Among patients with small renal masses (SRMs), active surveillance (AS) with the option of delayed intervention (DI) is becoming a viable alternative to urgent surgery. However, there needs to be more of comparable data on which to base decisions about SRM management. 

For patients over the age of 65 diagnosed with an incidental SRM, 4 different management strategies were analyzed using decision-analytic Markov modeling to estimate health outcomes and costs: AS (with possible DI), immediate partial nephrectomy, radical nephrectomy, and thermal ablation. The 10 years period, researchers looked at mortality, direct medical costs, quality-adjusted life-years, and incremental cost-effectiveness ratios. On average, patients with AS had a 10-year all-cause death rate of 22.6%, compared to 21.9% for those who underwent immediate partial nephrectomy and 22.4% for those who underwent immediate radical nephrectomy, respectively and 23.7% for those who underwent immediate thermal ablation. 

AS was the best cost-effective management method at a willingness-to-pay threshold of $100,000/quality-adjusted life-year. Univariate, multivariate, and probabilistic sensitivity studies all yielded consistent findings. Clinical decision analysis revealed that the metastatic potential of the tumor, patient age, patient preferences, and patient health state all had a role in determining the best course of treatment. Notably, AS would have higher health utility than the other methods provided the annual chance of metastatic progression from AS was sufficiently low (around 0.35%-0.45% for most ages at baseline), comparable with the normal metastatic potential of SRMs less than 2 cm. Managing patients with SRMs through AS with timely DI is a cost-effective and safe alternative to rapid intervention. 

There is some evidence that AS improves patient outcomes compared to prompt intervention for individuals with cancers that have a very low metastatic potential.