discussion after the presentation, Mohammad Allaf, MD, also of Johns Hopkins and a co-author of this study, said that a change in terminology may help guide patients and clinicians more toward the use of AS. “I would push toward calling [small renal masses] ‘growths’ in the kidney,” he said, because many patients will hear the word “tumor” or “cancer” and be much more likely to elect surgical treatment.

– David Levitan