Active Surveillance in Metastatic Renal Cell Carcinoma: Results From the Canadian Kidney Cancer Information System

Background: Active surveillance (AS) is a commonly used strategy in patients with slow-growing disease. We aimed to assess the outcomes and safety of AS in patients with metastatic renal cell carcinoma (mRCC). Patients and Methods: We used the Canadian Kidney Cancer information system (CKCis) to identify patients with mRCC diagnosed between January 1, 2011, and December 31, 2016. The AS strategy was defined as (1) the start of systemic therapy ≥ 6 months after diagnosis of mRCC, or (2) never receiving systemic therapy for mRCC with an overall survival (OS) of ≥1 year. Patients starting systemic treatment <6 months after diagnosis of mRCC were defined as receiving immediate systemic treatment. OS and time until first-line treatment failure (TTF) were compared between the two cohorts. Results: A total of 853 patients met the criteria for AS (cohort A). Of these, 364 started treatment >6 months after their initial diagnosis (cohort A1) and 489 never started systemic therapy (cohort A2); 827 patients received immediate systemic treatment (cohort B). The 5-year OS probability was significantly greater for cohort A than for cohort B (70% vs. 33.6%; P <.0001). After adjusting for International Metastatic RCC Database Consortium risk criteria and age, both OS (hazard ratio [HR] = 0.58; 95% confidence interval [CI], 0.47-0.70; P <.0001) and TTF (HR = 0.72; 95% CI, 0.60-0.85; P =.0002) were greater in cohort A1 compared with B. For cohort A1, the median time on AS was 14.2 months (range, 6-71). Conclusions: Based on the largest analysis of AS in mRCC to date, our data suggest that a subset of patients may be safely observed without immediate initiation of systemic therapy.