440 Background: The natural history of untreated T1b renal masses is poorly understood. We assessed the growth kinetics and outcomes of ≥cT1b cortical renal tumors which continue to remain on radiographic AS compared to those who underwent definitive surgery after a period of AS. Methods: Prospectively maintained, renal tumor database was reviewed to identify enhancing solid and cystic masses managed expectantly from 2000-2012. cT1a masses, transitional cell carcinoma or those suspected for metastatic disease were excluded from analysis. Localized tumors > 4.0 cm (≥T1b) that were radiographically followed for > 6 months were included for analysis. Clinical and pathological records were reviewed to determine tumor growth rate and clinical outcomes in those remained on AS or those who underwent delayed intervention. Mean for tumor size on presentation, annual linear tumor growth rate (LGR), Charlson comorbidity index (CCI), and follow-up (FU) were calculated. Chi−square test & Logistic regression were used for uni- and multi-variable analyses. Results: Of 457 pts managed with AS, 67 cT1b tumors (in 63 patients) were identified. 43 pts (67%) were managed solely with AS, while 21 pts (33%) progressed to intervention. The median age at presentation pts managed with AS and intervention was 77 and 60 yrs respectively (p=0.0002), while no difference was observed in median CCI (3 vs. 2, p=0.6). No difference was observed in tumor size at presentation between pts managed with AS and those undergoing delayed intervention (5.9 vs. 5.4 cm, p=0.8). In contrast, the mean LGR significantly differed between pts managed expectantly and pts progressed to intervention (0.37 vs. 0.73 cm/yr; p=0.02). On MVA, age (OR=0.9,CI:0.8−0.98) and LGR (OR=11,CI:1.8−60) were significant predictors of surgical intervention. With a mean FU period of 38.9 ± 24.0 months (6−105), 9 pts died (14%) from other cause and no pt progressed to metastatic disease. Conclusions: Localized cT1b≥ renal masses show comparable growth rates to small tumors managed expectantly with low rates of progression to metastatic disease with short term follow up. An initial period of AS to determine tumor growth kinetics is a reasonable option in select pts with significant competing risks and limited life expectancy.
Re: Long-term Follow-up of a Large Active Surveillance Cohort of Patients with Prostate Cancer
