ORLANDO, FL USA (UroToday.com) - With increasing interest in understanding active surveillance (AS) as an option for the management of small renal masses, the growth kinetics of masses under 4 cm has been characterized by a number of investigators. Although the specific growth rate varies, and level I evidence is lacking, previous investigations consistently report slow growing tumors. In this study out of Fox Chase Cancer Center, the growth kinetics of larger tumors (≥ 4 cm), managed with active surveillance, were evaluated and compared with those who ultimately underwent definitive intervention.
They reviewed their prospectively maintained database of patients with renal tumors and identified 68 patients with 72 tumors greater than 4 cm in diameter who were managed with AS. Of these, 23 patients ultimately received definitive intervention. At presentation, the average tumor size was 4.9 cm, with no difference between those managed solely with AS and those who received definitive intervention. There was a significant difference in age between the groups (76 versus 60 years for active surveillance versus intervention, respectively, p=0.0002). When comparing patients managed solely with AS versus those who received definitive intervention, the linear tumor growth rate (LGR) was higher in the intervention group (0.37 versus 0.68 cm/year, p=0.04), which is relatively consistent with kinetics for SRMs < 4 cm. On multivariate analysis, they found that tumor growth rate and younger age at presentation were associated with progression to surgery.
From these results they concluded that, as growth rates appear similar between small tumors (< 4 cm) and those they evaluated (cT1b or larger), initial management with active surveillance is reasonable, particularly in patients with "significant competing risks and limited life expectancy." During the discussion following the presentation, Dr. Mehrazin mentioned that two of the patients who demonstrated higher growth rates (0.9 and 1.2 cm/year) and progressed to surgery were found to have tumors of oncocytoma and chromophobe RCC on examination of surgical specimens, indicating poor correlation between growth rate and tumor histopathology/grade. This interesting work expands on evidence supporting active surveillance, but also raises the question whether growth rate is a useful predictor of outcomes when managing patients expectantly.
Presented by Reza Mehrazin, MD at the American Urological Association (AUA) Annual Meeting - May 16 - 21, 2014 - Orlando, Florida USA
Fox Chase Cancer Center, Philadelphia, PA USA
Written by Martin Hofmann, MD, University of California (Irvine), and medical writer for UroToday.com