The natural history of large renal masses followed on observation

The safety and feasibility of active surveillance in comorbid patients with renal masses ≥4.0cm is uncertain. The aim of this study is to describe our institutional experience with the observation of large renal masses.

One hundred patients were identified with renal masses ≥ 4.0cm that were followed on observation for at least 6 months without surgical intervention between 1994 and 2016. Linear regression was conducted to determine predictors for renal mass growth and competing risk methods were used to estimate the probability of progression in the setting of death from other causes.

Median age at diagnosis was 73 years and 73% of patients had a Charlson Comorbidity index ≥ 4. At presentation, the median mass size was 4.9cm. The median growth rate was 0.4cm/y and there were no significant predictors of growth. Surveillance was discontinued in 34 patients who underwent delayed intervention. Median follow up for metastasis-free survivors was 4 years. In total, 10 patients developed metastatic disease, 3 died from kidney cancer and 30 patients died from other causes. The 5-year probability of other cause mortality was 22% (95% CI: 14%-32%) compared to 6% (95% CI: 2%-13%) for metastatic progression of kidney cancer.

In highly comorbid patients, the observation of large renal masses has low likelihood for metastatic progression relative to the risk of nonkidney cancer related death. This data supports the use of surveillance as an acceptable strategy for highly selected patients with competing risks from other serious illnesses.