Watchful waiting for solid renal masses: insight into the natural history and results of delayed intervention

We describe the short-term outcomes of patients whose renal masses were managed expectantly (ie watchful waiting) to provide insight into the natural history of small renal tumors. Additionally, this study examined the effects of delayed intervention in patients who required intervention after a period of expectant management.

A total of 43 patients with 46 renal masses underwent planned expectant management of enhancing solid or cystic (Bosniak IV) renal masses. A subset of these patients (13) who underwent eventual intervention was also examined. Outcomes with regard to age, gender, growth rate, subsequent interventions and clinical followup are reported.

At a mean followup of 36 months 74% of patients had tumor growth with a mean (median) growth rate of 0.70 (0.35) cm per year. None of the patients had significant symptoms, disease progression or cancer specific death. There were 4 patients (10%) who died of other causes. The 13 patients undergoing eventual intervention were younger than those who did not undergo intervention (56 vs 72 years, respectively, p = 0.0006). Patients undergoing eventual intervention tended to have a higher tumor growth rate than those on continued observation (0.90 vs 0.61 cm per year, respectively, p = 0.1486). In patients undergoing eventual intervention 12 of 14 (87%) tumors were renal cell carcinoma. All were stage pT1, and 12 of 13 patients were alive after a mean followup of 41 months (1 patient died of other causes 30 months after surgery). No patient had up-staging of disease secondary to delay.

Watchful waiting for renal masses is a reasonable option for appropriately selected patients, especially those with competing comorbidities. Delayed intervention does not appear to adversely impact pathological outcomes.