Predictive role of changes in the tumor burden and International Metastatic Renal Cell Carcinoma Database Consortium class during active surveillance for metastatic renal cell carcinoma

Background: Despite important results achieved for metastatic renal cell carcinoma, some patients could benefit from local treatments or an initial active surveillance (AS) period for recurrent disease. We aim to analyze: changes in the International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) risk class, the number of metastases and the disease burden from the start of AS to the beginning of systemic therapy; and if these changes influenced patient outcomes.

Patients and methods: Patients who started AS at our institution from January 2007 to April 2016 were included. The Kaplan-Meier method was used to estimate total overall survival (tOS) and progression-free survival. Changes in IMDC class, number of metastatic sites, and tumor burden (TB) were evaluated and related to patient survival. Among the patients who started active treatment, progression-free survival and post surveillance OS (psOS) were evaluated.

Results: 52 patients were included in the analysis. Median time on AS and tOS were 18.3 and 80.1 months respectively. Baseline factors were not related to the time on AS apart from the IMDC classification (HR = 2.15; 95% CI: 1.19-3.87; P = 0.011). The increase in the number of metastatic sites during AS was correlated with poor tOS (HR = 2.86; 95% CI: 1.29-6.34; P = 0.010). The increase of the TB was a negative prognosis factor for tOS (HR = 1.16; 95% CI: 1.02-1.31; P = 0.024) and psOS (HR = 1.21; 95% CI: 1.07-1.40; P = 0.004). Both IMDC class and change in the TB at the start of therapy were related to psOS. The retrospective nature and the lack of an external review of the imaging are its main limitations.

Conclusions: During AS, patients rarely experience a deterioration of their IMDC prognostic class, and the change in the TB, more than the increase in the number of metastatic sites, may help physicians to make decisions about the early termination of AS and the start of systemic therapy.