Introduction

We reviewed our large single center experience with active surveillance (AS) for localized renal masses focusing on patients with > 5 years (yrs) of follow-up.

Methods

We queried our prospectively maintained kidney cancer database (n = 2574) for patients (pts) enrolled on AS. Estimated tumor volume (ETV) was calculated using a standard formula and linear growth rate (LGR) was evaluated. Wilcoxon rank sums and Chi-squared tests were used to assess for demographic differences in growth rates and cross-over to DI. Kaplan-Meier curves were used evaluate clinical outcomes. A sub-set analysis (n = 156) was performed of pts with ≥5 yrs follow-up and no cross-over to DI.

Results

We identified 601 pts enrolled in our AS program (60.1% male, mean age 67.3 yrs, mean ETV of 22.9 cm³). The median follow-up for the entire cohort was 62.6 months (mo). Mean change in ETV was 6.9 cm³/yr (IQR -0.03 to 4.14 cm³/yr) and mean LGR was 2.6 mm/yr. Mean change in ETV of solid masses was more rapid than cystic masses (11.4 vs. 5.8 cm³/yr, p <0.04). Of the entire cohort, 190 pts (32%) crossed over to DI (Figure 1). Among those who crossed over, median time to DI was 16.4 mo (IQR 9.2 to 32.6 mo). Cross over to DI was uncommon after 24 mo whereas nearly two-thirds of patients who crossed over to DI did so within 2 yrs and 77% crossed over within 36 mo of enrolling in AS. Younger pts (63.6 vs. 69.0 yrs, p < 0.0001) and pts with solid versus cystic masses (33.9% vs. 23.3%, p < 0.016) were more likely to cross-over to DI. A majority of pts (89.5%) were still alive at 60 mo follow-up. A subset of 156 pts had ≥5 years of follow-up without crossing over to DI (62.9% men and mean ETV at presentation of 4.26 cm³). 16 pts died, however, only 6 pts (1.5%) exhibited disease progression. One pt died from RCC and 5 developed lymph node or distant metastasis. Mean ETV growth rate for this sub-set was 2.81 cm³/year and mean LGR was 1.4 mm/yr.

Conclusions

AS with or without DI is a successful strategy in well selected pts with localized renal masses. Most patients who cross over into DI are likely to do so within the first 2 yrs on AS. Metastasis and death from disease are rare in well selected pts who have been followed for ≥5 yrs. AS of localized renal masses is a sound oncologic practice in select pts beyond 5 yrs of follow-up.

Funding

None