#AUA14 - Session Highlights: Tumor anatomic complexity predicts growth kinetics of renal masses under active surveillance

ORLANDO, FL USA (UroToday.com) - Active surveillance (AS) for small renal masses has emerged as a viable clinical strategy in patients with significant competing risks of death. Over the last few years, data appraising the natural history, progression, and outcomes of untreated clinically localized small renal masses (SRM) has emerged, showing slow average growth rate (~0.3 cm/year) with low metastatic potential. Although all studies have been limited by retrospective methodology and short term follow-up, the current body of evidence evaluating managed SRMs, expectantly, has emerged as a viable clinical strategy in patients with significant competing risks of death. While some urologists feel comfortable with the existing data to recommend expectant management for certain patients with localized SRM, some are hesitant about impending risk of poor outcome. To further support the role of AS in select patients, the authors used the largest single institutional active surveillance (AS) cohort to date to present the outcomes of cortical renal tumors (CRTs) which were solely managed by AS. Moreover, they explored the association between anatomic complexity and tumor linear growth rate (LGR).

auaAn institutional, prospectively maintained, renal tumor database at Fox Chase Cancer Center was reviewed to identify enhancing renal masses managed expectantly for at least 6 months from 2000−2012. Hereditary disease and biopsy proven non-renal cell lesions were excluded. Linear regressions of growth rates estimated by generalized estimating equations were used. The association between patient and tumor characteristics and LGR were assessed using generalized estimating equations, controlling for age, Charlson score, race, sex, and initial tumor size. 346 patients (401 masses) meeting inclusion criteria were identified (18% ≥ cT1b), with a median follow up of 37 months. Forty-four percent of patients progressed to definitive intervention with a mean duration of 27 months. Comparing patients managed expectantly to those requiring intervention, no difference was seen in tumor size at presentation (2.2 vs 2.2 cm), while significant differences in median age (74 vs 65 years, p < 0.001), Charlson co-morbidity score (3 vs 2, p < 0.001), and average LGR (0.23 vs 0.49 cm/year, p < 0.001) were observed between groups. Anatomic complexity quantified by the RENAL Nephrometry score (NS) was not different between groups (7 vs 7, p=0.7). In the adjusted model, for each 1 point increase in Nephrometry score sum, average tumor LGR increased by 0.037 cm/year (p=0.002). Of the entire cohort, 5 patients (1.4%) progressed to metastatic disease. This institutional experience adds to the growing body of literature that suggests a short- term period of AS to determine renal mass growth kinetics is safe in the elderly and comorbid. The demonstrated association between anatomic tumor complexity, as captured by the RENAL NS and tumor linear growth rate, may afford clinically useful cues to tailor individual patient radiographic surveillance schedules.

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 Reza Mehrazin MD, medical writer for UroToday.com